Nanomaterials: Risks and Benefits (NATO Science for Peace and Security Series C: Environmental Security)

Nanomaterials: Risks and Benefits

NATO Science for Peace and Security Series This Series presents the results of scientific meetings supported under the NATO Programme: Science for Peace and Security (SPS). The NATO SPS Programme supports meetings in the following Key Priority areas: (1) Defence Against Terrorism; (2) Countering other Threats to Security and (3) NATO, Partner and Mediterranean Dialogue Country Priorities. The types of meeting supported are generally "Advanced Study Institutes" and "Advanced Research Workshops". The NATO SPS Series collects together the results of these meetings. The meetings are coorganized by scientists from NATO countries and scientists from NATO's "Partner" or "Mediterranean Dialogue" countries. The observations and recommendations made at the meetings, as well as the contents of the volumes in the Series, reflect those of participants and contributors only; they should not necessarily be regarded as reflecting NATO views or policy. Advanced Study Institutes (ASI) are high-level tutorial courses intended to convey the latest developments in a subject to an advanced-level audience Advanced Research Workshops (ARW) are expert meetings where an intense but informal exchange of views at the frontiers of a subject aims at identifying directions for future action Following a transformation of the programme in 2006 the Series has been re-named and re-organised. Recent volumes on topics not related to security, which result from meetings supported under the programme earlier, may be found in the NATO Science Series. The Series is published by IOS Press, Amsterdam, and Springer, Dordrecht, in conjunction with the NATO Public Diplomacy Division. Sub-Series A. B. C. D. E.

Chemistry and Biology Physics and Biophysics Environmental Security Information and Communication Security Human and Societal Dynamics

http://www.nato.int/science http://www.springer.com http://www.iospress.nl

Series C: Environmental Security

Springer Springer Springer IOS Press IOS Press

Nanomaterials: Risks and Benefits Edited by

Igor Linkov

US Army Engineer Research and Development Center Concord, Massachusetts U.S.A. and

Jeffery Steevens US Army Engineer Research and Development Center Vicksburg, Mississippi U.S.A.

Published in cooperation with NATO Public Diplomacy Division

Based on the papers presented at the NATO Advanced Research Workshop on Nanomaterials: Environmental Risks and Benefits Faro, Portugal 27-30 April 2008

Library of Congress Control Number: 2008941252

ISBN 978-1-4020-9490-3 (PB) ISBN 978-1-4020-9489-7 (HB) ISBN 978-1-4020-9491 -0 (e-book)

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CONTENTS

Preface .................................................................................................................... ix Acknowledgements ................................................................................................ xi Part 1. Human Health Risks Human Health Risks of Engineered Nanomaterials: Critical Knowledge Gaps in Nanomaterials Risk Assessment ................................................................. 3 A. Elder, I. Lynch, K. Grieger, S. Chan-Remillard, A. Gatti, H. Gnewuch, E. Kenawy, R. Korenstein, T. Kuhlbusch, F. Linker, S. Matias, N. MonteiroRiviere, V.R.S. Pinto, R. Rudnitsky, K. Savolainen, A. Shvedova Disposition of Nanoparticles as a Function of Their Interactions with Biomolecules .......................................................................................................... 31 I. Lynch, A. Elder Assessment of Quantum Dot Penetration into Skin in Different Species under Different Mechanical Actions ...................................................................... 43 N.A. Monteiro-Riviere, L.W. Zhang Nanotechnology: The Occupational Health and Safety Concerns......................... 53 S. Chan-Remillard, L. Kapustka, S. Goudey Biomarkers of Nanoparticles Impact on Biological Systems ................................ 67 V. Mikhailenko, L. Ieleiko, A. Glavin, J. Sorochinska Nanocontamination of the Soldiers in a Battle Space ............................................ 83 A.M. Gatti, S. Montanari Part 2. Environmental Risk SMARTEN: Strategic Management and Assessment of Risks and Toxicity of Engineered Nanomaterials................................................................................. 95 C. Metcalfe, E. Bennett, M. Chappell, J. Steevens, M. Depledge, G. Goss, S. Goudey, S. Kaczmar, N. O’Brien, A. Picado, A.B. Ramadan Solid-Phase Characteristics of Engineered Nanoparticles: A Multi-dimensional Approach ........................................................................... 111 M.A. Chappell Nanomaterial Transport, Transformation, and Fate in the Environment: A Risk-Based Perspective on Research Needs .................................................... 125 G.V. Lowry, E.A. Casman

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Visualization and Transport of Quantum Dot Nanomaterials in Porous Media.................................................................................................... 139 C.J.G. Darnault, S.M.C. Bonina, B. Uyusur, P.T. Snee Developing an Ecological Risk Framework to Assess Environmental Safety of Nanoscale Products: Ecological Risk Framework........................................... 149 L. Kapustka, S. Chan-Remillard, S. Goudey Development of a Three-Level Risk Assessment Strategy for Nanomaterials ................................................................................................. 161 N. O’Brien, E. Cummins Classifying Nanomaterial Risks Using Multi-criteria Decision Analysis................................................................................................. 179 I. Linkov, J. Steevens, M. Chappell, T. Tervonen, J.R. Figueira, M. Merad Part 3. Technology and Benefits Nanomaterials, Nanotechnology: Applications, Consumer Products, and Benefits................................................................................................................. 195 G. Adlakha-Hutcheon, R. Khaydarov, R. Korenstein, R. Varma, A. Vaseashta, H. Stamm, M. Abdel-Mottaleb Risk Reduction via Greener Synthesis of Noble Metal Nanostructures and Nanocomposites............................................................................................. 209 M.N. Nadagouda, R.S. Varma Remediation of Contaminated Groundwater Using Nano-Carbon Colloids.......................................................................................... 219 R.R. Khaydarov, R.A. Khaydarov, O. Gapurova A Novel Size-Selective Airborne Particle Sampling Instrument (WRAS) for Health Risk Evaluation ................................................................................... 225 H. Gnewuch, R. Muir, B. Gorbunov, N.D. Priest, P.R. Jackson Nanotechnologies and Environmental Risks: Measurement Technologies and Strategies........................................................................................................ 233 T.A.J. Kuhlbusch, H. Fissan, C. Asbach Part 4. International Perspectives Processing of Polymer Nanofibers Through Electrospinning as Drug Delivery Systems .................................................................................... 247 E. Kenawy, F.I. Abdel-Hay, M. H. El-Newehy, G.E. Wnek Air Pollution Monitoring and Use of Nanotechnology Based Solid State Gas Sensors in Greater Cairo Area, Egypt........................................................... 265 A.B.A. Ramadan Advanced Material Nanotechnology in Israel...................................................... 275 O. Figovsky, D. Beilin, N. Blank

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Silver Nanoparticles: Environmental and Human Health Impacts ...................... 287 R.R. Khaydarov, R.A. Khaydarov, Y. Estrin, S. Evgrafova, T. Scheper, C. Endres, S.Y. Cho Developing Strategies in Brazil to Manage the Emerging Nanotechnology and Its Associated Risks ........................................................... 299 A.S.A. Arcuri, M.G.L. Grossi, V.R.S. Pinto, A. Rinaldi, A.C. Pinto, P.R. Martins, P.A. Maia The Current State-of-the Art in the Area of Nanotechnology Risk Assessment in Russia ................................................................................... 309 M. Melkonyan, S. Kozyrev Environmental Risk Assessment of Nanomaterials ............................................. 317 A.A. Bayramov Part 5. Policy and Regulatory Aspects Considerations for Implementation of Manufactured Nanomaterial Policy and Governance.................................................................................................... 329 F.K. Satterstrom, A.S.A. Arcuri, T.A. Davis, W. Gulledge, S. Foss Hansen, M.A. Shafy Haraza, L. Kapustka, D. Karkan, I. Linkov, M. Melkonyan, J. Monica, R. Owen, J.M. Palma-Oliveira, B. Srdjevic The Safety of Nanotechnologies at the OECD..................................................... 351 P. Kearns, M. Gonzalez, N. Oki, K. Lee, F. Rodriguez Nanomaterials in Consumer Products: Categorization and Exposure Assessment .................................................................................... 359 S. Foss Hansen, A. Baun, E.S. Michelson, A. Kamper, P. Borling, F. Stuer-Lauridsen Strategic Approaches for the Management of Environmental Risk Uncertainties Posed by Nanomaterials ........................................................ 369 R. Owen, M. Crane, K. Grieger, R. Handy, I. Linkov, M. Depledge Methods of Economic Valuation of the Health Risks Associated with Nanomaterials............................................................................................... 385 S. Shalhevet, N. Haruvy Nanomaterials: Applications, Risks, Ethics and Society ..................................... 397 A. Vaseashta Group Decision-Making in Selecting Nanotechnology Supplier: AHP Application in Presence of Complete and Incomplete Information..................... 409 B. Srdjevic, Z. Srdjevic, T. Zoranovic, K. Suvocarev Uncertainty in Life Cycle Assessment of Nanomaterials: Multi-criteria Decision Analysis Framework for Single Wall Carbon Nanotubes in Power Applications ........................................................................ 423 T.P. Seager, I. Linkov

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Knowing Much While Knowing Nothing: Perceptions and Misperceptions About Nanomaterials............................................................................................ 437 J.M. Palma-Oliveira, R.G. de Carvalho, S. Luis, M. Vieira Participants ......................................................................................................... 463 Author Index....................................................................................................... 471

PREFACE

Many potential questions regarding the risks associated with the development and use of wide-ranging technologies enabled through engineered nanomaterials. For example, with over 600 consumer products available globally, what information exists that describes their risk to human health and the environment? What engineering or use controls can be deployed to minimize the potential environmental health and safety impacts of nanomaterials throughout the manufacturing and product lifecycles? How can the potential environmental and health benefits of nanotechnology be realized and maximized? The idea for this book was conceived at the NATO Advanced Research Workshop (ARW) on “Nanomaterials: Environmental Risks and Benefits and Emerging Consumer Products.” This meeting – held in Algarve, Portugal, in April 2008 – started with building a foundation to harmonize risks and benefits associated with nanomaterials to develop risk management approaches and policies. More than 70 experts, from 19 countries, in the fields of risk assessment, decision-analysis, and security discussed the current state-of-knowledge with regard to nanomaterial risk and benefits. The discussion focused on the adequacy of available risk assessment tools to guide nanomaterial applications in industry and risk governance. The workshop had five primary purposes: ƒ Describe the potential benefits of nanotechnology enabled commercial products. ƒ Identify and describe what is known about environmental and human health risks of nanomaterials and approaches to assess their safety. ƒ Assess the suitability of multicriteria decision analysis for reconciling the benefits and risks of nanotechnology. ƒ Provide direction for future research in nanotechnology and environmental science to address issues associated with emerging nanomaterial-containing consumer products. ƒ Identify strategies for users in developing countries to best manage this rapidly developing technology and its associated risks, as well as to realize its benefits. The organization of the book reflects major topic sessions and discussions during the workshop. The papers in Part 1 review and summarize human health impact of nanomaterials. Part 2 includes papers on environmental risks. Part 3 presents benefits associated with nanomaterial enabled technologies over a wide range of applications. Part 4 encompasses a series of case studies that illustrate different applications and needs across nanomaterial development and use worldwide. The concluding Part 5 is devoted to policy implication and risk management. Each part of the book reviews achievements, identifies gaps in current knowledge, and suggests priorities for future research in topical areas. Each part starts with a group report summarizing discussions and consensus ix

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principles and initiatives that were suggested during the group discussions at the NATO workshop. The wide variety of content in the book reflects the workshop participants’ diverse views as well as their regional concerns. Simultaneous advances in different disciplines are necessary to advance nanotechnology risk assessment and risk management. Risk assessment is an interdisciplinary field, but progress in risk assessment has historically occurred due to advances in individual disciplines. For example, toxicology has been central to human health risk assessment, and advances in exposure assessment have been important for environmental risk assessment and risk management. Nanotechnology, however, ideally involves the planned and coordinated development of knowledge across fields such as biology, chemistry, materials science, and medicine. The workshop discussions and papers in the book clearly illustrate that while existing chemical risk assessment and risk management frameworks may provide a starting point, the unique properties of nanomaterials adds a significant level of complexity to this process. The goals of the workshop included the identification of strategies and tools that could currently be implemented to reduce technical uncertainty and prioritize research to address the immediate needs of the regulatory and risk assessment communities. Papers in the book illustrate application of advanced risk assessment, comprehensive environmental assessment, risk characterization methods, decision analysis techniques, and other approaches to help focus research and inform policymakers benefiting the world at large. U.S. Army Engineer Research and Development Center Concord, Massachusetts, USA

Igor Linkov

U.S. Army Engineer Research and Development Center Vicksburg, Mississippi, USA

Jeff Steevens

August, 2008

ACKNOWLEDGEMENTS

The editors would like to acknowledge Dr. Mohammed Haraza (NATO workshop co-director) and organizing committee members (Drs. Vicki Colvin, Delara Karkan, Abou Ramadan, Jeff Morris, Saber Hussain, Jose Figueira, Jose Palma-Oliveira and Carlos Fonseca) for their help in the organization of the event that resulted in this book. We also wish to thank the workshop participants and invited authors for their contributions to the book and peer-review of manuscripts. We are deeply grateful to Deb Oestreicher for her excellent management of the production of this book. Additional technical assistance in the workshop organization was provided by Elena Belinkaia and Eugene Linkov. The workshop agenda was prepared in collaboration with the Society of Risk Analysis Decision Analysis and Risk Specialty Group. Financial support for the workshop was provided mainly by NATO. Additional support was provided by the U.S. EPA, U.S. Army Engineer Research and Development Center, International Copper Association, American Chemistry Council and University of Algarve.

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HUMAN HEALTH RISKS OF ENGINEERED NANOMATERIALS Critical Knowledge Gaps in Nanomaterials Risk Assessment

A. ELDER Department of Environmental Medicine University of Rochester 575 Elmwood Avenue, Box 850 Rochester, NY 14642, USA [email protected] I. LYNCH Centre for BioNanoInteractions School of Chemistry and Chemical Biology University College Dublin Belfield, Dublin 4, Ireland K. GRIEGER Technical University of Denmark Department of Environmental Engineering Building 113 Kongens Lyngby 2800, Denmark S. CHAN-REMILLARD Golder Associates Ltd./HydroQual Laboratories Ltd. #4 6125-12th Street S.E. Calgary T2H 2K1, Canada A. GATTI University of Modena & Reggio Emilia Lab of Biomaterials Via Campi 213 A Modena 41100, Italy H. GNEWUCH Naneum Ltd. Canterbury Enterprise Hub Canterbury CT2 7NJ, UK E. KENAWY Polymer Research Group, Department of Chemistry Faculty of Science, University of Tanta Egypt

I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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R. KORENSTEIN Marian Gertner Institute for Medical Nanosystems Department of Physiology and Pharmacology, Faculty of Medicine Tel Aviv University 69978 Tel-Aviv, Israel T. KUHLBUSCH Institute for Energy and Environmental Technology Bliersheimer Street 60 Duisburg 47229, Germany F. LINKER Occupational Health Care Services, DSM ARBODienst DSM, Alert & Case Centre Kerenshofweg 200 NL-6167AE Geleen, The Netherlands S. MATIAS Instituto Superior Téchnico Universidade Téchnica de Lisboa Av. Rovisco Pais 1049-001 Lisboa, Portugal N. MONTEIRO-RIVIERE Center for Chemical Toxicology Research and Pharmacokinetics Department of Clinical Sciences, College of Veterinary Medicine North Carolina State University 4700 Hillsborough Street Raleigh, NC 27606, USA V.R.S. PINTO Rua Capote Valente 710 São Paulo 05409-002, Brazil R. RUDNITSKY Office of Space & Advanced Technology US Department of State OES/SAT, SA-23, 1990 K Street, NW, Suite #410 Washington, DC 20006, USA K. SAVOLAINEN Finnish Institute for Occupational Health, New Technologies and Risks Topeliuksenkatu 41 aA GI-00250 Helsinki, Finland

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A. SHVEDOVA CDC/NIOSH 1096 Willowdale Road Morgantown, WV 26505, USA

Abstract. There are currently hundreds of available consumer products that contain nanoscale materials. Human exposure is, therefore, likely to occur in occupational and environmental settings. Mounting evidence suggests that some nanomaterials exert toxicity in cultured cells or following in vivo exposures, but this is dependent on the physicochemical characteristics of the materials and the dose. This Working Group report summarizes the discussions of an expert scientific panel regarding the gaps in knowledge that impede effective human health risk assessment for nanomaterials, particularly those that are suspended in a gas or liquid and, thus, deposit on skin or in the respiratory tract. In addition to extensive descriptions of material properties, the Group identified as critical research areas: external and internal dose characterization, mechanisms of response, identification of sensitive subpopulations, and the development of screening strategies and technology to support these investigations. Important concepts in defining health risk are reviewed, as are the specific kinds of studies that will quickly reduce the uncertainties in the risk assessment process.1 1.

Introduction

Nanomaterials are commonly described as having at least one dimension smaller than 100 nm. A broader definition, though, refers to those materials that are manipulated at the atomic, molecular, or macromolecular scales in order to achieve functionality that is different from that found in the bulk or molecular form [106]. Many consumer items are already available that contain nanomaterials, such as electronics components, cosmetics, cigarette filters, antimicrobial and stain-resistant fabrics and sprays, sunscreens, and cleaning products [115]. According to a recent survey of the Wilson Institute web site [29], there are at least 580 consumer products on the market, including four with FDA approval for therapeutic use. Although the potential for human exposures has not been fully evaluated and is likely to be low in many cases, the safety of nanomaterials at a wide range of doses and throughout the product life cycle should be characterized to ensure consumer, occupational, and environmental health. Critical components of a systematic safety assessment for engineered nanomaterials include: evaluation of exposure concentrations in occupational and

1

Summary of the NATO ARW Working Group discussions.

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environmental settings; the physicochemical characteristics of the material at the portal of entry; the structure and function of epithelial barriers at the portals of entry; interactions of materials with biomolecules (proteins, nucleic acids, lipids); biodistribution and elimination kinetics and identification of possible target organs; characterization of dose-response relationships; elucidation of mechanisms of response; identification of target tissues for nanomaterials effects; and identification of human subpopulations with unique susceptibility to the effects of nanomaterials. These concepts are summarized in Figure 1. New products are rapidly emerging in the nanotechnology industry without a parallel development of critical information regarding their safety. Furthermore, risk assessments are currently proceeding in many cases without adequate methodologies to define risk. It should be noted that the assumptions used in assessing risks at the early stages of most emerging technologies are designed to be protective (precautionary principle) and to emphasize potential problems so that more attention is focused on managing or mitigating such risks. As the technology progresses through the product life cycle, more data becomes available and, thus, the assumptions used in risk assessment become more realistic [10, 94]. This article focuses on the critical knowledge gaps that impede the risk assessment process as well as strategies for rapid reductions in those uncertainties. 1

+ + ?

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(in gas or liquid)

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to blood, other organs? 5

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Figure 1. Key issues in assessing human health risk following nanomaterials exposures. (1) What is the nature of the nanomaterial at the portal of entry (e.g. agglomerated, charged, soluble, size?)?; (2) How do the physicochemical characteristics of nanomaterials change after deposition in the body (specific changes likely to depend on portal of entry)?; (3) Do nanomaterials penetrate epithelial barriers?; (4) Are nanomaterials transported away from the portal of entry to other organs (how much is transported? What are the target tissues?)?; (5) How do the nanomaterial properties changes as they are transported in the body (dissolution; protein/lipid binding)?; (6) How do responses at the cellular/tissue level affect transport of nanomaterials?

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Characterization of Nanomaterial Exposure

Although there is potential for occupational and environmental exposures to nanomaterials throughout their life cycle, very little is known about the concentrations of such exposures. Furthermore, the characteristics of nanoscale materials (e.g. size, shape, surface charge, agglomeration state, presence of secondary coatings from air or liquid carrier) as they might be encountered in the workplace or the environment are largely unknown. Workplace exposure data for nanoparticles is scarce. However, Maynard et al. [59] reported peak airborne levels of respirable particles of single-walled carbon nanotubes up to 53 μg/m3 in a small university laboratory. Han and colleagues [28] reported airborne levels of multi-walled carbon nanotubes during spraying, blending, and weighing operations in a research laboratory that ranged from undetectable levels to ~400 μg/m3. However, these data are from total particulate samples at the breathing zone and, thus, the total mass concentration was not comprised exclusively of nanotubes. Nevertheless, incorporation of control measures reduced the nanotube-containing dust concentrations to background levels. A recent leaflet from NIOSH regarding workplace exposures to nanomaterials states that current methods for controlling exposures are adequate, but that current measurement techniques “are limited and require careful interpretation” [69]. These somewhat contradictory statements reflect the need for personnel with extensive experience and specialized training in the handling and sampling of nanomaterials. Although NIOSH cites a lack of sufficient evidence as the basis for not recommending specific surveillance of nanoparticle-exposed workers, a framework for the safe exploitation of nanotechnology has recently been described that includes recommendations for methods and instrumentation to assess exposure levels, characterize particle size and surface area distributions, and to identify sources of nanoparticle release [58, 67, 68]. 2.1.

NANOMATERIALS CHARACTERIZATION

One critical research need is the development of methods and equipment for adequate nanomaterial characterization, as has been previously cited [4, 84, 95, 109, 110]. Nanomaterial properties may also be altered in both biotic and abiotic environments. Therefore, tools to detect and characterize chemical or physical modifications of nanomaterials in such environments are needed. There is also a pressing need to develop standardized assessments of particle characteristics including size, shape, size distribution, structure and surface area [70]. This would ensure that the same set of characteristics is described across studies, ultimately facilitating a comparison between materials and subsequent exposure. Another critical need is viewed to be the development of a set of reference nanomaterials that can serve as benchmarks for the investigation of other nanomaterials, thereby providing a basis for comparison. Reference materials are commonly used in traditional risk assessment frameworks for effects and exposure analyses. Significant efforts are being made in this regard, both by the National Institute of Standards

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and Technology (US) and the Institute of Reference Materials and Measurements (EU), although the initial focus is on reference materials for calibration of instrumentation with respect to size determination, rather than reference materials for benchmarking of potential toxicity. At present, the scientific community lacks a set of commonly accepted reference materials, including consensus on suitable positive and negative control nanoparticles for different testing systems. 2.2.

CHARACTERIZATION OF EXPOSURES

Assessing external human exposure to nanomaterials requires knowledge regarding the likelihood of exposure, changes in particle concentration over time, and identification and characterization of exposure directly prior to uptake. Workplace or ambient exposures to air- or liquid-suspended nanomaterials may occur. Although estimates have been reported for selected nanosized compounds [66], no data is available about actual levels of engineered nanomaterials in ambient environments, mainly due to the limitations of current measurement methods. There is clearly a need for a comparative exposure assessment which differentiates the routes and forms of exposure as well as the morphology of the nanomaterials. This section will mainly address inhalation exposures in the workplace, because this is currently seen as the most likely exposure scenario. However, skin and gastrointestinal tract exposures to gas- or liquid-suspended particles are also possible. Further details are provided in Kuhlbusch et al. [43] in this same edition. 2.2.1.

Measurement Methods

Measurement methods for detection of airborne (nano-) particles can be characterized as (1) online/offline detection methods that distinguish environmental from product materials, (2) methods for different matrices (gas/liquid/solid), (3) personal or fixed sampling methods, (4) methods for different exposure metrics (mass, surface area or number concentration (total and size-resolved), chemical composition, etc.), and (5) methods that predict lung regional deposited dose. No optimal method is currently available for measuring nanomaterials exposures, since, for example, the ideal metric is still a matter of debate. Certainly, the best method would be a personal sampler that determines all relevant physical and chemical properties in real time or near-real time within discrete particle size bins. This is, however, currently unavailable. Nevertheless, first steps towards simultaneously determining these properties are ongoing and are of extreme importance for realistic exposure assessment. Most exposure measurements have either used an online technique to determine particle size distribution [42, 46, 63, 114] or offline techniques like thermal or electrostatic precipitation or diffusion/impaction and subsequent particle characterization [23, 82]. The choice of using particle number-weighted, as opposed to mass-weighted, size distribution measurements is driven by the expense and availability of the equipment, the high sensitivity of number concentration measurements towards nanosized particles, the possible relevance of particle number concentration for health effects, and the requirement for speciation. Of

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similar importance with regard to linking particle properties to health may be the particle surface area, either as inhalable (Matter LQ 1-DC) or lung deposited fraction (TSI NSAM). An overview on measurement methods for nanoparticle detection can be found in Kuhlbusch et al. [44]. 2.2.2.

Measurement Strategies

One measurement challenge is the differentiation of environmental (background) from engineered nanoparticles. When deciding on measurement strategies and methods, the following points have to be taken into account. First, there is a need for a dynamic detection range, from a single particle to high number concentrations. Secondly, there is a need for particle physical and chemical characterization. Lastly, the time resolution (online/offline) must be considered. There are three particle concentration ranges in terms of number that can currently be evaluated [43]: single particle detection, a concentration of 1,000– 100,000 particles per cm3, and a concentration of more than 100,000 particles per cm3. Detection of single particles can be achieved using either single particle aerosol mass spectrometry (AMS) [72] or filter sampling with subsequent single particle analysis by TEM/EDX. Both techniques have their advantages and limitations, for example, the degree of chemical analysis that is possible. These methods would allow a differentiation of background from engineered nanoparticles. Detection of the source of particle concentrations >100,000 particles per cm3 should generally be easy since the source must be in the vicinity of the point of measurement. The source can either be visually identified or detected by determining spatial particle number concentration profiles. The difficulty in assessing nanoparticle exposure at levels between 1,000– 100,000 particles per cm3 is that background particle concentrations can be in the same concentration range. A first assessment of possible nanoparticle exposure can be conducted by concurrent measurements of ambient and workplace particle number concentrations and calculation of ambient particle penetration into the work area. This approach is possible for concentrations down to a few thousand particles per cubic centimeter [45]. Hence, clear differentiation of nanoparticles from environmental nanoscale particles can only be done by the methods described for single particle analysis. 2.2.3.

Levels of Exposure

The limited exposure measurements conducted thus far in the workplace generally show low levels or levels below the detection limits for exposure during normal production and handling of nanomaterials. However, the adequacy of existing detection instrumentation needs to be considered. The exposure-related measurements were conducted in all steps of production and handling from the reactor, to processing and handling/bagging of, for example, carbon black and titanium dioxide [38, 45]. Measurements conducted in the presence of a leak within the palletizing line showed high exposure values indicating that exposure can be

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possible, especially in cases where engineering controls fail or during cleaning and maintenance work in large scale nanomaterial production. Measurements of dustiness of powders containing nanomaterials were conducted by Dahman and Monz [14] in the framework of the NanoCare Project. This investigation showed that engineered particles below 100 nm were not normally released using a counter flow system. However, there were exceptions depending on the material investigated. This example shows that extrapolations from few measurements and generalizations to other materials should be done carefully. 2.2.4.

Future Tasks

Results are eagerly awaited from ongoing investigations focusing on possible human exposure during the life cycle of nanomaterials, from production, to their use in products, and during recycling. Several scenarios exist with different degrees of likelihood of possible release of nanomaterials into the environment and subsequent exposure. The following tasks are seen to bring advances in exposure assessments for nanoscale materials: the development of cost-effective screening methodologies for assessing exposure, the development of devices that measure personal exposure, evaluation of the adequacy of health surveillance protocols, strengthening current methods for assessing agglomerate stabilities in order to predict the potential for nanoparticle release during handling, the evaluation of nanoparticle aging during transport (e.g. airborne, in water), and improvements in the link between exposure assessments and dose metrics. 3.

Barrier Function of Skin, Gastrointestinal Tract, and Respiratory Tract

If it can be assumed that most exposures to nanomaterials will occur in air or via the food chain/drinking water, then the respiratory tract, skin, and gastrointestinal tract are the primary routes of exposure to nanomaterials. However, other routes such as intravenous, intradermal, and ocular are important to consider for specialized applications. A critical component in evaluating the health risks associated with nanomaterials exposure is knowledge regarding barrier function at the portal of entry. 3.1.

GASTROINTESTINAL TRACT

The gastrointestinal (GI) tract is not likely to be a primary route of exposure to nanomaterials. However, particles that deposit in the respiratory tract and taken up by alveolar macrophages are cleared via the mucociliary escalator and then expectorated or swallowed. Some of the particulate matter, then, that deposits in the lungs could be cleared to the GI tract (see following discussion about macrophage-mediated clearance of nanosized particles). However, the barrier function of the GI tract with respect to nanoparticles is somewhat equivocal. The transfer of nanoparticles into blood and subsequent tissue distribution is likely to be very dependent on particle surface characteristics because of the

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extreme shifts in acidity and the negatively charged mucous layer in the small intestine. Early work described the process of persorption, whereby micron-sized insoluble particles are transported from the intestinal lumen to the blood via paracellular pathways [113]. This process has been shown in in vivo studies to be size-dependent, with smaller particles (polystyrene microspheres, colloidal gold) being absorbed to a greater degree than larger ones [32, 35]. However, studies with highly insoluble radioactive metal nanoparticles have shown extremely low transfer into blood following GI tract exposures [41, 103], with some evidence for an inverse relationship between particle size and percent transfer as well as for negatively-charged particles having higher transfer rates [97]. Recent studies employing electron microscopy and elemental analysis have identified nanosized particulates, possibly from combustion sources or food, in human tissues such as liver, kidney, and colon [20–22]. Although it is not clear how the particles accumulated in these organs, both digestive and respiratory tact exposures are possible explanations. In vitro model systems are likely to have limited predictive power due to the absence of a mucous layer, which traps charged particles and potentiates their clearance via the feces. 3.2.

SKIN

Skin is the largest organ of the body. Its permeability to engineered nanomaterials with respect to depth of penetration and interactions with structural components as well as nanoparticle absorption into blood are not well understood. Recent in vitro studies have employed flow-through diffusion cells to assess nanoparticle penetration and absorption through skin. 3.2.1.

Potential for Nanomaterials Skin Penetration

Nanomaterials must penetrate the stratum corneum layer in order to exert toxicity in the lower cell layers. The quantitative prediction of the rate and extent of percutaneous penetration (into skin) and absorption (through skin) of topically applied nanomaterials is complicated due to many biological complexities, such as the diversity of the skin barrier function across species and body sites. The stratum corneum affords the greatest deterrent to absorption. Although the dead, keratinized cell layer itself is highly hydrophobic, the cells are also highly water-absorbing, a property that keeps the skin supple and soft as water is evaporated from the surface. Sebum appears to augment the water-holding capacity of the epidermis; however, its hydrophobic nature cannot be assumed to retard the penetration of xenobiotics, including nanomaterials. The rate of diffusion of topically-applied materials across the stratum corneum is directly proportional to the concentration gradient of the material across the membrane, the lipid/water partition coefficient of the material, and the diffusion coefficient of the material. It should be noted that organic vehicles may themselves penetrate into the intercellular lipids of the stratum corneum, thus affecting diffusion. Depending on the specific characteristics of the skin barrier, there is a functional molecular size/weight cut-off that prevents very large molecules from being passively absorbed across any membrane. The total

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flux of any material across the skin is also dependent upon the exposed area, with dose expressed as mass per square centimeter. In vitro studies of nanomaterial penetration of skin may only approximate the in vivo situation since a long period of time may be required to achieve steady state conditions and, thus, exceed the time constraints of in vitro evaluations. Transdermal flux (penetration) with systemic absorption of topically applied nanomaterials has obvious implications in toxicology and therapeutic drug delivery. However, knowledge of the depth and mechanism of particle penetration into the stratum corneum barrier is crucial. The skin provides an environment within the avascular epidermis where particles could potentially lodge and not be susceptible to removal by phagocytosis, yet be available for immune recognition through interaction with resident Langerhans cells. In fact, it is this relative biological isolation in the lipid domains of the epidermis that has allowed for the delivery of drugs to the skin using liposomal preparations. Several studies have evaluated the hypothesis that nanoparticles can get through or get lodged within the lipid matrix of skin. Zinc oxide (ZnO, 80 nm) and agglomerates of titanium dioxide (TiO2) smaller than 160 nm did not penetrate the stratum corneum of porcine skin in static diffusion cells [19]. Likewise, in vitro application of ZnO nanoparticles (26–30 nm) in a sunscreen formulation to human skin led to accumulation of nanoparticles in the upper stratum corneum with minimal penetration [13]. However, a pilot study conducted in humans about to undergo surgery showed penetration to the dermis of “microfine” TiO2 that was applied over a period of 2–6 weeks [105]. Block copolymer nanoparticles (40 nm) that were topically applied to hairless guinea pig skin in diffusion cells were able to penetrate the epidermis within 12 h [99]. Additional studies with spherical (QD565, the number refers to the fluorescence emission maximum) and elliptical (QD655) CdSe-ZnS semiconductor nanocrystals that were applied to porcine skin in flow-though diffusion cells showed that penetration is dependent on surface coating or charge. Polyethylene glycol (PEG)- and carboxylic acid-coated QD565 were localized primarily in the epidermis by 8 h, while the QD565 PEG-amine penetrated to the dermis. However, shape was also shown to be a determinant of nanocrystal localization by the fact that the carboxylic acid-coated elliptical crystals (QD655) did not penetrate into the epidermis until 24 h of exposure [88]. Studies have also reported that nanocrystal surface coatings and charge can influence their toxicity in human epidermal keratinocytes [89]. These results highlight the diversity in terms of size and composition of particles that could possibly penetrate the stratum corneum to reach the deeper, viable layers of skin. 3.2.2.

Factors that Affect Penetration Through Skin

Recent studies have demonstrated that mechanical action and perturbations of the skin barrier can affect the penetration of nanoparticles. For example, Tinkle et al. [108] reported that even large (0.5 µm) FITC-conjugated dextran beads could penetrate the stratum corneum of human skin and reach the epidermis following 30 min of flexing. However, the particles did not penetrate the skin at all if it was not mechanically flexed. Smaller amino acid-derivatized fullerene nanoparticles

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(3.5 nm) were able to penetrate to the dermis of porcine skin that was flexed for 60 min and placed in flow-through diffusion cells for 8 h; non-flexed control skin showed penetration that was limited to the stratum granulosum layer of the epidermis [65, 87]. QD655 and QD565 coated with carboxylic acid (hydrodynamic diameters of 18 and 14 nm, respectively) were studied for 8 and 24 h in flowthrough diffusion cells with flexed, tape stripped and abraded rat skin. No penetration occurred with the nonflexed, flexed, or tape-stripped skin. However, penetration to the viable dermal layer occurred in abraded skin. In some cases, retention of QD in hair follicles was observed in the abraded skin [117]. Another important consideration is the possible retention of nanoparticles in hair follicles, as has been alluded to above. Lademann and colleagues [48] showed that TiO2 microparticles and polystyrene nanoparticles could be localized near orifices in human hair follicles. Agglomerates of iron oxide and maghemite nanoparticles with organic coatings (primary particle sizes ~5 nm) have been shown to penetrate hair follicles and the epidermis of previously frozen human skin surgical samples, suggesting a potential capacity for nanoparticles to traverse the dermal barriers [6]. Other studies with TiO2 and methylene bis-benzotriazoyl tetramethylbutylphenol showed only 10% of the formulation remained in the furrows of the stratum corneum and infundibulum of the hair follicle of human skin [57]. QD621, nail-shaped PEG-coated CdSe-CdS nanocrystals that were topically applied to porcine skin in flow-through diffusion cells for 24 h penetrated the upper layers of the stratum corneum and were primarily retained in hair follicles and in the intercellular lipid layers, a situation also seen with carbon fullerenes [118]. Although it appears that only a small amount of the applied nanomaterial is retained in hair follicles, the kinetics of this retention and the possibility of subsequent systemic distribution must be evaluated. 3.2.3.

Potential for Nanomaterials Absorption into Blood from Skin

The evaluation of nanomaterial absorption into blood is a complex matter, so results from in vitro systems that do not have intact microcirculation should be carefully interpreted. Furthermore, human and porcine skin may react differently with respect to nanoparticle penetration as compared to smaller organic chemicals and drugs where, as described above, human and porcine skin are very similar. Nevertheless, most recent work has demonstrated that absorption into blood would not be predicted following topical application of nanomaterials to skin. For example, QD621 nanocrystals that were applied to porcine skin in flow-through diffusion cells were not found in the perfusate at any time point or concentration [118]. Likewise, studies with QD565 coated with PEG, PEG-amine, or carboxylic acid that were topically applied to human skin in diffusion cells for 8 or 24 h showed that all three QD preparations remained on the surface of the stratum corneum or were retained within hair follicle invaginations, but were not detected in the perfusate [64]. Similar observations were made by this same group with porcine skin exposed to the same particles [88]. A recent in vivo study, though, showed that nanosized TiO2 that was applied topically to pig skin in sunscreen

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formulation did not accumulate in lymph node or liver tissue following exposures for 5 days per week for 4 weeks [90]. These studies demonstrate the complexity of skin and the stratum corneum lipid barrier with respect to assessing nanoparticle penetration and absorption into blood. In most cases studied to date, topically applied nanoparticles have not been shown to be absorbed into the systemic circulation. However, penetration into the stratum corneum can occur in all animal species studied. This penetration could be significant relative to immunological and carcinogenic endpoints. Current findings suggest that surface coatings as well as nanoparticle geometry also seem to modulate penetration. All of these factors must be studied further if realistic risk assessments of manufactured nanomaterials are to be made. 3.3.

RESPIRATORY TRACT

3.3.1.

The Pulmonary Epithelial Barrier

Nanoparticles that are inhaled as singlets have high predicted deposition efficiencies via diffusional processes in all regions of the respiratory tract [34]. For singlet particles of ~20 nm, the highest fractional deposition occurs in the alveolar region, where bulk air flow is low or absent [93]. Nanosized particles are not efficiently taken up by resident phagocytic cells (alveolar macrophages) [1, 27] unless they are agglomerated, thus promoting their retention in the lung and increasing the likelihood of interactions with the epithelial barrier. The alveolar epithelial barrier has a large surface area (80–140 m2 in humans) [92] and is extensively vascularized. In a healthy lung, there are only a few cell types with which nanomaterials might interact in the alveolus: type I epithelial cells (which cover ~95% of the alveolar surface), type II epithelial cells, and macrophages. The basement membranes of the type I epithelial cells are continuous with those of endothelial cells in the pulmonary capillaries, so the total thickness through which nanoparticles have to travel to reach the blood is 0.3–2.5 μm, including the interstitial space [80]. The composition of lung lining fluid varies by region of the respiratory tract. In the alveolar region, the lining fluid consists of surfactants and an overlying aqueous phase. Pulmonary surfactant is ~90% lipids (mainly disaturated dipalmitoylphosphatidyl-choline and phosphatidylglycerol with smaller amounts of cholesterol) and 10% proteins, which are secreted by type II alveolar epithelial cells [26]. The alveolar lining fluid also contains plasma-derived proteins (e.g. albumin, transferrin, immunoglobulins) that are critical to host defense functions [39]. The degree to which nanomaterials might interact with these lipids and proteins in situ is largely unknown. 3.3.2.

Fate of Nanoparticles that Cross the Alveolar Epithelial Barrier

An important factor in assessing the toxicity of nanomaterials is their distribution throughout the body and persistence in tissues following exposure. Obviously, this

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is an issue that is difficult to fully address using in vitro model systems. Translocation to extrapulmonary tissues, including the liver and various brain regions (notably the olfactory bulb), has been demonstrated, albeit in small amounts, for inhaled nanosized poorly-soluble Mn oxide, 13C, Ag, and 192Ir [18, 41, 77, 78, 104]. In the case of the Mn oxide and 13C nanoparticles, the observed targeting of the olfactory bulb was reported to be due to transport along the olfactory nerve, which has projections terminating directly into the nasal cavity. In regards to targeting of neuronal structures, though, deposition in the nose or alveoli is not an absolute requirement. Studies by Hunter and Undem [33] showed that nodose and jugular ganglia of the vagus nerve could be targeted by the intratracheal instillation of dye tracer particles. Interestingly, Semmler and colleagues [96] showed that the retention and clearance kinetics of insoluble radioactive Ir nanoparticles (15–20 nm, count median diameter) was not different from reports in the literature for larger particles (polystyrene beads), although this was a mathematical exercise and not a direct comparison to larger particles with the same chemistry. However, later studies by this group showed that what was different was the degree of interstitialization of the nanosized 192Ir particles [98]. Oberdörster et al. [75] also reported that the interstitialization rates were ~10 times higher for nanosized TiO2 particles delivered to the lungs via intratracheal instillation as compared to larger particles of the same composition. More recently, Shvedova and colleagues [102] demonstrated that single-walled carbon nanotubes (SWCNT) delivered via inhalation exposure (deposited dose of 5 mg/mouse) resulted in the deposition of small SWCNT structures and the induction of cellular inflammation, LDH and protein release, and cytokine production that was two- to fourfold greater than responses that resulted from oropharyngeal aspiration exposure to larger agglomerated SWCNT structures. Morphometric evaluation of Sirius red-stained lung sections also showed that SWCNT inhalation caused a fourfold higher increase in fibrosis compared with that seen after pharyngeal aspiration, with collagen deposition in peribronchial and interstitial areas. Interestingly, Mercer et al. [60] demonstrated a fourfold greater fibrotic potency after pharyngeal aspiration of a well dispersed SWCNT compared to a less dispersed suspension. This potency difference was associated with a greater potential for smaller SWCNT structures to enter the alveolar walls and cause interstitial fibrosis. Overall, these results suggest that inhalation of dispersed SWCNTs leads to greater interstitialization and inflammation as compared to those delivered in an agglomerated bolus by aspiration. Thus, not only is the persistence or retention of the nanomaterials of importance, but so too is the distribution within an organ system. The liver, kidneys, and spleen have been shown to be the organs with the highest retention of nanoparticles that cross the alveolar epithelial barrier [96, 104]. It is not entirely clear, though, how primary particle size or in vivo dissolution may affect the accumulation of materials in extrapulmonary organs. Some studies have reported very rapid accumulation of nanoparticles, as determined via chemical means, in liver, kidney, and olfactory bulb following respiratory tract exposures [17, 85, 104]. In comparison to the respiratory tract, nanomaterials that

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are injected intravenously accumulate in almost all tissues that are harvested [12, 17], although this is somewhat size-and surface chemistry-dependent. Not surprisingly, surface coating has been shown to be an important determinant of nanoparticle tissue distribution. At least two studies have shown that the attachment of polyethylene glycol (PEG) to the surface of the semiconductor nanocrystals increases their circulatory half-life after intravenous injection [2, 5] due to lowered uptake efficiency by the liver and spleen (reticulo-endothelial system). Reduced efficiency of liver uptake has also been shown for PEGylated nanosized magnetite particles [52]. At least for CdSe-ZnS nanocrystals, the particle size has also been shown to be an important determinant of tissue retention following intravenous injection. Particles with hydrodynamic diameters smaller than ~5.5 nm are almost completely eliminated via urine within the first 4 h [12]. Partly due to the effective cut-off size of the kidney filter, somewhat larger particles are exclusively eliminated over time via the feces [98]. 4.

Nanomaterials Interactions with Biomolecules

Data from in vivo and in vitro studies suggesting lipid and/or protein oxidation as a result of nanomaterials exposure provides indirect evidence of interactions with biomolecules. For example, Oberdörster et al. [74] demonstrated lipid peroxidation, but not protein oxidation, in brain tissue obtained from largemouth bass that were exposed to aggregated nC60 fullerenes in tank water. Should such interactions be a surprise, though? It has long been known that implanted materials acquire a protein coating that ultimately determines the fate of the implant in terms of biocompatibility. While this is likely to be the case at the nanoscale, too, the challenge will be to identify those proteins, lipids, and other biomolecules that interact with nanoparticles in the target organs and then to characterize the kinetic nature of those interactions [54]. Progress along these lines has been made recently with detailed identification of the proteins bound to nanoparticles [8, 9, 16] and the first indications of inappropriate folding leading to protein aggregation in the presence of nanoparticles [50]. A further challenge will be to understand the predictive value of this information in the context of human risk assessment. 4.1.

INTERACTIONS WITH PROTEINS

Within the medical device community, it is now well accepted that material surfaces are modified by the adsorption of biomolecules such as proteins in a biological environment, and there is some consensus that cellular responses to materials in a biological medium reflect the adsorbed biomolecule layer, rather than the material itself [25, 55, 73]. Interestingly, recent studies suggest that nanomaterial surfaces, having much larger surface area than flat ones, are more amenable to studies to determine the identity and residence times of adsorbed proteins [9, 40]. The recently introduced concept of the nanoparticle-protein corona sees the adsorbed protein (biomolecule) layer as an evolving collection of

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proteins that associate with nanoparticles in biological fluids, and suggests that this is the biologically relevant entity that interacts with cells [53]. A recent systematic study of interactions of polystyrene nanoparticles with no modification (plain) or modified with positive (amine) or negative (carboxylic) charges indicates that the surface and the curvature (particle size) both influence the details of the adsorbed proteins, although in all cases, a significant fraction of the proteins bound were common across all particles [51]. The significance of this for safety assessment is clear, as it implies that detailed characterization of the nanoparticles in the relevant biological milieu is vital. Evidence is emerging in the scientific literature that coating of nanoparticles with specific proteins can direct them to specific locations – apolipoprotein E, for example, has been associated with transport of nanoparticles to the brain [61]. The binding of serum albumin to the surface of carbon nanotubes has also been shown to induce particle uptake and anti-inflammatory responses in a macrophage cell line [15]. However, there are several complicating factors, such as the fact that the biomolecule corona is not fixed, but is rather dynamic. The corona equilibrates with the surroundings, with high abundance proteins binding initially, but being replaced gradually by lower abundance, higher affinity proteins. Additionally, changes in the biomolecule environment, such as during particle uptake and distribution, will be reflected as changes in the corona. This makes for considerable difficulty in determining the nanoparticle biomolecule corona in-situ, as attempts to recover the particles for measurement by isolating them from their surroundings will by their very nature alter the subtle balance of the biomolecule corona. However, the situation is not all bad. A considerable portion of the biologically relevant biomolecules – the so-called “hard-corona” [51] – will remain associated with the nanoparticles for a sufficiently long time so as not to be affected by the measurement processes. First indications of a potential role for nanoparticles in misfolding and aggregation events [7, 50] as well as inhibition of misfolding [83] are emerging. A range of different nanoparticles, including polymer particles, cerium oxide, carbon nanotubes and PEG-coated quantum dots, enhanced the rate of fibrillation of the amyloidogenic protein β-2-microglobulin under conditions where the protein was in the slightly molton-globular state at pH 2.5 [50]. A mechanism based on a locally high concentration of the protein in the vicinity of the nanoparticle surface, thus increasing the probability of formation of a critical oligomer, was proposed. A recent report from Bellezza and colleagues [7] demonstrated the interaction of myoglobin (Mb) with phosphate-grafted zirconia nanoparticles. Adsorption induced marked rearrangements of Mb structure, particularly loss of the secondary structure (α-helices). Two distinct structures were observed: (i) globular aggregates, similar to those for the native protein, and (ii) very extensive, branching structures of Mb, with morphological properties similar to Mb prefibrillar aggregates. In this case, the authors suggest that the prefibril-like aggregates were always observed next to the zirconia nanoparticles, suggesting that these structures develop from the bound protein. Studies in animals have shown that C60 hydrated fullerene may have antiamyloidogenic capacity, as a single intracerebroventricular injection of a C60

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hydrated fullerene significantly improved the performance of a cognitive task in control rats, resulting from inhibition of the fibrillation of amyloid-beta 25-35 peptide [83]. These results may offer a significant therapeutic advantage towards diseases of the brain, which are often intractable, as well as raising the potential for risk. A recent review has summarized much of the current state-of-the-art in protein-nanoparticle interactions [54]. A major hope of this field of research is that it will be possible in the future to predict biological impacts of nanoparticles based on a screening of the proteins for which they have the highest affinity, and an understanding of the role of these proteins in nanoparticle uptake, trafficking and subcellular localization. 4.2.

INTERACTIONS WITH LIPIDS

There are almost no reports of the interaction between nanoparticles and lipids to date, although considerable work has been done to develop solid lipid nanoparticles for targeted drug delivery [36, 81] or using lipids such as phosphorylcholine or oleic acid to stabilize nanoparticles, including enabling their transfer from organic solvents to aqueous solutions [11, 24]. Several reports on the use of lipid coatings to reduce protein binding have also been published recently. Ross and Wirth [86] reported that laterally diffusible phosphocholine bilayers inside the pores of colloidal silica nanoparticles suppressed 93% of the binding of avidin relative to the unmodified silica colloidal crystals. Another recent report shows that gold nanorods can be coated with lipid bilayers and used as sensors for protein binding, but that the process is complex and requires issues such as membrane curvature and adhesion properties [3]. Some studies with the original aim of quantifying the binding of lipids to nanoparticles have been used as controls within broader studies of protein binding to nanoparticles. For example, a recent study of human serum albumin (HSA) binding to polymeric nanoparticles found that the thermodynamics of binding was very different in the presence and absence of oleic acid, which is a major binding ligand of HSA. Using isothermal titration calorimetry, the authors found that HSA binding to the polymeric particles is exothermic, whereas in the presence of oleic acid the adsorption is endothermic. Binding of oleic acid to the particles was found to be endothermic [49]. On the basis of the discovery that lipoproteins have a large affinity for nanoparticles of many different surface compositions, an obvious question that arises is whether the particles are actually binding the lipoprotein complexes. Thus, apolipoproteins in blood associate with lipoprotein particles, e.g. chylomicrons (>100 nm) and high density lipoproteins (8–10 nm), with diameters that are similar to engineered nanoparticles [56]. These lipoprotein complexes are composed of triglycerides and cholesterol esters in the core surrounded by proteins and a monolayer of phospholipids. A study of the binding of cholesterol and triglycerides to polymeric nanoparticles has shown that the ratio of bound cholesterol to bound triglyceride corresponds to the ratio in high density lipoprotein, suggesting that the nanoparticles bind the whole lipoprotein complex [31].

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Binding of lipoprotein complexes to nanoparticles could potentially explain why many of the nanoparticles that bind these proteins and complexes are not recognized by the body as foreign and as such do not elicit a toxic or immune response. However, it is early days yet, and considerably more research into nanoparticle-biomolecule interactions is needed. 5.

Mechanisms of Response to Nanomaterials

There is a plethora of studies in the literature regarding the in vitro and in vivo effects of engineered nanomaterials. However, much of this data is difficult to interpret because of inadequate particle characterization, exposure doses that are not well-justified in terms of realistic exposure conditions, or the elution of substances (impurities) of known toxicity (e.g. transition metals). Nevertheless, several studies have pointed to oxidative stress as an important mechanistic process related to nanomaterials toxicity. For example, Sayes et al. [91] showed that as nC60 fullerenes became more water-soluble through derivatization of the particle surface, toxicity was dramatically reduced. The reduction in cytotoxicity was correlated with a lowered oxygen radical production by the fullerenes. Nanoparticle oxidative capacity, as determined using acellular methods, has also been shown to correlate well with oxidant-sensitive reporter activity in cultured cells and acute in vivo inflammatory responses [76]. As mentioned above, Oberdörster’s study in bass [74] reported evidence of brain tissue lipid oxidation and a trend towards reduced glutathione depletion. Glutathione is an abundant tripeptide with broad antioxidant capacity and is gradually depleted in favor of the oxidized form as the severity of oxidative stress increases [71]. Shvedova and colleagues [101] exposed mice to singlewalled carbon nanotubes (SWCNTs) via oropharyngeal aspiration and showed dose-related increases in granuloma formation (in association with SWCNT aggregates in tissues), interstitial fibrosis (in areas where SWCNTs were not visible), neutrophilic inflammation, glutathione depletion, increases in 4-hydroxynonenal, and increases in soluble inflammatory mediators. Furthermore, in vitro studies using cultured human keratinocytes and murine macrophages supported the role of oxidant production in response to nanotubes, as evidenced by the intracellular formation of lipid peroxidation products and antioxidant depletion. The same studies also highlighted the role of trace amounts of iron from the synthetic process in the observed responses [37, 100]. This latter study, in particular, highlights the need to identify transition metals, either as contaminants or structural components, in nanomaterial preparations as part of a safety evaluation. In addition to the oxidative stress hypothesis, there is also compelling data regarding the role of surface coating or charge as a determinant of particle toxicity. Early studies using near micron-sized polystyrene micellar particles (~750 nm) demonstrated the principle that a negative surface charge was responsible for membrane depolarization and inflammatory cytokine induction in bronchial epithelial cells [112]. Likewise, a negative surface charge of micronsized ambient particulate matter from diverse sources was correlated with

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increases in intracellular calcium and cytokine induction [111]. These responses were thought to be related to the activity of acid-sensitive receptors on the cell surface, suggesting cell type specificity of response (e.g. neuroepithelial). RymanRasmussen and colleagues [89], though, recently showed that negatively-charged CdSe-ZnS semiconductor nanocrystals were more cytotoxic in human epidermal keratinocytes than positively-charged particles of the same size and composition. The extent to which these mechanisms may be involved in the responses of diverse cell types to nanosized particles remains to be determined. Following in vivo exposures, a combination of factors will ultimately determine the toxicity of a given material: oxidative capacity is likely to be related to acute responses and in vivo solubility; interactions with proteins and lipids may modify these processes (either increase or decrease toxicity) and also determine the biodistribution of the particles; and the persistence of the material will affect the long-term clearance and effects. 6.

Sensitive Subpopulations

Knowledge regarding the biodistribution of nanomaterials as well as the mechanisms of response to them will lead to reasonable hypotheses regarding subpopulations that might experience adverse effects following exposure where other individuals will not. For example, individuals with underlying cardiopulmonary disease are more susceptible to the effects of ambient particulate air pollution [47, 79, 107]. Pre-existing bacterial or viral infections or disease states (e.g. diabetes) can contribute to oxidant-antioxidant imbalance or the activation status of inflammatory cells such that nanomaterials exposure could lead to persistent and overwhelming oxidative stress and tissue injury. In addition, inflammatory disease states can affect epithelial barrier function [30, 62, 116], thus altering the distribution of nanomaterials that are deposited in the respiratory tract or that are circulating in the blood. Depending on the route of exposure and the characteristics of the nanoparticles, many studies have demonstrated accumulation in major organ systems and passage through epithelial barriers. This raises the possibility that nanosized particles can also accumulate in germ line cells or the placenta and perhaps be transferred to the developing fetus, although this is an issue that has not received a great deal of attention. 7. 7.1.

Summarizing Concepts ACCEPTABLE SCREENING STRATEGIES

In general, there are no commonly accepted screening assays for nanomaterials health effects. The American Society for Testing and Materials recently adopted a set a screening tests for the safety evaluation of nanomaterials intended for therapeutic use, including blood cell hemolysis, cytotoxicity in porcine kidney and human hepatocarcinoma cells, and the formation of mouse granulocyte-macrophage

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colonies. For nanomaterials that may be encountered in the workplace or the environment, though, any screening strategy needs to be related to known mechanisms of response and/or aspects of the material physico-chemistry that predict in vivo responses. Some examples could include measurements of the oxidative capacity of the particle surface and assessment of protein binding. However, these kinds of assays have not yet been validated. 7.2.

SUMMARY OF URGENT RESEARCH NEEDS

The most pressing research needs for the purpose of reducing the uncertainties in nanomaterials risk assessment are apparent from the preceding text. They include characterizations of external and internal exposures and identifications of mechanisms of response and sensitive subpopulations, all of which must be supported by thorough physicochemical characterization of test materials. This knowledge is likely to lead to useful screening approaches, as illustrated in Figure 2. Exposure Assessment

Target Organ Dose Nanomaterial Characterization

Mechanisms

Sensitive Subpopulations

Screening Strategies

Figure 2. Overview of the immediate research needs in regards to human health risk assessment of nanomaterials.

A full understanding of external exposure includes measurements of particle concentrations and physicochemical properties over time in gas or liquid carriers. In particular, the impact of agglomeration/deagglomeration behavior and soluble forms of the material need careful attention. Critical information for determining internal dose of nanomaterials includes an evaluation of the ability of the material to breech physiological barriers, the dose to and retention in target organs and cellular/subcellular structures, changes in the physicochemical properties of the material as it is distributed in the body, and how the interactions of the material with endogenous biomolecules ultimately affect target organ dose. Some of these efforts will require the development of new technologies, particularly for nanoparticle-containing aerosol characterization. Although it has presented a challenge for particle toxicologists in the past, in vivo-to-in vitro dose comparisons would be helpful not only in understanding the relevancy of in vitro test results, but also in the development of screening assays. Determinations of mechanisms of action also need to be clearly linked to realistic external and internal doses. However, it should be recognized that mechanistic

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information will be critical in identifying sensitive subpopulations that may have lower thresholds for responding to nanomaterials because of, for example, alterations in repair of tissue damage or oxidant/antioxidant imbalance. Lastly, it is imperative that there is strong global commitment to funding these essential research areas. It is more cost-effective in the long term to proactively address these critical knowledge gaps than to be reactive in regards to nanomaterials health risk assessment. Especially in light of significant scientific uncertainty and a lack of clear regulation, such an approach will allow the nanotechnology industry to flourish while increasing openness and transparency in decision-making processes.

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DISPOSITION OF NANOPARTICLES AS A FUNCTION OF THEIR INTERACTIONS WITH BIOMOLECULES

I. LYNCH Centre for BioNano Interactions School of Chemistry and Chemical Biology University College Dublin Belfield, Dublin 4, Ireland [email protected] A. ELDER Department of Environmental Medicine, University of Rochester 575 Elmwood Avenue, Box 850 Rochester, NY 14610, USA [email protected]

Abstract. This review focuses on emerging concepts in the fundamental understanding of how particle surfaces interact with components in biological fluids, with an emphasis on how these interactions may inform research regarding the biodistribution of nanosized materials from the portal of entry to other organ systems. The respiratory tract is given particular focus here because of expected occupational and environmental exposure scenarios. Information regarding the biodistribution of nanoparticles and how they might be altered during the process by their local environment is a critical part of a complete human health risk assessment. 1.

Introduction

Nanomaterials can be described as having at least one dimension smaller than 100 nm. More broadly, though, they are materials that are manipulated at the atomic, molecular, or macromolecular scales in order to achieve unique functionality [39]. Many consumer items are available that contain nanomaterials, as is a small number of FDA-approved therapeutic agents [42]. The likelihood of human exposures has not been fully assessed for the full product life cycle and is likely to be low in many cases (e.g. when the material is embedded in a solid). Nevertheless, the safety of these materials must be assessed in a systematic way to ensure standards of protection for consumer, occupational, and environmental health. In assessing human health risk from nanomaterials exposure, it is important to consider the likely routes of entry into the body. Such routes include the respiratory tract, gastrointestinal tract, and skin [7] for consumer, occupational, and environmental exposure scenarios. Determining the retained dose and effects at the portal

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of entry are critical components of nanomaterials risk assessment, as are the disposition of the material following exposure and effects in tissues distant from the portal of entry. The disposition of nanomaterials and their effects are likely to be dependent on properties of the surface, as this will determine interactions with biomolecules. This paper describes some of the current concepts and literature regarding how nanoparticles (NPs) interact with biomolecules and tissues. Common themes are highlighted, but not meant to be comprehensive, thus leaving room for new insights as this field grows into maturity. 2.

Interactions of Nanoparticles with Biomolecules

In the medical device community, it has long been understood than materials surfaces are covered by a layer of biomolecules immediately upon contact with physiological systems (e.g. upon implantation) which mediates the interaction of the material with the surrounding tissue [41]. It is likely that this phenomenon will also be the key to understanding much of the bio-nano-science world [25] and it has recently been argued that the effective unit of interest in the cell–nanomaterial interaction is not the NP per se, but the particle and its ‘corona’ of more or less strongly associated proteins from serum or other body fluids [26]. Ultimately it is this corona of more or less disrupted proteins ‘expressed’ at the surface of the particle that is ‘read’ by living cells. The high surface to volume ratio of NPs means that the adsorption potential is hugely amplified by the amount of surface exposed to living tissue (for example, there are 800 m2 surface area per litre solution at 1% concentration of 70 nm particles). There are additional complications relating to the particulate nature of NPs, and to the fact that (when sufficiently small) they can access almost every organ (see Section 3) and then be taken up into cells as opposed to interacting only with cell surface receptors, as is the case with the more traditional biomaterials. Thus, it is the nature of the organization of the adsorbed proteins and other biomolecules on the surface of NPs, and any subsequent colloidal instability of either the NPs (e.g. particle aggregation, flocculation, precipitation etc.) or the adsorbed proteins (such as protein aggregation, clustering, fibrillation etc.) that determines the initial biological responses to the presence of NPs. 2.1.

INTERACTIONS OF NANOPARTICLES WITH PROTEINS

Proteins constitute a major fraction of the dry mass of cells, and in fact represent about 18% (with water accounting for 70%) of a typical mammalian cell. Lipids (~5%), polysaccharides (~2%) and DNA and RNA are other macromolecular components of cells [2]. It is estimated that there are more than 1 million different proteins in the human proteome, while in plasma there are over 3,700 different proteins [28]. Thus, it is clear that the diversity of NP–protein interactions is enormous, and the potential impacts of NPs on protein functioning are significant. The recently introduced concept of the NP-protein corona sees the adsorbed

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protein (biomolecule) layer as an evolving collection of proteins that associate with NPs in biological fluids based on abundance (initially) and affinity (higher affinity proteins are selectively enriched over time), and suggests that this is the biologically relevant entity that interacts with cells [25]. If our understanding of the risks associated with NPs and nanomaterials is to evolve, we need to begin to make serious connections between the nature of the NP-protein complex following different routes of exposure and the biological consequences of NP uptake and translocation. This has particular relevance in terms of the portal of entry of NPs, which in many cases is the lung (based on collective experience from ultrafine particles), and subsequent translocation to the systemic circulation and extrapulmonary organs, as the particles will have initial contact with biomolecules from the lungs, including surfactant proteins and lipids. The protein and lipid milieu of the respiratory tract exhibits considerable regional variability. In the alveolar region, the lining fluid consists of surfactants and an overlying aqueous phase. Pulmonary surfactant is ~90% lipids and 10% proteins. The main physiological role of surfactant is to keep both the alveoli and bronchioles patent during respiration. The lipid component is composed largely of disaturated dipalmitoylphosphatidylcholine and phosphatidylglycerol with smaller amounts of cholesterol. Surfactant proteins are also associated with the lipid layer and are secreted by type II alveolar epithelial cells [18]. The alveolar lining fluid also contains plasma-derived proteins (e.g. albumin, transferrin, immunoglobulins) that are critical to host defense functions [22]. For ultrafine pollution particles (whose dimensions are similar to those of many NPs), it has been shown that particles deposited in the hypophase may interact with lung surfactant proteins A and D or glycoproteins [21]. This study identified 13 mass fragments, diagnostic of the amino acids alanine, arginine, asparagine, aspartic acid, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, serine, and valine, providing evidence that amino acids related to opsonin proteins adsorb to nonbiological particle surfaces exposed to human lung lining fluid. There is already considerable evidence that adsorbed biomolecules can (temporarily) mediate the effect of particles of known toxicity, such as quartz silica and kaolin clays. For example, binding of serum proteins to cristobalite (a form of crystalline silica) shifted the dose at which an inflammatory response was observed to a higher concentration; the same effect was found with titanium dioxide and asbestos [4]. Several studies have shown that simulated pulmonary surfactant delays the onset of cytotoxicity, DNA-damaging activity, and apoptosis induction by respirable quartz and kaolin in cultured cells [16, 17]. Another study also demonstrated that Diesel exhaust particles, but not carbon black, could bind to a pro-inflammatory molecule (interleukin-8) and that this binding was weakly inhibited with high serum concentrations [33]. Thus, there already exist clear linkages between adsorbed biomolecules and mediation of NP toxicity effects, and a systematic evaluation of the nature of the proteins that adsorb to NPs upon deposition in different sites in the lungs and correlation of this with biological effects would offer enormous potential for screening of the estimated >30,000 NPs that are under development in laboratories and industries worldwide.

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In order to really understand the implications of NPs on living systems, identification of the adsorbed proteins and their residence times is not sufficient, as the situation is dynamic and evolves as the NPs are transported around the system. As highlighted already in this volume [14], information is also required about the binding affinities and stoichiometries, and on the nature of the groups of proximate amino acid residues that are expressed at the outer surface of the adsorbed protein layer (the biological identity). This will require significant efforts from biophysicists and others over several years to really tease out these detailed (so-called) epitope maps [25]. However, there are several complicating factors, such as the fact that the biomolecule corona is not fixed, but is rather dynamic. The corona equilibrates with the surroundings, with high abundance proteins binding initially, but being replaced gradually by lower abundance, higher affinity proteins. Additionally, changes in the biomolecule environment, such as during particle uptake and distribution, will be reflected as changes in the corona. This makes for considerable difficulty in determining the NP biomolecule corona in-situ, as attempts to recover the particles for measurement by isolating them from their surroundings will by their very nature alter the subtle balance of the biomolecule corona. However, the situation is not all bad. A considerable portion of the biologically relevant biomolecules – the so-called “hard-corona” [44] – will remain associated with the NPs for a sufficiently long time so as not to be affected by the measurement processes. A recent review has summarized much of the current state-of-the-art in protein–NP interactions [45]. A major hope of this field of research is that it will be possible in the future to predict biological impacts of NPs based on a screening of the proteins for which they have the highest affinity, and an understanding of the role of these proteins in NP uptake, trafficking and subcellular localization. 2.2.

INTERACTIONS OF NANOPARTICLES WITH LIPIDS

Pulmonary surfactant is a phospholipid-protein complex, components of which are secreted by type II alveolar epithelial cells and Clara cells. Changes have been found in phospholipid concentrations in bronchoalveolar lavage fluid (BALF) of patients with pulmonary fibrosis, indicating that phospholipid is involved in fibrotic processes, such as occurs following prolonged, high-dose particulate exposures. Kuroda and colleagues [24] also demonstrated in rats that phospholipid concentrations in lung lavage fluid were increased significantly throughout a 6 month period following crystalline silica exposure and that the increases correlated with the severity of the inflammatory response. The interactions of fine particles (urban PM2.5) and surfactant removed from human lungs by bronchoalveolar lavage were studied using a surface analysis technique to identify which of the chemical components of lung lining fluid deposit on PM2.5. The most strongly associated mass fragment on PM2.5 surfaces exposed to BALF was di-palmitoyl-phosphatidylcholine, a component of lung surfactant [21].

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Thus, while there is significant literature on the interactions of ultrafine particles with lipids, evidence of engineered NPs interactions with lipids is only beginning to emerge [3]. A very recent study of the interaction of 15 nm gold NPs with semisynthetic pulmonary surfactant (dipalmitoyl-phosphatidylcholine (DPPC)/ palmitoyl-oleoyl-phosphatidyl-glycerol/surfactant protein B (SP-B) in the ratio 70:30) showed that low levels of gold NPs (3.7 mol% Au/lipid, 0.98% wt/wt) impeded the surfactant’s ability to reduce surface tension (gamma) to low levels during film compression and to re-spread during film expansion [3]. The authors concluded that gold NPs can interact with and sequester pulmonary surfactant phospholipids and, if inhaled from the atmosphere, could impede pulmonary surfactant function in the lung. Carbon nanotubes have also been shown to adsorb surfactant lipids and proteins, thereby modulating the function of pulmonary surfactant [33]. It is not yet clear if all nanomaterials can alter the concentration – as demonstrated for crystalline silica – or function of phospholipids in the lung or if lipid–NP interactions will change the “biological identity” of the particle surface. 3.

Disposition of Nanoparticles Following In Vivo Exposures

The physiological barriers with which nanomaterials are likely to interact – namely skin and the gastrointestinal and respiratory tracts – are diverse both structurally and physiologically. It is, therefore, somewhat unlikely that a single NP physicochemical property will explain all interactions with target tissues. For example, NPs that are taken up via the gastrointestinal tract are exposed to the highly acidic environment of the stomach and then interact with a mucous gel layer once they reach the intestines. These factors are not present in skin or lung, nor are there such extreme environmental shifts. For each of the barriers, it is important to understand how peculiarities of structure and physiology might impact interpretations regarding the physicochemical characteristics that are hypothesized to determine NP fate and effects following exposure. More details about the three different barriers are provided in Elder et al. [14]. Likewise, the unique protein and lipid environments at these barriers are likely to affect how NPs are initially, at least, transported in the body. This section will focus on the respiratory tract, as other papers in this book address skin and the gastrointestinal tract. 3.1.

THE RESPIRATORY TRACT BARRIER

It should be stated at the outset that in evaluating NP disposition, it is important to consider what it is that is being detected chemically or microscopically: the particle itself or a component of the particle (solute, tracer molecule). Obviously, the former is more desirable. Materials that lend themselves well to disposition and biokinetics studies are fluorescent (e.g. semiconductor nanocrystals, quantum dots, QDs) and electron-dense metal NPs. Nevertheless, physicochemical characteristics such as primary particle size, shape, surface coating, surface charge, hydrophobicity, agglomeration state in relevant solutions, and solubility are

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important parameters. QDs and metal NPs have been used extensively to evaluate the barrier function of the skin and respiratory tract in regards to nanomaterials. Another attractive feature of these two NP types is that it is possible to vary surface chemistry without changing particle core chemistry, but studies taking advantage of this are somewhat limited. There are many ways to deliver nanosized particles to the respiratory tract in order to gain information about their disposition, including intranasal and intratracheal instillation, oropharyngeal aspiration, intratracheal microspray, and nose-only, intratracheal, or whole-body inhalation. Both the dose rate and dose distribution are artificial with the instillation and aspiration methods. However, such delivery is acceptable for screening studies or when the exposure material is precious and follow-up studies are planned [12]. For nanosized particles delivered via inhalation as singlets, mathematical predictions suggest that they will efficiently deposit via diffusional processes in all regions of the respiratory tract, although the highest fractional deposition for particles of ~10–100 nm occurs in the alveolar region [20]. Two important anatomical features of this region of the respiratory tract are (1) the large surface area of the alveolar epithelium and (2) its high degree of vascularization. Deposition also occurs, though, in the tracheobronchial and nasopharyngeal-laryngeal regions, which contain projections of sensory nerves. Dendrites of the olfactory nerve, for example, project directly into the nasal epithelium. Clearly, then, given the different biological milieu represented by the various deposition sites (detailed in Section 2.1 above), a systematic investigation of the effects of NP size coupled to surface physicochemical properties and consequent adsorbed biomolecule coronas on NP biodistribution is a key direction for immediate research to begin to address one of the most significant gaps in current knowledge related to NP safety assessment. 3.2.

TRANSLOCATION OF NANOSIZED PARTICLES

In the alveolar region of the lung, where 10–100 nm diameter particles are predicted to deposit efficiently, there is a limited number of cells with which to interact in a healthy lung, namely alveolar macrophages and type I and type II alveolar epithelial cells. Particles that agglomerate and remain in that state in alveolar lining fluid may be taken up by alveolar macrophages and removed via mucociliary clearance. However, this clearance mechanism does not work well for NPs [1, 19], thus promoting their retention in the lungs and possibly leading to interactions with epithelial cells. Via mechanisms such as endocytosis and passive transcellular or paracellular translocation, NPs can gain access to the interstitial space and the blood. In the upper respiratory tract and in the tracheobronchial region, NPs can also be taken up by sensory neurons; the existence of sensory neurons in the alveolar region of the lung is somewhat controversial. Several studies have now shown that the alveolar epithelium, at least, permits transfer of nanosized particles into the interstitial space. Oberdörster et al. [29] showed that the interstitialization of nanosized TiO2 particles proceeded at a rate that was ~10 times faster than larger particles of the same composition that were

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delivered to the lungs via intratracheal instillation. Geiser et al. [15] reported that a substantial fraction (~20%) of inhaled nanosized TiO2 particles could be found in alveolar epithelial cells, the interstitium, and blood cells within 1 h of exposure. Other recent studies have also shown a high degree of interstitialization for nanosized 192Ir particles [35]. Evidence was also presented that suggested that the interstitialized particles could then be transported back to the airway epithelium for elimination. These studies have been done with spherical NPs, but work with single-walled carbon nanotubes, which are fibrous in nature, suggests that those particles that are better dispersed upon delivery to animals (e.g. via inhalation) have a greater interstitial fibrotic potential [27, 36]. Although the amounts of deposited NPs that leave the alveolar surface and travel into the interstitium and blood are small, several studies have demonstrated that they accumulate in extrapulmonary organs [13, 23, 30, 31, 37, 38]. NPs of various compositions were used (Ag, Au, Mn oxide, 13C, and 192Ir) and were generated in the gas phase and delivered via whole-body or intratracheal inhalation. It is important to note that it is likely that the NP itself and not a solute or label was being tracked in these studies. With the exception of Mn oxide and Ag NPs, which would be predicted to have limited in vivo solubility, the other particle types are very poorly soluble. In addition to tissues such as liver and spleen, the central nervous system was also shown to be a site of NP accumulation [13, 30, 31, 38]. It is proposed that NPs that are deposited onto the nasal epithelial surface after inhalation exposures are translocated to the olfactory bulb via the olfactory nerve and, possibly, to more distal brain structures [5, 6, 10, 11]. The liver, kidneys, and spleen have been shown to be the organs with the highest retention of NPs that cross the alveolar epithelial barrier [34, 38]. Similar to what was observed for NPs accessing the interstitium, it also appears that NPs accumulate very rapidly in extrapulmonary organs [38]. In comparison to the respiratory tract, nanomaterials that are intravenously injected accumulate in almost all tissues [9], although this is somewhat dependent on particle size and surface chemistry. It is to be expected that NPs will encounter very different protein and lipid milieu as they are transported from the lungs to extrapulmonary tissues, both in terms of distinct species and their relative abundances. The degree to which biodistribution depends on interactions of the NP surface with endogenous proteins and lipids is largely unknown, but is the subject of current research. One last issue is that the integrity of the epithelial barrier must be considered. This is likely to be of importance for two reasons. For one, inflammation can alter that the permeability of epithelial barriers [40, 43], thus potentiating transfer of NPs from the site of deposition to more distal organs. Indeed, a recent study by Chen and colleagues [8] showed that the transfer of radiolabeled nanosized, but not 200 nm, polystyrene beads into the blood following intratracheal instillation exposures in rats was potentiated by pre-exposure to bacterial lipopolysaccharide, a known inflammatory stimulus. Secondly, soluble inflammatory mediators that are present at the site of injury could become associated with the NP surface and either affect distribution or induce effects in tissues where the particles accumulate. Thus, the possibility exists that individuals with compromised barrier function

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(e.g. ongoing inflammation due to underlying disease or concurrent exposure to inflammatory stimuli) may be more susceptible to the effects of NPs. 4.

Summary and Concluding Remarks

Several important concepts were reviewed here in regards to the biodistribution of NPs that are deposited in the respiratory tract. First, translocation is dependent on particle size. Secondly, the organs in which NPs accumulate is likely to reflect the site of deposition in the lung and the physicochemical characteristics of the NPs (agglomerate state, solubility, e.g.). These parameters (deposition site and physicochemical characteristics) also determine the proteins and other biomolecules that adsorb onto the NPs immediately upon contact with the cells of the lung, and thus confer a “biological identity” to the NPs, which interacts with the cellular machinery and determines uptake and translocation pathways. The integrity of epithelial barrier is also a critical factor (e.g. lung inflammation). Lastly, it should be clear from the concepts reviewed herein that a well-done nanomaterials risk assessment requires a multidisciplinary approach, a global commitment to research funding, and a need for the development of new technologies such as screening assays and measurement tools. Such an approach should result in a rapid reduction in the uncertainties of the current risk paradigm and ensure the future success of the nanotechnology industry. Acknowledgements The authors are supported by the following funding: NIEHS Center grant P30 ESO1247, EPA STAR grant RD 83172201, DoD MURI FA9550-04-1-0430, NIH R01 CA134218, EU FP6 project NanoInteract (NMP4-CT-2006-033231), ESF Network EpitopeMap, IRCSET, SFI SRC BioNanoInteract (07/SRC/B1155) and HEA PRTLI4. References 1. Ahsan, F., Rivas, I. P., Khan, M. A., and Torres Suárez, A. I., 2002, Targeting to macrophages: role of physicochemical properties of particulate carriers - liposomes and microspheres - on the phagocytosis by macrophages, J. Control. Release 79: 29–40. 2. Alberts, B., Bray, D., Lewis, J., Raff, M., Roberts, K., and Watson, J. D., 1994, Molecular Biology of the Cell, 3rd Edition. Garland Publishing, London. 3. Bakshi, M. S., Zhao, L., Smith, R., Possmayer, F., and Petersen, N. O., 2008, Metal nanoparticle pollutants interfere with pulmonary surfactant function in vitro, Biophys. J. 94: 855–868. 4. Barrett, E. G., Johnston, C., Oberdorster, G., and Finkelstein, J. N., 1999, Silica binds serum proteins resulting in a shift of the dose-response for silica-induced chemokine expression in an alveolar type II cell line, Toxicol. Appl. Pharmacol. 161: 111–122. 5. Bodian, D., and Howe, H. A., 1941b, The rate of progression of poliomyelitis virus in nerves, Bull. Johns Hopkins Hosp. 69: 79–85.

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6. Bodian, D., and Howe, H. A., 1941a, Experimental studies on intraneural spread of poliomyelitis virus, Bull. Johns Hopkins Hosp. 68: 248–267. 7. Borm, P. J. A., Robbins, D., Haubold, S., Kuhlbusch, T., Fissan, H., Donaldson, K., Schins, R., Stone, V., Kreyling, W., Lademann, J., Krutmann, J., Warheit, D., and Oberdörster, E., 2006, The potential risks of nanomaterials: a review carried out for ECETOC, Part. Fibre Toxicol. 3(11): 35. 8. Chen, J., Tan, M., Nemmar, A., Song, W., Dong, M., Zhang, G., and Li, Y., 2006, Quantification of extrapulmonary translocation of intratracheal-instilled particles in vivo in rats: effect of lipopolysaccharide, Toxicology 222: 195–201. 9. Choi, H. S., Liu, W., Misra, P., Tanaka, E., Zimmer, J. P., Ipe, B. I., Bawendi, M. G., and Frangioni, J. V., 2007, Renal clearance of quantum dots, Nat. Biotechnol. 25(10): 1165–1170. 10. DeLorenzo, A. J. D., 1970, The olfactory neuron and the blood-brain barrier. In: Wolstenholme, G. E. W. and Knight, J. (eds.), Taste and Smell in Vertebrates. London: J&A Churchill, pp. 151–176. 11. DeLorenzo, J., 1957, Electron microscopic observations of the olfactory mucosa and olfactory nerve, J. Biophys. Biochem. Cytol. 3: 839–850. 12. Driscoll, K. E., Costa, D. L., Hatch, G., Henderson, R., Oberdörster, G., Salem, H., and Schlesinger, R. B., 2000, Intratracheal instillation as an exposure technique for the evaluation of respiratory tract toxicity: uses and limitations, Toxicol. Sci. 55(1): 24–35. 13. Elder, A., Gelein, R., Silva, V., Feikert, T., Opanashuk, L., Carter, J., Potter, R., Maynard, A., Ito, Y., Finkelstein, J., and Oberdörster, G., 2006, Translocation of inhaled ultrafine manganese oxide particles to the central nervous system, Environ. Health Perspect. 114(8): 1172–1178. 14. Elder, A., Lynch, I., Grieger, K., Chan-Remillard, S., Gatti, A., Gnewuch, H., Kenawy, E., Korenstein, R., Kuhlbusch, T., Linker, F., Matias, S., Monteiro-Riviere, N., Pinto, V., Rudnitsky, R., Savoleinen, K., and Shvedova, A., 2008, Human health risks of engineered nanomaterials. In: Linkov, I. and Steevens, J. (eds.), Nanotechnology: Risks and Benefits. Dordrecht: Springer. 15. Geiser, M., Rothen-Rutishauser, B., Kapp, N., Schurch, S., Kreyling, W., Schulz, H., Semmler, M., Im Hof, V., Heyder, J., and Gehr, P., 2005, Ultrafine particles cross cellular membranes by nonphagocytic mechanisms in lungs and in cultured cells, Environ. Health Perspect. 113: 1555–1560. 16. Gao, N., Keane, M. J., Ong, T., Ye, J., Miller, W. E., and Wallace, W. E., 2001, Effects of phospholipid on apoptosis induction by respirable quartz and kaolin in NR8383 rat pulmonary macrophages, Toxicol. Appl. Pharmacol. 175: 217–225. 17. Gao, N., Keane, M. J., Ong, T., and Wallace, W. E., 2000, Effects of simulated pulmonary surfactant on the cytotoxicity and DNA-damaging activity of respirable quartz and kaolin, J. Toxicol. Environ. Health 60: 153–167. 18. Griese, M., 1999, Pulmonary surfactant in health and human lung diseases: state of the art, Eur. Respir. J. 13: 1455–1476. 19. Hahn, F. F., Newton, G. J., and Bryant, P. L., 1977, In vitro phagocytosis of respirablesized monodisperse particles by alveolar macrophages, ERDA Ser. 43: 424–435. 20. International Committee on Radiological Protection, 1994, Human Respiratory Tract Model for Radiological Protection, A Report of Committee 2 of the ICRP. 21. Kendall, M., 2007, Fine airborne urban particles (PM2.5) sequester lung surfactant and amino acids from human lung lavage, Am. J. Physiol. 293: L1053–L1508. 22. Kim, K. J., and Malik, A. B., 2003, Protein transport across the lung epithelial barrier, Am. J. Physiol. 284(2): L247–L259.

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37. Takenaka, S., Karg, E., Kreyling, W. G., Lentner, B., Möller, W., Behnke-Semmler, M., Jennen, L., Walch, A., Michalke, B., Schramel, P., Heyder, J., and Schulz, H., 2006, Distribution pattern of inhaled ultrafine gold particles in the rat lung, Inhal. Toxicol. 18(10): 733–740. 38. Takenaka, S., Karg, E., Roth, C., Schulz, H., Ziensis, A., Heinzmann, U., Schramel, P., and Heder, J., 2001, Pulmonary and systemic distribution of inhaled ultrafine silver particles in rats, Environ. Health Perspect. 109(Suppl. 4): 547–551. 39. The Royal Society and the Royal Academy of Engineering, Nanoscience and Nanotechnologies: Opportunities and Uncertainties, The Royal Society, 2004. 40. Wagner, J. G., Hotchkiss, J. A., and Harkema, J. R., 2001, Effects of ozone and endotoxin coexposure on rat airway epithelium: potentiation of toxicity-induced alterations, Environ. Health Perspect. 109(Suppl. 4): 591–598. 41. Wilson, C. J., Clegg, R. E., Leavesley, D. I., and Pearcy, M. J., 2005, Mediation of biomaterial-cell interactions by adsorbed proteins: a review, Tissue Eng. 11: 1–18. 42. Woodrow Wilson International Center for Scholars, Project on Emerging Nanotechnologies, Consumer Products Inventory. http://www.nanotechproject.org/inventories/ consumer/. 43. Xiao, H., Banks, W. A., Niehoff, M. L., and Morley, J. E., 2001, Effect of LPS on the permeability of the blood-brain barrier to insulin, Brain Res. 896: 36–42. 44. Lundqvist, M., Stigler, J., Elia, G., Lynch, I., Cedervall, T., Kenneth A., and Dawson, K.A., 2008, Nanoparticle size and surface properties determine the protein corona with possible implications for biological impacts. PNAS, 105(38): 14265–14270. 45. Lynch, I., and Dawson, K. A., 2008, Protein-nanoparticle interactions, Nano Today 3: 40–47.

ASSESSMENT OF QUANTUM DOT PENETRATION INTO SKIN IN DIFFERENT SPECIES UNDER DIFFERENT MECHANICAL ACTIONS

N.A. MONTEIRO-RIVIERE, L.W. ZHANG Center for Chemical Toxicology Research and Pharmacokinetics North Carolina State University 4700 Hillsborough Street Raleigh, NC 27606, USA [email protected]

Abstract. Skin penetration is one of the major routes of exposure for nanoparticles to gain access to a biological system. QD nanoparticles have received a great deal of attention due to their fluorescent characteristics and potential use in medical applications. However, little is known about their permeability in skin. This study focuses on three types of quantum dots (QD) with different surface coatings and concentrations on their ability to penetrate skin. QD621 (polyethylene glycol coated, PEG) was studied for 24 h in porcine skin flow-through diffusion cells. QD565 and QD655 coated with carboxylic acid were studied for 8 and 24 h in flow-through diffusion cells with flexed, tape stripped and abraded rat skin to determine if these mechanical actions could perturb the barrier and affect penetration. Confocal microscopy depicted QD621 penetration through the uppermost layers of the stratum corneum (SC) and fluorescence was found in the SC and near hair follicles. QD621 were found in the intercellular lipid layers of the SC by transmission electron microscopy (TEM). QD565 and 655 with flexed and tape-stripped skin did not show penetration; only abraded skin showed penetration in the viable dermal layers. In all QD studies, inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis for cadmium (Cd) and fluorescence for QD did not detect Cd or fluorescence signal in the perfusate at any time point, concentration or type of QD. These results indicate that porcine skin penetration of QD621 is minimal and limited primarily to the outer SC layers, while QD565 and 655 penetrated into the dermis of abraded skin. The anatomical complexity of skin and species differences should be taken into consideration when selecting an animal model to study nanoparticle absorption/penetration. These findings are of importance to risk assessment for nanoscale materials because it indicates that if skin barrier is altered such as in wounds, scrapes, or dermatitis conditions could affect nanoparticle penetration deeper into the dermal layers and skin is an important organ and can serve as a potential route of exposure and should not be overlooked.

I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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1.

Background

Quantum dot (QD) nanoparticles have potential use in diagnostics, drug delivery and imaging in biomedicine or therapeutic applications due to their optical characteristics that result in strong fluorescence without photobleaching [1]. QD conjugated with streptavidin have been bound to cytoskeletal elements and surface receptors when visualized with monoclonal antibodies [2, 3]. A series of carboxylic acid coated QD with different emission wavelengths are now commercially available making QD a useful tool to mark certain proteins in cells. Prostate tumors in mice were imaged with a QD-antibody conjugate that provided a novel method of cancer labeling in vivo [4]. QD biocompatibility should be evaluated in cells and in tissues before incorporating them into structures for biomedical devices or implants. Currently, there is little information regarding QD permeability in skin. Their potential for toxicity and interactions with biological systems is needed before nanomaterial risk assessments can be made. QD565/655 contain a cadmium/selenide (CdSe) core with a zinc sulfide (ZnS) shell. By TEM, QD565 are spherical with a diameter of 4.6 nm, while QD655 are ellipsoid with a diameter of 6 (minor axis) X 12 nm (major axis). The hydrodynamic diameters for QD565 are 35 nm for the polyethylene glycol, (PEG), uncharged, 14 nm for the carboxylic acid (COOH), negatively charged, and 15 nm for the (PEG-amine (NH2), positively charged. The hydrodynamic diameters QD655 were 45 (PEG), 18 (COOH), and 20 nm (NH2) [5]. In comparison, QD621-PEG coated have a CdSe core and CdS shell coated with PEG polymer coils, and are nail shaped by TEM with the mean width of 5.78 ± 0.97 nm and length of 8.40 ± 1.9 nm with a hydrodynamic size of 39 ± 1 nm evaluated by sizeexclusion chromatography [6]. The heavy metals Cd and Se may have toxic effect on cells or tissues. QD have been shown to degrade in oxidative environments [7, 8]. Therefore, QD degradation and the potential Cd release in vivo may pose a toxic risk. Skin has been shown to be permeable to some engineered nanomaterials in commercial products, medicines, cosmetics and can serve as a portal of entry for localized or systemic exposure to humans, especially in an occupational scenario. Therefore, the objective of these studies was to assess if QD nanoparticles of different sizes, shapes, and surface coatings could penetrate the skin of different species under different mechanical actions. 2.

Interaction of Different QD Topically Applied to Intact Skin

Our laboratory investigated the effects of penetration by QD565 and 655 with diverse physicochemical properties in porcine flow-through diffusion cells. QD565 with PEG, PEG-NH2, or COOH showed penetration into the stratum corneum (SC) and localization within the epidermal and dermal layers by 8 h. PEG and PEG-NH2 coated QD655 were localized within the epidermal layers by 8 h. The penetration of COOH coated QD655 into epidermal layers was evident only at 24 h [5]. Recently, we have studied another type of QD, QD621 that has a

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different shape (nail shaped) and different shell coating (CdS shell). QD621 was topically applied to porcine skin in flow-through diffusion cells to assess penetration. At the low concentration of 1 μM, QD621 were located primarily in the normal intact SC layers of the skin (Figure 1, left column). No QD621 fluorescence was detected in the stratum granulosum, stratum spinosum, or stratum basale layers of the epidermis. At the high concentration of 10 μM (right column) QD621 were primarily present in the SC layers or in between the stratum granulosum-corneum interface, although a small amount of fluorescence was detected in the upper epidermal layers. Occasionally, QD621 were seen in the outer root sheath of the hair follicle [9].

Figure 1. QD621-PEG applied to porcine skin flow-through diffusion cells for 24 h. Left column: 1 μM dose. Right column: 10 μM dose. Top row across: confocal-DIC images depicting the skin section by DIC. Middle row across: fluorescence indicating QD621-PEG. Bottom row across: overlay of DIC and fluorescence depicting QD on the surface and in the outer root sheath of the hair follicle (right). Bars = 100 μm.

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The penetration differences seen with QD565, QD655 and QD621 in flowthrough diffusion porcine skin cells showed how differences in composition, size, configuration, surface charge and other physicochemical parameters could influence penetration. PEG-QD621 with a hydrodynamic diameter of 39 ± 1 nm were capable of penetrating only the uppermost layers of the porcine SC after 24 h of exposure, while confocal microscopy showed that all three surface coatings of the QD565 penetrated at 8 and 24 h but only the QD655 COOH took 24 h to penetrate the skin. No fluorescence was detected in the perfusate. The above study showed that QD synthesized with the same core/shell with similar surface coatings and hydrodynamic diameters but different shapes and penetration rates can penetrate intact skin [5]. QD621-PEG was dissolved in water as stock solution, while QD565-PEG and QD655-PEG were in a borate buffer (pH 8.0) to prevent agglomeration and had a similar viscosity and similar pH with water. QD565 and QD655 penetrated through porcine skin faster and deeper than QD621. The SC layers remained intact and no other morphological alterations were noted by either laser scanning confocal microscopy or TEM due to pH effects that possibly could alter the skin barrier formation or cell morphology that would allow for penetration. Therefore, QD565-PEG, QD655-PEG and QD621-PEG penetration of porcine SC is independent of the vehicle or pH. These three QD have the same chemical composition including a “rigid” core and a “soft” surface coating. Penetration may not only be determined by size and charge, but also by the shape of the rigid core and durability of the coating. It has been reported that elastic particles were able to distribute through the epidermis faster, while rigid particles were found to remain on the surface of the upper SC [10]. The most common route of penetration in skin is via the intercellular lipid spaces between the corneocytes. Our previous study showed the diameter of porcine corneocytes to be 32 μm and the vertical and lateral gaps between corneocytes are 19 nm [11]. Therefore, the QD could potentially pass through the corneocytes lateral intercellular spaces since the QD621 has a rigid core length of 8.4 nm and width of 5.8 nm but overall size of 39–40 nm. It is theoretically possible that the outer PEG coating is a “soft” coating thereby allowing the QD621 to “squeeze” through the intercellular space and remain lodged within the SC lipid bilayers (Figure 2A, B). QD621-PEG penetration may be limited through the epidermis due to their large size and irregular configuration and this fact could explain the different behavior between the nail shaped QD621 (5.78 by 8.4 nm) and spherical QD565 (4.6 nm core) or elliptical QD655 (6 by 12 nm). Therefore, the 1 μM QD621 did not penetrate deep into the SC or epidermis, while the QD565 and QD655 (smaller and more regular in shape) would have less difficulty penetrating the lipid layers of the stratum corneum. QD nanoparticle studies in our lab reported on the penetration of QD into the SC layers or outer root sheath of hair follicles, but not within the deeper layers of skin [9, 12, 13] except for QD565/655 in porcine skin flow-through diffusion cells [5]. Other types of nanoparticles have been topically applied to the skin to assess penetration. TiO2 and ZnO nanoparticles are key ingredients that are added to sunscreens to protect the skin from UV induced damage. Cross et al., 2007 [34]

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Figure 2. TEM of QD621-PEG in the SC of flow-through porcine diffusion cells. (A) QD621-PEG in the intercellular lipid layers of the SC. Bar = 250 nm. (B) Higher magnification of the enlarged area of 2A depicting individual nail-shaped QD621 (arrow) and some small agglomerates. Bar = 50 nm.

reported that most micronized transparent ZnO nanoparticles of 26–30 nm in oil/water formulations topically applied to human skin in in vitro static cells for 24 h remained on the surface of the SC. Microfine ZnO of 80 nm and agglomerates of titanium dioxide less than 160 nm did not penetrate the porcine SC layer in in vitro static diffusion cells [14]. Maghemite nanoparticles of 5.9 nm have been shown to penetrate hair follicles and the SC layer of the epidermis, suggesting a potential route for nanoparticles to traverse the dermal barriers [16]. Polystyrene nanoparticles of 20 nm tend to distribute in human hair follicles [15]. Minoxidil loaded polymeric nanoparticles of 40 nm were able to penetrate the skin of hairy guinea pigs, probably through hair follicles [17]. Hair follicles are often envisioned as special channels for absorption of topical compounds, which could by pass the SC barrier [18]. If hair follicles are a route of exposure for QD then nanoparticles penetrating into the skin may be independent of particles size and may be a safety issue. All of the above studies have demonstrated that the penetration and distribution in skin for topical administration of QD or other nanoparticles are minimal. However, it will be interesting to investigate if smaller nanoparticles can penetrate deeper into the skin after repetitive applications and for longer durations. However, these types of studies will need to be conducted in vivo because there are limitations to in vitro cell systems. 3.

QD Penetration in the Skin via Mechanical Forces

Species differences may be a function of intercellular lipid structure or hair follicle density that could modify penetration processes [19]. Rat skin is sometimes used in toxicity studies and widely used due to the ease of handling and low cost. Pig and human skin have a sparse hair coat compared to that of rodent skin. Porcine skin is widely used in penetration studies because it is anatomically, biochemically

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and physiologically similar to human skin [20–22]. Skin from the back of pigs and abdomen of humans have 11 ± 1 hair follicles/cm2, while rat has a 289 ± 21 [23]. Our laboratory investigated the penetration of QD655 and QD565 coated with COOH in rat skin for 8 and 24 h in flow-through diffusion cells. Skin was flexed, tape stripped and abraded to determine if these mechanical actions could perturb the barrier and affect penetration. The hair was clipped on the back of rats 24 h prior to experiment. Skin from the back was removed and placed dermal side down on flow-through diffusion cells. QD655 or QD565 of 1 µM dosed for 8 or 24 h in intact skin showed both QD on the surface of the SC and on the hair without penetration into the epidermal layers. The irregular and uneven staining of QD on the surface of rat skin is probably due to the high hair follicle density that prevents QD from reaching the SC surface, thereby showing fluorescence on the surface of the hairs. Furthermore, QD655 or QD565 were found on the surface of the SC in a homogeneous and continuous pattern, but there was no difference in QD penetration between flexed skin and intact skin. Rat skin was tape stripped ten times to remove the SC layers. In tape-stripped skin, QD were deposited evenly and homogeneously on the surface of the viable epidermal layers. Rat skin was also abraded with sandpaper 60 times, until the skin was slightly red but not bleeding. This mechanical action removes the SC layers and viable epidermal layers so that penetration of QD can be facilitated through skin. QD655 and QD565 showed slight penetration into the dermis at both 8 and 24 h (Figure 3). Since QD consist of a Cd core, we evaluated for Cd leaching from the QD to detect absorption in the perfusate samples collected at different time points. No fluorescence was emitted or Cd detected in any of the perfusate samples at any time points. ICP-OES supported the fluorescence measurements that there was no evidence of absorption in the flow-through diffusion cells. These results suggested that barrier perturbation by flexion and tape stripping did not cause penetration of QD, but only abraded skin allowed QD to penetrate deeper into the dermal layers of skin. Additional studies in our laboratory with QD in tape stripped and intact human skin in flow through diffusion cells found similar results. QD penetration through human skin was minimal [13]. All of these observations demonstrate that there are species differences and these anatomical complexities may interfere with the penetration of QD in skin. Skin exposed to different mechanical actions such as tape stripping or abrasion is often used in skin pharmacokinetic research to study drug absorption in skin. Tape stripping of the SC facilitates the percutaneous absorption of a compound across skin providing a noninvasive procedure to predict human skin absorption for the compound [24]. Tape stripping has been used to assess the absorption of cosmetic products, heavy metals and other chemicals to determine the amount of a compound that has been absorbed [25–27]. Rat skin was tape stripped and investigated by its permeability of QD in flow-through diffusion cells. The macroscopic and microscopic results depicted tape stripping ten times removed most of the hairs and completely removed all the SC layers, and the effects of tape stripping showed QD565 or QD655 deposited evenly and homogeneously on the surface of viable epidermal layers without penetration into the epidermis at 24 h [12].

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Figure 3. QD565-COOH applied to abraded rat skin in flow-through diffusion cells for 24 h. Left column: 1 μM dose of QD565-COOH. Bar = 100 μm. Right column: higher magnification of the left column depicting QD565 in the dermal layers of the skin. Bar = 25 μm.

Skin abrasion is often used in clinical settings for skin resurfacing, drug delivery [28, 29] or to increase vitamin C absorption [30]. We abraded the skin and laser scanning confocal microscopy depicted penetration of QD565 and QD655 into the dermis at 24 h. Rat epidermis typically contains one to two layers of keratinocytes, and after abrasion, the epidermis was removed. In this study, QD penetrated into the abraded skin but not tape stripped skin indicating that the basement membrane had been partially removed so that QD could easily penetrate into the dermis without the basement membrane acting as another selective barrier. Flexed skin and its permeability to nanoparticles are of interest especially in an occupational setting. Skin flexion is a method that simulates flexing movements such as repetitive wrist bending. Polymeric nanoparticles coated with a 40 nm thick PEG block copolymer layer topically applied to hairless guinea pig skin for 12 h were able to penetrate the epidermis [17]. FITC-conjugated dextran beads of 0.5 μm penetrated the SC of human skin and reached the epidermis after 30 min of flexing [31]. Studies in our lab have shown that a fullerene amino acid-derivatized peptide nanoparticles of 3.5 nm were capable of penetrating the dermal layers of

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porcine skin flexed for 60 min and placed in flow-through diffusion cells for 8 h, while non-flexed control skin showed limited penetration to the upper epidermal layers [32, 33]. TEM found the derivatized fullerene was localized within the intercellular space of the stratum granulosum layer. In our study, rat skin was flexed at 45° with a frequency of 20 flexes/min similar to the porcine study above. The apparatus provides tension and compression that mimics repetitive skin movement. After 60 min of flexing, QD655-COOH and QD565-COOH were found on the surface of the SC in a homogeneous and continuous pattern in rat skin. Perhaps flexion of the skin enhanced the rate of QD penetration along the side of the hair shaft. Also, repetitive motions may alter the structural organization of skin and lead to an increase in penetration by compromising the permeability barrier. 4.

Conclusion

In summary, we showed that QD621 penetration into skin was minimal and limited to the uppermost SC layers and the outer root sheath of hair follicles. We did not detect any Cd in the perfusate by ICP-OES or QD by fluorescence indicating lack of dermal absorption or below the level of detection. When different mechanical stressors were applied to rat skin, QD showed no penetration in nonflexed control, flexed and tape stripped skin, but minimal penetration in abraded skin. The above studies provided a better understanding on the penetration of different types of QD with different types of surface coatings in different species. QD penetration depends on its size, charge, shape and other physicochemical parameters. Also, different mechanical actions on skin could alter the barrier properties that would effect nanoparticles penetration into skin and flexion could cause nanoparticles to penetrate deeper. This research suggests that there is risk for potential health care workers that suffer defects in their skin barrier such as atopic dermatitis, psoriasis or eczema on their hands and other parts of their body with a compromised skin barrier that could be susceptible to nanoparticle penetration. In addition, this study also provided information on nanoparticle absorption that could occur in abraded skin that could relevant in certain occupations exposure scenarios and potentially as a method of drug delivery. References 1. Michalet, X., Pinaud, F. F., Bentolila, L. A., Tsay, J. M., Doose, S., Li, J. J., Sundaresan, G., Wu, A. M., Gambhir, S. S., and Weiss, S., 2005, Quantum dots for live cells, in vivo imaging, and diagnostics. Science 307: 538–544. 2. Wu, X., Liu, H., Liu, J., Haley, K. N., Treadway, J. A., Larson, J. P., Ge, N., Peale, F., and Bruchez, M. P., 2003, Immunofluorescent labeling of cancer marker Her2 and other cellular targets with semiconductor quantum dots. Nat. Biotechnol. 21: 41–46.

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3. Wang, J., Yong, W. H., Sun, Y., Vernier, P. T., Koeffler, H. P., Gundersen, M. A., and Marcu, L., 2007, Receptor-targeted quantum dots: fluorescent probes for brain tumor diagnosis. J. Biomed. Opt. 12: 044021. 4. Gao, X., Cui, Y., Levenson, R. M., Chung, L. W., and Nie, S., 2004, In vivo cancer targeting and imaging with semiconductor quantum dots. Nat. Biotechnol. 22: 969–976. 5. Ryman-Rasmussen, J., Riviere, J. E., and Monteiro-Riviere, N. A., 2006, Penetration of intact skin by quantum dots with diverse physicochemical properties. Toxicol. Sci. 91: 159–165. 6. Yu, W. W., Chang, E., Falkner, J. C., Zhang, J., Al-Somali, A. M., Sayes, C. M., Johns, J., Drezek, R., and Colvin, V. L., 2007, Forming biocompatible and nonaggregated nanocrystals in water using amphiphilic polymers. J. Am. Chem. Soc. 129: 2871–2879. 7. Derfus, A. M., Chan, W. C. W., and Bhatia, S. N., 2006, Probing the cytotoxicity of semiconductor quantum dots. Nano Lett. 4: 11–18. 8. Chang, E., Thekkek, N., Yu, W. W., Colvin, V. L., and Drezek, R., 2006, Evaluation of quantum dot cytotoxicity based on intracellular uptake. Small 12: 1412–1417. 9. Zhang, L. W., Yu, W. W., Colvin, V. L., and Monteiro-Riviere, N. A., 2008, Biological interactions of quantum dot nanoparticles in skin and in human epidermal keratinocytes. Toxicol. Appl. Pharmacol. 228: 200–211. 10. Honeywell-Nguyen, P. L., Gooris, G. S., and Bouwstra, J. A., 2004, Quantitative assessment of the transport of elastic and rigid vesicle components and a model drug from these vesicle formulations into human skin in vivo. J. Invest. Dermatol. 123: 902– 910. 11. Van der Merwe, D., Brooks, J. D., Gehring, R., Baynes, R. E., Monteiro-Riviere, N. A., and Riviere, J. E., 2006., A physiologically based pharmacokinetic model of organophosphate dermal absorption. Toxicol. Sci. 89: 188–204. 12. Zhang, L. W., and Monteiro-Riviere, N. A., 2008, Assessment of quantum dot penetration into intact, tape stripped, abraded and flexed rat skin. Skin Pharmacol. Physiol. 21: 166–180. 13. Monteiro-Riviere, N. A., and Inman, A. O., 2008, Evaluation of quantum dot nanoparticle penetration in human skin. The Toxicologist CD-An official. J. Soc. Toxicol. 102: S-1, 1029, 211. 14. Gamer, A. O., Leibold, E., and van Ravenzwaay B., 2006, The in vitro absorption of microfine zinc oxide and titanium dioxide through porcine skin. Toxicol. In Vitro 20: 301–307. 15. Alvarez-Roman, R., Naik, A., Kalia, Y. N., Guy, R. H., and Fessi, H., 2004, Skin penetration and distribution of polymeric nanoparticles. J. Control. Release 99: 53–62. 16. Baroli, B., Ennas, M. G., Loffredo, F., Isola, M., Pinna, R., and López-Quintela, M. A., 2007, Penetration of metallic nanoparticles in human full-thickness skin. J. Invest. Dermatol. 127: 1701–1712. 17. Shim, J., Seok, K. H., Park, W. S., Han, S. H., Kim, J., and Chang, I. S., 2004, Transdermal delivery of minoxidil with block copolymer nanoparticles. J. Control. Release 97: 477–484. 18. Monteiro-Riviere, N. A., 1998, Integument. In: Dellmann, H. D., and Eurell, J. A. (Eds.), Textbook of Veterinary Histology. Williams & Wilkins, Baltimore, MD, pp. 303–332. 19. Monteiro-Riviere, N. A., 2008, Anatomical Factors that Affect Barrier Function. In: Zhai, H., Wilhelm, K. P., and Maibach, H. I. (Eds.), Dermatotoxicology. CRC Press, New York, pp. 39–50. 20. Monteiro-Riviere, N. A., 1991, Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin. In: Hobson, D.W. (Ed.), Dermal and Ocular Toxicology Fundamentals and Methods. CRC Press, Boca Raton, FL, pp. 3–71.

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21. Monteiro-Riviere, N. A., and Riviere, J. E., 1996, The Pig as a Model for Cutaneous Pharmacology and Toxicology Research. In: Tumbleson, M. E., and Schook, L. B. (Eds.), Advances in Swine in Biomedical Research. Plenum, New York, pp. 425–458. 22. Monteiro-Riviere, N. A., 2001, Integument. In: Pond, W. G., and Mersmann, H. J. (Eds.), The Biology of the Domestic Pig. Cornell University Press, Ithaca, NY, pp. 625– 652. 23. Bronaugh, R. L., Stewart, R. F., and Congdon, E. R., 1982, Methods for in vitro percutaneous absorption studies. 2. Animal models for human skin. Toxicol. Appl. Pharmacol. 62: 481–488. 24. Schaefer, H., and Redelmeier, T. E., 1996, Skin Barrier. In: Schaefer, H., and Redelmeier, T. E. (Eds.), Skin Barrier: Principles of Percutaneous Absorption. Karger Basel, Switzerland, pp. 146–148. 25. Treffel, P., and Gabrad, B., 1996, Skin penetration and sun protection factor of ultraviolet filters from two vehicles. Pharmaceut. Res. 13: 770–774. 26. Hostýnek, J. J., Dreher, F., Pelosi, A., Anigbogu, A., and Maibach, H. I., 2001, Human stratum corneum penetration by nickel: In vivo study of depth distribution after occlusive application of the metal as powder. Acta. Derm. Venereol. 212(Suppl.): 5–10. 27. Fent, K. W., Jayaraj, K., Gold, A., Ball, L. M., and Nylander-French, L. A., 2006, Tape-strip sampling for measuring dermal exposure to 1,6-hexamethylene diisocyanate. Scand. J. Work Environ. Health 32: 225–240. 28. Orentreich, N., and Orentreich, D. S., 1995, Dermabrasion, in Dermatol. Clin. 15: 313– 327. 29. Grimes, P. E., 2005, Microdermabrasion. Dermatol. Surg. 31: 1160–1165. 30. Lee, W. R., Shen, S. C., Wang, K. S., Hu, C. H., and Fang, J. Y., 2003, Lasers and microdermabrasion enhance and control topical delivery of vitamin C. J. Invest. Dermatol. 121: 118–1125. 31. Tinkle, S. S., Antonini, J. M., Rich, B. A., Roberts, J. R., Salmen, R., DePree, K., and Adkins, E. J., 2003, Skin as a route of exposure and sensitization in chronic beryllium disease. Environ. Health Perspect. 111: 1202–1208. 32. Rouse, J. G., Yang, J., Barron, A. R., and Monteiro-Riviere, N. A., 2006, Fullerenebased amino acid nanoparticle interactions with human epidermal keratinocytes. Toxicol. In Vitro 8: 1313–1320. 33. Monteiro-Riviere, N. A., Inman, A. O., and Ryman-Rasmussen, J. P., 2007, Dermal Effects of Nanomaterials. In: Monteiro-Riviere, N. A., and Tran, C. L. (Eds.), Nanotoxicology: Characterization, Dosing, and Health Effects. Informa Healthcare, New York, pp. 317–337. 34. Cross, S. E., Innes, B., Roberts, M. S., Tsuzuki, T., Robertson, T. A., and McCormick, P., 2007, Human skin penetration of sunscreen nanoparticles: In-vitro assessment of a novel micronized zinc oxide formulation. Skin Pharmacol. Physiol. 20: 148–154.

NANOTECHNOLOGY The Occupational Health and Safety Concerns

S. CHAN-REMILLARD Golder Associates Ltd., and HydroQual Laboratories Ltd. #4, 6125 – 12th Street S.E. Calgary, Alberta T2H 2K1, Canada [email protected] L. KAPUSTKA LK Consultancy 8 Coach Gate Place SW Calgary, AB T3H 1G2 Canada [email protected] S. GOUDEY HydroQual Laboratories Ltd. #4, 6125 – 12th Street S.E Calgary, Alberta T2H 2K1, Canada

Abstract. Nanotechnology is a rapidly emerging field. There are currently over 500 consumer products available in the marketplace and the field of nanotechnology itself that will be worth over $1 trillion by 2012. However, with an increasing number of products emerging, there is also a consequent rise in ecological and human exposure. The risk and degree of exposure to nanoscale particles (NP) will vary depending on the form of the particle, for example, powder, liquid or encapsulated, when contact occurs. Although, general public exposure to NP is increasing due to the shear number of products available, the majority of human exposure still occurs in an occupational setting. Preliminary exposure studies demonstrate that NP may enter the body via the gastrointestinal, respiratory and integumentary systems and then translocate to other vital organs and systems (for example via the olfactory bulb). Historical data on ultrafine particles have shown a higher incidence of lung cancer and respiratory disorders associated with exposure. Due to these data and evidence emerging directly on NP, precautionary measures may be warranted to ensure worker safety. Regulatory agencies and manufacturers are beginning to consider standard practices that adequately protect workers from nanoscale particle exposure. The occupational hazards associated with exposure and the current safety recommendations will be discussed.

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1.

Introduction

The concept of nanoscale particles (NP) and processes in the nanoscale is not novel. Humans have been exposed to NP from the natural environment long before recorded history. However, it has only been in the last couple of decades where exposures to NP that are anthropogenic in origin, specifically the engineered forms, have become a potential health and safety issue. Nanotechnology has been compared to the industrial and computer revolutions for its ability to change/create many technologies and how we approach science. Many benefits may be realized through the integration of nanotechnology in existing and previously unattainable technologies. Although there is much excitement for nanotechnology within the scientific and commercial/industrial communities, there is a large gap in our knowledge regarding how NP exposure may impact living organisms. This lack of toxicity data may seriously hamper the progression and commercialization of this science. Nanoscale particles can be classified according to their source origin. Under this classification scheme they can be categorized as natural, incidental or engineered NP. Natural NP, as the name implies, are found naturally in the environment (e.g. viruses, products of bacterial processes, many of the functions that occur within living organisms are within the nanoscale), incidental NP are created as a function of industrial processes (e.g. combustion of diesel engines, welding fumes) and engineered NP have been specifically created for a function or property. As compared to natural NP, incidental and engineered forms are both anthropogenically introduced into the environment. Engineered NP are created with a specific chemical signature, homogeneous morphology, and size. Often times with specific functionality whereas incidental NP are a heterogeneous mixture for each of these characteristics. Due to the unique physical-chemical characteristics of engineered NP, our understanding of how they may react and defenses against these particles in biological systems is not very well known. Furthermore, the intrinsic toxicity of individual NP must also be factored into health impact assessments. 2.

Exposure

Although there are an increasing number of products with nanotechnology incorporated into them available on the consumer marketplace exposure to engineered NP is still occurring primarily within the occupational realm. Workers are exposed to the NP either through manufacturing of the particles directly or products that have these NP incorporated into them. Due to the lack of toxicity information on how NP react within biological systems key questions regarding the health and safety of frontline workers still remain. Do existing engineering controls and personal protective equipment guidelines adequately protect workers from NP exposure? Are the current tools/instruments used to measure exposure levels sensitive enough for measuring such small particulate matter?

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The degree of exposure to NP is highly dependent on the initial form of the particle and the organism that comes in contact with it. There are higher risks of exposure to NP that are within the dust or aerosolized forms due to their increased mobility, whereas exposure to particles that are immobilized within a liquid or a more rigid matrix (e.g. steel) will have a much lower risk of exposure [1]. However, it must be noted that exposure to NP in an immobilized structure may increase if the product breaks down resulting in the release of smaller particles into the environment. 3.

Routes of Entry

Nanoscale particles may enter into the body via three primary routes: inhalation, skin exposure and ingestion where the toxicity targets are the respiratory, integumentary and gastrointestinal systems respectively. 3.1.

RESPIRATORY SYSTEM

Epidemiological studies into ultrafine/incidental particles are beginning to demonstrate that there are some serious health effects associated with chronic exposure. Occupational workers exposed to particles from combustion engines or welding fumes for prolonged periods have higher incidences of lung cancer, chronic obstructive pulmonary disease, fibroids and cardiovascular diseases [3, 11, 13] as compared to the general population. Studies on chronic inhalation of ultrafine or incidental particles may provide some insight into the health impact of chronic exposure to engineered NP. The respiratory tract has three distinct regions: the nasopharyngeal, tracheobronchial and the alveolar. The regional deposition rate of NP within each of these compartments is highly dependent on the size of the particle. The deposition of NP that are 1 nm in dimension is primarily within the nasopharyngeal region whereas slightly larger particles (20 nm) deposit further down the respiratory tract in the alveolar macrophage regions where it is much more difficult for the body’s clearance mechanisms to remove these particles [23]. The respiratory tract has several clearance mechanisms for particulate matter. The respiratory tract has a thick layer of mucus that traps particles as they are inhaled. Within the tracheobronchial region, particles trapped in the mucus layer are removed via the mucociliary escalator. The particles are either expelled through expectoration or may enter the gastrointestinal tract through swallowing. The primary clearance mechanism within the alveolar region is a phagocytic activity through the action of alveolar macrophages. Alveolar macrophages phagocytose the particles and move them upwards into the tracheobronchial region where they are then removed by the mucociliary escalator. Under normal circumstances these respiratory clearance mechanisms are highly effective at clearing particulate matter that enters into the respiratory tract. However, due to the unique physico-chemical properties and the size and aspect ratio characteristics of NP the effectiveness of these clearance mechanisms is

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uncertain. The impairment of phagocytic activity and cytotoxic action towards alveolar macrophages exposed to several carbon based NP have previously been observed [10]. The impairment of respiratory defense mechanisms may consequently result in the persistence of NP in the lung, movement of the particles deeper into the lung tissue or translocation to other target organs. The presence of nanoscale carbon (black, nanofibers and multiwalled nanotubes) were toxic to human lung cells after only 24 h of exposure; toxicity increased with prolonged exposure (5 days). Morphological changes, such as decreased cellular contact, detachment from cellular matrix, condensation of nuclei and cytoplasmic retraction were observed in exposed cells [18]. The persistence of particles in lung tissue may result in an elevated inflammatory response and ultimately various lung diseases as observed in epidemiological studies on ultrafine particles [3, 11, 13]. Persistence of NP within the lung may increase the potential for translocation to other target organs. Translocation of NP into the blood stream can occur via the air/blood barrier, through the lymphatic system, move further into the lung tissue or interstitium or via the sensory neurons (e.g. olfactory bulb or the vagus nerve [24]). Nanoscale particles have been found to penetrate beyond the basement membrane into the capillary lumen and then attach directly onto red blood cells [29], which may explain the cardiovascular consequences of exposure. Inhaled NP have been detected in the liver and bladder [20, 23], heart and spleen [28], lymph nodes [24] and in the olfactory bulb and different regions of the brain [7] after varying periods of exposure. 3.2.

INTEGUMENTARY SYSTEM

Another major route of entry for NP is the integumentary system or the skin. The skin is made up of three distinct layers: the epidermis, dermis and the subcutaneous fatty layer. The epidermis is the top few layers of skin that includes the horny outer layer composed of dead keratinized skin cells (stratum corneum), prickle cell layer (stratum spinosum) and the basal cell layer (stratum basal). Collectively these three layers of the epidermis form a tight protective barrier for the underlying dermis that contains a rich blood supply, immune cells (macrophages/dendritic cells), lymph vessels and sensory nerve endings. Traditionally, the thick stratum corneum (0.5–1.5 mm thick) layer was thought of as a relatively impermeable barrier to many compounds as experienced in the pharmaceutical industry where creating effective topical medications with a high absorbance rate is a challenge. Skin flexion studies demonstrate that smaller particles (0.5–1 um) are able to penetrate into deeper skin layers than larger particles (2–4 um) suggesting a size dependent gradient for penetration [30]. However, due to the smaller size and unique physicochemical properties of NP is the epidermal layer as effective of a barrier against penetration by NP based formulations? The movement of NP into the dermal layer increases the chances of further translocation via the blood supply, lymph system, immune cells and sensory neurons to secondary target organs with potential unintended consequences.

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The most commonly used NP in topical applications are nanoscale titanium dioxide and zinc oxide in sunscreens. These NP have been used for over 2 decades. Prior to the use of NP in sunscreen formulations the application of sunscreen left a non-aesthetically pleasing white film on the skin. The advantage of using NP for sunblocks is that in the nanoscale range, titanium dioxide and zinc oxide still retain their UV blocking capabilities but are also transparent. This has a major impact on improving public health. Several studies have demonstrated that the epidermal layer is highly effective in preventing the passage of NP. Nanoscale titanium dioxide and zinc oxide did not penetrate beyond the stratum corneum of the protective outer epidermal layer [8, 6, 19, 27]. In a presentation to the FDA public forum on nanomaterials, the Cosmetic, Toiletry and Fragrance Association (CTFA) indicated that these particles have been rigorously tested and are deemed safe for human usage [26]. Nohynek et al. [22] also conclude that titanium dioxide and zinc oxide that are currently used in cosmetic preparation do not pose a risk to human health. However, caution should still be taken with other types of NP through dermal contact [4]. Another potential route for dermal penetration of NP is through the follicle. The follicular pathway may represent a route for NP to bypass the protective epidermal layer. The hair follicle penetrates deep into the dermal layer where there is a rich supply of blood and immune cell activity directly connected to the follicle. The potential for these particles to enter systemic circulation via the follicle is a mechanism that many topical drug delivery systems exploit. Lademann et al. [16] demonstrated that dyes carried by NP are able to penetrate deeper and persist longer in hair follicles than non-particulate counterparts. They also found that mechanical massage or motion aids the penetration of particles deeper into the follicle. The follicle not only acts as a transit point but also as a reservoir for topically applied medications. Although from a pharmaceutical perspective, this is advantageous. The unintended consequences of nonprescriptive particles depositing in the follicles may result in systemic circulation of particles with unknown sequelae. Follicular penetration studies using fluorescence microscopy found that larger particles remained in the upper regions of the follicle, whereas, 40 nm particles were found in the follicle as deep as the viable dermal layers. There was also increase immune cell sampling for 40 nm particles than larger particles [31]. Deposits of iron NP in and around the follicle were observed as far as 30–170 um below the viable epidermal layer [4]. With titanium dioxide (20 nm) deposition was observed as deep as 400 um into the follicle, however, no particles were found in the vital tissue or near sebaceous glands [17]. A key factor that may pose a challenge in the case of drug delivery systems or protection in the case of penetration of non-prescriptive NP is the opened or closed state of the follicle orifices. Follicles are open during periods of active sebum production or hair growth but during the resting phase a protective layer of sebum and desquamated cells covers the follicle opening [15, 25]. The open or closed state of the follicles may be a factor in penetration and persistence of NP inside the follicular orifice.

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GASTROINTESTINAL SYSTEM

The third major route of entry for NP is via the gastrointestinal tract. Entrance of NP into this system may occur via direct ingestion or as previously discussed, via the mucociliary escalator. The entire gastrointestinal tract is approximately 6.5 m in length. It is divided into the two distinct regions, the upper (mouth, pharynx, esophagus and stomach) and lower gastrointestinal tract (large/small intestine and anus). Not only do absorptive/digestive/defecation processes occur throughout the tract, the digestive tract plays a prominent role in immune functioning via the gut associated lymphoid tissue (GALT) and is intricately associated with key accessory organs like the liver, gallbladder and pancreas. Similar to the respiratory tract, the gastrointestinal tract is lined with a thick mucus membrane that is in direct contact with the contents of the gastrointestinal tract. When inhalation or whole body NP exposure occurs, there is a high likelihood that these particles will be entering into the gastrointestinal tract. Considering the large surface area involved for absorptive/digestive processes the potential for ingested NP to disrupt this system may be considerable. What is the fate of these NP once in the gastrointestinal tract? Are they excreted, do they persist only in the intestinal tissue or do they translocate through the gut wall into other secondary organs? The efficacy of many oral pharmaceuticals is highly dependent on the ability of the gastrointestinal system to absorb the active ingredients. Much of our current understanding of how NP act at the gut wall/systemic circulation interface has arisen from research looking at the use of NP to enhance the delivery of drugs across the gut wall into systemic circulation. The implications of NP enhancing drug absorption and is great, however, the absorption of particles that are not physiologically relevant may have unintended consequences. The mucosal lining is composed of millions of villus lined with cells (enterocytes/epithelial) that are constantly and rapidly turned over. A key route to systemic access by NP is the ability to penetrate through this lining. Gold NP (4 and 10 nm) were able to gain access through the gut wall via tiny little pores that formed from enterocyte turnover through a process called persorption. The smaller the NP the further they were able to penetrate into the gut wall. Gold NP were observed on the apical and basolateral sections of the villi. There were also some particles observed near lymph vessels, suggesting another potential mechanism that NP may cross into the blood stream [12]. Through fluorescence imagery, nanoscale chitosan particles have been observed in epithelial cells lining the jejunum, duodenum and ileum. Chitosan were also found deeper in the lamina propria, suggesting movement of particles through the epithelium. Similar to the study by Hillyer and Albrecht, NP were also found in the peyer’s patches, which are key cells within the gut involved in immune surveillance [5]. The movement of gold nanoparticles was not isolated just to the deeper layers of the gut wall but was found in secondary organs. Four nanometer gold particles were isolated in the blood, brain, lung heart, kidney, spleen, liver, small intestine and stomach 7 days post exposure [12]. When compared to larger particles (58 nm),

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the 4 nm particles had the highest degree of translocation. Similar to the respiratory tract, this suggests a size dependent gradient for translocation across the gut wall. Yet others have found that ingested NP primarily transit through the gastrointestinal system and are excreted in fecal matter and urine [14, 28]. 4.

Occupational Health and Safety

The previous section discusses the impact of NP on the three key target exposure sites in humans illustrates the variability that the type of NP tested and the target sites evaluated can have on conclusions regarding physiological effects/responses. Although these studies contribute to the current database of information there is still not a large enough body of evidence or consensus on the ultimate effects NP have on living organisms to truly inform or regulate nanotechnology. This is one of the key issues surrounding the nanotechnology industry and how it is to be effectively regulated and the hazards and risks effectively managed. Until there is enough information to effectively inform regulatory agencies and industry, health and safety guidelines to the best of our knowledge must be developed and implemented to prevent human exposure to the potential health hazards of NP. Exposure to engineered NP will vary depending on the context of exposure. Currently, the majority of human exposure to NP is isolated to frontline workers, in the occupational setting, who are directly involved in producing or incorporating NP into products. Due to the rapid emergence of products containing NP available for consumer consumption, there will be a parallel increase in exposure levels among the general public. However, general public exposure will differ from occupational exposure in the form of the nanoparticle that exposure will occur. The majority of NP exposure to the general public will occur in the form of products where NP are bound within some sort of matrix. For example, titanium dioxide NP will be bound within the liquid matrix of a lotion or carbon nanofibers will be bound within the steel structure of an automobile frame. The matrix that binds the particles will confer a degree of protection to the consumer against exposure to free NP. Within the occupational setting, there is a higher likelihood of exposure to NP that are in the free form. The adequacy of health and safety protocols within an occupational setting remains uncertain due to our limited understanding of the toxicity of NP. 4.1.

NIOSH

There are several worldwide organizations (ASTM, NIOSH, ICON, SCENHIR) involved in assessing the safety protocols for handling nanomaterials. A key organization involved in this initiative is the National Institute of Occupational Safety and Health (NIOSH), an organization within the Centers for Disease Control and Prevention (CDC). The key mandate of NIOSH is to ensure that beneficial applications of nanotechnology are developed in a responsible manner with a high priority focus on the societal, human and environmental implications

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of nanotechnology. In 2004, the Nanotechnology Research Center (NTRC) was developed under the auspice of NIOSH. The NTRC was developed to specifically focus on nanotechnology research. Since 2005 NIOSH has internally redirected US$11 million of funding towards this initiative. The role of the NTRC is to (1) Determine whether NP and nanomaterials pose a human health risk to workers, (2) Conduct research on the use of nanotechnology to prevent work related injuries and illnesses, (3) Promote healthy workplaces through interventions, recommendations and capacity building and (4) Enhance global workplace safety and health through national and international collaborations on nanotechnology research and guidance. The research under the NTRC encompasses ten critical topic areas: (1) toxicity and internal dose, (2) risk assessment, (3) epidemiology and surveillance, (4) engineering controls and personal protective equipment, (5) measurement methods, (6) exposure assessment, (7) fire and explosion safety, (8) recommendations and guidance, (9) communication and education and (10) applications [1]. Currently, there is a knowledge gap in our understanding of the toxicity of NP to living organisms. Are NP toxic and at what dose or exposure level do NP pose a risk? Several different but complementary key critical topic areas have been established to answer these key questions. Scientists involved in the first critical topic area are investigating the physicochemical properties of NP that influence toxicity, determining the fate of NP once they have entered into biological systems and the short and long term effects of exposure to organ systems and tissues. Scientists involved in the exposure assessment group are evaluating possible inhalation and dermal exposure to nanomaterials, determining how exposure may differ by work process and determining the key factors that influence the production, dispersion, accumulation and re-entry of nanomaterials into the workplace environment. Scientists within risk assessment work stream are evaluating whether current exposure-response data for fine and ultrafine particles are adequate in assessing/identifying the hazards related to NP and are developing a risk-based framework for evaluating the potential hazards and occupational risk of exposure to NP. Researchers funded under the third critical topic area are involved in identifying what knowledge gaps can be filled with epidemiological studies to further advance our knowledge of NP. Scientists involved in the engineering controls and personal protective equipment stream of research have a twofold mandate. They are actively evaluating whether current engineering controls and personal protective equipment used are effective at protecting workers from NP exposure. The second mandate of this group involves looking at ways to enhance worker safety through incorporation of nanotechnology into personal protective equipment. Research from scientist working under the applications umbrella are also working on identifying ways to apply nanotechnology to enhance occupational health and safety. Scientists involved in the fifth work stream are actively involved in evaluating, developing and testing methods and validating sampling instruments to accurately measure airborne nanomaterials in the workplace. Due to the different physicochemical properties of compounds in the nanoscale range, there is a possibility that these materials may become flammable and

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explosive. An example of a compound that does not have explosive tendencies in the macro form but is highly explosive and volatile upon contact with air and water is zinc. One of the key research streams funded by the NTRC is identifying the physicochemical properties of nanoscale that contribute to their combustibility and flammability. This group then makes recommendations for alternative work practices that decrease or eliminate exposure to such situations. As previously discussed, the pace that nanotechnology products are emerging on the consumer marketplace is not paralleled by toxicity research. This poses a significant challenge to regulators and industry alike. A critical topic area under the mandate of the NTRC is to provide interim recommendations and guidance for workplace safety and health practices in handling nanomaterials using the current state of knowledge. To aid in the collection and dissemination of the most up to date information, the communication and education stream is actively involved in fostering international partnerships to ensure the sharing of research needs, approaches and results. 4.2.

ENVIRONMENTAL HEALTH AND SAFETY PLANS

There are many companies worldwide that are engaged in some level of nanotechnology development or usage. Since nanotechnology is a relatively new field of research, whether the health and safety plans of these organizations can adequately protect workers from the potential hazards of nanotechnology must be evaluated. In collaboration with the International Council on Nanotechnology (ICON), an interdisciplinary team of scientists from the University of California at Santa Barbara (UCSB) interviewed 64 organizations from private sector companies, research labs, university labs and consultant companies within North America, Australia, the Europe and Asia that claimed to work with nanotechnology in some capacity on their environmental health and safety (EHS) plans regarding nanotechnology [9]. Many of the respondents (38/64) to the survey had some sort of EHS program in place ranging from having guideline documents, using risk assessment approaches, EHS programs modeled after those for fine or ultrafine particles and more sophisticated programs that monitor actual exposure to NP. The EHS training programs included information on the safe handling and standard operating procedures for nanomaterials, the proper use of personal protective equipment, the hazards and toxicities associated with handling nanomaterials and engineering controls for decreasing exposure to nanomaterials. Fewer programs included information on emergency procedures to handle accidental exposure, proper waste handling practices, the potential for/implications of environmental release of nanomaterials, consumer protection, exposure monitoring and regulations governing nanomaterials. There seemed to be an association between the size of the company and the level of nano-specific safety training, with larger companies having more sophisticated health and safety programs. When asked why their organizations administered a nano-specific safety protocol, several organizations indicated that this was a safety precaution against unknown hazards that include potential toxicity, the

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minimization of employee exposure, a proactive approach to address potential risks from nanomaterials exposure or the unique hazards related to nanomaterials and compliance with safety regulations for fine particles. However, 26 out of the 64 companies surveyed did not have a nano-specific safety protocol in place. These companies sited reasons for not having EHS plans ranged from planning to implement a training protocol, employees were not in direct contact with the materials, they treated nanomaterials as a hazardous waste to the companies that deem the nanomaterials were not dangerous or there was not enough time or resources to implement a plan [9]. This report also describes internal and external barriers to implementing an EHS program. The respondents cited the major external barrier to implementing an EHS program was the lack of useful information and consistent guidelines regarding the safe handling of nanomaterials, while less frequently the ineffective techniques for detecting and measuring the presence of NP in the work place was also cited as a barrier. The most frequently cited internal barrier to instituting a health and safety plan was the costs that were associated with implementation. An interesting internal barrier to implementation cited was the attitudes of the workers towards EHS and nanomaterials risk. Workers either believed that implementation of these plans required too much effort and did not acknowledge the importance of safety protocols in handling nanomaterials, also described as the naïve approach or they had a cavalier approach where they felt that the safety protocols were ineffective and that there was little risk associated with handling the nanomaterials [9]. The knowledge gaps identified by the NIOSH research initiatives and the lack of toxicity data illustrates the many impediments that face regulators and industry in assessing the level of safety protocols that need to be implemented to protect occupational workers from being exposed to the potential hazards of handling NP. 4.3.

NANOMATERIALS – OCCUPATIONAL HEALTH AND SAFETY EXPOSURE CONTROLS

Although there are many barriers to implementing health and safety protocols, interim guidelines based on the most current information available have been developed to provide regulators and industry guidance on minimizing occupational exposure [1, 2, 9, 21]. The current guidelines to minimize work place exposure to NP suggest substituting or eliminating the hazardous material(s) from the process or when that is not possible to implement engineering and administrative controls. In the event that is not possible to implement or the effectiveness of engineering/ administrative controls is uncertain, the use of personal protective equipment (PPE) is recommended. Industrial hygiene specialists recommend the first line of defence against exposure to hazardous materials is to completely eliminate or substitute a compound for one that is less hazardous from a process. For example, the substitution of a powdered form of a NP, which is easily aerosolized and has a high likelihood of being inhaled or ingested, for a form that is bound within a liquid matrix would decrease the risk of exposure. In some instances, the complete elimination of the

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compound from the process would remove the likelihood of exposure to a toxic substance [1, 9]. However, in situations where elimination or substitution of a compound in a product or process is not a realistic option, the implementation of safety programs that incorporate engineering controls, administrative controls or PPEs are necessary to ensure worker safety. The use of engineering controls developed to control gases is the most effective means of controlling the movement of NP out of designated workspaces. The types of engineering controls that are recommended are local ventilation systems for the immediate work area (e.g. total enclosures [e.g. glove box], partial enclosures [e.g. chemical hoods, low flow vented balances], weigh hoods for dry materials, and exterior hoods located adjacent to workspace [e.g. receiving or draft hoods that draw in particles]), general exhaust ventilation (e.g. scrubbing systems, negative pressure), specific designation of a workspace by encapsulating/isolating the area as a nanomaterials zone or the use of specialized filters (e.g. HEPA filters). Encapsulation/isolation of work processes that involve nanomaterials may also be achieved through distance, physical separation/barriers or the use of isolation or control rooms [1, 21]. An important supplement to engineering controls is the use of administrative controls, which are driven by good laboratory practices and standard operating procedures, will also decrease the risk of occupational exposure to NP. The implementation of administrative controls involves extensive safety training of personnel exposed to processes that involve the use of NP. Important elements of administrative controls are the cleaning procedures that are used within a facility. The use of wet wiping procedures and HEPA vacuums systems but not blowers or fans to prevent the accumulation of NP within workspaces is recommended [1, 9, 21]. ASTM further suggests the use of surfactants during cutting/drilling to minimize dust production and the requirement for workspaces/equipment/furniture to be constructed of smooth, non-porous materials to simplify cleaning to further decrease the risk of occupational exposure. Another important facet of administrative controls is worker training and education. Worker education and training into the potential hazards of NP may help to decrease the previously described ‘naïve’ or ‘cavalier’ attitudes towards health and safety experienced by workers. Educating workers to the hazards associated with or suspected of NP may have a larger impact on attitudes towards personal health and safety within an occupational setting than simply advising on the need for protection. Educational programs should not only involve training/ education on proper handling procedures and safety issues surrounding NP, but should also include information on the prevention of transfer (e.g. no eating around NP workspaces, have designated lab coats/gloves/goggles, enclosed vessels), proper hazard labeling procedure, the availability of material safety data sheets and emergency response and medical surveillance procedures [1, 21]. The final method to control worker exposure to NP is through the use of PPEs. Personal protective equipment is recommended as the primary defense against exposure only in instances where engineering and administrative controls have been deemed ineffective at minimizing occupational exposure to NP. Types of PPEs used are respirators, eye protection and protective clothing and gloves that

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are specifically designated for NP use. Respirators fitted with N100 filters are recommended by NIOSH as being completely effective at blocking NP inhalation. However, the type of respirator (e.g. half or full faced mask) and proper fitting of the mask will affect the degree of protection offered by the respirator. If possible, the use of powered air purifying respirators fitted with a HEPA filter is recommended. When using the half faced masks, it is highly recommended that the type of eye protection used include at a minimum side shields around the eye. 5.

Conclusion

Many wonderful advances in science and technology have been or yet to be realized through the use and manipulation of material within the nanoscale range. In addition to the search for new applications for nanotechnology, there is also the responsibility to understand the impact these NP have on living organisms and to protect living organisms from potentially toxic exposure. The toxicity of these particles still remains relatively unknown. The new emerging science of nanotoxicology that studies how NP impact living organisms is not progressing at a parallel pace to product development. The lack of toxicity data introduces a serious gap in knowledge that may hamper our ability to further develop/introduce products, ensure consumer safety and effectively regulate these products. Until there is adequate toxicity data available interim safety guidelines based on the most current information have been developed. Proper education/training programs and implementation of EHS programs based on these guidelines will minimize the level of NP exposure to frontline workers. Further research needs to be conducted to enhance worker safety and to ensure consumer and environmental safety of nanotechnology. References 1. ASTM International (2007) Standard Guide for Handling Unbound Engineered Nanoscale Particles in Occupational Settings, E 2535-07. 2. Aitken, R.J., Creely, K.S., and Tran, C.L. (2004) Nanoparticles: An Occupational Hygiene Review, Institute of Occupational Medicine for the Health and Safety Executive. Research Report 274. Retrieved October 6, 2006, from http://www. hse.gov.uk/research/rrpdf/rr274.pdf 3. Attfield, M.D., and Kuempel, E.D. (2008) Mortality among U.S. underground coal miners: A 23-year follow-up, Am. J. Ind. Med. 51(4), 231–245. 4. Baroli, B., Ennas, M.G., Loffredo, F., Isola, M., Pinna, N., and Lopez-Quintela, M.A. (2007) Penetration of metallic nanoparticles in human full thickness skin, J. Invest. Dermatol. 127, 1701–1702. 5. Behrens, I., Vila Pena, A.I., Alonso, M.J., and Kissel, T. (2002) Comparative uptake studies of bioadhesive and non-bioadhesive nanoparticles in human intestinal cell lines and rats: The effect of mucus on particle absorption and transport, Pharm. Res. 19(8), 1185–1193.

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6. Cross, S.E., Innes, B., Roberts, M.S., Tsuzuki, T., Robertson, T.A., and McCormick, P. (2007) Human skin penetration of sunscreen nanoparticles: In vitro assessment of a novel micronized zinc oxide formulation, Skin Pharmacol. Physiol. 20(3), 148–154. 7. Elder, A., Gelein, R., Silva, V. Feiker, T., Opnanshuk, L., Carter, J., Potter, R., Maynard, A., Ito, Y., Finkelstein J., and Oberdorster G. (2006) Translocation of inhaled ultrafine manganese oxide particles to the central nervous system, Environ. Health Perspect. 114(8), 1172–1178. 8. Gamer, A., Leibold, E., and van Ravenzwaay, B. (2006) The in vitro absorption of microfine ZnO and TiO2 through porcine skin, Toxicol. In Vitro 20(3), 301–307. 9. Gerritzen, G., Huang, L., Killpack, K., Mircheva, M., Conti, J., Magali, D., Harthorn, B.H., Appelbaum, R.P., and Holden, P. (2006) A Report to ICON: Review of Safety Practices in the Nanotechnology Industry, 30–36. 10. Guang, J., Haifang, W., Lei, Y., Xiang, W., Rongjuan, P., Tao, Y., Yuliang, Z., and Xinbiao, G. (2005) Cytotoxicity of carbon nanomaterials: Single walled nanotubes, multiwalled nanotubes, and fullerenes, Environ. Sci. Technol. 39, 1378–1383. 11. Harber, P., Muranko, H., Solis, S., Torossian, S., and Merz, B. (2003) Effect of carbon black exposure on respiratory function and symptoms, J. Occup. Environ. Med. 45(2), 144–155. 12. Hillyer, J.F., and Abrecht, R.M. (2001) Gastrointestinal persorption and tissue distribution of differently sized colloidal gold nanoparticles, J. Pharm. Sci. 90(12), 1927–1936. 13. Järvholm, B., and Silverman, D. (2003) Lung cancer in heavy equipment operators and truck drivers with diesel exhaust exposure in the construction industry, Occup. Environ. Med. 60(7), 516–520. 14. Kreyling, W.G., Semmler, M., Erbe, F., Mayer, P., Takenaka, S., Schulz, H., Oberdorster, G., and Ziesenis, A. (2002) Translocation of ultrafine insoluble iridium particles from lung epithelium to extrapulmonary organs is size dependent but very low, J. Toxicol. Environ. Health 65, 1513–1530. 15. Lademann, J., Otberg, N., Richter, H., Weigmann, H.J., Lindemann, U., Schaefer, H., and Sterry, W. (2001) Investigation of follicular penetration of topically applied substances, Skin Pharmacol. Appl. Skin Physiol. 14(Suppl. 1), 17–22. 16. Lademann, J., Richter, H., Teichmann, A., Otberg, N., Blume-Peytavi, U., Luengo, J., Weib, B., Schaefer, U.F., Lehr, C-M., Wepf, R., and Sterry, W. (2007) Nanoparticles – An efficient carrier for drug delivery into the hair follicles, Eur. J. Pharm. Biopharm. 66, 159–164. 17. Lekki, J., Stachura, Z., Dabros, W., Stachura, J,, Menzel, F., Reinert, T., Butz, T., Pallon, J., Gontier, E., Ynsa, M.D., Morretto, P., Kertesz, Z., Szikszai, Z., and Kiss, A.Z. (2007) On the follicular pathway of percutaneous uptake of nanoparticles: Ion microscopy and autoradiography studies, Nucl. Instrum. Meth. Phys. Res. B. 260, 174– 177. 18. Magrez, A., Kasas, S., Salicio, V., Pasquier, N., Seo, J., Celio, M., Catsicas, S., Schwaller, B., and Forro, L. (2006) Cellular toxicity of carbon based nanomaterials, Nano Lett. 6(6), 1121–1125. 19. Mavon, A., Miquel, C., Lejeune, O., Payre, B., and Morretto, P. (2007) In vitro percutaneous absorption and in vivo stratum corneum distribution of an organic and a mineral sunscreen, Skin Pharmacol. Physiol. 20, 10–20. 20. Nemmar, A., Hoet, P.H.M., Vanquickenborne, B., Dinsdale, D., Thomeer, M., Hoyleaerts, M.F., Vanbilloen, D., Mortelmans., L., and Nemery B. (2002) Passage of inhaled particles into the blood circulation in humans, Circulation 105(4), 411–441. 21. NIOSH (2007) Progress Toward Safe Nanotechnology in the Workplace. Department of Health and Human Services, Centers for Disease Control and Prevention, National

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24. 25. 26. 27. 28.

29. 30. 31.

S. CHAN-REMILLARD ET AL. Institute of Occupational Health and Safety. DHHS (NIOSH), Publication No. 2007-123, June 2007. Nohynek, G.J., Lademann, J., Ribaud, C., and Roberta, M.S. (2007) Grey Goo on the skin? Nanotechnology, cosmetic and sunscreen safety, Crit. Rev. Toxicol. 37, 251–277. Oberdorster, G., Sharp, Z., Viorel, A., Elder, A., Gelein, R., Lunts, A., Kreyling, W., and Cox, C. (2002) Extrapulmonary translocation of ultrafine carbon particles following whole body inhalation exposure of rats, J. Toxicol. Environ. Health A 65, 1531–1543. Oberdorster, G., Oberdorster, E., and Oberdorster J. (2005) Nanotoxicology: An emerging discipline evolving from studies of ultrafine particles, Environ. Health Perspect. 113(7), 823–839. Otberg, N., Richter, H., Knuttel, A., Schaefer, H., Sterry, W., and Lademann, J. (2004) Laser spectroscopic methods for the characterization of open and closed follicles, J. Laser Phys. 1(1), 46–49. Santamaria, A. (2006) Safety of nanoscale materials in personal care products, Presentation to the FDA Public Meeting on Nanomaterials, October 10, 2006. Available at: http://www.fda.gov/nanotechnology/meetings/santamaria.html. Schulz, J., Hohenberg, H., Pflucker, F., Gartner, E., Will, T., Pfeiffer, S., Wepf, V., Wendel V., Gers-Barlag, H., and Wittern, K.D. (2007) Distribution of sunscreens on skin, Adv. Drug Deliver. Rev. 54(Suppl. 1), S157–S163. Semmler, M., Seitz, J., Erbe, F., Mayer, P., Hayder, J., Oberdorster, G., and Kreyling, W.G. (2004) Long term clearance kinetics of inhaled ultrafine insoluble iridium particles from the rat lung, including transient translocation into secondary organ247s16, Inhal. Toxicol. 16, 453–459. Shimada, A., Kawamura, N., Okajima, M., Kaewamatawon, T., Inoue, H., and Morita T. (2006) Translocation of intratracheally instilled UF particles from lung into the blood circulation in the mouse, Toxicol. Pathol. 34(7), 949–957. Tinkle, S.S., Antonini, J.M., Rich, B.A., Roberta, J.R., Salmen, R., DePree, K., and Adkins, E.J. (2003) Skin as a route of exposure and sensitization in chronic beryllium disease, Environ. Health Perspect. 111(9), 1202–1206. Vogt, A., Combadier, B., Hadam, S., Stieler, K.M., Lademann, J., Schaefer, H., Autran, B., Sterry, W., and Blume-Peytavi, U. (2006) 40 nm, but not 750 nm or 1500 nm nanoparticles enter epidermal CD1a+ cells after transcutaneous application on human skin, J. Invest. Dermatol. 126, 1316–1322.

BIOMARKERS OF NANOPARTICLES IMPACT ON BIOLOGICAL SYSTEMS

V. MIKHAILENKO, L. IELEIKO, A. GLAVIN, J. SOROCHINSKA R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology of National Academy of Sciences 45 Vasilkivska Street 03022 Kyiv, Ukraine [email protected]

Abstract. Studies of nanoscale mineral fibers have demonstrated that the toxic and carcinogenic effects are related to the surface area and surface activity of inhaled particles. Particle surface characteristics are considered to be key factors in the generation of free radicals and reactive oxygen species and are related to the development of apoptosis or cancer. Existing physico-chemical methods do not always allow estimation of the nanoparticles impact on organismal and cellular levels. The aim of this study was to develop marker system for evaluation the toxic and carcinogenic effects of nanoparticles on cells. The markers are designed with respect to important nanoparticles characteristics for specific and sensitive assessment of their impact on biological system. We have studied DNA damage, the activity of xanthine oxidoreductase influencing the level of free radicals, bioenergetic status, phospholipids profile and formation of 1H-NMR-visible mobile lipid domains in Ehrlich carcinoma cells. The efficiency of the proposed marker system was tested in vivo and in vitro with the use of C60 fullerene nanoparticles and multiwalled carbon nanotubes. Our data suggest that multiwalled carbon nanotubes and fullerene C60 may pose genotoxic effect, change energy metabolism and membrane structure, alter free radical level via xanthine oxidase activation and cause mobile lipid domains formation as determined in vivo and in vitro studies on Ehrlich carcinoma cells. 1.

Introduction

Among engineered nanoparticles (NP) currently being produced, the most common are fullerenes C60 and carbon nanotubes (CNT). These materials possess nanostructure-dependent properties that may potentially lead to unusual biological activity which typically increases as the particle size decreases. Highly increased surface area of NP may be toxicologically relevant. Studies of mineral particles have demonstrated that the toxic and carcinogenic effects are mostly related to the surface area of inhaled particles and their surface activity [1]. Data yielded from I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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animal and cell culture studies pointed to an increase in pulmonary inflammation, oxidative stress incidence, an increased risk of carcinogenesis, inflammatory cytokine production, apoptosis, and activation of certain gene expression and cell signaling pathways [2]. A common mechanism of NP impact on cell damage is oxidative and nitrosative stress development. Fullerenes and CNT’s have been shown to produce superoxide and induce free radical damage to cells [3–6]. However, currently the potential adverse effects of engineered NP on human health and the environment can not be fully estimated due to insufficient knowledge of mechanisms of action and lack of standardized testing protocols. In our study we have develop a marker system to evaluate the toxic and carcinogenic effects of nanoparticles on cells in order to address their involvement into free radical processes, energy metabolism, membrane structural changes and genotoxic mechanisms. We studied DNA damage, the activity of xanthine oxidoreductase (XOR) influencing the level of free radicals, bioenergetics status, phospholipids profile and formation of 1H-NMR-visible mobile lipid domains (MLD) in Ehrlich ascites carcinoma (EAC) cells. Xanthine oxidoreductase is a complex molybdoflavoprotein identified as a terminal enzyme of purine catabolism, catalyzing the hydroxylation of hypoxanthine to xanthine and of xanthine to urate. The XOR protein is apparently expressed as xanthine dehydrogenase form (XDH; EC 1.1.1.204) but partially can be converted, either reversibly or irreversibly, to xanthine oxidase form (XO; 1.1.3.22) by posttranslational modification [7, 8]. The forms of XOR enzyme are differentiated by the preference of oxidizing substrate, and generation of reactive oxygen species (ROS) – hydrogen peroxide and superoxide radical [7, 9]. XOR plays an important role in maintaining the balance of free radicals, takes part in NO circulation, decomposition of S-nitrosothiols and can be source of reactive nitrogen species (RNS) – NO and peroxynitrite [8, 10]. In fact, peroxynitrite can be produced by XOR itself [11]. At normal conditions, the XDH form predominates in vivo, producing the potent antioxidant uric acid. Conversion of XDH to XO form results in overproduction of the superoxide radicals in tissues and may cause intensification of lipid peroxidation (LPO) and production of additional quantities of hydrogen peroxide in tissues [12, 13]. Activation of XOR and conversion of its XDH form to XO form leads to apoptosis and death of the damaged cells at pathological processes [14]. At the same time connection between enzyme activation, ROS and RNS production, and subsequent damage of a genetic material which can cause tissues malignization was observed in a number of studies [15, 16]. 1 H NMR-visible MLD increased formation are reported as a peculiar feature of malignant cells in vitro and in vivo [17]. Cell membrane rearrangements coincident with malignancy and proliferation of tumor cells may contribute to the increase in the ratio of methylene (CH2 at 1.3 ppm) to methyl (CH3 at 0.9 ppm) resonance signal intensity as observed by proton nuclear magnetic resonance (1H NMR). Cellular origin of these resonances is related to lipid turnover and cell membrane structure and arises from the isotropically tumbling molecules, with sufficient molecular mobility. NMR signals from CH2 and CH3 groups originate mainly from mobile fatty acyl chains of tissue triacylglycerides with lesser contributions

BIOMARKERS OF NANOPARTICLES IMPACT ON BIOLOGICAL SYSTEMS 69

from free fatty acids and cholesteryl esters. The presence of NMR-detectable lipids in cells can originate from triacylglycerides in globular plasma membrane microdomains (22–28 nm in diameter) or intracellular lipid bodies, either adjacent to the plasma membrane or within the cytoplasm [18, 19]. Bioenergetic status of cells was characterized by 31Р-NMR spectroscopy by phosphorylated metabolites and their ratios: inorganic phosphate/β-nucleoside triphosphates (Рi/βNTP), inorganic phosphate/phosphocreatine (Рi/PCr), inorganic phosphate/phosphomonoesters (Pi/PME) that characterize the level of energy metabolism and phosphomonoesters/β-nucleoside triphosphates (PME/βNTP), inorganic phosphate/phosphomonoesters (Pi/PME) that indicate the level of hypoxia. The metabolism of membrane components was characterized by the phosphomonoesters/phosphodiesters (PME/PDE) ratio. The increase in the PME/PDE ratio indicates activation of membrane components synthesis, ratio reduction point to an intensive breakdown of cells membranes. Lipids profile was characterized by the contents of phosphor-containing lipids. It is known that cardiolipin is involved in apoptosis and oxidative phosphorylation, provides osmotic stability of mitochondria [20, 21]. Phosphatidylserine could affect the regulation of protein kinase C activity and apoptosis [22]. Decrease of phosphatidylinositol content may be caused by the processes of intensive degradation or by the inhibition of its synthesis. Degradation of phosphatidylinositol leads to the formation of such second messengers, as diacylglycerol and inositol1,4,5-triphosphate. Diacylglycerol is bound to the inner layer of the plasma membrane and participates in activation of proteine kinase C. Inositol-1,4,5triphosphate diffuses through the plasma membrane into cytoplasm and binds to the specific receptors on the endoplasmic reticulum causing the release of calcium ions into the cytosol. Alterations of the phosphatidylcholine/sphingomyelin (PtdCho/SpM) ratio points out to changes of the level of membrane structuring [23]. Ratio increases reflect reduction of membrane structuring and increased membrane permeability, whereas ratio decreases indicates increased membrane viscosity. The single-cell gel electrophoresis (or comet) assay is a rapid, simple and sensitive technique for visualizing and measuring DNA damage in individual cells. It is used as a primary method of screening for genotoxic compounds. The method is based on detection of various mobility damaged DNA contained in cells embedded in agarose gel and subjected to a constant electric field. Thus DNA migrates to the anode, forming a trace reminding a “tail of a comet” which parameters depend on the level of DNA damage [24]. The aim of this study was to develop marker system for complex evaluation the toxic and carcinogenic effects of nanoparticles on cells. Existing physicochemical methods, due to insufficient knowledge of mechanisms of action, do not always allow estimation of the nanoparticles impact on organismal and cellular levels. The proposed marker system is based on studies of DNA damage, the activity of XOR, bioenergetics status, phospholipids profile, and formation of MLD in cells and is hypothesized to reveal mechanisms of NP damaging effects on cells. The current marker system was used to test in vivo and in vitro the effects

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of C60 fullerene nanoparticles and multiwalled carbon nanotubes (MWCNT) on EAC cells. 2.

Materials and Methods

Investigations were carried out on white inbred male mice weighting 19–22 g, 2– 2.5 months old, bred by vivarium of R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology of National Academy of Sciences of Ukraine (Kyiv, Ukraine). All experiments with animals were approved by the Regional Animal Ethics Committee. 2.1.

ANIMAL STUDIES

Ehrlich ascites carcinoma (EAC) obtained from the Bank of Cell Line of the R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology (Kyiv, Ukraine). EAC were maintained and propagated by serial intraperitoneal transplantation of EAC cells in an aseptic environment. Cells of EAC (106 cells/mice) were injected intraperitoneally (i.p.) at the volume of 0.5 ml of physiologic solution. All the experiments on tumor bearing mice were conducted 6 days after the EAC transplantation. MWCNT’s suspension in physiologic solution was i.p. administered (0.5 ml per mouse) in concentrations of 0.5 and 1.5 mg/mouse for 24 h. 2.2.

CELL CULTURE

EAC cells were obtained from male mice with Ehrlich ascite tumor. Cells from ascites, after washing, were suspended in Dulbecco’s modified Eagle’s medium (DMEM, Sigma, St. Louis, MO, USA), supplemented with 10% fetal calf serum (FCS, Gibco Laboratory, Carlsbad, CA, USA) and maintained by culturing in a humidified atmosphere of 5% CO2 at 37°C for at least 12 h. EAC cells (7 105 cells/ml of DMEM) were treated for 24 h with carbon nanoparticles (CNP) suspensions: MWCNTs (0.07 0.035 and 0.017 mg/ml) and fullerene C60 (0.066 mg/ml). The percentage of living and dead cells was determined by trypan blue exclusion test. 2.3.

NANOPARTICLES

Two different type of CNP were examined in this study. MWCNT, obtained from Dr. J.I. Semencov and T.A. Alekseeva (TMSpetsmash Ltd., Kyiv, Ukraine), were acid treated to reduce the catalyst impurity, washed and resuspended in physiologic solution. Fullerene C60 was obtained from ALSI (Ukraine). All CNP suspensions were freshly sonified under 4°C before administration (6 x 30 s) to break up agglomerates.

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2.4.

NMR ASSAY

Dual extraction of cellular lipids and water-soluble metabolites from tissue samples was made by the methanol-chloroform-water extraction method proposed by Tyagi et al. [25]. This method facilitates the simultaneous extraction of both the water-soluble metabolites and the organic-soluble lipid components from the same tissue sample. Water-soluble dried extract samples were re-dissolved in D2O, organic-soluble lipid dried extract samples were re-dissolved in CDCl3. 31Р-NMR spectroscopy allows simultaneous level assessment of the main phosphorylated metabolites. 31 P and 1H spectra of tissue extracts were acquired using Varian Mercury BB NMR spectrometer (Varian, Palo Alto, CA, USA), operating at frequency 300 MHz. All NMR measurements were carried out at temperature 20°C and all samples were spun at 20 Hz. Chemical shifts in 31P NMR spectra were recorded with respect to methylenediphosphonic acid, trisodium salt (MDP, Sigma, St. Louis, MO, USA), used as an external standard. The resonance of phosphocreatine was set at 0 ppm. Chemical shifts in 1H NMR spectra were recorded with use of 0.1% solution of sodium 3-trimethylsilyl[2,2,3,3-D4] propionate in D2O as a reference at 0 ppm. The acquisition parameters of 1H spectra of water-soluble metabolites: relaxation delay time 4 s; spectral width 6 kHz; number of points 7,218; 30° flip angle. The intense water resonance was partially suppressed by the use of presaturation of the residual water protons in the solvent. The acquisition parameters of 31P spectra of water-soluble metabolites: relaxation delay time 2.4 s; spectral width 6.5 kHz; number of points 6,503; 90° flip angle. Proton scalar coupling interactions were removed by using continuous low power proton coupling. The acquisition parameters of 31P spectra of phospholipids: relaxation delay time 5 s; spectral width 3 kHz; number of points 6,000; 90° flip angle. Proton scalar coupling interactions were removed by using continuous low power proton coupling. 2.5.

THE ALKALINE COMET ASSAY

EAC cells were washed in PBS and suspended in agarose gel (0.5 · 106– 0.7 · 106 cells/ml). Cells were then lysed, subjected to alkaline denaturation, and electrophoresis [26]. Slides were stained with acridine orange solution (20 μg/ml). Comet images were observed at 100x magnification with a fluorescence microscope connected to a video camera (CCD, Webbers, USA). One hundred images were randomly selected from each sample and analyzed by an image-analysis program “CometScore” (TriTek Corp, Sumerduck, VA, USA). The extent of DNA damage was estimated by the following parameters: Comet Area (AC) – the area covered by the whole comet; Tail Length (lT) – the horizontal distance from the centre of the head (start of tail) to the end of the tail; %DNA in Tail (DNAT) – the DNA percentage in the tail – %DNAT = 100DNAT/( DNAT+ DNAH); Tail Moment (MT) – the product of tail length and fraction of DNA in the

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tail – MT = lT% DNAT; Olive tail moment – the product of the proportion of tail intensity and the displacement of tail centre of mass relative to the centre of the head. 2.6.

MLD ASSAY

Cells were harvested and washed once with PBS then washed twice with PBS made with D2O to reduce protons signal from H2O. Cells (8–10 · 107 cells/ml) were suspended in a final volume of 0.6 ml of PBS-D2O, transferred to a 5 mm NMR tube and placed on ice until analysis. The percentage of viable cells, determined by Trypan blue exclusion test, ranged between 85% and 95%, both before and after NMR analyses. 1H NMR spectra were acquired using a 300 MHz Varian Mercury 300BB NMR spectrometer (Varian, Palo Alto, CA, USA) at 20°C, 90° flip angle, repetition time 10 s, 200 excitations, 16000K data points and 5 kHz spectral width. A glass capillary with 0.1% solution of TSP in D2O was used as a reference at 0 ppm for each sample. NMR spectra were obtained using presaturation of the residual water protons in the solvent, and samples were spun at 20 Hz to prevent settling of cells during the experiment. The standardized areas of the methylene and methyl protons resonances (at 1.3 and 0.9 ppm, respectively) were integrated using VNMR software (Varian, Palo Alto, CA, USA) and expressed in relative units. 2.7.

XOR ASSAY

Total XOR activity and activity of XO were examined in EAC cells [27]. Activity of XOR enzyme was estimated by the production of uric acid from xanthine (absorbance at 295 nm). Reaction kinetics were measured for 30 min at 26°С in special 96-well plates on the microplate reader Synergy™ HT (Bio-Tek Instruments, Winooski, VT, USA). In each well 250 μl of incubation mixture (50 mM sodium phosphate buffer with 0.3 mM EDTA, 0.5 mM xanthine, 0.5 mM NAD+ and 0.24 mM oxonic acid) and 3.6 · 105 EAC cells in 50 μl of 50 mM sodium phosphate buffer with 0.3 mM EDTA were added. Oxonic acid was used as uricase inhibitor [28]. XOR activity was expressed in nM uric acid formed by 1 . 106 AEC cells during 1 h. Total protein concentration was determined according to Greenberg and Craddock [29]. 2.8.

LPO ASSAY

Intensity of lipid peroxidation (LPO) was evaluated by spontaneous accumulation of malonic dialdehyde (MDA) and expressed in nanomoles of MDA per gram of cells per hour. The absorbance of the colored thiobarbituric acid-reactive substances was measured at 532 nm on a Diode-matrix UV-Vis spectrophotometer Agilent 8453 (Agilent, Santa Clara, CA, USA) [30, 31].

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2.9.

STATISTICAL ANALYSIS

Statistical analysis was performed in cases when experiments were carried out at least in triplicate using Student’s t-test. Values are reported as mean ± standard error. 3.

Results and Discussion

The EAC cells used in our study are a well characterized biochemically and morphologicaly tumor model and is commonly applied in toxicological studies. The ascite form of EAC can be used for in vivo experiments and can be easy transferred into culture for in vitro studies. The EAC cells were treated with CNPs for 24 h in in vivo and in vitro experiments, after which the bioenergetics status, phospholipids profile, DNA damage, XOR activity, LPO level, and MLD formation were simultaneously quantified. 3.1.

CHARACTERISATION OF BIOENERGETIC STATUS AND PHOSPHOLIPIDS PROFILE OF EAC CELLS TREATED BY CNP

3.1.1.

Energy Metabolism of EAC Cells

The bioenergetic status of cells was characterized by 1H and 31P NMR spectroscopy. The quantity of individual phosphor-containing metabolites were determined: Glucose 6-phosphate (G6-P), Phosphoethanolamine (PE), Phosphocholine (PC), Inorganic Phosphate (Pi), Glycerophosphocholine (GPC), Glycerophosphoethanolamine (GPE), Phosphomonoesters (PME represented by PE + PC), Phosphodiesters (PDE represented by GPC + GPE), Nucleoside triphosphate (NTP), Nucleoside diphosphate (NDP), Choline (Cho), Creatine (Cr), and Phosphocreatine (PCr), as shown in Figure 1. Cells exposure to fullerene C60 caused a 2.6-fold decrease in the Pi/PME ratio and 1.4-fold decrease in the PME/PDE ratio. Thus, fullerene C60 activated energetic metabolism, leading to a decline in membrane component synthesis and reduced hypoxia level (Figure 2B). Exposure to fullerene C60 caused a decrease in lactate (1.2-fold) and taurine (1.3-fold) contents, as well as an increase in Cho + PC + GPC (twofold) and Cr + PCr (4.53-fold) contents. Such changes of lactate content indicated a decline in anaerobic glycolysis (data not shown). Treatment with low concentration of MWCNT caused 1.2-fold increase of the Pi/β-NTP and PME/β-NTP ratios, that reflected inhibition of energetic metabolism and intensification of hypoxia. High doses of MWCNT caused a 1.5-fold rise in the PME/β-NTP ratio which indicates an intensification of hypoxia, however a 1.6-fold decline in the Pi/PME ratio indicates activation of energetic metabolism.

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Figure 2. Energy metabolism level in EAC cells treated in vivo with CNP. (A) Effect of MWCNT on Pi/β-NTP, PME/β-NTP, Pi/PME and PME/PDE ratios in EAC cells – ■ – control cells; – MWCNTtreated cells (0.5 mg/mouse); □ – MWCNT-treated cells (1.5 mg/mouse). (B) Effect of fullerene C60 (0.066 mg/ml) on Pi/PME and PME/PDE ratios – ■ – control cells; – fullerene C60 treated cells. 1 – Pi/β-NTP, 2 – PME/β-NTP, 3 – Pi/PME, 4 – PME/PDE.

The PME/PDE ratio increased 1.6 and 2.9 times under the influence of low and high doses of MWCNT, respectively. Increase in the PME/PDE ratio pointed to the activation of membrane components synthesis (Figure 2A). Low and high concentrations of MWCNT caused a modest decline of taurine content. Exposure to low doses of MWCNT caused a 1.3-fold decrease of Cho + PC + GPC content and a 1.2-fold increase of lactate content. However, high concentration of MWCNT caused a 1.5-fold decline of lactate content (data not shown).

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3.1.2.

Phospholipids Profile of EAC Cells

Phospholipids of EAC cells were characterized by the contents of phosphatidylcholine (PtdCho), plasmalogen phosphatidylcholine (PlPtdCho), phosphatidylinositol (PtdIns), sphingomyelin (SpM), phosphatidylserine (PtdSer), phosphatidylethanolamine (PtdEtn), plasmalogen phosphatidylethanolamine (PlPtdEtn) and cardiolipin (Card) by 31Р-NMR spectroscopy (Figure 3).

Figure 3. Typical 31P NMR spectra of phospholipids obtained by dual extraction of EAC cells. 1 – Card, 2 – PlPtdEtn, 3 – PtdEtn, 4 – PtdSer, 5 – SpM, 6 – PtdIns, 7 – PlPtdCho, 8 – PtdCho.

Exposure to fullerene C60 decreased PtdCho (1.2-fold), PlPtdCho (1.4-fold), PtdSer (1.6-fold), PtdEtn (1.3-fold), and PlPtdEtn (1.5-fold). Treatment with fullerene C60 was followed by a 1.4-fold decrease in the PtdCho/SpM ratio (Figure 4A). Low concentration of MWCNT caused decreases in PtdCho (1.2-fold), PlPtdCho (twofold), SpM (1.6-fold), PtdSer (1.4-fold), and PtdEtn (1.4-fold) contents. The PtdCho/SpM ratio increased 1.3 times under the influence of low doses of MWCNT. High concentration of MWCNT caused an increase in SpM (1.2-fold), PtdSer (1.4-fold), PlPtdEtn (1.3-fold), and Card (1.5-fold). Treatment with high doses of MWCNT caused small decrease of the PtdCho/SpM ratio (Figure 4B). Thus, fullerene C60 caused decrease of almost all phospholipids content and increase of plasma membrane structuring as determined by the PtdCho/SpM ratio. However, low doses of MWCNT caused decrease of phospholipids content and increase of membrane permeability. On the contrary, high concentrations of MWCNT caused increase of phospholipids content and a small rise of plasma membrane structuring.

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Figure 4. Phospholipids level in EAC cells treated with CNP: (A) Effect of fullerene C60 (0.066 mg/ml) – ■, control cells; , fullerene C60 treated cells. (B) Effect of MWCNT – ■ – control cells; – MWCNT treated cells (0.5 mg/mouse); □ – MWCNT treated cells (1.5 mg/mouse). 1 – PtdCho, 2 – PlPtdCho, 3 – PtdIns, 4 – SpM, 5 – PtdSer, 6 – PtdEtn, 7 – PlPtdEtn, 8 – Card.

3.2.

ASSESSMENT OF MLD BY PROTON NMR

The ratio of CH2/CH3 signal intensity was moderately increased (1.2 times) in fullerene C60-treated EAC cells, but the choline resonance signal (at 3.2 ppm) decreased twofold as compared with untreated EAC cells. This effect may be related to apoptosis-associated changes in fullerene C60 treated cells. Exposure to MWCNT was accompanied by small decreases in the CH2/CH3 ratio and choline resonance signal (Figure 5A). 25 15 5 -5 %

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Figure 5. Levels of MLD and Cho in EAC cells treated with CNP. (A) Typical 1H NMR spectra of EAC cells. Peak assignments: 1 – CH3 signal mainly from protein residues and lipids at 0.9 ppm; 2 – (-CH2)n signal from mobile lipids resonate at 1.3 ppm, 3 – creatine at 3.03 ppm and 4 – choline-based metabolite signal at 3.23 ppm. (B) The ratio of treated to untreated cells for Cho and CH2/CH3, % ■, fullerene C60 treated cells (0.066 mg/ml); , MWCNT treated cells (1.5 mg/mouse). 1

H NMR analysis revealed an increase in MLD formation in fullerene C60treated cultured cells in contrast with MWCNT effect after administration into peritoneal cavity. Neither CNP caused any significant cytotoxicity in the range of concentrations used, as evidenced by trypan blue exclusion test.

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3.3.

XOR ACTIVITY AND LPO LEVEL

The activity of XOR was studied in EAC cells. Formation of uric acid in samples did not depend on the presence of NAD+ in incubation mixture. These data indicate that nearly all XOR in cells was present in the oxidase form, and dehydrogenase form was absent [32]. Presence of fullerene C60 in cultural medium resulted in a moderate increase of enzyme activity (21.5%) and more distinct decrease of LPO intensity (49.2%). Treatment with MWCNT also increased XO activity in EAC cells (Figure 6). The maximum effect was observed at the middle concentration of MWCNT in cultural medium (0.035 mg/ml), resulting in a 91.8% increase in XO activity. At MWCNT concentrations 0.017 and 0.07 mg/ml XO activity was raised on 39.2% and 45.3%, respectively. When MWCNT were administered into peritoneal cavity in concentration of 1.5 mg/animal, the XO activation was lower (23.5%), and LPO level in EAC was decreased to 86.5%. 200 150

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Thus, effects of fullerene C60 and MWCNT on XOR activity and LPO intensity of the EAC had unidirectional character. The activity of XOR was raised and level of the LPO was decreased. The alteration of XOR activity depended on MWCNT concentrations. Effects of MWCNT on XOR activity of EAC was more pronounced in cell culture than in the peritoneal cavity of mice. Lower effect of MWCNT in peritoneal cavity is probably related to adhesion of a considerable amount of MWCNT on organs of experimental animals. The decrease in LPO was unexpected and needs further investigation since the majority of publications observe the opposite effect. Taking into account that such an effect was observed in parallel

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with the activation of XO, which is capable of generating superoxide radicals, hydrogen peroxide, NO. and peroxinitrite [7, 8, 10], the decrease in LPO was probably caused by elimination of free radical compounds due to binding to CNP surface [33]. 3.4.

DNA DAMAGE

The ability of CNP to induce the formation of DNA strand breaks was assessed using the comet assay and the obtained results were compared to untreated EAC cells (Figure 7). Treatment of EAC cells during 24 h with fullerene C60 (0.066 mg/ml) induced comet area threefold, the tail length 2.3-fold, and the tail moment and Olive tail moment twofold.

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Figure 7. DNA damage in EAC cells treated with CNP by comet assay. (A) Comet area and (B) tail length. 1 – control cultured cells; 2 – fullerene C60 treated cells (0.066 mg/ml); 3 – MWCNT treated cells (0.07 mg/ml); 4 – MWCNT treated cells (0.035 mg/ml); 5 – MWCNT treated cells (0.017 mg/ml); 6 – control ascitic cells; 7 – MWCNT treated cells (0.5 mg/mouse); 8 – MWCNT treated cells (1.5 mg/mouse).

The effect of MWCNT on DNA damage was inversely related to doses used for cells treatment. Treatment of EAC cells with MWCNT (0.07 mg/ml) induced the moderate increase of DNA damage (1.2–1.3 times) compared to untreated cells. At the time of analysis most of cells (98%) were not stained with Trypan blue. Treatment cells with MWCNT at 0.035 mg/ml was followed by a moderate rise in comet area, tail length, Olive tail moment increase of 1.5-fold, and tail moment increase of twofold. The number of cells with comets was increased 17%. Treatment cells with MWCNT in concentration of 0.017 mg/ml caused the largest effect on DNA damage. The comet area was increased threefold, the tail length and tail moment twofold, and the Olive tail moment 1.6-fold. The number of cells with comets rose 38%. The DNA damage was also assayed when EAC cells were treated with MWCNT in vivo. Low concentration of MWCNT (0.5 mg/mouse) induced the increase of the comet area in 1.5 times and the tail length and tail moment 1.3fold. The Olive tail moment did not change significantly. The higher MWCNT dose (1.5 mg/mouse) induced an increase in the comet area of 1.6-fold, the tail length 1.3-fold, the tail moment threefold, and the Olive tail moment twofold. The

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number of cells with comets increased 4–10% in 0.5 ng MWCNT/mouse and 1.5 mg MWCNT/mouse, respectively. 4.

Conclusion

Insufficient knowledge of NP mechanisms of action and large variety of interactions with biological molecules require new approaches to estimate nanoparticle impacts on organismal and cellular levels. The complex estimation of toxic and carcinogenic effects of NP on cells was carried out to address their involvement in free radical processes, energy metabolism, membrane structural changes and genotoxic damage in EAC cells exposed to CNP. The use of EAC model provided an opportunity to study CNP impact in vitro on cultured cells as well as in vivo when NP were administered i.p. to tumor-bearing mice. Our data suggest that MWCNT and fullerenes may pose genotoxic effect, change energy metabolism and membrane structure, alter free radical level via XO activation, and cause MLD formation, as determined in the in vivo EAC model and in vitro cell culture. Exposures of cells to CNP (fullerene C 60 and MWCNT) induced DNA damages both on in vivo and in vitro systems. MWCNT-induced DNA damage was inversely related to doses used for cells treatment. Cells exposed to MWCNT in vitro exhibited a greater degree of DNA damage than cells exposed in vivo. XOR enzymatic activity did not depend on the presence of NAD+ in incubation mixture, this indicates that nearly all XOR in cells was present in the oxidase form and dehydrogenase form was absent. The effect of fullerene C60 and MWCNT on XOR activity and LPO intensity of the EAC had a unidirectional character. The activity of XOR was raised and level of the LPO was decreased. The effects of MWCNT on XOR activity in EAC was more pronounced in cell culture than in peritoneal cavity of mice. This may be due to transperitoneal absorption of a considerable part of substance or its adhesion to organs. Decrease of LPO levels were unexpected, possibly caused by the elimination of free radical compounds due to binding to CNP surface. Treatment with MWCNT caused intensification of hypoxia and activation of membrane component synthesis, yet fullerene C60 caused the opposite effect. Fullerene C60 and high doses of MWCNT revealed activation of energy metabolism and a reduction of membrane permeability, however low doses of MWCNT caused opposite changes. Phospholipid metabolism decreased after treatment with fullerene C60 or low concentration of MWCNT but conversely exposure to high doses of MWCNT caused elevation of phospholipids content. The obtained results demonstrate a possible link between cells exposed to CNP and corresponding changes of the proposed markers. The use of a wide variety of indicators allowed us to acquire information about major mechanisms of NP damaging effect on organism. Thus, the developed system of biomarkers can be suggested as a sensitive and efficient approach for assessment of toxic and carcinogenic CNP impact on organism.

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NANOCONTAMINATION OF THE SOLDIERS IN A BATTLE SPACE

A.M. GATTI Laboratory of Biomaterials University of Modena and ReggioEmilia Via Campi 213 A 41100 Modena, Italy [email protected] S. MONTANARI Nanodiagnostics srl Modena, Italy

Abstract. The paper deals with the unusual pathologies some soldiers contracted after exposure in battle theatres in Iraq and in the Balkans, and considers the hypotheses the Authors developed to explain the origin of those diseases, that proved to be lethal in a few cases. The scenario of particulate nanopollution generated by high-temperature combustions characteristic of some weapons is described. The electron-microscopy observations carried out in 37 soldiers’ pathological tissues verified the internal dissemination of toxic metallic micro and nano-particles. The article considers the way of entrance of those nanopollutants: the lung for inhalation and the digestive system for the ingestion of polluted food. Battle theatre pollution is also discussed. 1.

Introduction

The actual number has never been published and probably is not known, but what is unquestionable is that veterans from the first Gulf War, and most of them are American and British, have come home ill and some of them died. In a few instances, their symptoms, seemingly unhomogeneous and never experienced together before, were not recognized as belonging to a definite pathology. For that reason, they were either ignored or underestimated or, in the best of circumstances, classed as the expressions of something new christened “Gulf Syndrome” [1–13]. Something similar and sometimes even absolutely superimposable occurred after the war fought in the Balkans. When that war was declared concluded, Italian troops were sent to former Yugoslavia as peacekeepers and returned ill or, more often, grew ill after having been repatriated.

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As far as we know, that pathology or, to be more accurate, that collection of pathologies, looked to be shared by French, Hungarian, Danish, Spanish, Portuguese, Belgian, Dutch and Greek soldiers [14] and, being a collection of symptoms and pathologies, was called a syndrome: the “Balkans Syndrome”. The symptoms observed can evolve into more serious diseases like, for example, various forms of cancer, Hodgkin’s and non-Hodgkin’s lymphoma or leukaemia. Also pathologies involving the blood have been diagnosed, pathologies that did not look particularly important but that, after a certain lapse of time, could result in a myeloma. All those post-war illnesses started to appear in 1991, to show up again after the second Gulf War among the American veterans, but also soldiers engaged in another war theatre, Afghanistan, reported similar conditions. As a rule, those soldiers leave in perfect health (such condition is testified by medical report written before the mission begins and, in any case, a soldier on active service must be in good health condition), but after a comparatively short time of stay they may start to show symptoms, sometimes trivial, but growing more and more serious and even fatal. For information completeness’ sake it is necessary to mention how some American and British soldiers who fell ill after the first Gulf War showed also neurological symptoms, something not observed or, in any case, not reported in Italian Balkans veterans. This piece of evidence is particularly important as a clue, because it means that, though the activities undertaken were unquestionably similar, there was something that made them somehow different. According to the Nuclear Regulatory Commission, Depleted Uranium (DU) may not contain more than 0.711% of U235 and the one used to make DU ammunitions contains less than 0.2%. Its radioactivity is so low that it is only reasonable to rule it out as directly accountable for the pathologies observed. As a matter of fact, people employed to work that metal where DU weapons are manufactured do not show any of the symptoms reported by the veterans nor any other particular pathology attributable to radioactivity. Nevertheless, it is impossible to exclude and, rather, it is very reasonable to say that if radioactive particles are ingested or inhaled, they find themselves in a particularly restricted biological environment where they can easily induce adverse reactions. If we look at the reports issued by the UNEP in 2003 about “DU in Bosnia ed Erzegovina: Post Conflict Environmental Assessment “ by the United Nations Environment Programme, Switzerland 2003 (www.unep.org), we read that places exist where a residual radioactivity still persists (see map in the report [15]), particularly when unexploded darts remain stuck or buried in the ground, but nobody has ever checked and documented if Italian soldiers were stationed there or had ever had a chance to come in contact with them. In order to identify the causal agent of the pathologies we are dealing with, it is imperative to locate place and possibility of exposure. Once determined those two factors, it is necessary to verify if the hypothesis may fit to the same pathologies in other cohorts of subjects like soldiers operating in firing grounds, people living in proximity to those posts and, in particular, civilians and NGO effectives present

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in war theatres. It is only by evaluating the whole situation that we can single a causal agent out shared by all those classes of subjects. DU has been chosen because of a few favourable characteristics, among which its hardness, high specific weight, high melting point, excellent armour-piercing penetration and pyrophoricity. When the projectile is launched, its pointed penetrator can pierce relatively thick armour plates or virtually any other mark, and the explosion ensuing has part of the material involved vaporize, as the temperature induced is in the range 3,036–3,063°C [16]. After sublimation, everything is present in the volume involved gives origin to an aerosol and than to condensation dust that, because of the very high temperature, is often of nanometric size. The chemical composition of those particles is the result of the fortuitous combination of the elements present in the occasional crucible represented by the target and, on a smaller scale, by the bomb itself. The main factor conditioning the size of that particulate matter (sometimes within the order of magnitude of the tens of nanometres) is temperature and, as a general rule, the higher it is, the smaller the particles are. As a consequence, the particles generated close to the core of the explosion will be smaller than those formed in a more peripheral area. Similar results occur when a great quantity of conventional ammunitions is used, an event common when weapons must be disposed of and that is done by setting them off, or when an explosion in an arsenal occurs out of control. Such an event has been reported, for example, in a site close to Baghdad [17]. The ultramicroscopic analyses showed the presence of micro- and nanoparticles with unusual chemical compositions, in all cases metallic. Among other compositions, we found alloys of Lead and Tin, Zinc–Iron–Titanium, Lead–Bismuth and Bismuth alone, Tin–Silver, Iron–Copper–Zinc, Titanium–Iron, Silicon–Zirconium, Strontium–Sulphur, Cadmium–Silicon and also Uranium–Thorium. All these compounds are toxic due to at least one of their components and, because of their morphology and dimension, they show a physical aggressiveness towards the organism. The formation of a brand new pollution, never experimented before, with a chemical composition that at times is certainly toxic as is composed by non biodegradable, non biocompatible heavy metals represents a novel stimulus to which the human body is not prepared to react in a positive way nor is likely to be capable of adapting [18]. Our organism needs Oxygen to live, along with a variety of nutrients, and without Oxygen our cells can survive only for a very short time. Particularly in modern warfare, because of high-temperature weapons, a novel, particulate pollution is created that permeates man, animals and the whole environment, and that form of pollution can be inhaled with the air and ingested with the vegetables grown under the inevitable fallout that ensues. The school of Leuven (Belgium) [19] demonstrated that inhaling 100-nm particles is risky for our health, since dust that size negotiates the alveolar barrier within 60 s reaching the blood stream and, within an hour, the liver and all other tissues and organs. As has been observed by our group, those particles are trapped in any tissues acting like any mechanical

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filter or can penetrate cell nuclei where can induce adverse effects both as foreign bodies and as being composed of toxic elements. The evidence we found consistently in the pathological-tissue specimens of the more than 100 cases of ill soldiers studied is the most irrefutable demonstration of this theory [20]. Other Authors chose to keep looking for a Uranium contamination in the soldiers’ urine [21]. To be sure, the measurements they carry out can verify a possible contamination from Uranium radioactivity, but do not take into consideration the unavoidable lack of information about the quantity of radiations each patient absorbed before a presumed exposure in a war theatre (zero reference). For that reason, the value found is at least partially independent of the Uranium that may have entered that organism. In addition to that, that value depends on the capability the subject’s kidneys have to get rid of Uranium as an ion resulting from the solution of materials present in the body, nor can we know whether those materials are of natural or anthropic origin, and, in the latter case, if they come from the use of weapons. And that hypothesis does not offer any explanation about how subjects showing similar excretion values come to suffer from different pathologies and, in particular, offers no explanation about the neurological diseases reported by American and British soldiers (no systematic observations exist for other nationalities). Symptomatology caused by radiations is very well-known and is amply described in medical literature dealing with Japanese subjects exposed to A bomb radiations in August 1945. The symptoms reported there do not coincide with those found in the veterans from the Balkans and the Gulf and, therefore, the hypothesis that those syndromes may be caused by radioactivity looks hard to accept. It is a fact that, if at the beginning the symptoms observed were hardly attributable to a single disease, as the different pathologies develop, the soldiers died for cancerous diseases of different districts of the body; but cancer is very frequent among the population (the incidence now is that it affects 1 subject out of 3) who was never exposed to Uranium radiations. It is well known that chemicals, but radiations as well, can cause cancer, but it sounds strange that in a battle theatre that group if pathologies is triggered only by radiation. These considerations should lead to search for a cause compatible with the objective data and the events occurred, and equally shared by soldiers, civilians and animals. The analyses completed in our laboratory on the bioptical and autoptical samples taken from American, French and Italian soldiers, those on the same kind of samples from soldiers and civilians active in firing grounds along with the environmental analyses carried out in war theatres and in firing grounds induce us to sketch out a different scenario and another possible causal agent, i.e. the submicronic pollution created by weapon and target together. As briefly described above, a temperature like the one brought about by DU explosions generates extremely fine inorganic particles that can be inhaled and ingested by men and animals alike. One of the peculiarities of such anthropic

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pollution is its small size, and to that size they owe their capability to penetrate so easily virtually any organ and tissue, none excluded, from the lymph nodes to the brain to the gonads. Our analyses on about 1,000 cases involving soldiers, civilians and workers busy in polluted sites is evidence of the presence of such particulate matter and its dissemination inside the organism. In some circumstances, the assessment of their morphology and chemical composition identifies unambiguously those particles as coming from random and very particular combustions like a high-temperature explosion. It is a matter of fact that those particles are neither biodegradable nor biocompatible and can interact in a noxious way with the organism. For a long time medical literature has described pathologies due to small foreign bodies: silicosis, the lung disease caused by inhalation of silica microparticles; asbestosis and mesothelioma from the exposure to asbestos dust; foreignbody granulomatosis of various tissues. On the other hand, toxicology relevant to the exposure to nanoparticles is a fairly new subject and is still a matter of tentative approach in all technologically advanced countries. Proof of that are the several American and European projects in the field of nanotoxicology in progress at the moment. From 2002 to 2005, one of the Authors of this text (Dr. Gatti) was the coordinator of a European project called Nanopathology (www.nanopathology.it) at is now the coordination of a second project called DIPNA (Development of an integrated platform for the nanoparticle risk assessment). Yet, a number of studies exist about the easiness with which nanoparticulate enters the organism and is disseminated once inhaled or ingested. Their entry in the brain may even be possible through the olfactory nerve as described by Öberdörster [22, 23]. As soon as they are in the brain, they can represent an irritative factor because of their characteristic of acting as electrical conductors and/or, occasionally, because of their magnetic properties. The whole of all those anomalous activities and their non biodegradability can be the cause of local toxicity. One of the characteristics of this kind of particulate is its capability of moving from pregnant mother to foetus. We did not have the chance to examine tissues taken from miscarried, malformed foeti, the offspring of veterans, but checked those from stillborn, malformed lambs whose mothers grazed in meadows occupied by firing grounds. Pregnant sheep fed on grass polluted by the dust created by explosions, and that dust, delivered to the embryo, was then found in the dead lamb. It is evident that particulate matter can be compatible with the development of an embryo, but that development is abnormal and in most cases incompatible with life outside the mother’s womb. Similar cases did we find in human malformed foeti, but, in those circumstances, the cause was attributable to industrial or urban pollution. A few other hypotheses have been put forward to explain the so-called Balkans and Gulf syndromes. One of them is the use of multiple, certainly too close in time, vaccinations. That could be taken into account, but only if in those cases where a temporal consequence can be demonstrated, i.e. when, immediately after the vaccines have been administered, the subject shows an ailment that grows worse.

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It is a well-known fact that so-called adjuvants (http://www.emea.europa.eu/pdfs/ human/vwp/13471604en.pdf) are added to vaccines in order to improve the immune response so a lesser quantity of drug is needed and enhance the organism reaction because of their pyrogenicity. Adjuvants can be inorganic matter that can be made up by heavy metals. Mercury was widely used before it was banned because of its obvious toxicity. As shown by our studies, inorganic, non biodegradable and non biocompatible particulate like that used in vaccines cannot been disposed of by the organism and the consequences of its introduction into the body are the ones mentioned above. As briefly reported, it is not just soldiers who suffer from the Balkans and Gulf syndromes or from similar collections of symptoms and diseases, but it is also soldiers active in firing grounds or civilians living in war theatres. Especially civilians were never subject to multiple vaccinations nor took cocktails of drugs the way soldiers, in some circumstances, do, and, therefore, it is really hard to blame the vaccines when only part of the patients were exposed to them. Nevertheless, ruling out the possibility that using vaccines and drugs in a way that is so concentrated and outside medical experience may be an aggravation and make the onset of the disease easier, does not look correct and the hypothesis deserves further investigation. Hypotheses like the one linked to the use of sprays against bacteriological war shows the same weak points as the theory above. In conclusion, the analysis on pathological tissues aimed at detecting particulate matter looks the most meaningful test to assess the exposure the subject underwent. 2.

The Contamination

The soldiers’ pathological tissues we analyzed showed the presence of micro- and, more commonly, nanoparticles. The chemistry we came across was sometimes unusual: Mercury–Selenium, Antimony–Cobalt, Zirconia. It was somewhat surprising to find inside soldiers’ tissues particles we thought to be confined in nanotechnological laboratories. Zirconia, for instance, as we found in a soldier’s spleen (see Figure 1), has a melting point of about 2,400°C and the generation of nanoparticles of that material, outside a nanotechnological laboratory, implies temperatures peculiar to special combustions. During the blast of high-technology weapons or of an accumulation of ammunition, a very high temperature is created that can cause the formation of aerosolized material that are disseminated in all the solid angle around the explosion site. As a consequence of the blast power and the meteorological conditions (presence of wind, rain, etc.) this fresh pollution can be disseminated to a distance of many kilometres from its origin. A different stratification in the space of the micro and nanoparticles is possible and logic, but no scientific data are available in a battle theatre.

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Figure 1. Zirconia micro and nanoparticles embedded in a spleen tissue in a patient affected by nonHodgkin lymphoma. The Energy Dispersive spectroscopy identifies the particles composed of Carbon, Zirconium, Oxygen, Chlorine, Iron.

Immediately after the explosions a fresh contamination of the environment occurs that can involve humans and animals for the pollution of air and soil. Grass can act as a repository for the fall-out of this pollution and since it is a food for animals, it can pollute them. That way, animals ingest biodegradable grass containing not-biodegradable and non-biocompatible particles. The analyses we carried out on malformed lambs born inside a firing range confirm the hypothesis of a pollution in the mother and its translocation through the fetal circulation to the embryo. Also the observations on cigarettes and tobacco leaves from Sarajevo immediately after the bombing confirm the existence of a characteristics war pollution on the flora. (The tobacco industry was the only manufacturing plant that still operated during the siege and bombing of Sarajevo because, unlike other industries, it did not need electricity that was very scarce.) Figure 2 shows the so-called war contamination of a tobacco leaf where a particle containing also uranium and thorium is visible. As a conclusion, it is indispensable that the new wars take into account the micro and nanopollution generated by the explosions [24].

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Figure 2. Tobacco leaf surface with particles of environmental dust. The whiter debris is a compound of Phosphorus, Oxygen Carbon, Cerium, Lanthanium, Neodymium, Silicon, Aluminum, Magnesium, Chlorine, Potassium, Thorium, Uranium and Iron.

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4. Verret C, Jutand MA, De Vigan C, Bégassat M, Bensefa-Colas L, Brochard P, Salamon R. Reproductive health and pregnancy outcomes among French gulf war veterans. BMC Public Health. 2008 Apr 28; 8:141. 5. Nelson C. Veterans’ mysterious maladies: studies continue to examine the effects of depleted uranium on returning soldiers. State Legis. 2008 May; 34(5):28–29. 6. Hokama Y, Empey-Campora C, Hara C, Higa N, Siu N, Lau R, Kuribayashi T, Yabusaki K. Acute phase phospholipids related to the cardiolipin of mitochondria in the sera of patients with chronic fatigue syndrome (CFS), chronic Ciguatera fish poisoning (CCFP), and other diseases attributed to chemicals, Gulf War, and marine toxins. J Clin Lab Anal. 2008 22(2):99–105. 7. Golomb BA. Acetylcholinesterase inhibitors and Gulf War illnesses. Proc Natl Acad Sci U S A. 2008 Mar 18; 105(11):4295–300. Epub 2008 Mar 10. 8. Hooper TI, Debakey SF, Nagaraj BE, Bellis KS, Smith B, Smith TC, Gackstetter GD. The long-term hospitalization experience following military service in the 1991 Gulf War among veterans remaining on active duty, 1994-2004. BMC Public Health. 2008 Feb 13; 8:60. 9. Cazoulat A, Lecompte Y, Bohand S, Castagnet X, Laroche P. Urinary uranium analysis results on Gulf war or Balkans conflict veterans, Pathol Biol (Paris). 2008 Mar; 56(2):77–83. 10. Pols H, Oak S. War & military mental health: the US psychiatric response in the 20th century. Am J Public Health. 2007 Dec; 97(12):2132–2142. 11. Levine PH, Richardson PK, Zolfaghari L, Cleary SD, Geist CE, Potolicchio S, Young HA, Simmens SJ, Schessel D, Williams K, Mahan CM, Kang HK. A study of Gulf War veterans with a possible deployment-related syndrome. Arch Environ Occup Health. 2006 Nov–Dec; 61(6):271–278. 12. Barach P, Brautbar N, Richter ED, Friedman L. Latency: an important consideration in Gulf War syndrome. Neurotoxicology. 2007 Sep; 28(5):1043–4; author reply 1044– 1045. 13. Ismail K, Kent K, Sherwood R, Hull L, Seed P, David AS, Wessely S. Chronic fatigue syndrome and related disorders in UK veterans of the Gulf War 1990-1991: results from a two-phase cohort study. Psychol Med. 2008 July; 38(7):953–961. 14. Gatti, A, Montanari S. Approccio bioingegneristico alla sindrome dei Balcani, Fisica in Medicina, 2004, 2:107–114. 15. DU in Bosnia ed Erzegovina in Post Conflict Environmental Assessment, United Nations Environment Programme, Switzerland 2003 (www.unep.org). 16. Technical Report of the Air Force Armament Laboratory – Armament Development and Test Center, Eglin Air Force Base, FL, USA, From October 1977 to October 1978, Project no. 06CD0101 17. Report of Parliamentary Committee of Inquiry into cases of death and serious illness among Italian Military personnel engaged in International peace missions and into the storage conditions of Depleted uranium and its possible use in military exercise on national soil”, 2004, XIV LEGISLATURA, Doc. XXII-bis, no. 4. 18. Report of the “Parliamentary Committee of Inquiry on the cases of death and severe illnesses affecting Italian personnel assigned to military missions abroad, firing ranges and the sites where munitions are stocked, as well as civilian populations in war zones and in areas adjacent to military bases on the national territory, with special attention to the effects of depleted uranium shells and of the dispersion in the environment of nanoparticles of heavy minerals produced by the explosion of warfare material”, 11 October 2006, Doc. XXII-bis, no. 2. Available at: http://www.senato.it/documenti/ repository/commissioni/uranio15/final_report.pdf

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19. Nemmar A., Hoet P.H.M., Vanquickenborne B., Dinsdale D., Thomeer M., Hoylaerts M.F., Vanbilloen H., Mortelmans L., Nemery B. Passage of inhaled particles in to the blood circulation in humans, Circulation. 2002; 105(4):411–441. 20. Gatti A, Montanari S. Nanopathology: The health impact of nanoparticles – Ed. By Pan Stanford - Singapore 2008 (www.worldscibooks.com /nanosci/v001.html). 21. Durakovic A, Horan, D, The quantitative analysis of depleted Uranium isotopes in British, Canadian and US Gulf war Veteran, Mil Med. 2002; 167(8):620. 22. Oberdörster G, Sharp Z, Atudorei V, Elder A, Gelein R, Kreyling W, Cox C., Translocation of inhaled ultrafine particles to the brain. Inhal Toxicol. 2004 June; 16(6–7):437–445. 23. Elder A, Gelein R, Silva V, Feikert T, Opanashuk L, Carter J, Potter R, Maynard A, Ito Y, Finkelstein J, Oberdörster G. Translocation of inhaled ultrafine manganese oxide particles to the central nervous system. Environ Health Perspect. 2006 Aug; 114(8):1172–1178. Erratum in: Environ Health Perspect. 2006 Aug; 114(8):1178. 24. Gatti A, Montanari S, Nanopollution: the invisible fog of future wars, The futurist. 2008 May–June 32–34.

SMARTEN Strategic Management and Assessment of Risks and Toxicity of Engineered Nanomaterials

C. METCALFE Environmental and Resource Studies Trent University Peterborough, Ontario, Canada [email protected] E. BENNETT Intertox, Inc. Salem, Massachusetts, USA M. CHAPPELL, J. STEEVENS Environmental Laboratory U.S. Army Corps of Engineers Vicksburg, Mississippi, USA M. DEPLEDGE Peninsula Medical School Plymouth, UK G. GOSS Department of Biology University of Alberta Edmonton, Alberta, Canada S. GOUDEY HydroQual Laboratories Golder Associates Ltd. Calgary, Alberta, Canada S. KACZMAR O’Brien and Gere Engineers Inc. Syracuse, New York, USA N. O’BRIEN School of Agriculture, Food Science and Veterinary Medicine College of Life Sciences University College Dublin Dublin, Ireland A. PICADO Instituto Nacional de Engenharia Tecnologia e Inovação Lisbon, Portugal

I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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A.B. RAMADAN National Egyptian Environmental and Radiation Monitoring Network Cairo, Egypt

Abstract. Traditional risk assessment procedures are inadequate for predicting the ecological risks associated with the release of nanomaterials (NM) into the environment. The root of the problem lies in an inadequate application of solid phase chemical principles (e.g. particle size, shape, functionality) for the risk assessment of NMs. Thus, the “solubility” paradigm used to evaluate the risks associated with other classes of contaminants must be replaced by a “dispersivity” paradigm for evaluating the risks associated with NM. The pace of development of NM will exceed the capacity to conduct adequate risk assessments using current methods and approaches. Each NM product will be available in a variety of size classes and with different surface functionalizations; probably requiring multiple risk assessments for each NM. The “SMARTEN” approach to risk assessment involves having risk assessors play a more proactive role in evaluating all aspects of the NM life cycle and in making decisions to develop lower risk NM products. Improved problem formulation could come from considering the chemical, physical and biological properties of NMs. New effects assessment techniques are needed to evaluate cellular binding and uptake potential, such as biological assays for binding to macromolecules or organelles, phagocytic activity, and active/passive uptake processes. Tests should be developed to evaluate biological effects with multiple species across a range of trophic levels. Despite our best efforts to assess the risks associated with NM, previous experience indicates that some NM products will enter the environment and cause biological effects. Therefore, risk assessors should support programs for reconnaissance and surveillance to detect the impacts of NM before irreversible damage occurs. New analytical tools are needed for surveillance, including sensors for detecting NMs, passive sampling systems, and improved methods for separation and characterization of NMs in environmental matrices, as well as biomarker techniques to evaluate exposure to NMs. Risk assessors should use this information to refine data quality, determine future risk assessment objectives and to communicate interim conclusions to a wide group of stakeholders.1 1.

Introduction

Engineered nanomaterials (NM) are generally regarded as man-made materials with at least one dimension below 100 nm [6]. Nanoparticles can occur naturally (e.g. ash, colloids, large biomolecules), or can be produced unintentionally (e.g. diesel exhaust), but concern over the potential adverse environmental impacts of 1

Summary of the NATO ARW Working Group discussions.

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nanoparticles has been directed at engineered NMs. Engineered NM can be divided into four different classes: carbon-based materials (e.g., fullerenes), metalbased materials (e.g., gold or titanium dioxide nanoparticles), dendrimers (e.g., nano-sized polymers), and composites (i.e., mixtures of nanoparticles). Nanoparticles typically have different physico-chemical properties compared to their respective bulk material, including different optical properties, thermal behaviour, material strength, solubility, conductivity and catalytic activity [8]. Probably the most significant change in the properties of nanoparticles is the increase in surface to volume ratio [4]. The proportion of atoms at the particle surface increases inversely with particle size, so that the surface properties of nanoparticles can dominate the properties of the bulk material [43]. These particles can also transfer energy to nearby oxygen molecules, which leads to the formation of reactive oxygen species (ROS). Exposure to oxyradicals can lead to cell damage and death [12]. Nanoparticles are similar in size to biological macromolecules such as proteins, DNA and phospholipids, so it is possible that NMs can cause disruptions at the molecular and cellular level. Many other physical and chemical factors can influence the toxicity of NMs, including surface reactivity, the dissolution ratio, and particle shape [42]. 2.

Ecotoxicology and Risk Assessment Techniques

Ecotoxicology is an integrative field that includes evaluations of the environmental fate and the biological effects of chemicals. Assessments of environmental impacts are based on a weight-of-evidence approach that combines environmental chemistry, acute and chronic toxicity testing with single species, evaluation of biomarkers of exposure and effect, and studies of ecosystem-level responses. Laboratory-based bioassays are typically performed using model species representing different feeding strategies and positions in food webs. Multiple species toxicity tests are of value to identify sensitive species and to study the variations in toxic effects across taxonomic groups. Elements of ecotoxicology are also included in methods for ecological risk assessment. In these procedures basic data gathering involves an “Exposure Assessment” and an “Effects Assessment”. In the Effects Assessment, efforts are made to determine the thresholds for toxicity in organisms, and in the Exposure Assessment, efforts are made to determine the concentrations to which organisms may be exposed in the environment. Risk Characterization involves comparing the Exposure Assessment and Effects Assessment data to give an indication of the “risk” of toxic effects occurring among organisms exposed to a chemical. In the context of exposures to NM, risk assessments must be conducted to try to evaluate the environmental hazards associated with new NM products that are to be introduced into the marketplace, or to assess the hazards associated with existing NM products that may already be present in the environment. For new NMs that have not yet been introduced into the marketplace, there are no data regarding the concentrations in the environment, and so the predicted environmental concentrations must be estimated. For NM that have the same elemental or chemical composition,

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but differ in size, shape or surface properties, is not clear whether separate risk assessments will be required for each individual product. Various jurisdictions have called for integrated risk assessment procedures for nanomaterials [6, 35]. In this review, we present a case for a fundamentally different approach to risk assessments for NM released into the environment. The “SMARTEN” approach requires that several elements of traditional risk assessments be abandoned or reformulated in order to address the unique characteristics of NM. 3.

The “Nano-effect” Paradigm

The “nano-effect” may be defined as unique or enhanced NM properties, reactions or biological interactions that occur below a specific particle size threshold. This term implies that such effects are not observed with larger particle sizes. Enhanced properties are associated with decreasing particle size, as a function of increased particle surface area. Incorporation of the principles of the nano-effect into traditional environmental risk assessment procedures requires a paradigm shift from the concepts that are applied to “conventional” environmental contaminants, such as pesticides and industrial chemicals. Table 1 summarizes the novel characteristics of nanoparticles that must be considered in an environmental risk assessment, relative to the parameters that are considered in risk assessments of other classes of contaminants. TABLE 1. Characteristics of NM that must be considered for environmental risk assessments, relative to the characteristics considered for “conventional” classes of contaminants. Characteristic Distribution in water Distribution in porous media Biological availability Cellular uptake Toxic mechanisms Target trophic systems

Nanoparticles Dispersivity Filtration

Other contaminants Solubility Adsorption/desorption

Sorption? Vesicular transport? Steric hindrance, photo-chemical effects, oxidative damage, inflammation Bottom of the food chain?

Lipophilicity Passive or facilitated diffusion Interactions with cellular macromolecules and receptors, narcosis Top of the food chain

3.1.

DISTRIBUTION IN THE ENVIRONMENT

3.1.1.

Interactions

NM may interact in the environment in the following ways: (a) Flocculation: Most NMs tend to readily flocculate. NM dispersions may be temporarily stabilized by severe agitation, such as sonication, but this has the potential to introduce artifacts onto the NM surface. NM dispersions are also stabilized by derivatizing the particle surface by introducing charged groups. However, experimental evidence shows that adding very dilute salt is sufficient for NMs to again readily flocculate. NM dispersions are readily stabilized in the presence of dissolved humic substances. This behavior

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appears linked to the surfactive character of dissolved humic substances, which minimizes NM particle size and poly-dispersivity [9]. Aggregation of carbon nanotubes was inhibited by the addition of humic and fulvic acids [24]. Dissolved organic material commonly occurs at concentrations in natural aqueous systems that are capable of stabilizing NM dispersions [34]. These type of changes may alter the behavior of NMs in water and soils. Nanoparticulate FeO coated with sodium dodecylsulphate was stable in a soil suspension for 14 days, without changes in the particle size distribution [18]. In solid-gas systems (water-limited), the small size of NM makes them readily aerosolized. For example, Murr and Garza [31] showed that so-called cleanburning technologies produce extremely small-sized combustion products (i.e., carbon nanotubes) that easily form aerosols, compared to products created with older technologies. (b) Dissolution: Most NMs are highly insoluble, yet some material may dissolve in the presence of organic chelators, resulting in the release of its metallic constituents into the environment. For example, there is some evidence that FeO nanoparticles are dissolved in the presence of acetate/lactate [33]. (c) Sorption: NMs may readily sorb other constituents in the aqueous phase. For example, Madden et al. [29] observed that smaller FeO particles (7 nm) undergo greater specific adsorption by Cu2+ ions than larger FeO particles (25 nm). NMs themselves may also be sorbed onto soil surfaces. In a sense, NM sorption in a soil is analogous to flocculation of individual NM particles in which NMs are simply “added” to the bulk environmental solids. (d) Transformation and degradations: Most inorganic NMs are used in oxidized forms that are stable under ambient conditions. On the other hand, organic NMs may be degraded when exposed to the environment. For example, fullerenes appear to be spontaneously but slowly oxidized in solution. Ozone has proved much more reactive, however than molecular oxygen to fullerenes [10], which may be a relevant transformation mechanism in advanced treatment systems for water and wastewater. CNTs are highly resistant to degradation (analogous to soil black carbon). However, manufacturers appear to introduce limited functionalization in even so-called non-derivatized CNTs in order to facilitate separation and purification during manufacturing. There is little information available concerning the microbial transformation of NMs. Redox reactions are often mediated by microorganisms; either directly through enzymatic activity, or indirectly through the formation of biogenic oxidants or reductants [28]. Biological modifications, as well as degradation of the surface functionalization may result in modified NM structures and freed constituents. 3.1.2.

Distribution

Perhaps the most important paradigm shift that must be understood for risk assessments of NM relates to the concept of “solubility” of chemicals and the “dispersivity” of nanoparticles in aqueous media. The capacity of nanoparticles to disperse in aqueous media will govern their environmental fate. NM dispersed

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within the aqueous phase are more mobile, and aggregation of NM reduces mobility [17, 24]. This concept is fundamentally different from the solubility paradigm that drives our predictions of the environmental fate and biological availability of other classes of contaminants. Properties such as water solubility and octanol/water partition coefficients (i.e. log Kow) are the basic parameters used to assess the risks associated with exposure to contaminants that are governed by the solubility paradigm. Similar key properties have not yet been identified for risk assessment of nanoparticles, but the characteristics that influence the “dispersivity” of nanoparticles in aqueous media include particle size, charge, speciation, crystallinity, surface area, and adsorbed phase composition. These properties are reviewed elsewhere in this book. The distribution of NM in porous media, such as soils and sediments is also governed by the size, shape and charge distribution of the particles. Filtration of nanoparticles through porous media is influenced by electrostatic interactions between the particles and soil/sediment. However, physical interactions that “sieve” the particles within the media are also an important factor [13]. Data from laboratory experiments indicate that NM may be relatively immobile in soils [41], or they may be relatively mobile [26], depending on the characteristics and size of the NM. 3.2.

BIOLOGICAL AVAILABILITY AND UPTAKE

For small organic molecules, lipophilic compounds are more biologically available than hydrophilic compounds, and uptake of lipophilic compounds occurs through passive diffusion across the cell membrane. For metal cations, uptake occurs as a result of facilitated diffusion of metal-protein complexes across cell membranes. The factors governing the biological availability and cellular transport of NM are less well understood. For fish, it has been suggested that the first step governing biological availability is trapping of NM in the mucous layers of the skin, gills and gut epithelium [20]. It is unlikely that NM are transported by passive or facilitated diffusion across cellular membranes. Indeed, Moore [30] suggests that vesicular transport (i.e. endocytosis, pinocytosis) may be the most important mechanism of NM transport into cells. If this is the case, then some invertebrates (e.g. bivalves) that have a high capacity for vesicular transport within gastrointestinal tissues may be especially susceptible to uptake of NM. Fish are capable of greater uptake by endocytosis in the gut than higher vertebrates. It is clear that some NM can be transported through tissues, including the blood-brain barrier [25]. It is possible that this type of transport occurs through para-cellular routes, such as transport across tight junctions. However, much remains to be learned about the mechanisms of uptake and transport of NM in organisms. 3.3.

MECHANISMS OF TOXICITY

Once NM enter the tissues of organisms or are transported across cell membranes, toxicity is likely to occur principally through one or a combination of four mechanisms (Figure 1). The first mechanism involves the release of the chemical

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constituents from the NM, which produces toxicity through more or less “conventional” processes, such as the release of toxic cadmium ions from CdTe nanoparticles [11, 44]. The other three mechanisms of NM toxicity are typically not observed for the classes of contaminants that are considered when using traditional risk assessment methods. Thus, a second mechanism of NM toxicity is related to the size and shape of the particle, which produces steric hindrances or interferences with macromolecules such as phospholipids, nucleic acids and proteins. For instance, the penetration and toxicity of CdTe quantum dots in vitro in nerve and glial cells was more pronounced with small (2.2 nm diameter) positively charged CdTe than large (5.2 nm diameter), equally charged CdTe. [27]. A third mechanism involves the surface properties of the NM, such as photochemical properties, local electric fields, charge densities, and electronic semi-conductance. These surface properties may result in the formation of oxygen radicals that can damage macromolecules [3, 36], but it is also possible that the surface reactivity of NM could directly disrupt cellular processes, such as energy production in mitochondria [28]. In some cases, it is not clear whether damage as a result of the presence of oxyradicals is due to the direct effects of the NM (i.e. mechanism 3), or due to the indirect effects of macrophage and granulocytes involved in an inflammatory response induced by the presence of the NM in tissues (i.e. mechanism 2). Duffin et al. [16] observed that the extent of lung inflammation depended not only on the particle surface area, but also on the surface reactivity in rats exposed to nanoparticles. The fourth mechanism of toxicity is related to the capacity for NM to act as vectors for the transport of other toxic chemicals to sensitive tissues. In a study with fish (i.e. carp), cadmium accumulation was increased 2.5-fold when TiO2 nanoparticles were added concurrently with cadmium salts [45]. 3.4.

VULNERABLE LOCI IN TROPHIC WEBS

Organisms occupying particular loci in trophic webs may be at increased risk of nanotoxicity. Toxicity tests have been performed with NMs using a variety of test organisms, ranging from bacteria to algae to benthic invertebrates and fish [7, 28]. In many cases, bacteria, plants and invertebrates were the most sensitive organisms to the biological effects of NM. Adams et al. [1] evaluated the toxicity of three photosensitive NMs (FeO, TiO 2, SiO2) to two bacterial species, Bacillus subtilis and Escherichia coli, and the cladoceran, Daphnia magna. The most sensitive species was the suspension feeding cladoceran. In a study of the toxicity of ultrafine TiO2, a green alga, Pseudokirchneriella subcapitata, was the most sensitive species in comparison to rainbow trout and D. magna [42]. In addition, deposit feeders or filter feeders are the most likely organisms to accumulate NM from water, soil and sediments. There is considerable evidence that a range of NM exhibit anti-bacterial activity [32].

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Release of NM constituents

Other contaminants

Physical effects of size and shape

Effects on membranes

Effects on gene expression

Effects on macromolecules

Effects on enzyme activity

Inflammatory Response

Surface reactivity

Vector for other contaminants Light

Figure 1. Mechanisms of toxicity of nanomaterials in organisms.

These results indicate that the biological effects of NMs may be observed first in organisms from lower trophic levels. In conventional risk assessments, more weight is placed on toxicity testing using fish species, and special emphasis is placed on chemicals that show potential for bioaccumulation and biomagnification through food chains. For risk assessments of NM, it is logical to assume that biological effects will be observed among mainly invertebrate species and microorganisms at the lower levels of the food web, or organisms that are important in geochemical and nutrient cycling. For instance, Tong et al. [40] observed that fullerenes impacted the composition of soil microbial communities. 4.

The Strategic Management and Assessment of Risks and Toxicity of Engineered Nanomaterials (SMARTEN)

Risk assessments for NM will require a shift in approach from the methods of exposure assessment and effects assessment that have been used previously for other classes of contaminants [21, 37]. As discussed above, conventional risk assessment procedures are hampered by adherence to paradigms that focus on the solubility and partitioning of chemicals, and fate and exposure pathways that may not be relevant for NM. Extensive use of lethality data for toxicity endpoints may also be inappropriate as our greatest concerns for NM center around sublethal effects, such as genotoxicity and inflammatory responses. The diverse properties of NM and the lack of clearly defined approaches are currently a major impediment to risk assessment of these materials. Among companies producing NM products in Germany and Switzerland, 65% indicated that they do not currently conduct risk assessments [23]. At the moment, there is a relatively short list of NM products in commercial production that require environmental risk assessment, but there is looming on the horizon a much greater

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challenge. As we approach the next few decades, the large investments made in nanoscience around the world will yield a myriad of new products. The penetration of many new NM products into the marketplace will outstrip the ability to perform full risk assessments. Will a change of a single moiety on a given nanomaterial that alters its physical characteristics (e.g. water solubility) but not its functionality require a new risk assessment? Will the same NM product marketed over different size ranges require an individual risk assessment for each size class? The sheer magnitude of new materials will quickly outstrip the capacity of the regulatory agencies and industry to respond in a timely manner, resulting in reduced investment in the technology. Methods are needed to prioritize new NM products and target them for environmental risk assessment, while minimizing the potential for adverse environmental effects. An overall goal should be to provide industry with information on potential mechanisms of toxicity or biological interactions early in the product development cycle. Thus, the specific properties of the product can be tailored to minimize any unwanted effects, while maintaining the commercially desirable properties of the material. This “green-nano” approach will allow industry to develop their products using the best available information; regulators to prioritize particles of concern and provide industry with a structure under which they can introduce new products to the marketplace. One approach to effective risk assessment of new NM products is to more thoroughly examine the existing information available from the manufacturer, such as anticipated volumes of production, the product life cycle and the basic physical and chemical information available for the material. This conceptual model should accommodate non-traditional measures that provide evidence regarding the source, fate, expected media, exposure pathways, and potential receptors. As illustrated in Figure 2, some of this information can be used to make predictions about the likely transport processes into the environment, exposure pathways and receptors for biological effects. In spite of a lack of fate, transport and effects data normally associated with traditional risk assessment, this approach may allow predictions to be made of the environmental hazards of NM. To develop a strategy that provides this required information, it is absolutely necessary that toxicologists and physical scientists work together to identify the physical and chemical properties that make NMs hazardous. In a recent review, Handy et al. [21] identified the need to understand the biological implications of differences in NM shape, size, surface charge, coatings, attached functional groups, core metals, intracellular dissolution, etc. A logical effort will require specific manipulation of the physical characteristics of a singe base class of NM (and repeated for different classes of NMs), followed by toxicity testing with a number of in vitro and in vivo models. Moreover, similar testing should be crossvalidated in at least two independent laboratories to ensure the validity of the results. While this effort seems extensive (and expensive), a logical hypothesis based scientific approach offers a practical mechanism for the provision of baseline data in the near and far term to understand the nature of biological interaction with different NM classes.

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1. Sources

3. Exposure Pathways and Receptors

2. Media and Transport Processes Air

Engineered Nanodevices Reaction Intermediates Production Waste

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Aggregation / UV Degradation

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Ingestion

Figure 2. Conceptual framework for utilizing information from the NM manufacturer to make predictions about the environmental fate and effects of NM.

To address these issues, the SMARTEN approach involves thinking more carefully about the likely fate, exposure and effects of NM, such as considering the characteristics summarized in Table 1. For example, many NM with particle sizes in excess of 4 nm that enter aquatic environments are likely to aggregate and be deposited in sediments or floc layers that overly sediments. This suggests that it might be wiser to investigate the effects of these NM on deposit feeding organisms rather than species that live in the water column. Current laboratory methods that have been developed to provide the data for conventional risk assessments, such as the OECD test methods [14] may not be appropriate for evaluating NM. It may be necessary to develop new test methods, such as assays to evaluate binding to synthetic skin or nano-sensors, or uptake across biofilms. Test systems to evaluate phagocytosis or inflammatory responses as a result of exposure to NM may be more relevant endpoints than acute toxicity tests with whole organism models. 5.

Environmental Surveillance and Reconnaissance

The current regulatory frameworks in North America and Europe that require environmental risk assessments to be conducted prior to the introduction of new chemicals into the marketplace have only been in place for the past 15–20 years. However, there are now several examples of the failure of these regulatory approaches to predict the impacts of chemicals on ecosystems. For instance,

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perfluorinated substances used in fluoropolymer products are accumulating in the environment [38] including in humans [2], despite earlier evaluation of the risks that these substances might pose. Since it appears that current risk assessment protocols are not adequate for the surveillance of conventional chemical classes, it is reasonable to assume that some NM products will be approved for commercial production that will have impacts in aquatic and/or terrestrial ecosystems. Environmental surveillance and reconnaissance programs are required to safeguard against these eventualities. The traditional analytical approaches that are used to detect others classes of contaminants in the environment will not be appropriate and new analytical techniques will be needed for surveillance purposes [22, 39]. Modified and/or novel sampling devices may be needed, such as passive sampling devices or nano-sensors that can be deployed in water, air or soil to detect the presence of NM. Over the years, biomarkers have been developed that are efficient at providing an early warning of deleterious effects on biological systems [15]. Goldberg and Bertine [19] argued that the analysis of the detoxifying enzymes, cytochrome P-450 activity, metallothioneins and estrogenic responses can provide useful information on the effects of contaminants in the aquatic environment. It may be possible to develop a unique set of biomarkers that can be used in surveillance programs to monitor for the biological effects of NM. Toxicogenomics methods may be valuable biomarkers for evaluating exposure to NM. 6.

Overview

The SMARTEN framework can also be integrated into wider concepts of “Environmental Security”, which involves actions that guard against environmental degradation in order to preserve or protect humans and natural resources at scales ranging from global to local in a sustainable manner. Environmental security can best be viewed as a response to one or more of three categories of events: (a) Manmade gradual changes that slowly erode economic and environmental sustainability, and, in some cases, may even be irreversible. (b) Natural catastrophic events that, to some extent, may be predictable, so it is possible to plan response and protection measures. (c) Manmade catastrophic events, which are typically sudden and unpredictable. The different perspectives on environmental security are time, spatial scales (i.e. local, regional, national, trans-national, global). Nanotechnology risk management challenges may be viewed according to the rankings illustrated in Figure 3. The field of environmental security is changing rapidly. Government and academic research in western countries appears to be undergoing a process of reshaping on an annual basis as a result of public health scares and sudden tragic world events. Environmental security will continue to change and evolve as new threats, both manmade and natural, reveal themselves at local, national or international spatial scales. Frameworks for organizing environmental security programs for nanotechnology, therefore, must be flexible and must adapt as either current or

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new challenges and response to those challenges manifest in additional or unforeseen consequences. Assessment and Ranking of Risks Comprehensive, but qualitative Develop a list of potential threats and vulnerabilities

Qualitative to semi-quantitative Rank risks in terms of potential costs (e.g., $, injuries, fatalities, lost opportunities) and time scales over which risks occur

Semi-quantitative to quantitative Detailed analysis of ranked risks in order of ranking

Integrative Integration of risk analyses to identify shared attributes, Common variables, and risk synergies. Re-order Ranking accordingly

Figure 3. Rankings of risks associated with exposure to NM.

In addition to decision frameworks, new or improved technologies and environmental monitoring programs are needed to enhance prevention, response, and mitigation strategies and to anticipate or forecast when threats might occur. In future, environmental surveillance programs must: (a) support real-time decision making, (b) provide accurate and impartial data to avoid human interference, (c) provide for stable, long-term safekeeping of data, (d) support other environmental applications, and (e) support long-term planning schemes such as early warning systems. This paper presents a suggested framework for evaluating the potential environmental and ecological hazards of NM. This framework, referred to as SMARTEN outlines some ideas about the fundamental informational needs. However, with recognition of the wide range of physical and chemical properties of NM, their uses and the rate at which new products and applications are likely to be developed, it is not intended to be a comprehensive “check list” of required testing strategies that must be performed before NM products enter into commercial production. SMARTEN is intended as a starting point of an iterative process by which a NM product can be evaluated. The process features and emphasizes decision points where the new information is combined with and compared against previous information, as well as available data on similar materials. In each step, a conceptual model of the potential hazards of the material is refined, questions and data quality objectives are raised, and a decision is made as to the need for and scope of additional testing. This approach is intended to provide a degree of flexibility that reflects the current degree of uncertainty and the need to provide a means for the expedited evaluation of products of nanotechnology. References 1. Adams, L.K., Lyon, D.Y., McIntosh, A., and Alvarez, P.J. (2006) Comparative toxicity of nano-scale TiO2, SiO2 and ZnO water suspensions, Water Sci. Technol. 54, 327– 334.

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2. Apelberg, B.J., Goldman, L.R., Calafat, A.M., Herbstman, J.B., Kuklenyik, Z., Heidler, J., Needham, L.L., Halden, R., and Witter, F.R. (2007) Determinants of fetal exposure to polyfluoroalkyl compounds in Baltimore, Maryland, Environ. Sci. Technol. 41, 3891–3897. 3. Aryal, B.P., and Neupane, K.P. (2006) Metallothioneins initiate semiconducting nanoparticle cellular toxicity, Small 2, 1159–1163. 4. Banfield J.F., and Zhang, H.Z. (2001) Nanoparticles in the environment, Nanoparticles and the Environment 44, 1–58. 5. Borm, P.J.A., Robbins, D., Haubold, S., Kuhlbusch, T., Fissan, H., Donaldson, K., Schins, R., Stone, V., Kreyling, W., Lademann, J., Krutmann, J., Warheit, D., and Oberdoerster, E. (2006) The potential risks of nanomaterials: a review carried out for ECETOC, Part. Fibre Toxicol. 3, 12–22. 6. Borm, P.J.A., and Hreyling, W. (2004) A need for integrated testing of products in nanotechnology. In: Nanotechnologies: A Preliminary Risk Analysis on the Basis of a Workshop Organized in Brussels on 1–2 March 2004, Health and Consumer Protection Directorate General of the European Commission. Available online at http://europa. eu.int/comm/health/ph_risk/events_risk_en.htm (last accessed 31 July 2008). 7. Boxall, A.B.A., Tiede, K., and Chaudry, Q. (2007) Engineered nanomaterials in soils and water: how do they behave and could they pose a risk to human health? Nanomedicine 2, 919–927. 8. Burleson, D.J., Driessen, M.D., and Penn, R.L. (2004) On the characterization of environmental nanoparticles, J. Environ. Sci. Health Part A 39, 2707–2753. 9. Chappell, M.A., George, A.J., Porter, B.E., Price, C.L., Dontsova, K.M., Kennedy, A.J., and Steevens, J.A. (2008) Surfactive properties of dissolved soil humic substances for stabilizing multi-walled carbon nanotubes dispersions. In: Nanoparticles in the Environment: Implications and Applications, Proceedings of a workshop at Centro Stefano Franscini, Monte Verita, Ascona, Switzerland. 10. Chibante, L.P., and Heymann, D. (1993) On the geochemistry of fullerenes: stability of C60 in ambient air and the role of ozone, Geochim. Cosmochim. Acta 57, 1879–1881. 11. Cho, S.J., Maysinger, D., Jain, M., Roder, B., Hackbarth, S., and Winnik, F.M. (2007) Long-term exposure to CdTe quantum dots causes functional impairments in live cells, Langmuir 23, 1974–1980. 12. Choi, A.O., Cho, S.J., Desbarats, J., Lovric, J., and Maysinger, D. (2007) Quantum dotinduced cell death involves Fas upregulation and lipid peroxidation in human neuroblastoma cells, J. Nanotechnol. 5, 1–2. 13. Christian, P., Von der Kammer, F., Baalousha, M., and Hofmann, T. (2008) Nanoparticles: structure, properties, preparation and behaviour in environmental media, Ecotoxicology 17, 326–343. 14. Crane, M., Handy, R.D., Garrod, J., and Owen, R. (2008) Ecotoxicity test methods and environmental hazard assessment for engineered nanoparticles, Ecotoxicology 17, 421– 437. 15. Depledge, M.H., Amaral-Mendes, J.J., Daniel, B., Halbrook, R.S., Kloepper-Sams, P., Moore, M.N., and Peakall, D.B. (1992) The conceptual basis of the biomarker approach. In: Peakall, D.B., and Shugart, L.R. (eds.), Biomarkers: Research and Application in the Assessment of Environmental Health, NATO ASI Series H: Cell Biology 68, Springer, Berlin, pp. 15–29. 16. Duffin, R., Tran, L., Brown, D., Stone, V., and Donaldson, K. (2007) Proinflammogenic effects of low-toxicity and metal nanoparticles in vivo and in vitro: highlighting the role of particle surface area and surface reactivity, Inhal. Toxicol. 19, 849–856.

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17. Dunphy-Guzman, K.A., Finnigan, M.P., and Barfield, J.P. (2006) Influence of surface potential on aggregation and transport of titanium nanoparticles, Environ. Sci. Technol. 40, 7688–7693. 18. Gimbert, L.J., Hamon, R.E., Casey, P.S., and Worsfold, P.J. (2007) Partitioning and stability of engineered ZnO nanoparticles in soil suspensions using flow field-flow fractionation, Environ. Chem. 4, 8–10. 19. Goldberg, E.D., and Bertine, K.K. (2000) Beyond the mussel watch – new directions for monitoring marine pollution, Sci. Total Environ. 247, 165–174. 20. Handy, R.D., Henry, T.B., Scown, T.M., Johnston, B.D., and Tyler, C.R. (2008a) Manufactured nanoparticles: their uptake and effects on fish – a mechanistic analysis, Ecotoxicology 17, 396–409. 21. Handy, R.D., Owen, R., and Vadsami-Jones, E. (2008b) The ecotoxicology of nanoparticles and nanomaterials: current status, knowledge gaps, challenges, and future needs, Ecotoxicology 17, 315–325. 22. Hasselov, M., Readman, J.W., Ranville, J.F., and Tiede, K. (2008) Nanoparticle analysis and characterization methodologies in environmental risk assessment of engineered nanoparticles, Ecotoxicology 17, 344–361. 23. Helland, A., Scheringer, M., Seigrist, M., Kastenholz, H.G., Weik, A., and Scholz, R.W. (2008) Risk assessment of engineered nanomaterials: a survey of industrial approaches, Environ. Sci. Technol. 42, 640–646. 24. Hyung, H., Fortner, J.D., Hughes, J.B., and Kim, J.H. (2007) Natural organic matter stabilizes carbon nanotubes in the aqueous phase, Environ. Sci. Technol. 49, 179–184. 25. Kashiwada, S. (2006) Distribution of nanoparticles in the see-through medaka (Oryzias latipes), Environ. Health Perspect. 114, 1697–1702. 26. Lecoanet, H.F., Bottero, J-Y., and Wiesner, M.R. (2004) Laboratory assessment of the mobility of nanomaterials in porous media, Environ. Sci. Technol. 38, 5164–5169. 27. Lovric, J., Bazzi, H.S., Cuie, Y., Fortin, G.R.A., Winnik, F.M., and Maysinger, D. (2005) Differences in subcellular distribution and toxicity of green and red emitting CdTe quantum dots, J. Mol. Med. 83, 377–385. 28. Lyon, D.Y., Thill, A., Rose, J., and Alavarez, P.J. (2007) Ecotoxicological impacts of nanomaterials. In: Weisner, M.R., and Bottero, J-Y., (eds.), Environmental Nanotechnology: Applications and Implications of Nanomaterials, McGraw-Hill, New York, pp. 445–479. 29. Madden, A.S., Hocella, M.F.J, and Luxton, T.P. (2006) Insights for size-dependent reactivity of hematite nanomineral surfaces through Cu2+ sorption, Geochim. Cosmochim. Acta 70, 4095–4104. 30. Moore, M.N. (2006) Do nanoparticels present ecotoxicological risks for the health of the aquatic environment? Environ. Int. 32, 967–976. 31. Murr, L.E., and Garza, K.M. (2008) Natural and anthropogenic environmental nanoparticulates: their microstructural characterization and respiratory health implications. In: Nanoparticles in the Environment: Implications and Applications, Proceedings of a Workshop at Centro Stefano Franscini, Monte Verita, Ascona, Switzerland. 32. Neal, A.L. (2008) What can be inferred from bacterium-nanoparticel interactions about the potential consequences of environmental exposure to nanoparticles? Ecotoxicology 17, 362–371. 33. Neely, B., Morris, P.J., Shields, J.P., Sutter, A.G., Bearden, D.W., and Bertsch, P.M. (2007) Microbial growth affects of zinc oxide nanoparticle structure and toxicity. Proceedings of the Annual Meeting of Society for Environmental Chemistry and Toxicology, North America, Milwaukee, WI, USA, 19–23 November 2007. 34. Nowack, B., and Bucheli, T.D. (2007) Occurrence, behavior and effects of nanoparticles in the environment, Environ. Pollut. 150, 5–22.

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SOLID-PHASE CHARACTERISTICS OF ENGINEERED NANOPARTICLES A Multi-dimensional Approach

M.A. CHAPPELL U.S. Army ERDC 3909 Halls Ferry Road Vicksburg, MS 39056, USA [email protected]

Abstract. The challenge associated with determining the environmental fate and risk of engineered nanomaterials lies in understanding the fundamentally associated solid-phase chemistry. The solid phase represents the most complex, most thermodynamically “powerful”, yet the least understood phase among the three phases (solid, liquid, gas) commonly present in environmental systems. This difficulty is compounded by the fact that the nanoparticle size range represents a frontier field in itself in solid-phase chemistry, being the smallest size particles, close to the solid-phase – macromolecule boundary yet the most chemically reactive fraction in solid mixtures. This chapter contains a brief review of some important properties or characteristics of solid phase particles. These properties are presented theoretically as directed interactions among multiple linkages of any single property to another. Selected properties discussed in this chapter include particle charge, crystal structure, surface and bulk speciation, surface area, and adsorption phase composition. This discussion is presented in the context of solid-phase characteristics that influence nanoparticle dispersion stability and potential bioavailability by controlling particle size. 1.

Introduction

The intended purpose of this paper is to review solid phase chemical properties of nanoparticles important for describing their reactivity in environmental systems. In doing so, it is important to realize that the current level of knowledge for solid-phase chemistry is far inferior to that of the chemical knowledge of liquid and gas phase systems. This knowledge gap is attributed to the higher order of complexity of the solid phase and the difficulty of probing these systems. When studying solids, one not only deals with the unique chemistry of the solids’ constituents, but the bonding and coordination environment among the constituents confers a super-molecular complex that exhibits its own unique dynamics, I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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structural order, vibration, electronic, and magnetic properties, to name a few. It is this ability that makes solid phase chemistry so formidable. Yet, it’s the power of this behavior that makes the solid phase the dominant phase controlling geologic and biological chemistry on the Earth’s surface. A major obstacle to deciphering this chemistry lies in probing the solid phase systems. While liquid and gas phases are easily captured and mobilized through elaborate analytical systems, environmental solids are neither fluid nor (typically) transparent. Numerous techniques have been developed to facilitate analysis of solid phases. Chief among these are extraction techniques designed to transfer the solid phase constituents to the liquid phase for ease of analysis. But aside from the elemental analysis and stoichiometries, most of the fundamental information is lost, particularly in terms of the constituent speciation (yet, there do exist some liquid phase techniques for this), coordination environment, long-term order, and macroscopic properties. More often than not, little is preserved of the solids’ inherent chemistry, often relegating atomic constituent speciation to arbitrary delineations based on the properties of the extractant. Adding to the complexity of solid phase analysis is the unique behavior of solids at their surface interface. A solid surface, typically defined as the first few atomic layers at the “outer edge” of the solid, is where most of the solid’s excess energy is exhibited, and potentials are created to promote chemical and physical work. While liquid and gas phase solutes enjoy high degrees of freedom of movement to alleviate energy excesses, the confining environment of solid phases forces these excesses to be transferred to the surface atomic layers. Three common means by which surface excess energy is reduced are (1) phase transitions, (2) surface reconstructions, and (3) adsorption of liquid or gas phases and associated solutes [1]. The relative small size of the surface compared to the rest of the material, termed the “bulk”, makes it difficult to probe as well. Solids exhibit a variety of seemingly unrelated or even contradictory properties so that adequate descriptions based on one or two properties are (if ever) adequate. And in addition, these properties can seem contradictory to each other. For example, a solid can be charged but behave hydrophically. Because the chief defining property of engineered nanomaterials is particle size, this review will focus on the relationship of solid phase properties to the particle size of nanomaterials. Figure 1 shows a theoretical chart proposing relationships between solid phase nanoparticle properties and linkages to particle size, and potentially stabilizing nanoparticle dispersions [2]. This list is by no means complete nor represents all of the properties of nanoparticles, but is presented to the reader as a guide for the following discussion of different solid phase properties. Notice in the schematic that particle size is predominantly represented as a property resulting from other properties. Thus, this review focuses on the other properties viewed as controlling nanoparticle size.

SOLID-PHASE CHARACTERISTICS OF ENGINEERED NANOPARTICLES 113 2

5

3

4

1

8

6

7 Figure 1. Schematic showing hypothetical relationships between solid-phase properties discussed in this review and particle size (controlling dispersion potential). 1 = particle size, 2 = crystal structure, 3 = interior strain, 4 = species, 5 = surface area, 6 = surface charge density, 7 = surface electrical potential, and 8 = adsorbed phase. For this paper, edge sizes are all assumed = 1.

2. 2.1.

Particle Charge CHARGE DEVELOPMENT AND THE DDL

Perhaps, the best understood mechanism for influencing particle size is particle charge. Charge can develop on the surface through different ways, such as at the solid’s crystal edges or functionalization/degradation of the nanomaterial (NM) surface. For example, NMs may be functionalized with external COOH groups, which will deprotonate as the system pH is increased away from the functional group’s pKa. A material that develops charge in this way is termed “variablecharged” because the total charge of the solid phase is affected by the system pH. Charge that arises from internal deficits in the particle bulk composition (such as geologic isomorphous substitution) result in “constant-charge” materials. This review will focus solely on descriptions of variably charged materials. A variably charged surface experiences charge with a change in pH. Classical colloidal theory describes a situation at the solid-solution interface where charge developed on the surface is expressed out into the surrounding solution a certain distance away from the particle. This charged volume around the particle is called the “diffuse double layer” or DDL. The DDL is an electrical field driven by a surface electrostatic potential, ψo [3], which has formed to electro-neutralize the

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surface. In classical theory [4], the DDL is filled with oppositely charged counterions swarming around the wetted surface, attempting to establish electroneutrality – the distribution of cations and anions matching the electrical potential of the interfacial field. The DDL is generally divided into two layers (although more layers have been added on in modern times): The Stern layer and the diffuse layer (Figure 2). The Stern layer is a very thin volume of the solid-solution interface directly adjacent to the surface. The tight complexation of coordinating water and counterions makes the Stern layer rigid and compact, forming what is known as the plane of slippage or the plane of shear [5]. Beyond the Stern layer is a layer composed of moreloosely complexed counterions and coordinating water called the diffuse layer. Here, the influence of ψo pulls oppositely charged counterions toward the surface while diffusion forces allow some same-charged ions to approach the surface as well. Much of the charge-related chemistry that occurs at particle surfaces is controlled by the surface electrical potential and the distance in which that potential “influences” the bulk solution. The extent in which the surrounding solution “feels” ψo decays with distance from the surface. In the Stern layer, ψo decays linearly with distance d to ψd (known as the Stern potential). In the diffuse layer, ψo decays exponentially, beginning with ψd and approaching zero as d → ∞. The decay of ψ0 with distance (x) from the surface (see Figure 2) is mathematically represented as: ψ = ψoexp (-kx)

(1)

where ψ = the surface potential expressed in the DDL with distance from the surface (in nm) and k = inverse DDL thickness, which is equal to: 12

⎛ 8C O ⎞ ⎟⎟ k = ev ⎜⎜ ⎝ DKT ⎠

(2)

where, Co = bulk solution concentration, K = Boltzmann constant, T = absolute temperature, v = valence of ions in solution, D = medium dielectric constant, and e = elementary charge of an electron. Equation 2 predicts that increasing the concentration of counterions in solution (i.e., increasing the ionic strength) will increase k or compress the DDL. With the DDL compressed, the repulsive interactions from overlapping DDLs is minimized, thereby allowing the particle surfaces to come within the distance of the Stern layer, and flocculating through van der Waals forces. 2.2.

DISPERSION/FLOCCULATION PROCESSES

Inter-particle repulsive forces (RF), are influenced by ionic concentration and ionic valence. This response is described in the classical DLVO theory ([6], and references therein) as

SOLID-PHASE CHARACTERISTICS OF ENGINEERED NANOPARTICLES 115

RF =

64 ⎛ vFψ o ⎞ tanh ⎜ ⎟ C o RT exp (− k d ) K ⎝ 4RT ⎠

(3)

where, F = Faraday’s constant, R = molar gas constant, and d = separation between planar surfaces. Equations 1–3 predict that increasing k will reduce RF by reducing the DDL size. Note, however, in Eq. 3, the term CoRT represents the expression for osmotic potential or pressure, showing that DDL size is also affected by the osmotic pressure exerted by the constituents in the DDL. The osmotic potential of the DDL is controlled by the concentration of counterions adsorbed at the solid-liquid interface – which again is controlled by ψo – a property of the surface. Thus, the DLVO theory models changes in repulsive forces via two different mechanisms: One dependent on the properties of the solid, the other dependent on the bulk solution. The net result is the effect of ionic strength on the dispersion potential of differently charged colloids (e.g., one high charge, the other low charge). When increasing the ionic strength of the bulk

ψ°

ψd

or

Counterion conc.

Stern layer ~ plane of slippage

Diffuse layer

Low ionic strength

High ionic strength

Distance from surface (nm) % Dispersion

ZPC

σ2

Bioavailability index

σ1

− 0 + Zeta potential (mV) or pH − pHo Figure 2. (Top) Theoretical plots showing the change in ψ(x) of charged NM particle with distance from the surface and changing solution ionic strength. This plot is overlain with a plot showing the distribution of counterions in the Stern and Diffuse layers. (Bottom) Relationship in the change in zeta potential (ξ) away from the ZPC (the rate of change with respect to surface charge density σ where |σ1| > |σ2|) and increase in particle dispersion and bioavailability. In both plots, it is assumed the solution phase does not contain any specifically adsorbing solutes.

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solution, Eq. 2 predicts the DDL size will reduce equivalently on both particles. Yet, the higher osmotic pressure exhibited in the DDL of the higher charged solid will enhance the pace of dispersion in the particles with higher ψo [7], as represented in Figure 2. 2.3.

ZETA POTENTIAL (ξ) AND ZPC

Zeta potential (ζ in mV) measurements are measures of the magnitude of charge (ψ in Eq. 1) expressed in the DDL at the plane of slippage (x = d). When the charged particle moves through aqueous media, all material within the plane of slippage (also called the plane of shear) “slides” along with it. The plane of shear/slippage is considered analogous to the Stern layer, which is roughly equivalent to the distance of the first hydration shell surrounding a surface. Zeta potential changes can be summarized by a property called the zero point-of-charge or ZPC, which is the pH in which NM zeta potential = 0. If we set ζ ~ ψ0 (given the very short distance of the plane of slippage from the surface), then the relationship between ζ and the ZPC can be simply represented as, ζ ~ ψ0 = 59.2 (pH0 – pH)

(4)

where pH0 = pH of the ZPC and pH = the pH of the bulk solution. For surfaces with mono-functionality, ZPC represents a minimum in which no charge is expressed, analogous a functional group pKa. For surfaces with poly-functional groups, ZPC represents the average of the different surface pKa values. It turns out that as a matter of convenience, solids exhibiting a ZPC will buffer the solution pH at that ZPC at equilibrium. The ZPC provides a simple parameter for estimating NM bioavailability. When ξ = 0, the pH is at the NM’s ZPC. Here, no charge is expressed at the plane of shear, and the particle essentially behaves as a hydrophobic solid. On the other hand, when ξ ≠ 0, the particle is charged at the plane of shear, and exhibits hydrophilic behavior. This information is directly relevant to the bioavailability of NM to organisms. Fully dispersed NMs are expected to exist at their minimum particle sizes in solution. In this form, NMs are expected to be the most bioavailable. At the ZPC, the material is expected to exhibit maximum flocculation. Thus, ZPC provides an appropriate estimation of the dispersion behavior, and bioavailability of NMs. 3.

Surface Charge Density/Distribution

While ZPC gives a relative sense of what pH a variably charged surface will exhibit charge at the plane of shear, the actual magnitude of charge controlling the surface potential is given by the specific charge density. Surface charge density is a measure of the total distribution of charged functional groups normalized to the total surface area of the material. The relationship between the surface electrical potential and the surface charge density (σ) is modeled as:

SOLID-PHASE CHARACTERISTICS OF ENGINEERED NANOPARTICLES 117

σ = [(2/π) CoDKT)]1/2 sinh(vFψ0/2RT)

(5)

For simplicity’s sake, this equation can be reduced by assuming ψ0 is small (<25 mV) and by lumping constants in Eq. 5 into a single variable (λ): σ = (λ1/2Co1/2 D/4π) ψ0

(6)

The above equations simulate the properties of variably charged systems. Since σ is variable, changing pH is evaluated using Eq. 4, then in Eq. 6, ψ0 is held constant as the change in C0 is evaluated on σ. Surface electrical potentials for surfaces with high specific charge densities quickly decay so that zeta potential approaches zero with small changes in ionic strength relative to surfaces with lower specific charge densities, as represented in the bottom plot of Figure 2. Specific charge densities can also impact the interaction of NM with other contaminants or charged surfaces. In theory, a NM possessing a high charge density describes a situation where the charge is dispersed through out the particle surface, so that the particle overall behaves as a hydrophilic material. But, if a NM has a low charge density, it suggests that charged domains exist sporadically on the NM surface, surrounded by other noncharged domains, which are expected to behave hydrophobically. Thus, NMs with lower charge densities may exhibit some surfactive characteristics because of the limited separation of hydrophilic and hydrophobic domains on the surface. This consideration is important from a chemical standpoint as partial surfactive behavior enhances the complexity of environmental domains in which the NM may associate in. 4.

Crystal Structure

Crystallinity is a property that describes the regular, repeating arrangement of constituent elements in a nanomaterial. Crystal structure of a NM can be described by the unit cell, a component of the crystal that represents the whole crystal when stacked together repeatedly [8]. Crystal structures can vary widely depending on the elemental composition, elemental ratios, and packing geometry of constituents. Crystallinity is important because it directly impacts the surface chemistry of solid materials. For example, the catalytic reduction of organic molecules by Feoxides varies with Fe mineralogy [9–11]. Fe-oxides nanoparticles exhibit enhanced reactivity for degrading organics over the larger particles, yet this reactivity exceeds the expectation based on the larger surface area for the smaller sized particles. One contributing factor may be related to conditions that destabilize or add strain to the internal crystal structure of NM relevant to bulk particles [1, 12, 13]. X-ray evidence reveals that the long-range order of ZnS (spheralite) solids degrades as particle size is decreased to the nanoparticle range as evidenced by translational shifts of atomic sheets in the crystal lattice [14]. Internal crystal strain may be alleviated by surface complexation of solvents or specific solute on the nanoparticle surface. For example, dried or MeOH-suspended ZnS nanoparticles showed significant internal strain which was alleviated when particles were resuspended in water [15, 16]. Internal crystal strain may also promote spontaneous

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surface derivitization or functionalization. Gilbert et al. [16] observed decreased interior strain of ZnS nanoparticles with increasing strength of surface solute complexation. As surface sites generally show evidence of increased strain on the crystal structure of surface atoms, interior crystal strain may only increase the surface excess energy of nanoparticles [15]. 5.

Speciation

In general, speciation refers to the electron status of the atomic orbitals of an element. For most elements, atomic species is defined by the element’s valence state, which is an important distinction with respect to toxicity. For As, the common valence states are 0, +3, and +5, each exhibiting their own particular toxicity. But, in solid phase systems, the complexation environment of the material must be also distinguished. For example, Cd(II) is toxic and bioavailable to organisms as a soluble cation or weakly complexed on a surface. However, Cd(II) bound to a Fe-oxide surface is extremely stable [17, 18] and generally nonbioavailable. On the other hand, the growing concern over nano-Ag stems from its ready leaching from fabrics containing the material [19]. This suggests that the nano-Ag is very weakly complexed in the material. Thus, the benefits of nano-Ag may be better realized if it can be added to textiles as a stronger complex. For the graphene-based nanomaterials, speciation generally refers to the surface functionalization, in terms of transformations of the surface carbons. For example, reaction of carbon nanotubes in acid results in the formation of variably 4.5

4

pH

3.5

3

2.5

2 0

100

200

300

400

-1

OH consumed (cmol kg ) Figure 3. Titration of 100 mg l−1 MWCNT (freshly obtained from manufacturer) suspended in 5 mM NaNO3 and titrated in pH-stat mode (180 s equilibrium period) using 50 mM HNO3 [32]. The pKa centered at approx. pH 3.25 is indicative of COOH groups.

SOLID-PHASE CHARACTERISTICS OF ENGINEERED NANOPARTICLES 119

charged COOH groups from cleavage of some of the surface aromatic groups. In this case, speciation has a direct impact on other properties (as represented in Figure 1) such as particle size (which effects dispersion potential), particle morphology, solubility, and particle charge [20–22]. Recent information has revealed the common practice of manufacturers to partially functionalize the surface of carbon nanotubes to facilitate separation and purification by acid precipitation (Figure 3). The net speciation of a nanomaterial is, in effect, the mean speciation of the smaller domains on the material’s surface. Thus, nanomaterial speciation is influenced by crystal structure and surface morphology. For example, edge sites on clays and Fe-oxides exhibit a higher pKa than other sites on the material [23, 24]. While the reason for this behavior is not known, it is suspected to be associated with the higher water coordination number and possibly greater stability of OH groups at the high-angle sites. 6.

Surface Area

Particle surface area is defined as area of particle surface per mass of particle. In Figure 1, surface area is represented as the only characteristic of nanoparticles influenced by particle size. As Oberdörster et al. [25] explain, particle surface area increases exponentially as particle size decrease below 100 nm. This relationship is important in controlling the chemical equilibrium of systems. If the nanoparticle size is stable, NM particle chemistry could dominate the chemistry of the mixed solid phase system because it possesses the dominant surface area, even at dilute proportions of the total. However, if NM aggregates due to the composition of the system, then surface area and control of the equilibrium is minimized unless the concentration of the total NM is increased. For this reason, it is essential that NM particle size be measured before and after experiments. TABLE 1. Relationship between crystal structure, atomic composition, and surface area of iron oxide minerals. (Information taken from Schwertmann and Cornell [26].) Mineral name Hematite Magnetite Goethite Lepidocrocite Ferrihydrite Feroxyhite Akaganeite

Formula α-Fe2O3 Fe3O4 α-FeOOH γ-FeOOH variable δ´-FeOOH β-FeOOH

Crystal system Trigonal Cubic Ortho rhombic Ortho rhombic Trigonal Hexagonal Monoclinic

Surface area (m2 g−1) 30–90 4 20–130 70–80 300 200 30

NM surface area is also influenced by the material’s crystal structure (Figure 1). Table 1 shows how the Fe-oxide minerals with similar compositions can have very different surface areas because of their differences in crystallinity. Surface area also serves as the denominator in charge density (σ) calculation. Decreasing particle size is expected to decrease the charge density of the particle and according to

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Figure 2, reduce the degree in which the NM flocculates with small changes in (pH0–pH). 7.

Adsorbed Phase

A very common way to probe the surface of any material is to study its sorption abilities. Sorption of solutes with different properties (e.g., polarity, functional group composition) provides the basis for arbitrary classification of sorbents by the shape of the sorption isotherm. However, interpretation of sorption behavior is complicated by the fact that the adsorbed phase promotes transitions in the solid phase, such as influencing crystal strain. These complexities are experienced at the simplest levels. For example, a common method for dispersion environmental solids is to saturate the surface with Na+ cations. The high osmotic coefficient (Eq. 3) generated by packing the DDL with the Na osmolyte causes the DDL to swell, and force individual particles apart through inter-particle repulsions. Thus, saturating the adsorbed phase of the solid with Na forces the materials into dispersion by decreasing the particle size. On the other hand, insufficient control of the adsorbed phase can induce flocculation of the particles. Table 2 lists a selection of articles taken from the toxicology literature. Out of the sixteen articles, 13 record the NM size before experiments while four record the size after the experiments. In all cases, the final particle sizes are different from the initial sizes – a result that is attributable to the adsorbed phase on the particle as affect by the system matrix. TABLE 2. Example of the results of a brief survey of the scientific literature with respect to the analysis of nanoparticle size in the experimental matrix. Nanomaterial ZnO

30 nm

Size in system OD: 102 nm to several micrometers

Lipid coated CNT

~1.2 nm

−

SWCNT

OD: 1 nm Length: several micrometers 10–200 nm Aggregates

−

−

OD: 1.1 nm Length: 5– 30 um In SDS OD: 190– 800 nm

−

Partially OHnC60 SWCNT

Initial size

Test matrix 0.01 M Ca(NO3)2 in Milli-Q water, pH7.5 w/2 mM PIPES MHW in 0–20 mg l−1

Dispersion treatment Teric N30

Reference Franklin et al., 2007

Lysophopha tidylcholine /sonicate

Roberts et al., 2007

Mouse serum

Brief shearing/so nication

Lam et al., 2004

Milli-Q water, RHW-freshwater or Artificial sea water (35 ppt) Dechlorinated tap water

Stirring

Oberdorster et al., 2005

Sodium dodecyl sulphate and sonication

Smith et al., 2007

SOLID-PHASE CHARACTERISTICS OF ENGINEERED NANOPARTICLES 121 Nanomaterial

Initial size

nC60

10–200 nm

Ag(0)

5–46 nm ~diameter 11.6 nm

SWCNT

−

Alumina

Size in system −

Test matrix RHW

Dispersion treatment THF or stirring Sodium citrate and sodium borohydride

Reference

Templeton et al., 2006

Zhu et al., 2006 Lee et al., 2007

Stable in 10 nM NaCl but aggregated in 100 mM NaCl −

Incubated egg water 1.2 nM NaCl

~13 nm N4+: 201 nm particles aggregates size OD: 1 nm Length: 102 nm nC60: 1020nm TiO2: 30nm

−

Milli-Q water

Incorporatio n of hydroxyl and carboxylic acid functional groups −

−

Buffered BSA

Sonication

Leeuw et al., 2007

−

MHRW

Lovern et al., 2007

nC60

−

50–300 nm

Milli-Q water w/instant ocean

nC60

30–100nm aggregates OD: Filtered, 10–20 nm Sonicated, 20–100 nm Filtered TiO2, 30 nm Sonicated TiO2, 100– 500 nm 39.4–42,000 nm

−

RHW

THF which was filter off and evaporated three times Stirring and sonication or THF THF

−

MRHW

THF or sonication

474 nm in eggs & oil droplets, 39.4 nm in yolk & gallbladder −

Medaka eggs in ERM at pH 7.2

−

Kashiwada, 2006

Filtered seawater

Agitation

Templeton, 2006

SWCNT nC60, TiO2

TiO2 and nC60

Fluorescent latex particles

SWCNT AP-SWCNT

−

30 g l−1 seawater

Yang and Watts, 2005

Henry et al., 2007 Oberdorster, 2004 Lovern and Klaper, 2005

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Franklin, N.M., N.J. Rogers, S.C. Apte, G.E. Batley, G.E. Gadd, and P.S. Casey. 2007. Comparative toxicity of nanoparticulate ZnO, bulk ZnO, and ZnCl2 to a freshwater microalga (Pseudokirchneriella subcapitata): The importance of particle solubility. Environ. Sci. Technol. 41:8484-8490.; Henry, T.B., F.-M. Menn, J.T. Fleming, J. Wilgus, R.N. Compton, and G.S. Sayler. 2007. Attributing effects of aqueous C60 nano-aggregates to tetrahydrofuran decomposition products in larval zebrafish by assessment of gene expression. Environ. Health Perspectives 115:1059-1065.; Kashiwada, S. 2006. Distribution of nanoparticles in the see-through medaka (Oryzias latipes). Environ. Health Perspectives 114:1697-1702.; Lam, C.-W., J.T. James, R. McClusky, and R.L. Hunter. 2004. Pulimonary toxicity of single-walled carbon nanotubes in mice 7 and 90 days after intratracheal instillation. Toxicol. Sci. 77:126-134.; Lee, K.J., P.D. Nallathamby, L.M. Browning, C.J. Osgood, and X.-H.N. Xu. 2007. In vivo imaging of transport and biocompatibility of single silver nanoparticles in early development of zebrafish embryos. Nano 1:133-143.; Leeuw, T.K., M. Reith, R.A. Simonette, M.E. Harden, P. Cherukuri, D.A. Tsyboulski, K.M. Beckingham, and R.B. Weisman. 2007. Single-walled carbon nanotubes in the intact organism: Near-IR imaging and biocompatibility studies in Drosophilia. Nano Lett. 7:2650-2654.; Lovern, S.B., and R. Klaper. 2006. Daphna magna mortality when exposed to titatium dioxide and fullerene (C60) nanoparticles. Environ. Toxicol. Chem. 25:1132-1137.; Lovern, S.B., J.R. Strickler, and R. Klaper. 2007. Behavior and physiological changes in Daphnia magna when exposed to nanoparticle suspensions (titanium dioxide, nano-C60, and C60HxC70Hx). Environ. Sci. Technol. 41:4465-4470.; Oberdorster, E. 2004. Manufactured nanomaterials (fullerenes, C60) induce oxidative stress in the brain of juvenile largemouth bass. Environ. Health Perspectives 112:1058-1062.; Oberdörster, E., S. Zhu, T.M. Blickey, P. McClellan-Green, and M.L. Haasch. 2005. Ecotoxicology of carbon-based engineered nanoparticles: effects of fullerene (C60) on aquatic organisms. Carbon 44:1112-1120.; Roberts, A.P., A.S. Mount, B. Seda, J. Souther, R. Qiao, S. Lin, P.C. Ke, A.M. Rao, and S.J. Klaine. 2007. In vivo biomodification of lipid-coated carbon nanotubes by Daphnia magna. Environ. Sci. Technol. 41:2657-2658.; Smith, C.J., B.J. Shaw, and R.D. Handy. 2007. Toxicity of single walled carbon nanotubes to rainbow trout, (Oncorhynchus mykiss): Respiratory toxicity, organ pathologies, and other physiological effects. Aquatic Toxicol. 82:94-109.; Templeton, R.C., P.L. Ferguson, K.M. Washburn, W.A. Scrivens, and G.T. Chandler. 2006. Life-cycle effects of singlewalled carbon nanotubes (SWNTs) on an estuarine meiobenthic copepod. Environ. Sci. Technol. 40:7387-7393.; Yang, L., and D.J. Watts. 2005. Particle surface characteristics may play an important role in phytoxicity of alumina nanoparticles. Toxicol. Lett. 158:122-132.; Zhu, S., E. Oberdörster, and M.L. Haasch. 2006. Toxicity of an engineered nanoparticle (fullerene, C60) in two aquatic species, Daphnia and fathead minnow. Marine Environ. Res. 62:S5-S9.

A number of papers have shown that NM dispersions can be stabilized by addition of surfactants or soluble humic materials [27–31]. Our recent work [2] demonstrated that NM particle size and polydispersivity minimized when saturated with adsorbed surfactant. This saturation point was predictable by the surfactant’s CMC based on the equilibrium concentration of surfactant in solution because the hydrophobic moiety preferentially adsorbed to the graphene surface of the carbon nanotubes tested. Humic materials were also shown to stabilize CNT dispersions according to their ability to imitate surfactive behavior. Humic material with highly carbohydrate-based carbon domains were shown to be poorly surfactive. Acknowledgements Assistance with titration analysis in Figure 3 was provided by Aaron George SpecPro, Inc., Huntsville, AL) and Cynthia Price (US Army ERDC). Table 2 was prepared by Jen Chappell (SpecPro, Inc., Huntsville, AL).

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References 1. H. Zhang; J. F. Banfield, Thermodynamic analysis of phase stability of nanocrystalline titania. J. Mater. Chem. 1998, 8, 2073–2076. 2. M. A. Chappell; A. J. George; B. E. Porter; C. L. Price; K. M. Dontsova; A. J. Kennedy; J. A. Steevens, Surfactive properties of dissolved soil humic substances for stabilizing multi-walled carbon nanotubes dispersions. Environ. Pollut. 2008 (submitted). 3. J. W. Bowden; A. M. Posner; J. P. Quirk, Ionic adsorption on variable charge mineral surfaces. Theoretical-charge development and titration curves. Aust. J. Soil Res. 1977, 15, 121–136. 4. G. Uehara; G. Gillman, The Mineralogy, Chemistry, and Physics of Tropical Soils with Variable Charged Clays. Westview Press: Boulder, CO, 1981. 5. A. M. James, Molecular aspects of biological surfaces. Chem. Soc. Rev. 1979, 8, 389– 418. 6. V. P. Evangelou, Environmental Soil and Water Chemistry: Principles and Applications. Wiley: New York, 1998. 7. H. S. Arora; N. T. Coleman, The influence of electrolyte concentration on flcculation of clay suspensions. Soil Sci. 1979, 127, 134–139. 8. D. F. Shriver; P. Atkins; C. H. Langford, Inorganic Chemistry. 2nd edition. W.H. Freeman: New York, 1998. 9. T. B. Hofstetter; C. G. Heijman; S. B. Haderlein; C. Holliger; R. P. Schwarzenbach, Complete reduction of TNT and other (poly)nitroarmatic compounds under ironreducing subsurface conditions. Environ. Sci. Technol. 1999, 33, 1479–1487. 10. T. B. Hofstetter; R. P. Schwarzenbach; S. B. Haderlein, Reactivity of Fe(II) species associated with clay minerals. Environ. Sci. Technol. 2003, 37, 519–528. 11. K. Pecher; S. B. Haderlein; R. P. Schwarzenbach, Reduction of polyhalogenated methanes by surface-bound Fe(II) in aqueous suspensions of iron oxides. Environ. Sci. Technol. 2002, 36, 1734–1741. 12. H. Zhang; B. Gilbert; F. Huang; J. F. Banfield, Water-driven structure transformation in nanoparticles at room temperature. Nature 2003, 424, 1025–1029. 13. J. M. McHale; A. Auroux; J. Perrotta; A. Navrotsky, Surface energies and thermodynamic phase stability in nanocrystalline aluminas. Science 1997, 277, 788–791. 14. B. Gilbert; F. Huang; H. Zhang; G. A. Waychunas; J. F. Banfield, Nanoparticles: Strained and stiff. Science 2004, 305, 651–654. 15. B. Gilbert; H. Zhang; F. Huang; J. F. Banfield; Y. Ren; D. Haskel; J. C. Lang; G. Srajer; A. Jurgensen; G. A. Waychunas, Analysis and simulation of the structure of nanoparticles that undergo a surface-driven structural transformation. J. Chem. Phys. 2004, 120, 11785–11795. 16. B. Gilbert; F. Huang; Z. Lin; C. Goodell; H. Zhang; J. F. Banfield, Surface chemistry controls crystallinity of ZnS nanoparticles. Nano Lett. 2006, 6, 605–610. 17. G. M. Hettiarchachchi; J. A. Ryan; R. L. Chaney; C. M. La Fleur, Sorption and desorption of cadmium by different fractions of biosolids-amended soils. J. Environ. Qual. 2003, 32, 1684–1693. 18. G. M. Hettiarchachchi; K. G. Scheckel; J. A. Ryan; S. R. Sutton; M. Newville, μXANES and μ-XRF investigations of metal binding mechanisms in biosolids. J. Environ. Qual. 2006, 35, 342–351. 19. T. M. Benn; P. Westerhoff, Nanoparticle silver released into water from commercially available sock fabrics. Environ. Sci. Technol. 2008, 42, 4133–4139.

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20. A. J. Kennedy; M. S. Hull; J. A. Steevens; K. M. Dontsova; M. A. Chappell; J. C. Gunter; C. A. Weiss, Jr., Factors influencing the partitioning and toxicity of nanotubes in the aquatic environment. Environ. Chem. Tox. 2008 (in press). 21. M. A. Chappell; A. J. George; B. E. Porter; C. L. Price; K. M. Dontsova; A. J. Kennedy; J. A. Steevens, Surfactive properties of dissolved soil humic substances for stabilizing multi-walled carbon nanotubes dispersions. In Nanoparticles in the Environment: Implications and Applications. Centro Stefano Franscini: Monte Verita, Ascona, Switzerland, 2008. 22. C. M. Sayes; J. D. Fortner; W. Guo; D. Lyon; A. M. Boyd; K. D. Ausman; Y. J. Tao; B. Sitharaman; L. J. Wilson; J. B. Hughes; J. L. West; V. L. Colvin, The differential cytotoxicity of water-soluble fullerenes. Nano Lett. 2004, 4(10), 1881–1887. 23. V. P. Evangelou; M. Marsi, Stability of Ca2+, Cd2+, and Cu2+-illite complexes. J. Environ. Sci. Health A 2002, 37(5), 811–828. 24. J. R. Rustad; A. R. Felmy, The influence of edge sites on the development of surface charge on goethite nanoparticles: A molecular dynamics investigation. Geochim. Cosmochim. Acta 2005, 69, (6), 1405–1411. 25. G. Oberdörster; E. Oberdörster; J. Oberdörster, Nanotoxicology: An emerging discipline evolving from studies of ultrafine particles. Environ. Health Perspect. 2005, 113, 823–839. 26. U. Schwertmann; R. M. Cornell, Iron Oxides in the Laboratory: Preparation and Characterization. Wiley-VCH Verlag GmbH: Weinheim, Germany, 2000. 27. Q. Chen; C. Saltiel; S. Manickavasagam; L. S. Schadler; R. W. Siegel; H. Yang, Aggregation behavior of single-walled carbon nanotubes in dilute aqueous suspension. J. Colloid Interface Sci. 2004, 280(1), 91–97. 28. L. K. Duncan; J. R. Jinshcek; P. J. Vikesland, C60 colloid formation in aqueous systems: Effects of preparation method on size, structure, and surface charge. Environ. Sci. Technol. 2008, 42, 173–178. 29. B. Espinasse; E. M. Hotze; M. R. Wiesner, Transport and retention of colloidal aggregates of C60 in porous media: Effects of organic macromolecules, ionic composition, and preparation method. Environ. Sci. Technol. 2007, 41(21), 7396–7402. 30. H. Hyung; J. D. Fortner; J. B. Hugues; J.-H. Kim, Natural organic matter stabilizes carbon nanotubes in the aqueous phase. Environ. Sci. Technol. 2007, 41, 179–184. 31. M. F. Islam; E. Rojas; D. M. Bergey; A. T. Johnson; A. G. Yodh, High weight fraction surfactant solubilization of single-wall carbon nanotubes in water. Nano Lett. 2003, 3, 269–273. 32. M. Chappell, A. George, B. Porter, C. Price, R. Kirgan, K. Dontsova, A. Kennedy, and J. Steevens. Microstructure and solid-phase chemistry of multi-walled carbon nanotubes in the environment. In: MidSouth SETAC Annual Meeting, Environmental Security: Coastal Protection, Natural Resources, and Emerging Materials, Vicksburg, MS, 14–16 May, 2008.

NANOMATERIAL TRANSPORT, TRANSFORMATION, AND FATE IN THE ENVIRONMENT A Risk-Based Perspective on Research Needs

G.V. LOWRY Carnegie Mellon University, Civil & Environmental Engineering Pittsburgh, PA 15213, USA [email protected] E.A. CASMAN Carnegie Mellon University, Engineering and Public Policy Pittsburgh, PA 15213, USA [email protected]

Abstract. The existing approaches for assessing the environmental risks of nanomaterials need to be adapted to the behaviors of nanomaterials before they can provide reliable information. Assessing or predicting these risks requires understanding of the potential sources of these materials to the environment, their distribution once released, their transformations and persistence, and their potential negative effects. In this chapter we discuss the potential sources of nanomaterials released to the environment, then we present potential physical and biogeochemical processes that can affect the fate, transport, and transformations of manufactured nanomaterials released into the environment. Finally, we discuss modifications of existing risk analysis methods needed and the most important data gaps that must be filled in order to assess the environmental risks associated with these materials. 1.

Introduction

Nanomaterials are just now emerging into the global marketplace. They are found in consumer goods, in cosmetics and health care products, recreational equipment, paint, plastics, and electronics. The two most common nanomaterials currently used in consumer goods are silver nanoparticles and titanium dioxide nanoparticles. Silver nanoparticles are antibacterial. They appear in humidifiers, washing machines, cutting boards, and even in food packaging. Titanium dioxide, which is a photoactive surface coating, is found in cosmetics, paint, and batteries and is likely the most prevalent manufactured nanomaterial. Many additional products are being developed, and it is reasonable to assume that as goods penetrate the markets, their nanomaterial components will enter the biosphere in large numbers. A 2004 report by Lux Research [9] entitled “Sizing Nanotechnology’s Value Chain” estimates that the value of nano-intermediates and nano-enabled products in 2008 is I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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approximately US$0.2 trillion. This is projected to be more than US$2.5 trillion by 2014. Even if a fraction of this estimate were to be realized, substantial quantities of nanomaterials will enter the environment in the coming decade. Given the impending releases of these materials, their known (and predicted) biological activities, and our current ignorance of their effects on natural systems, it is prudent to examine the risks to the environment and to human health associated with these materials. Currently there are many unanswered questions associated with their releases, their fate, transport, and transformation in the environment, and in their potential toxic effects. It is currently impossible to conduct a traditional environmental risk assessment for these materials, which requires a well developed understanding of all these factors. A traditional environmental risk assessment starts with a significant observed negative effect. None have been reported to date. Moreover, regulators have expressed the desire for a tool that will predict an as yet unidentified negative effect. Just as there is no algorithm in the engineering toolkit that could have linked DDT to thinning bald eagle egg shells a priori, we don’t know enough about nanomaterials or biology to predict such a specific impact. In the near term, regulators will have to resign themselves to more approachable goals – to advance the science so at least we can predict with some confidence where nanoparticles go in the environment, whether they persist, in what form, if they accumulate, their interactions with other substances, and the kinds of biological effects that are consistent with their chemical properties. We must begin to develop new frameworks for describing the potential risks associated with these materials. We must integrate laboratory results into a risk analytic framework as they are generated. Such preliminary risk analyses will help to identify and prioritize the most relevant data gaps that must be filled before a traditional risk assessment is feasible. In this chapter we focus mostly on the physical and biogeochemical processes that can affect the fate, transport, and transformations of manufactured nanomaterials released into the environment, and discuss the most important data gaps that must be filled in order to assess the environmental risks potentially associated with these materials. 2.

Sources of Nanomaterials and Potential for Exposure

Many naturally occurring nanomaterials exist in the environment at concentrations many orders of magnitude greater than any manufactured nanomaterial. Biological systems have evolved coping mechanisms for recognizing and clearing these particles, whereas manufactured nanomaterials present new challenges for environmental systems. This is especially true if the manufactured nanomaterials do not have any natural analog, e.g. quantum dots and the heavy metals they contain. Further, man-made nanomaterials are often coated with a surfactant, polymer, or polyelectrolyte. The combination of the particle and the organic surface coating, often used to make the materials water soluble or biocompatible, are not likely to have natural analogs.

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In some cases, manufactured nanomaterials may be used in products where they would enter the environment as individual nanoparticles or small agglomerates (e.g., silica nanoparticles used as solid lubricants, fullerenes added to cosmetics, metal and metal oxide nanoparticles injected for groundwater remediation). In other cases, manufactured nanomaterials may be incorporated into consumer products as composites or mixtures that would likely initially be released to the environment in an encapsulated form (e.g., nanotube composites used to make tires, tennis rackets, and video screens). The form of the released nanomaterials is an important consideration for risk assessment and risk prediction. Accidental releases to the environment may come from point sources such as nanomaterial manufacturing facilities, from the waste products from these facilities, from intermediates and finished products containing them. Products disposed of in landfills may serve as point sources of nanomaterials into the environment. Nanomaterials used for targeted drug delivery will be excreted and sent to wastewater treatment plants which may ultimately serve as point sources of nanomaterials. With appropriate controls, releases of nanomaterials from these point sources should be minimal, but accidental releases are possible. As with many environmental contaminants, non-point sources of nanomaterials will be the most difficult to control and will likely be the majority of nanomaterial releases to the environment. Many release mechanisms are possible including wet deposition of particles from the atmosphere, attrition from products containing nanomaterials, storm-water runoff from manufacturing sites or city roads and highways. As nanotubes find their way into automobile tires and brake pads, attrition from these products will constitute a large source of nanomaterials into the environment. Recent published works are developing the understanding of how the properties of materials influence their transport, transformation and fate in the environment. The locations, concentrations, and properties of the nanomaterials released to the environment are all factors that will affect their distribution, concentration, and ultimately their effects on the health of an ecosystem. Many nanomaterials will transform either physically or biologically once released to the environment (e.g., aggregation, loss of surface coatings, photolysis, etc.) These transformations will affect the distribution and concentration of these materials in the subsurface, and ultimately will control the magnitude of the negative (or positive) effects that these materials may have on the environment. A conceptual model of these processes is shown in Figure 1. We will have to understand the sources of the materials, the characteristics of those materials, as well as the transformations of those materials and the effect on the surface properties of those materials in order to predict or assess the risks that those materials may pose. Given the great variety in nanomaterials properties, size, morphology, chemical composition, and the even greater variability in the types of surface coatings, we will have to understand these processes from first principles in order to generalize these findings across classes or types of nanomaterials.

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Finished Products Raw NM

Intermediate products Biotic

Releases NM Properties

Transformations & Degradation

Modified NM Properties

Abiotic Distribution, Concentration, and Effects Figure 1. Schematic of processes affecting the distribution, concentration, and effects of nanomaterials released to the environment.

3.

Traditional Risk Assessment and the Need for a New Framework for “Risk Prediction”

Traditional risk assessment starts with an observed effect on a specific organism caused by a known pollutant. The emissions of the pollutant are quantitatively tracked through the relevant parts of the environment, partitioned, degraded, transformed and bioamplified, as appropriate, so exposure, dose, and morbidity estimates for the affected species can be calculated. Currently for nanomaterials, every part of this process is uncertain, from the emissions and their rates of entry into the environment, through to the endpoint, e.g. toxicity to an organism, an ecosystem, an acute effect, an evolutionary effect, or disruption of an ecosystem service. Nanomaterials do not behave like conventional chemicals. Properties, such as solubility and octanol/water partition coefficients – so useful for describing the movement of conventional materials in the environment in traditional risk assessment – do not capture the behavior of nanomaterials, which congregate at interfaces. Naturally occurring and anthropogenic chemicals in the environment can alter a nanomaterial’s mobility, toxicity, bioavailability, and visa versa, invalidating single-chemical transport models. Matrix effects may be the most important and complex problem of modeling nanomaterial fate in the environment, as the matrix in which they are embedded in their initial product life imparts properties that change as the matrix is degraded.

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Traditional risk assessment requires specific end points for analysis. However, for nanomaterials scientists are more confident talking about the properties of the nanomaterials that give them their potential biological activity (ability to transport electrons and create reactive oxygen species, penetration of the blood brain barrier, immunostimulation, ability to carry other molecules, photo-catalytic activity) in regards to toxicity testing (in many cases these are the same properties that make nanoparticles so useful in their intended applications), rather than real ecotoxicity end-points. It is currently unclear as to when these presumptive mechanisms of biotoxicity rise to a level where precaution would dictate controls on nanomaterials, especially as effects observed under laboratory conditions are often not reproducible in nature. For example, C60 was shown to be bactericidal in pure cultures, however, addition of C60 to an extremely high concentration (1 g/kg or 1,000 ppm added to a real soil) showed no effects on microbial survival and DGGE analysis suggested limited effect on the diversity of the most prevalent organisms. Despite impressive knowledge gaps, existing risk assessment tools may provide some insight. A recent paper by Mueller and Nowack [10] is a good example of a high level (in terms of abstraction) estimate of potential environmental risk from nanomaterials. These authors estimated the expected average concentrations of nanomaterials in the environment at the national level using a conceptual compartmental model. By comparing these concentrations to published no-effects levels for those materials, a rough risk ranking of the materials was possible. We might quibble with every assumption in the paper, but the risk ranking of the three nanomaterials studied seems nevertheless plausible. Such a highly aggregated result cannot be used in a standard-setting context, but demonstrates the creative use of judgment and fragmentary data to improve understanding. Another risk ranking method, based on certain properties of the nanomaterials, is proposed by Linkov, Figueira and Merad in this volume. These authors argue that such a risk ranking should be used to prioritize nanomaterials for further study, an urgent need, considering the proliferation of new nanomaterials. To move the field forward, other risk frameworks capable of dealing with preliminary data and missing information will have to be developed. The problem can and should be approached from many angles, in anticipation of the time when we have sufficient understanding to build and parameterize more traditional risk assessment models. One such framing is the probabilistic network. These models track probability rather than mass and are particularly useful for reasoning under uncertainty. Their structure can integrate expert judgment with empirical observation and accommodates updating as new data become available. 4. 4.1.

Primary Data Gaps for Risk “Prediction” and Assessment BIOLOGICAL END-POINT

Assessing the risks of nanomaterials relies, at the very least, on understanding the processes leading to exposure of organisms to the released materials, and on the

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negative effects that they may have on an organism (toxicity). Exposure and toxicity are not enough, however, to predict environmental risks of nanomaterials to the environment. Some understanding of the effect of these materials at an ecosystem level must also be determined. This requires a good understanding on how the elements of an ecosystem function synergistically, and an understanding of the natural redundancy existing in ecosystems to help maintain homeostasis with respect to ecosystem services. This is currently out of range of our abilities, and therefore risk prediction is a distant goal. Regardless, there are many primary data gaps regarding the transport, transformation, and fate of nanomaterials that can help lay the foundation for risk prediction, even in the absence of a systems level understanding of ecosystem function. These data gaps are outlined briefly here. 4.2.

TRANSPORT

Once released in to the environment, nanomaterials may be transported away from the point of release and be redistributed in the environment, or may not travel significantly away from the point of release. Predicting the concentration of nanomaterials in the environment requires some understanding of their transport away from the point of release. If transport is facile, the materials may distribute widely in the environment, and average concentrations would be relatively low. If they do not readily migrate from the point of release, concentrations may be locally high, forming “hot spots”. Thus the transport of nanomaterials in the environment is inseparable from the risk prediction. Guestimates regarding the transport of nanomaterials are insufficient. We need a better understanding of the factor controlling the transport of nanomaterials in the environment in order to predict the risks they may pose. Aggregation and deposition are the primary processes affecting transport of transformation of nanomaterials in the environment. Many nanomaterials are produced as distinct particles with diameters of 1–100 nm, but these particles aggregate to form much larger, colloidal aggregates in water. For example, 20-nm titanium dioxide particles form aggregates in water and in biological fluids [7]. Similarly, fullerene C60 and hydroxylated C60 (fullerols) forms aggregates ~20– 200 nm in diameter in pure water which may be highly stable, showing little propensity to continue to aggregate or to disaggregate over periods of several months or more [1]. The basis for this stability is not clear. Hydrophobicity or chemical bonding between nanoparticles can also promote their aggregation in water. The rate and extent of aggregation depends on ionic strength, ionic composition, and other environmental factors. Generally increasing ionic strength and the presence of divalent cations such as Ca2+ and Mg2+ increases the rate and extent of aggregation, and may affect the stable size of aggregates that are formed. Thus nanoparticles will tend to aggregate more in seawater (high ionic strength) than in fresh water. For some materials, the particle’s intrinsic properties can affect their rate and extent of aggregation. For example, magnetic attractive forces between Fe0 nanoparticles used for groundwater remediation cause them to aggregate more rapidly than less magnetic iron oxide nanoparticles with similar

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dimensions [13]. Aggregation can significantly affect the transport of particles in porous media [17], the bioavailability of the materials to bacteria and to eukaryotic cells [7, 8], and the potential for sedimentation from a water column and ultimately the exposure to these materials. Aggregates or agglomerates of nanoparticles that settle can be expected to accumulate in sediments of lakes or rivers in the absence of nanoparticle degradation. Those that do not will travel much further in the water column from the point of release. Some evidence suggests that the deleterious effects on bacterial populations are greater for smaller aggregates of C60 than for larger ones. Thus, aggregation of nanoparticles may mitigate both exposure and toxicity in some cases. Another critical, but often overlooked factor affecting the transport and distribution of manufactured nanomaterials in the environment is the surface coatings that are engineering onto the particles, or surface coatings that are acquired upon release to the environment. For example, nanoscale zerovalent iron used for groundwater remediation must be engineered with a polyelectrolyte, surfactant, or polymer coating in order make them mobile in the subsurface [4, 15–17]. Quantum dots are engineered with an organic surface coating such as polyethylene glycol to make them dispersible in water and biocompatible. It should be no surprise that these surface coatings will also significantly affect their distribution in the environment. The magnitude of the effect these surface coatings on their transport will depend on the type of coating and the repulsive forces that those coatings provide. For example, small molecular weight coatings such as the surfactant sodium dodecylsulfate (SDS) commonly used to stabilize nanoparticles against aggregation in water, provide primarily electrostatic stabilization by imparting a surface charge to the particle. These are fairly weak repulsive forces and are readily blocked by cations in solution, rendering them ineffective. Large molecular weight polymers (uncharged) can provide steric repulsions that stabilize particles against aggregation and enhance transport. Large molecular weight polyelectrolytes such as polystyrene sulfonate (70000k molecular weight) provide electrosteric stabilization that reduces sensitivity to changes in ionic strength and composition of the water and provides much more resistance against aggregation, enhancing transport more so than surfactants [12, 15]. Natural organic matter (NOM) such as humic and fulvic acids can also stabilize particles against aggregation in water, which may enhance their transport in aqueous environments and in groundwater. For example, Sewanee River fulvic acids were shown to be much more efficient at stabilizing single-walled carbon nanotubes in water than was SDS [3]. Nanoparticles have high surface-to-volume ratios and therefore high surface energy. Any natural organic matter in a system will tend to adsorb to the particle surfaces, altering their surface properties and enhancing their mobility. Much of the natural organic matter in the environment is similar in molecular weight and charge as a moderate to high molecular weight polyelectrolyte, so the enhanced migration of polyelectrolyte modified Fe0 nanoparticles relative to the bare Fe0 nanoparticles observed by Saleh and coworkers [15] may be a good indication of the effect of NOM on the transport of manufactured nanoparticles in water. The mechanisms by which adsorbed organic coatings affect aggregation and deposition are under investigation e.g. [12], but

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the conditions under which enhanced transport will be observed is a current data gap in our understanding of the behavior of manufactured nanomaterials in the environment. The same processes affecting transport of nanomaterials in the environment affect the efficacy of water treatment systems that may be used to remove them. For example, coagulation and sand and membrane filtration are used to remove particles from drinking water. These traditional processes have been shown to be ineffective at removing some manufactured nanomaterials (e.g. quantum dots) from drinking water [19]. While not yet systematically evaluated, the engineered and acquired coatings on manufactured nanoparticles will undoubtedly affect these processes. 4.3.

TRANSFORMATIONS AND FATE

Once released into the environment, manufactured nanomaterials can be transformed biotically or abiotically. These transformations may alter the size, shape, and surface chemistry of the particles and their coatings and will affect their ultimate distribution in the environment. Some examples of biotic and abiotic transformations of manufactured nanomaterials include the removal of surface coatings from single walled carbon nanotubes by freshwater Daphnia. Roberts et al. [14] demonstrated that the lysophophatidylcholine coating on single-walled carbon nanotubes was removed as the tubes moved through the guts of the Daphnia. The Daphnids used the phospholipid coating on the nanotubes as a food source under food limited conditions. The nanotubes excreted by the Daphnia were less resistant to aggregation as a result of the removal of the lysophophatidylcholine coating. There are a host of other types of biotransformations that may occur to the particles, or to the coatings on the particles upon release to the environment. For example, microbial transformations of nanomaterials or the bioavailability of the surface coatings to bacteria are unexplored at this time. It is feasible that bacteria can oxidize or reduce nanomaterials or the attached coatings via electron transport in pili, or through direct reduction by membrane bound cytochromes (Figures 2 and 3). For example, dissimilatory iron reducing bacteria are known to respire on nanoparticulate iron oxides which could alter the particle surfaces by reductively dissolving Fe-oxides or Fe-oxyhydroxides formed at the water/particle interface [2] or by generating reactive surface-associated Fe(II) species [18]. Microbially induced corrosion could also ensure the localized dissolution of the iron nanoparticles, thereby eliminating possible concerns from off-site migration and risk. These microbial transformations are very likely to occur for many types of nanomaterials (carbon, metals, and metal oxides), but have not yet been well characterized. Transformations by fungi, nature’s decomposers, are also likely but have not yet been explored in detail. It is these types of biological transformations on the particle coatings that will affect their transport, and will determine the ultimate fate of manufactured nanomaterials in the environment.

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Figure 2. Microbial reduction/oxidation of nanoparticle coatings and functional surface coatings. (Courtesy of Professor Kelvin Gregory.)

Figure 3. Hypothetical microbial reduction of surface groups on nanoparticles by geobacteraceae. (Courtesy of Professor Kelvin Gregory.)

The physical and chemical transformations of manufactured nanomaterials that may occur after release to the environment include dissolution, disaggregation, photolysis, hydrolysis, and a variety of other non-biological redox transformations. All of these transformations can affect the concentration, persistence, toxicity effects on individual organisms and ecosystems. Very few of these abiotic reactions have been studied in detail, given the novel nature of most nanomaterials, but some examples do exist and illustrate the potential effect that these transformations may have on their distribution in the environment. For example, fullerenes (or C60) aggregate and acquire a surface charge after stirring in water. Stable 50– 200 nm clusters of C60 known as n C60 are formed. The processes are not certain, but the formation of these dispersible clusters is certain and may be the expected for of C60 released to the environment. However, the interaction of these clusters

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with carboxylic acids such as maleic acid, tends to dissolve or disaggregate these clusters (Figure 4). It is clear that this process will affect the size, number, and distribution of C60 in the environment. It is also likely that the adsorption of carboxylic acids to the particles will change their surface chemistry.

Figure 4. Disaggregation or nC60 cluster due to exposure to carboxylic acid. (Courtesy of Professor Peter Vikesland.)

Abiotic redox transformations of nanomaterials can also affect their fate. For example, Fe0 nanoparticles used for in situ remediation of chlorinated solvent and heavy metals are designed to oxidize, thereby supplying electrons for the reductive

Figure 5. TEM images of fresh nanoiron samples showing before reaction and after reaction with TCE in water. Both particle types have an apparent core-shell morphology. RNIP, made from gas phase reduction of Fe-oxides in H2, appear to have a shrinking core during reaction in water. Fe(B), made from reduction of Fe2+ in a water/methanol solution using sodium borohydride appear to undergo oxidative dissolution followed by precipitation of the dissolved Fe to hematite [5]. The shell on Fe(B) is predominantly borate [11].

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dechlorination of chlorinated solvents or reductive sequestration of heavy metals [6]. The data thus far on the fate of nanoiron have been largely collected in the laboratory in deionized water. They suggest that different types of Fe0 particles will undergo different transformations (Figure 5). In one case, RNIP (a Fe0/Fe3O4 core/shell nanoparticle) is oxidized from the outside in, yielding particles of similar size and shape, but the Fe0 has been oxidized to the Fe-oxides, magnetite and maghemite. Another type of Fe0 synthesized by a different process and nanocrystalline to amorphous appears to undergo reductive dissolution resulting in Fe-oxide particles that are of a different size, shape, and chemical composition [5]. From a risk assessment point of view, it is essential to understand the ultimate fate (end products) of the particles once released to the environment. Very few, if any, well controlled in situ investigations of the fate of nanoiron or any other type of nanoparticle in the subsurface have been conducted. 5.

Summary and Conclusions

The emergence of nanotechnology and the incorporation or nanomaterials into consumer goods, medications, etc. is currently in its infancy. The effects that these products will have on the environment and on human health are unknown, and precautionary measures are warranted until the risks that these materials may pose have been elucidated. The co-evolution of a new technology along with the understanding of the potentially negative environmental consequences is unprecedented. We typically forge ahead with the technology and manage the repercussions in the future. In some cases the negative effects outweigh the positive ones. There are many research needs with respect to environmental transport, fate, and effects of nanomaterials. In particular we need to gain a fundamental understanding of the factors affecting the aggregation, deposition, and ultimately the distribution of manufactured nanomaterials in the environment. The surface coatings engineered or acquired upon release to the environment will dramatically affect all of the process affecting the transport of these materials in the environment. Transformations that affect these surface coatings, either biotic or abiotic, need to be elucidated in detail. Processes affecting the persistence of these materials must also be determined. Only then can we assess the potential for exposure and estimate the concentrations that would be expected in different parts of the environment. Once the potential for exposure is clear, and the nature of the material that an organism may be exposed to is known, we can begin to estimate the potential effects due to these exposures. Performing traditional risk assessments for nanomaterials will not be possible until these obstacles are overcome, but interim assessments using fragmentary information will help us appreciate the environmental implications of the data as they become available.

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References 1. Brant, J., H. Lecoanet and M. Wiesner (2005). “Aggregation and Deposition Characteristics of Fullerene Nanoparticles in Aqueous Systems.” J. Nanopart. Res. 7(4– 5): 545–553. 2. Gerlach, R., A. B. Cunningham and F. Caccavo (2000). “Dissimilatory Iron-Reducing Bacteria Can Influence the Reduction of Carbon Tetrachloride by Iron Metal.” Environ. Sci. Technol. 34(12): 2461–2464. 3. Hyung, H., J. D. Fortner, J. B. Hughes and J.-H. Kim (2007). “Natural Organic Matter Stabilizes Carbon Nanotubes in the Aqueous Phase.” Environ. Sci. Technol. 41(1): 179–184. 4. Kanel, S. R., R. R. Goswami, T. P. Clement, M. O. Barnett and D. Zhao (2008). “Two Dimensional Transport Characteristics of Surface Stabilized Zero-Valent Iron Nanoparticles in Porous Media.” Environ. Sci. Technol. 42(3): 896–900. 5. Liu, Y., H. Choi, D. Dionysiou and G. V. Lowry (2005b). “Trichloroethene Hydrodechlorination in Water by Highly Disordered Monometallic Nanoiron.” Chem. Mater. 17(21): 5315–5322. 6. Liu, Y., S. A. Majetich, R. D. Tilton, D. S. Sholl and G. V. Lowry (2005a). “TCE Dechlorination Rates, Pathways, and Efficiency of Nanoscale Iron Particles with Different Properties.” Environ. Sci. Technol. 39(5): 1338–1345. 7. Long, T., N. Saleh, R. Tilton, G. V. Lowry and B. Veronesi (2006). “Titanium Dioxide (P25) Produces Oxidative Stress in Immortalized Brain Microglia (BV2): Implication of Nanoparticle Neurotoxicity.” Environ. Sci. Technol. 40(14): 4346–4352. 8. Long, T., J. Tajuba, N. Saleh, P. Sama, J. Parker, C. Swartz, G. Lowry and B. Veronesi (2007). “Nanosize Titanium Dioxide Stimulates Reactive Oxygen Species in Brain Microglia and Damages Neurons In Vitro.” Environ. Health Perspect. 115(11): 1631– 1637. 9. LuxResearch (2004). Sizing Nanotechnology’s Value Chain. New York, Lux Research. 10. Mueller, N. C. and B. Nowack (2008). “Exposure Modeling of Engineered Nanoparticles in the Environment.” Environ. Sci. Technol. 42(12): 4447–4453. 11. Nurmi, J. T., P. G. Tratnyek, V. Sarathy, D. R. Baer, J. E. Amonette, K. Pecher, C. Wang, J. C. Linehan, D. W. Matson, R. L. Penn and M. D. Driessen (2005). “Characterization and Properties of Metallic Iron Nanoparticles: Spectroscopy, Electrochemistry, and Kinetics.” Environ. Sci. Technol. 39(5): 1221–1230. 12. Phenrat, T., N. Saleh, K. Sirk, H. Kim, K. Matyjaszewski, R. Tilton and G. V. Lowry (2008). “Stabilization of Aqueous Nanoscale Zerovalent Iron Dispersions by Anionic Polyelectrolytes: Adsorbed Anionic Polyelectrolyte Layer Properties and Their Effect on Aggregation and Sedimentation.” J. Nanopart. Res. 10: 795–814. 13. Phenrat, T., N. Saleh, K. Sirk, R. D. Tilton and G. V. Lowry (2007). “Aggregation and Sedimentation of Aqueous Nanoscale Zerovalent Iron Dispersions.” Environ. Sci. Technol. 41(1): 284–290. 14. Roberts, A. P., A. S. Mount, B. Seda, J. Souther, R. Qiao, S. Lin, P. C. Ke, A. M. Rao and S. J. Klaine (2007). “In vivo Biomodification of Lipid-Coated Carbon Nanotubes by Daphnia magna.” Environ. Sci. Technol. 41(8): 3025–3029. 15. Saleh, N., H. Kim, K. Matyjaszewski, R. Tilton and G. V. Lowry (2008). “Ionic Strength and Composition Affect the Mobility of Surface-Modified NZVI in WaterSaturated Sand Columns.” Environ. Sci. Technol. 42(9): 3349–3355. 16. Saleh, N., T. Phenrat, K. Sirk, B. Dufour, J. Ok, T. Sarbu, K. Matyjaszewski, R. D. Tilton and G. V. Lowry (2005). “Adsorbed Triblock Copolymers Deliver Reactive Iron Nanoparticles to the Oil/Water Interface.” Nano Lett. 5(12): 2489–2494.

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17. Saleh, N., K. Sirk, T. Phenrat, B. Dufour, K. Matyjaszewski, R. D. Tilton and G. V. Lowry (2007). “Surface Modifications Enhance Nanoiron Transport and NAPL Targeting in Saturated Porous Media.” Environ. Eng. Sci. 24(1): 45–57. 18. Williams, A. G. B., K. B. Gregory, G. F. Parkin and M. M. Scherer (2005). “Hexahydro-1,3,5-trinitro-1,3,5-triazine Transformation by Biologically Reduced Ferrihydrite: Evolution of Fe Mineralogy, Surface Area, and Reaction Rates.” Environ. Sci. Technol. 39(14): 5183–5189. 19. Zhang, Y., Y. Chen, P. Westerhoff and J. C. Crittenden (2008). “Stability and Removal of Water Soluble CdTe Quantum Dots in Water.” Environ. Sci. Technol. 42(1): 321– 325.

VISUALIZATION AND TRANSPORT OF QUANTUM DOT NANOMATERIALS IN POROUS MEDIA

C.J.G. DARNAULT, S.M.C. BONINA, B. UYUSUR University of Illinois at Chicago Department of Civil and Materials Engineering 842 W. Taylor Street, ERF# 2071 Chicago, IL 60607, USA [email protected] P.T. SNEE University of Illinois at Chicago Department of Chemistry 845 West Taylor Street Chicago, IL 60607, USA

Abstract. This paper presents our research on the visualization and transport phenomena of quantum dot nanomaterials in porous media. It includes the development of a non-intrusive, high spatial and temporal resolution method to visualize transport and measure quantum dot nanomaterials concentration in porous media, allowing to characterize the mechanisms that control the transport, or lack of mobility, of engineered nanomaterials – quantum dots – in subsurface complex and heterogeneous environment. The visualization technique used to explore the transport of quantum dot nanomaterials is a toolbox that allows to characterize a wide range of flow and transport phenomena due to mesoscale heterogeneities. The characterization of these flow and transport phenomena includes the visualization and/or quantification of flow, fluid content and nanoparticle concentrations. The visualization technique selected to investigate transport of quantum dot nanomaterials in two-dimensional variably saturated porous media is a non-intrusive method based on fluorescence resulting from the quantum dots optical properties. The visualization procedure consists of exciting fluorescent quantum dots in porous media by using a UV light located in the front of the chamber and in characterizing the water content with the light transmitted through the porous media by using light emitted devices (LEDs) as a light source placed in the back of the chamber. The visualization, calibration and image analysis are performed using an image software. Experiments investigating quantum dot nanomaterials transport in unsaturated zone demonstrates the effects of preferential flow and gas-water interfaces on the transport of quantum dot nanomaterials through the vadose zone.

I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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1.

Introduction

Nanomaterials are at the leading edge of the rapidly growing field of nanotechnology. Their unique size-dependent properties make these materials superior and indispensable in many areas of human activity. Nanotechnology has considerable global socio-economic value, and is expected to have significant impacts on everyday life. Nanomaterials have numerous commercial and technological applications in chemical, biomedical, energy, electronics and space industries. A wide range of nanomaterials such as carbon nanotubes, fullerene derivatives, and quantum dots are used in almost all industries and all areas of society and the prevalence of these materials in society will be increasing, as will the likelihood of exposures [11, 21, 22]. Once nanomaterials are released into the environment via manufacturing, use or disposal, their transport is the critical parameter in assessing their exposure and impact on the public health and the ecosystem, therefore understanding the fate of nanomaterials in the environment is critical [1, 4, 27, 29, 31]. Initial work on nanomaterials mobility in saturated and homogeneous porous media has shown that fullerol may be very mobile while nC60 mobility is very limited [3, 15, 16]. Nanoscale iron particles designed for environmental remediation can flow with groundwater over 20 m distance [33]. pH and therefore surface potential and aggregate dominate titania nanoparticles interaction with each other and surface, while the transport speed of these nanoparticles aggregates did not vary with pH [10]. Among the various types of nanomaterials, the semiconductors, quantum dots are key enablers in nanosciences, engineering and technology. Since they were discovered in early 1980s they have a longer impact on nanotechnology compared to the other nanomaterials such as carbon nanotubes and composites emerged in 1990s. Currently, the data and literature on the fate and transport of quantum dots, currently is sparse and there is a great need for knowledge and detailed information. Quantum dot nanomaterials are a potentially new source of contaminants, and because of the broad suite of physical-chemical properties, could exhibit a wide range of transport properties. Furthermore, their unique fluorescence properties make them an excellent material to use for the investigation of the transport of nanomaterials in porous media as it greatly facilitate their detection and quantification through visualization. Therefore, our research goal aims at developing a visualization method and imaging process to investigate the fate and transport of quantum dot nanomaterials in variably saturated porous media using a non-intrusive high spatial and temporal visualization technique based on white light transmission and UV fluorescence detection. 2. 2.1.

Materials and Methods SEMICONDUCTOR NANOCRYSTALS

The development of fluorescent probe technology is essential towards gaining a fundamental understanding of many basic physical processes. While emissive organic sensing dyes have existed for over 100 years, there are very few materials that are

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photochemically stable. This fact has generated enormous interest in the study and development of highly fluorescent and photochemically robust inorganic nanocrystals (NCs, also known as quantum dots) [30]. Since their discovery in the early 1980s, semiconductor NCs have gained a large amount of attention due to their unique optical and electronic properties [8, 23]. The effects of exciton quantum confinement, the high crystallinity, and the organic surface passivation of semiconducting NCs results in tunable and efficient emission quantum yields compared to the bulk materials [2]. The size-dependent luminescent spectra are much narrower compared to fluorescent organic dyes and are highly resistant to photobleaching. Further, colloidal NC suspensions can be prepared using simple one-step chemical procedures [18, 20]. Shown in Figure 1 is a TEM micrograph of cadmium sulfide overcoated with zinc sulfide (CdS/ZnS) NCs. The nanoscopic size and sharp crystallinity of the materials can be discerned from the image while the inset showcases the effect of size and material composition on the emission wavelength. Although NCs are intrinsically hydrophobic, the emission is not quenched using our method of water solubilization as shown in the inset. For this study, we have specifically synthesized ~2.8 nm diameter CdSe NCs by injecting Trioctylphosphine Selenide into a 350°C solution containing Cadmium Acetylacetonate, Tetradecylphosphonic acid (TDPA) in a solution of Trioctylphosphine (TOP) and Trioctylphosphine Oxide (TOPO). The NCs were then precipitated using methanol, resuspended in hexane and then injected to a solution of Cadmium Acetylacetonate, TOPO, TOP, Decylamine and TDPA. After removal of the hexane under vacuum, a layer of Cadmium doped Zinc Sulfide was added through the slow (~2 h) addition of a solution of Diethyl Zinc in 3 ml of TOP concurrently with a 3 ml solution of Hexamethyldisilathiane in TOP at 150°C [5, 12]. The CdSe/CdZnS NCs are then precipitated, dried and mixed with a 40% octylamine modified Poly(acrylic Acid) in chloroform. The

Figure 1. TEM micrograph of CdS/ZnS nanocrystals. Inset: Size and composition dependent emission from CdS/ZnS (blue), small to large (green to red emitting) CdSe/ZnS NCs in aqueous solution.

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chloroform is then removed under vacuum and the NCs are resuspended in water. Excess polymer is removed using 100K high molecular weight centrifuge filters from Millipore. 2.2.

VISUALIZATION OF QUANTUM DOT NANOMATERIALS IN VARIABLY SATURATED POROUS MEDIA

The visualization method was derived from a light transmission method developed by Darnault et al. [7]. The visualization technique selected to investigate transport of quantum dot nanomaterials in two-dimensional variably saturated porous media is a non-intrusive method based on fluorescence resulting from the quantum dots optical properties. The visualization procedure consists of exciting fluorescent quantum dots in porous media by using a UV light on front side of the chamber and by using a light emitted devices (LEDs) as a light source in the back of the chamber and detecting the light transmitted through the porous media to characterize the water content (Figure 2). Images were acquired through a Q-IMAGING MicroPublisher RTV camera located in front of the chamber. The visualization, calibration and image analysis was performed using IPLab software.

Figure 2. Visualization experimental set-up.

To calibrate the fluorescence intensity to the quantum dots concentration in variably saturated sand, calibration cells were used. A stock solution of quantum dot nanomaterials was prepared and diluted by 4, 6.6, 10, 13.3, 20, 50 and 100 to obtain a wide range of concentrations (corresponding to 25%, 15%, 10%, 7.5%, 5%, 2% and 1% respectively of the stock solution concentration). Calibration cells consist of plastic cuvettes (1.1 × 1.1 × 4.5 cm) filled with sand as porous media and with various degree of water saturations to obtain both saturated and unsaturated systems as well as a wide range of quantum dots concentrations. The saturated cells were filled by five steps. Dry sand was poured into the cuvette and then the quantum dots solution was added for saturation. 1.45 g of sand and 0.32 ml of quantum dots solution were used in each step. For the unsaturated cells, the quantum dots solution and the dry sand were first mixed in a beaker. Afterwards, the mixture was put into the cuvettes. Two calibration curves were obtained to

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determine the relationship between water saturation and intensity; as well as quantum dots concentration and hue. Each experiment includes a two-step process. In the first step, the light source placed behind the calibration cells is switched on in a dark room and the resulting transmitted light from the cells is recorded with the camera. In the second step, the UV light is placed in front of the calibration cells (about 25 cm away) and the fluorescence resulting from the cells is recorded. Both images are recorded in RGB format and processed with IPLab software as follow: the image resulting from the light transmission is converted in intensity format to relate the intensity parameter to water saturation, and the image resulting from the cell fluorescence is converted in hue format to relate the hue parameter to quantum dot nanomaterials concentration in variably saturated porous media. 3. 3.1.

Results CALIBRATION

“Water content of each calibration cell was obtained from the intensity image of the light transmitted and quantum dot concentration of each calibration cell was obtained from the hue image representing the fluorescence detected with the UV light (Figures 3 and 4). Calibration curves where developed to establish relationships between intensity versus water content (Figure 5) and hue versus quantum dots concentrations (Figure 6). Quantum dots concentrations versus hue values for various degrees of saturation of porous media are presented in Figure 6. The procedure to

Figure 3. Intensity image of the calibration cells resulting from transmitted light.

Figure 4. Hue image of the calibration cells under UV light.

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Intensity

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quantify the quantum dots concentration in variably saturated porous media includes two steps: first the water content in porous media is quantified using intensity values resulting from the image obtained through light transmission through porous and then, once the water content is determined, the quantum dots concentration is obtained from hue values resulting from the image obtained through fluorescence using the UV light. A linear relationship is observed between hue value and quantum dots concentration for a constant water content (Figure 6). 200 180

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QD Concentration Figure 6. Quantum dots concentrations versus hue values for various degrees of saturation of porous media (25%, 50%, 75% and 100%).

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Legend for Figure 5 should be “Figure 5. Degree of saturation versus intensity values for various degrees of quantum dots concentrations.” 3.2.

APPLICATION: QUANTUM DOTS TRANSPORT THROUGH FINGERED FLOW IN VADOSE ZONE

Vadose zone processes play a pivotal role in the fate and transport of subsurface contaminants as it is typically the first subsurface environment encountered by contaminants before reaching the groundwater [17, 32]. Groundwater contamination is influenced by the hydrodynamics of vadose zone system, and the two main processes controlling water in the vadose zone are gravity which moves water downward and capillary process that moves water in all directions, stores it and releases it [9, 17]. As a result of the various geologic processes that lead to soils formation, there are heterogeneities in these materials over a wide range of length scales. These heterogeneities in the flow paths of the vadose zone are a critical feature because they can lead to the development of preferential flow. Preferential flow is a non-ideal behavior of flow in porous media that occurs in a non-volumeaveraged fashion along localized, preferential pathways, by-passing a fraction of the porous space [28]. Preferential flow can be found to occur by a number of different mechanisms, such as fingered flow, macropores flow [19]. Particles migrating in the soil matrix can be filtered by small pores, but preferential flow (e.g. soil macropore) leads to rapid breakthrough of the particles [6, 13, 14, 24– 26]. Once mobilized, particles move by advection and dispersion and may be deposited by mass transfer reaction that take place at mineral–grain surfaces and at air–water interfaces. In this context, a two-dimensional flow experiment in homogeneous sand was designed to assess the role of preferential flow – fingered flow – on the transport of quantum dot nanomaterials in vadose zone. This experiment was analyzed and processed by the visualization technique and imaging procedures. The experimental system consisted of a two-dimensional chamber – height: 30 cm, width: 20 cm – with 1 cm thick inner compartment that was filled with sand porous media and various degree of water saturation were achieved through saturation and drainage. The resulting initial experimental conditions simulated both vadose zone and aquifer system. A quantum dots solution was applied as a point source on the sand surface to simulate the release of nanomaterials in the subsurface environment. This simulation resulted in the formation of a fingered flow phenomena. The fate and transport of quantum dot nanomaterials in the vadose zone were observed and analyzed with the visualization method. The image obtained under the UV light exposure were converted to hue system to visualize and quantify the quantum dots nanomaterials in porous media (Figure 7a, b). The mobility and transport of quantum dot nanomaterials through the vadose zone by preferential flow phenomena – fingered flow – were demonstrated (Figure 7a). The role of gas-water interfaces on the retention of quantum dot nanomaterials at the capillary fringe was also established (Figure 7b).

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Figure 7. Fate and transport of quantum dots nanomaterials in vadose zone in Hue format (Quantum dots are visualized in red color). Transport of quantum dots by fingered flow in vadose zone (a). Retention of quantum dots nanomaterials by gas-water interface located at the capillary fringe (b).

4.

Conclusions

A non-intrusive, high spatial and temporal resolution technique was developed to visualize and quantify quantum dots nanomaterials in variably saturated porous media. The impacts of preferential flow – fingered flow – as well as gas–water interfaces on the fate and transport of engineered nanomaterials, such as quantum dots in the vadose zone environment were demonstrated. Acknowledgements This research was funded by the University of Illinois at Chicago, U.S.A. and Regione Puglia and High Cultural Activities, Italy (Assessorato al Lavoro, Copperazione e Formazione Professionale POR Puglia 2000-2006, Asse III; Misura 3.7). References 1. Biswas, P., and Wu, C.-Y., 2005, Nanoparticles and the Environment, Journal of Air and Waste Management Association, 55:708–746. 2. Brus, L. E., 1983, A simple model for the ionization potential, electron affinity, and aqueous redox potentials of small semiconductor crystallites, Journal of Chemical Physics, 79:5566. 3. Cheng, X., Kan, A. T., and Tomson, M. B., 2005, Study of C60 transport in porous media and the effect of sorbed C60 on naphtalene transport, Journal of Material Research, 20(12):3244–3254. 4. Colvin, V. L., 2003, The potential environmental impact of engineered nanomaterials, Nature Biotechnology, 21(10):1166–1170. 5. Dabbousi, B. O., Rodriguez-Viejo, J., Mikulec, F. V., Heine, J. R., Mattoussi, H., Ober, R., Jensen, K. F., Bawendi, M. G., 1997, (CdSe)ZnS core-shell quantum dots: synthesis

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and optical and structural characterization of a size series of highly luminescent materials, Journal of Physical Chemistry B, 101:9463. Darnault, C. J. G., Steenhuis, T. S., Kim, Y. J., Garnier, P., Jenkins, M., Ghiorse, W. C., Baveye, P. C., and Parlange, J.-Y., 2004, Preferential flow and the transport of Cryptosporidium parvum oocysts through the vadose zone: experiments and modeling, Vadose Zone Journal, 3:262–270. Darnault, C. J. G., DiCarlo, D. A., Bauters, T. W. J, Jacobson, A. R., Throop, J. A., Steenhuis, T. S., Parlange, J.-Y., and Montemagno C. D., 2001, Measurement of fluid contents by light transmission in transient three-phase oil-water-air systems in sand, Water Resources Research, 37:1859–1868. Ekimov, A. I., and Onushchenko, A. A., 1984, Size Quantization of the electron-energy spectrum in a microscopic semiconductor crystal, JETP Letters, 40:1136. Faybishenko, B., Bandurraga. M., Conrad, M., Cook, P., Eddy-Dilek, C., Everett, L., FRx Inc. of Cincinnati, Hazen, T., Hubbard, S., Hutter, A. R., Jordan, P., Keller, C., Leij, F. J., Loaiciga, N., Majer, E. L., Murdoch, L., Renehan, S., Riha, B., Rossabi, J., Rubin, Y., Simmons, A., Weeks, S., and Williams, C. V., 2000, Vadose Zone Characterization and Monitoring. Current Technologies, Applications, and Future Developments, pp 133–509, in Vadose Zone Science and Technology, Brian B, Looney and Ronald W. Falta eds., Volume 1, Battelle Press, Columbus, OH. Guzman, K. A., Taylor, M. R., and Banfield, J. F., 2006, Environmental risks of nanotechnology: national nanotechnology initiative funding, 2000-2004. Environmental Science and Technology 40(5), 1401–1407. Hardman, R., 2006, A toxicology review of quantum dots: toxicity depends on physicochemical and environmental factors, Environmental Health Perspectives, 114:165–172. Hines, M. A., Guyot-Sionnest, P., 1996, Synthesis and characterization of strongly luminescing ZnS-Capped CdSe nanocrystals, Journal of Physical Chemistry, 100:468. Jacobsen, O. H., Moldrup, P, Larsen, C., Konnerup., L., and Petersen, L. W., 1997, Particle transport in macropores of undisturbed soil columns, Journal of Hydrology, 196:185–203. Laegdsmand, M., Moldrup, P., and De Jonge, L. W., 2007, Modelling of colloid leaching from unsaturated soil, European Journal of Science, 58:692–703. Lecoanet, H. F., Bottero, J. Y., Wiesner, M. R., 2004, Laboratory assessment of the mobility of nanomaterials in porous media, Environmental Science and Technology, 38:5164–5169. Lecoanet, H. F., and Wiesner, M. R., 2004, Velocity effects on fullerene and oxide nanoparticle deposition in porous media, Environmental Science and Technology, 38, 4377–4382. Looney, B., and Falta, R., 2000, Vadose Zone What It Is, Why It Matters, and How It Works, pp 3–59, in Vadose Zone Science and Technology, Brian B, Looney and Ronald W. Falta eds., Volume 1, Battelle Press, Columbus, OH. Murray, C. B., Norris, D. J., Bawendi, M. G., 1993, Synthesis and Characterization of Nearly Monodisperse CdE (E = Sulfur, Selenium, Tellurium) Semiconductor Nanocrystallites, Journal of the American Chemical Society, 115:8706. Nieber, J. L., 1978, The Relation of Preferential Flow to Water Quality, and its Theoretical and Experimental Quantification, pp 1–10, in Preferential Flow, Water Movement and Chemical Transport in the Environment, D.D. Bosch and K.W. King eds., Proceedings of ASAE 2nd International Symposium, Honolulu, HI. 3–5 Jan. 2001. American Society of Agricultural Engineers, St. Joseph, MI. Natural Resources Conservation Service.

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20. Peng, Z. A., and Peng, X., 2001, Formation of high-quality CdTe, CdSe, and CdS nanocrystals using CdO as precursor, Journal of the American Chemical Society, 12:183. 21. Roco, M. C. and W. Baunbridge, eds., 2001, Societal implications of nanoscience and nanotechnology. National Science Foundation Report. 22. Roco, M. C., 2003, Broader societal issues of nanotechnology, Journal of Nanoparticle Research, 5:181–189 23. Rossetti, R., Nakahara, S., and Brus, L. E., 1983, Quantum size effects in the redox potentials, resonance Raman spectra, and electronic spectra of CdS crystallites in aqueous solution, Journal of Chemical Physics, 79:1086. 24. Rousseau, M., Di Pietro, L., Angulo-Jaramillo, R., Tessier, D., and Cabibel, B., 2004, Preferential transport of soil colloidal particles: physicochemical effects on particle mobilization, Vadose Zone Journal, 3:247–261. 25. Saiers, J. E., and Lenhart, J. J., 2003, Colloid mobilization and transport within unsaturated porous media under transient-flow conditions, Water Resources Research, 39:1019. 26. Saiers, J. E., Hornberger, G. M., Gower, D. B., and Herman, J. S., 2003, The role of moving air-water interfaces in colloid mobilization within the vadose zone, Geophysical Research Letters, 30:2083. 27. Sayre, P., June 30, 2007, Nanomaterials and the Environment. Priority Research Areas http://www.nano.gov/html/meetings/ehs/uploads/Sayre_EHS_20070104.pdf. 28. Tindall, J. A., and Kunkel, J. R., 1999, Unsaturated Zone Hydrology for Scientists and Engineers, Prentice-Hall, Englewood Cliffs, NJ. 29. USEPA, June 30, 2007, Nanotechnology White Paper, http://es.epa.gov/ncer/nano/ publications/whitepaper12022005.pdf 30. West, J. L., and Halas, N., 2003, Engineered nanomaterials for biophotonics applications: improving sensing, imaging, and therapeutics, Annual Review of Biomedical Engineering, 5:285. 31. Wiesner, M. R., Lowry, G. V., Alvarez, P., Dionysiou, D., and Biswas, P., 2006, Assessing the Risks of Manufactured Nanomaterials, Environmental Science and Technology, 40(14):4336–4345. 32. Witherspoon, P. A., 2000, Forewords, p xxii-xxv, in Vadose Zone Science and Technology, Brian B, Looney and Ronald W. Falta, eds., Volume 1, Battelle Press, Columbus, OH. 33. Zhang, W., 2003, Nanoscale iron particles for environment remediation: an overview, Journal of Nanoparticle Research, 5:323–332.

DEVELOPING AN ECOLOGICAL RISK FRAMEWORK TO ASSESS ENVIRONMENTAL SAFETY OF NANOSCALE PRODUCTS Ecological Risk Framework

L. KAPUSTKA LK Consultancy 8 Coach Gate Place SW Calgary, AB T3H 1G2 Canada [email protected] S. CHAN-REMILLARD, S. GOUDEY HydroQual Laboratory Ltd. Calgary, Alberta, Canada

Abstract. The nanotechnology industry is developing rapidly and promises to spawn many exciting products in the field of medicine, manufacturing, and various environmental fields, such as bio-control agents, and remediation catalysts. However, as legitimate questions of environmental safety go unanswered, opposition to the industry is accelerating just as rapidly. Unique physico-chemical properties of compounds within the nano-range present unknown toxicities relative to similar substances of larger dimensions. There is a critical need for a framework to assess risk of nanoscale particles that both the public and industry can accept. 1.

Introduction

Nanotechnology is a rapidly developing industry that is capitalizing on the novel physical and chemical characteristics of nanoscale particles (NPs). The novel properties of NPs that hold the promise for revolutionary advances in medicine, manufacturing, and numerous domestic uses also may present unanticipated environmental consequences. Early indications are that some NPs can be assimilated into organisms, translocated through vascular systems, and loaded into tissues and cells. Though some preliminary laboratory investigations have shown toxic responses in various test species, there are legitimate questions regarding the realism of these tests conditions. Consequently, we still do not know if these test results portend unacceptable risks or merely indicate intriguing curiosities. Here we discuss the need for a risk framework that can guide decision-makers through the critical nodes in the lifecycle of nanoscale products. We describe the

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characteristics that such a framework should include and reflect on the many efforts underway in industry, governments, academia, and public interest groups. 2.

Public Perception of Risk

The successful development of new technologies, including nanotechnology, requires input from diverse groups of stakeholders. Often, perception of risk weighs heavily in the progression of the technology from early conceptualization to the reduction to practice (Figure 1). The evolution of any technology begins with an inspiration by theoreticians who develop the initial concept; this is followed by scientists who move a theory from concept to the experimental stage. Once the technology has taken on a tangible form, entrepreneurs and sometimes venture capitalists begin to invest in the technology resulting in the emergence of consumer products. Ideally, in the eyes of the entrepreneurs, a new technology progresses through this product development curve in a direct, unhindered fashion. As new participants enter, a linear path may take on a series of iterative loops. This occurs as investors, regulators, or interested publics ask new questions, explore additional scenarios, and seek comfort that any known or suspected risk, including financial or environmental, are acceptable. With any new perspective and any new question, the path to successful commercialization may be altered, even blocked. A major factor that may affect the realization of the full potential of nanotechnology is the publics’ perception of the risks associated with nanotechnology with regard to socioeconomic and environmental health impacts [1, 2]. Prior experience with the public backlash to genetically modified organisms (GMO) [3] and the nuclear power industries [4] provide the nanotechnology industry with precedence to consider these factors early in the evolution of product development [5]. The occurrence of an event that causes morbidity or mortality due to use of or exposure to nanotechnology likely would trigger negative public perception and bring heightened attention from news media and activists groups [6]. The question is whether the nanotechnology industry will address consumer challenges candidly and respectfully or will it be constrained in a manner similar to the GMO industry. Much depends on the publics’ confidence that appropriate measures to manage risks are being taken from the initial stages of product development through product disposal. Although consumer products that incorporate nanotechnology are rapidly emerging and already available [7] there is still opportunity to address environmental concerns, manage risks, and engage in meaningful communications with the interested public [8].

PROGRESS TOWARD VIABLE MARKETS

Engineers

Applied Scientists

Figure 1. Stages in the continuum from concept to commercialization.

Anticipatory

BEST OPPORTUNITY TO SAVE RESOURCES, COST, REDUCE RISK AND NEGATIVE PUBLIC PERCEPTION

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Interest Groups: • Regulatory Agencies • Environmental Groups • Technology Companies

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Funding Sources: • Academic Institutions • Entrepreneurs • Economic Development Programs

CURRENT STATE OF NANOTECHNOLOGY RESEARCH AND DEVELOPMENT

Effective Management of Risk and Perceptions

EFFECTIVENESS OF A RISK ASSESSMENT FRAMEWORK TO INFORM PUBLIC PERCEPTION

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Risk Assessment Framework

Modern-day risk assessment has evolved over the past two decades as a useful tool to inform environmental management decisions [9–11]. In its basic form, risk assessment examines one or more scenarios to characterize the likelihood of occurrence. In this process, the magnitude of exposure that receptors may realistically experience is estimated. Next, the range of exposures to stressors is related to expected effects. Finally, the likelihood of occurrence and consequences are weighed against incertitudes. Though substantive inherent and contrived limitations exist in the practice of risk assessment [12], the basic framework still provides the best means of focussing information on specific stakeholder issues in the process of developing coherent risk management and risk mitigation strategies. Though ecological risk and human health risk assessment have largely developed as independent disciplines, there has been substantial movement in recent years toward an integrated approach consistent with the World Health Organization [13] definition, which states “Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.” An integrated risk assessment thus begins with the Problem Formulation stage by inclusion of socioeconomic, psychological, spiritual, human health, and ecological consideration into the guiding conceptual model. If broad stakeholder involvement is fostered [14], proactive dialogue can be developed [15]. In this fashion, the emerging nanotechnology industry would benefit from application of an integrated decision framework that addresses the publics’ concerns over the full lifecycle of a given product [16]. Public safety and environmental protection are important and shared obligations of proponents and regulators in any industry. The risk assessment framework, as noted above, provides one tool that can be used effectively to organize information that can be useful to foster informed dialogue and to assist in making critical decisions. There is growing recognition of the need for risk assessments of NP [17–21]. The risk framework can be applied at different stages of a product beginning with experimental work of formulation through disposal of all waste streams and products. The degree of sophistication used in assessing risks should increase along the product life-cycle. Characteristically, the assumptions used in assessing risk at the early stages are designed to be protective, that is to trip flags about possible problems so that more attention is focused on managing or mitigating such risks. As one progresses through the product lifecycle, more data become available and thus the assumptions used in the assessment become more realistic. At any level of analysis, absence of data typically triggers precaution. In the absence of solid defensible scientific information that addresses public concerns, the nanotechnology industry likely will face restrictive measures based on precautionary principles. Clear communication on risk issues requires common understanding of terms. Important aspects of such communications include distinguishing between hazard and risk as well as exposure and effect.

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ƒ Hazard – the inherent properties of a stressor (biological, chemical, or physical agent) that can have an adverse effect on a receptor (humans, other animals, plants, or microbes). ƒ Exposure – the magnitude, concentration, dose, or other measure of the degree of contact a receptor has with a hazard. ƒ Effect – the biological response of an organism, population, or ecological system to a stressor. ƒ Risk – the likelihood of an adverse effect occurring as a result of being exposed to a hazard. ƒ Risk Assessment – a process (usually within a formalized framework) that examines scenarios to evaluate the likelihood of an adverse event occurring. This is accomplished through estimation of the magnitude of exposure and relating effects that occur from such exposures to one or more hazards. Studies of algae, invertebrates, plants, and fish have shown that organisms incorporate NP into their tissues and, at the concentrations/doses tested, exhibit some toxic responses [22]. A key outstanding question is whether the laboratory test concentrations are realistic (i.e., will such concentrations occur in the environment? if so, under what circumstances?). At this stage in the development of the nanotechnology industry, we do not know enough to judge whether adverse effects are likely to be manifested in occupational settings or the environment. Therefore, there is some urgency to adapt the risk framework to address the specific issues pertaining to the nanotechnology industry. Concurrently, the need is equally urgent for data on toxicity (hazard), fate and transport of particles across environmental media, and quantitation of exposure for various receptors (human and ecological). Finally, the output of an integrated risk assessment generally contains multiple components that must be judged in terms of societal values. Thus, societal values dictate both the structure of the questions addressed and the interpretation of the results of the risk assessment. To do so requires getting the right questions right – and this demands consideration of ecological imperatives [12, 23]. In particular, ecological systems are dynamic, self-organizing entities that cannot be restored, they can only be emulated. Change is inevitable and predictions of future conditions are tenuous at best. There also must be clear recognition of the interface between science and public policy that lead to regulations [24, 25]. Though we all bring certain biases to any analysis and discussion, the power of science, including ecology, derives from the desire to provide objective explorations of how the world works, in other words free of normative science [25]. We should remain cognizant that the specific values of ecological resources, both goods and services, are contextual (i.e., the values are based on human needs and desires, which vary among cultures, ethnicities, economic status, age, gender, and many other sociological considerations). Moreover, economies are based (whether acknowledged or not) on the flow of ecological goods and services. Therefore, public policy that emerges with respect to the nanotechnology industry should incorporate long-range objectives of

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sustaining predictable flows of ecological goods and services along with the shorter-term economic benefits accrued from specific nano-materials. Information derived from a formal risk assessment approach is compatible with multi-criteria decision analysis tools. Perhaps the most important feature that comes from the marriage of risk assessment and decision analysis is the opportunity to focus explicitly on the sufficiency of information required to make a decision. Not only does this provide for a more satisfying result, but it also gives added value to the risk assessment. From personal examination of risk assessments conducted on hazardous waste sites (and Lee Nikl, Golder Associates, Vancouver, British Columbia, Canada, personal communications, 2007), the value in savings is $50 and $500 for every $1 spent on a risk assessment. Communicating the results of a risk assessment and the decisions to be made can be challenging. One of the most difficult barriers to overcome is to develop a common language to translate highly technical jargon into a form that people outside the immediate field can relate to. After all, the collection of persons who contribute to a decision on such matters as those facing the nanotechnology area range from physicists, chemists, economists, social scientists, sociologists, politicians, ethicists, and many more. We have found it useful to classify the results of risk assessment into a risk matrix that provides an expression of the likelihood of an event occurring and the consequence if the event does occur [26]. Though agreeing on the operational definitions of risk categories is far from trivial, once basic agreement has been achieved, it becomes relatively easy for stakeholders, regardless of their areas of expertise, to grasp the meaning of the risk categories and to act accordingly in moving toward a decision. 4.

A Risk-Based Life-Cycle Analysis Approach

We believe there is need for a comprehensive program to address issues emerging in the broadly defined nanotechnology arena. This can be achieved by adapting the basic constructs of the risk assessment framework by staging a sequence of tiered assessments tailored to address different phases along the product commercialization continuum. 4.1.

CONCEPTUAL BEGINNING

At the earliest stages of designing a new nanoscale substance, whether achieved through a directed theoretical focus or a serendipitous discovery, a few basic considerations should be examined. Clearly at the outset, there are minimum data; most information will be generalized deductions from rules of physical chemistry. Nevertheless, some insights into potential hazards may be anticipated from knowledge of the expected behaviours of the substances in different media. Drawing from experiences with conventional chemical substances, an initial characterization may be attempted using correlative information from similar substances and similar molecular configurations. As the body of information increases, something akin to the quantitative structure activity relationships (QSAR) should emerge.

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Clearly, in these early stages of amassing data, there will be large uncertainties, but as the database grows, some classes of substances will be resolved such that reasonable projections of risks to humans or to ecological resources should be possible. We envision a check-list type analysis, based on QSAR-like decision rules should be possible fairly soon that would serve as a pre-feasibility scoping exercise that would serve a few large objectives: ƒ Establish a basis for laboratory hygiene that is protective of staff who may encounter the products and by-products of production ƒ Identify types of data that could be confirmatory of hazard ranking (an especially useful way of demonstrating lower hazards that could lead to relaxation of stringent safety requirements) and ƒ Focus on gathering additional characterization data that would be useful in assessing risks at later stages of the product development and commercialization continuum 4.2.

BENCH-SCALE TESTING

With successive stages of development, characterization data should continue to address questions of potential hazards and fate of substances in the intended media. During bench-scale production, generic measurements should provide better characterization of the nanoscale particle structure and behaviour in aqueous and nonaqueous media. The data gathered should confirm predictions based on QSARlike predictions and extend the database for future uses. The focus of bench-scale testing should be on characterizing the environmental fate of both the primary nano-material and on the waste-streams generated in production of the intended product. Generally, these data should provide the foundation for predictions of toxicity to different receptors (human and ecological), though at this stage, laboratory toxicity tests similar to the safety tests used in conventional chemical and pesticide registration guidelines would not be conducted. 4.3.

PILOT PRODUCTION

At the time commercialization looks to be feasible and pilot production begins, expanded safety testing in relevant media should be started. A small number of tests that examine in-life toxicity responses would be warranted. The choice of test methods is likely to evolve as more data are generated, but the focus of these early tests will always be to ensure that Type II errors (i.e., declaring something to be safe that is indeed harmful) are avoided. Simplified conceptual models are needed at this stage to guide the selection of tests appropriate to characterize risks to humans in the work place, other humans that may be exposed to the substances, and ecological receptors. Generic conceptual models should be developed to achieve consistent decisions across the industry with respect to the rigour of testing. We anticipate that these initial tests would use species suspected to be maximally sensitive to the particular products being tested. Currently, there is no consensus as to whether existing laboratory tests are appropriate and robust for determining toxicity of NPs. Efforts are underway

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within various research laboratories and standardization organizations to determine if standardized test methods used for conventional product safety testing will require modification. At a minimum, there is consensus that different methods are needed to characterize the NPs including for particle size, aggregation, surface area, and reactive surfaces; mere concentration of the base substance is insufficient. 4.4.

COMMERCIALIZATION

Information gathered along the path to this point will be needed to construct more detailed conceptual models for use in expanded safety testing and determination of risks to humans and to ecological receptors. Specific scenarios relevant to both the intended uses and accidental releases that occur during manufacturing, distribution, use, and disposal would be required. The product-specific conceptual model should be used to guide the data requirements for completion of a detailed, integrated risk assessment. Some scenarios, we can anticipate, will be addressed through generalized narratives that draw upon information already assembled up to this stage. However, parts of some scenarios may require focused measurements of fate and transport of the NPs, by-products, and break-down products. The suite of laboratory toxicity tests may need to be expanded to develop relevant toxicity data for the specific scenarios. The ultimate goal of this stage of the product risk assessment should be to demonstrate safety to humans and ecological receptors. This should engender sufficient confidence for regulators to write regulations and issue permits and for the public to trust both the information and the decision to permit production and commercialization. 4.5.

POST-COMMERCIALIZATION

At least for the next several years, the industry will benefit from some form of risk-based monitoring to validate the assumptions used to obtain the permits for production and commercialization. The conceptual model that was used to guide the risk assessments in the previous stage should inform the type of post-commercialization monitoring that would be warranted. As the regulatory bodies and the public become convinced that the permitting process is sufficiently protective, the magnitude of monitoring is likely to be relaxed. If, however, unexpected indications of human health or ecological injury are detected, such information logically would flow back to earlier stages of the process and result in increased rigour in characterizing risks. Such a risk-based approach meshes with the processes of active adaptive management, a strategy that serves the dual goals of promoting commercialization and maintaining environmental protection [27–29]. Findings in such a monitoring program can be used in real time to avoid, minimize, or mitigate adverse effects – especially if made part of the permitting process.

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Contemporary Activities

Professional societies have rallied around the perceived need to address data gaps that currently stymie characterization of risks associated with NPs. The Society for Risk Analysis organized a Section on Nanotechnology at its annual North American meeting in 2006. The Society of Environmental Toxicology and Chemistry (SETAC) formed working group in 2007 that is examining five topical areas relevant to the field. The topics being addressed by the more than 90 members from Europe, North America, and Australia are (1) terminology, (2) environmental fate and behaviour, (3) toxicokinetics and bioconcentration, (4) ecotoxicology, and (5) risk assessment framework. In addition to professional societies, government bodies such as the US EPA, Environment Canada and Health Canada, and the European Community have launched exploratory studies of nanoscale products. In the US, some states and municipalities [30, 31] have considered policies pertaining to the nanotechnology industry. Collaboration between industry and consultancies has led to articulation of policy needs (CIELAP) [32] as well as initial efforts to develop risk approaches tailored to the nanotechnology industry [19]. The American Society for Testing and Materials-International (ASTM-I), the Organization for Cooperation and Development (OECD), and the International Standards Organization (ISO), have initiated work to develop standards for testing and handling nanomaterials. ASTM-I for example is examining the full suite of toxicity test methods to determine if the tests as described are adequate for addressing the unique properties of NPs. Early emphasis will be to consider the special characterization steps required to document exposure regimes. Other aspects of the tests to be evaluated will include consideration of test volumes, relevant endpoints, and interpretation of effects data. In all of these areas of interest, the field is progressing rapidly. An important challenge faces all who work in this area to remain current and to the extent practical, minimize duplication of effort. References 1. Siegrist, M., Kelle, C., Kastenholz, H., Frey, S., and Wiek, A. (2007) Laypeople’s and experts’ perception of nanotechnology hazards, Risk Analysis 27, 59–69. 2. The Royal Society. (2004) Nanoscience and nanotechnologies: Opportunities and uncertainties. ISBN 0 85403 604 0. Available online at http://www.nanotec.org.uk/ finalReport.htm, last accessed on 15 July 2008. 3. Frewer, L.J., Lassen, J., Kettlitz, B., Scholderer, J., Beekman, V., and Berdahl, K.J. (2004) Societal aspects of genetically modified foods, Food and Chemical Toxicology 42, 1181–1193. 4. Warner, M. (2001) Nuclear Power. The News Hour with Jim Lehrer. Transcript 22 May 2001. Available at http://www.pbs.org/newshour/bb/environment/jan-june01/nuclear_ 5-22. html, last accessed on 15 July 2008. 5. Begtrup, G., and Kessler, B. (2006) Preparing for the Backlash: Pre-emptive Policy for the Nanomaterials Revolution. Published by the authors online at http://socrates. berkeley.edu/~bkessler/STEP_WP.pdf, last accessed on 15 July 2008.

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6. Mittelstaedt, M. (2008) Micro Materials Could Pose Major Health Risks, Globe and Mail, 10 July 2008. Available online at http://www.theglobeandmail.com/servlet/story/ RTGAM.20080710.wnano0710/EmailBNStory/Science, last accessed 15 July 2008. 7. Woodrow Wilson International Center for Scholars. Available online at http://www. nanotechproject.org/inventories/consumer/, last accessed 15 July 2008. 8. Council of Canadian Academies. (2008) Small is Different: A Science Perspective on the Regulatory Challenges of the Nanoscale. Report in Focus July. Available online at http://www.scienceadvice.ca/documents/(2008_07_10)_Nano_Report_in_Focus.pdf, last accessed on 15 July 2008. 9. Dale, V.H. et al. (2008) Enhancing the ecological risk assessment process, Integrated Environmental Assessment Management 4, 306–313. 10. Suter, G.W. (2008) Ecological risk assessment in the United States environmental protection agency: A historical overview, Integrated Environmental Assessment Management 4, 285–289. 11. Barnthouse L. (2008) The strengths of the ecological risk assessment process: Linking science to decision making, Integrated Environmental Assessment Management 4, 299– 305. 12. Kapustka L. (2008) Limitations of the current practices used to perform ecological risk assessment, Integrated Environmental Assessment Management 4, 290–298. 13. Preamble to the Constitution of the World Health Organization as adopted by the International Health Conference, New York, 19 June–22 July 1946; signed on 22 July 1946 by the representatives of 61 States (Official Records of the World Health Organization, no. 2, p. 100) and entered into force on 7 April 1948. The definition has not been amended since 1948. Available online at http://www.who.int/governance/ eb/who_constitution_en.pdf, last accessed 15 July 2008. 14. ASTM-I (2006) E 2348-06 Standard Guide for Framework for a Consensus-based Environmental Decision-making Process. In ASTM-I Annual Book of Standards, American Society for Testing and Materials-International, West Conshohocken, PA. 15. Kapustka, L.A. (2006) Current Developments in Ecotoxicology and Ecological Risk Assessment. In Arapis, G., and Goncharova, N. (eds.), Ecotoxicology, Ecological Risk Assessment, and Multiple Stressors, pp 3–24, Kluwer, The Netherlands. 16. Curran, M.A., Frankl, P., Heijungs, R., Kohler, A., and Olsen, S.I. (2007) Nanotechnology and Life Cycle assessment: A Systems Approach to Nanotechnology and the Environment, European Commission and Woodrow Wilson International Center for Scholars. Available online at ftp://ftp.cordis.europa.eu/pub/nanotechnology/ docs/lca_nanotechnology_workshopoct2006_proceedings_en.pdf, last accessed 15 July 2008. 17. European Commission, SCENHIR. (2007) Opinion on the Appropriateness of the Risk Assessment Methodology in Accordance with the Technical Guidance Documents for New and Existing Substances for Assessing the Risks of Nanomaterials. Available on line at http://cordis.europa.eu/nanotechnology, last accessed 15 July 2008. 18. United States Environmental Protection Agency. (2007) Nanotechnology White Paper, 100/B-07/001. Available on line at http://es.epa.gov/ncer/nano/publications/index.html, last accessed 15 July 2008. 19. Environmental Defense and Dupont. (2007) NANO Risk Framework, E.I. duPont de Namours and Company, Wilmington, DE, and Environmental Defense, Washington, DC. Available online at http://www.edf.org/documents/6496_Nano%20Risk%20 Framework.pdf, last accessed 15 July 2008. 20. Environment Canada & Health Canada. (2007) Proposed regulatory framework for nanomaterials under the Canadian Environmental Protection Act, 1999. Available online at http://nanotech.lawbc.com/2007/09/articles/legalregulatory-issues/canada-

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publishes-proposed-regulatory-framework-for-nanomaterials-under-cepa/, last accessed 15 July 2008. Linkov, I., and Satterstrom, F.K. (2008) Nanomaterial Risk Assessment and Risk Management: Review of Regulatory Frameworks. In Linkov, I., Ferguson, E., and Magar, V.S. (eds.), Real-Time and Deliberative Decision Making, Springer, The Netherlands, at 1–1. Handy, R.D., Owen, R., and Valsami-Jones, E. (2008) The ecotoxicology of nanoparticles and nanomaterials: Current status, knowledge gaps, challenges, and future needs, Ecotoxicology 17, 315–325. Kapustka, L.A., and Landis, W.G. (1998) Ecology: The science versus the myth, Human and Ecological Risk Assessment 4, 829–838. Lackey, R.T. (2001) Values, policy, and ecosystem health, BioScience 51, 437–443. Lackey, R.T. (2007) Science, scientists, and policy advocacy, Conservation Biology 21, 12–17. Kapustka, L.A., and Mitton, J. (2007) Risk-based Environmental Approval Management System. Technical Report prepared by Golder Associates for the Alberta Environment, Environmental Management Division, Spruce Grove, AB. Linkov, I., Varghese, A., Jamil, S., Seager, T.P., Kiker, G., and Bridges, T. (2004) Multi-Criteria Decision Analysis: Framework for Applications in Remedial Planning for Contaminated Sites. In Linkov, I., and Ramadan, A. (eds.), Comparative Risk Assessment and Environmental Decision Making, Kluwer, Dordrecht/Boston/London. Kiker, G.A., Bridges, T.S., Varghese, A., Seager, T.P., and Linkov, I. (2005) Application of Multicriteria Decision analysis in Environmental Decision Making, Integrated Environmental Assessment and Management 1, 95–108. Linkov, I., Satterstrom, F.K., Kiker, G.A., Bridges, T.S., Benjamin, S.L., and Belluck, D.A. (2006) From optimization to adaptation: Shifting paradigms in environmental management and their application to remedial decisions, Integrated Environmental Assessment and Management 2, 92–98. http://www.nanolawreport.com/tags/regulation, last accessed 15 July 2008. http://www.nanowerk.com/news/newsid=1340.php, last accessed 15 July 2008. Holtz, S. (2008) Update on a Framework for Canadian Nanotechnology Policy: A Second Discussion Paper. Canadian Institute of Environmental Law and Policy (CIELAP). Available online at http://www.cielap.org/pdf/2008NanoUpdate.pdf, last accessed 15 July 2008.

DEVELOPMENT OF A THREE-LEVEL RISK ASSESSMENT STRATEGY FOR NANOMATERIALS

N. O’BRIEN, E. CUMMINS Biosystems Engineering UCD School of Agriculture, Food Science and Veterinary Medicine College of Life Sciences, Agriculture and Food Science Centre Belfield, Dublin 4, Ireland [email protected]

Abstract. The release of nanomaterials and, in particular, free nanoparticles into the environment from secondary sources such as industrial manufacturing and consumer products as well as from intentional environmental application has compelled a need for a broad and pre-emptive analysis of nanomaterial fate and transport in the environment and subsequent potential human exposure pathways. The novel and potentially reactive characteristics of nanomaterials have lead to predictions on potential undesirable ramifications of exposure to these materials on human health. The three-level risk assessment strategy presented in this work has its basis in qualitative model equations that represent the inter-relationships between the different material and process characteristics and environmental behaviors and their relationship to potential exposure scenarios. The factors that influence these behaviors are examined, and the potential application of this risk assessment strategy in a semi-quantitative model is considered. 1.

Introduction

Nanomaterials have been developed for use in many environmental applications such as nanoscale sensors for monitoring and detection of pollutants as well as nanoparticle additives in coatings. Examples include TiO2 in paint to aid in oxidizing volatile organic compounds and iron oxide based nanoparticle remediation of polluted soil and groundwater. While these intentional releases into the environment are intended to provide solutions to or pre-empt environmental problems, there is concern that nanomaterials and free nanoparticles, particularly from unintentional or incidental industrial and domestic releases, may result in the creation of new environmental and subsequent human health hazards. There are two principle concerns about nanomaterials. First, there is very little precedent to compare the fate of such a potentially mobile group of materials, some of which are functionalized especially to disperse in aqueous media [27]. Large scale environmental

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fate studies are difficult to execute. The range of products into which nanoresearch is currently being applied, such as cosmetics, electronics, fuel additives, paints and coatings, means that an unprecedented number of routes of release and exposure are possible. The second principle concern is that of potential reactivity. Nanoparticles are found naturally in the environment, and man-made nanoparticles have been produced incidentally in large amounts since the industrial revolution. However, engineered nanomaterials are produced to undertake certain functions as efficiently as possible, often involving maximizing and functionalizing the surface area, which in turn increases their potential toxicity. It is this reactivity, coupled with their potential mobility, which fuels concern over nanomaterial fate and transport in the environment and subsequent human exposure. An analysis of the development and release into the marketplace of any new technology, especially those with environmental applications, often boils down to an assessment of risk versus benefit. With nanomaterials, the environmental benefits of nano-remediation and fuel additives are obvious but often it is difficult to form a realistic picture of the potential risks associated with these new products and processes due to the uncertainties associated with materials at this scale. This is the problem faced by regulators in incorporating nanomaterials into current risk assessment or regulatory frameworks or developing new frameworks in order to ensure the responsible and sustainable development of nanotechnology and nanomaterials. A major obstacle in developing new frameworks, or adapting old ones, is that those charged with assessing nanomaterial risk cannot as yet definitely specify those common characteristics or mechanisms inherent in nanoscale materials, or even those characteristics and mechanisms that demand that such a broad grouping of materials should even be regulated as a single entity. The strategy for nanomaterial exposure assessment presented here isolates five common behaviors of nanomaterials in the environment. Characteristics which relate to these behaviors and the human exposure scenarios resultant from these behaviors are presented, and hence nanomaterial characteristics may be related to potential human exposure scenarios by means of an assessment of nanomaterial behavior in the environment. This assessment strategy is presented within a three-level framework in which the exposure related questions/concerns to be addressed by the assessment are identified, the characteristics associated with the particular material and process and its behavior in the environment are isolated while the behavior and characteristics are subsequently linked to potential exposure scenarios. The common behaviors of nanomaterials in the environment that underpin this strategy and the material characteristics and inter-relationships influencing these behaviors are discussed and linked to exposure scenarios of possible concern. The strategy presented has potential to form the basis of a user input based exposure model with which risks from nano-materials may be evaluated, with potential use in providing regulators with some measure of nanoparticle risk, an area in which there is little guidance at present.

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Nanomaterial Exposure Analysis

Comprehensive fate studies are difficult to execute with novel substances such as nanomaterials as there is very little risk assessment precedent associated with the analysis of materials with such potential mobility and reactivity released into the environment. Exposure models can become very complicated due to uncertainty, assumptions and data gaps in our knowledge of the fate and characteristics of these materials, environmental pathways and transformations, as well as detection and analysis. Therefore, qualitative or semi-quantitative exposure models offer the most realistic measures of potential hazard and exposure with our current level of knowledge. The novel three level risk analysis strategy proposed here may aid in overcoming this uncertainty and deficiency in data, as the most basic hazard and exposure based questions to be answered by the risk assessment are identified and potential realistic exposure scenarios are linked to these questions via the treatment, transformation and environmental behavior of these nanomaterials. A risk assessment model based on this strategy would involve the input of particle and process characteristics by the user, which are correlated to potential behavior in the environment and subsequent exposure scenarios derived from fate and exposure studies from literature. The characteristic, process and treatment variables presented in this strategy are not an exhaustive list of all possible factors that may determine nanomaterial exposure, fate and transport, but is comprised of variables that may be familiar to the user, applicable in many exposure scenarios and about which a reasonable amount of research has been undertaken. 3.

Three-Level Strategy

The proposed overall risk assessment strategy is comprised of three levels as seen in Figure 1. The exposure related questions/concerns to be addressed by the assessment are determined in level 1. The characteristics associated with the particular material and process and its behavior in the environment are identified in level 2 by means of three inter-related modules: characteristics, treatment and behavior. These behaviors and characteristics are linked to potential exposure scenarios in level 3, which comprises of a fourth module: exposure scenarios. The strategy has its basis in qualitative model equations that represent the interrelationships between the different material and process characteristics and behaviors. The qualitative model equations linking each module were derived from literature and expert opinion. The individual modules associated with Levels 2 and 3 and their elements are discussed in later sections.

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Example exposure questions to be answered by RA: Level 1

1. 2. 3. 4.

E_con: Release of environmentally relevant concentrations? E_sprd:Local Vs Widespread exposure? E_freq: Exposure frequency? E_rts: Primary routes of human exposure?

Particle:

C_sol: Solubility/ Persistence C_form: Form

Process:

C_sd: Size distribution

C_lcs: Life cycle stage

C_agg:Aggregate size

C_con: Quantities/ Concentr

C_sa: Surface area

C_freq: Frequency

T_dis: Disposal methods

Level 2

Treatment module

Characteristics module

C_sc: Surface charge

C_mat: Material

Behaviour module B_mda: Exposure media B_trpt: Transport

T_ww: Wastewater treatment T_wat: Water release T_slg: Sludge release

B_ads: Adsorption

T_fil: Filter efficiency

B_rd /pht: Redox/Photoact

T_chr: Characteristic transform

B_agg: Aggregation B_acc: Accumulation

E_con: Function of: C_lcs: C_con, C_freq, T_dis, T_fil E_sprd: FII of: C_lcs, C_con, C_freq, T_dis, B_trpt, B_ads, B_agg, B_acc E_freq: FII of: C_lcs, C_con, C_freq, T_dis, B_trpt, B_agg, B_acc E_rts: FII of: B_trpt, B_agg, B_acc

Figure 1. Three-level risk assessment strategy.

Level 3

1. 2. 3. 4.

Exposure scenarios module

Answers to initial exposure questions:

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LEVEL 1: RISK ASSESSMENT FOCUS

The exposure concentrations, frequencies, routes and spread/reach associated with a particular nanomaterial are outlined in this section. Pertinent concerns are selected for examination, the relevant material and process characteristics determined and resultant potential environmental behaviors extrapolated, with the original concerns addressed considering the predicted behaviors and initial material and process characteristics. Some initial Level 1 questions/concerns, as can be seen in Figure 1, are outlined and addressed in Level 3. 3.2.

LEVEL 2: CHARACTERISTICS MODULE

The characteristics module concerns the elements associated with the characteristics of the material and process to be assessed and may be seen in Figure 1. While the material and process characteristics this risk assessment strategy employs are not exhaustive, considering the data gaps and uncertainty associated with nanomaterial exposure and behavior, they may allow a preliminary assessment of the materials potential mobility and behavior. 3.2.1.

Material

The material assessed may be one intentionally released into the environment, such as zero valent nanoscale iron used for remediation, or a material released unintentionally or incidentally such as cerium oxide nanoparticles used as fuel additives. The material in question will determine its possible environmental or health risks. A survey into workplace health and safety practices in international nanomaterial firms and laboratories indicated that when asked if they believed there were any special risks associated with nanomaterials that they either handled or produced, 35 organizations reported that there were none, 25 described risks, and 12 reported either not knowing or not having enough information [5]. Of those describing risks, 12 organizations specified inhalation, 6 reported flammability, 1 dermal, and 1 environmental, and 11 generalized regarding possible risk. All organizations working with metals or metal oxides, 30, other than quantum dots reported no risk. The model strategy is tailored to include common individual nanoparticles likely to be used in the environment, such as those discussed above, as well as broad particle groupings such as metals, metal oxides, carbonaceous, organic and non-metals [20]. 3.2.2.

Form

Form relates to the form in which the particle is present in the particular product, process or life cycle stage. An ICON workplace report [20] highlighted the different forms such as dry powder, bound in solids and bound in liquids in which nanomaterials are handled in the workplace. Each form is associated with a different probability of release, exposure and behavior in the environment. Kaegi et al. [21] traced 50–200 nm TiO2 particles, used as whiteners and for the

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volatizing of organic compounds in paint, from their source on a building facade to a retrieving sink, such as rivers and storm drains. The National Research Centre for the Working Environment, Denmark have conducted tests on consumer pump and spray products containing nanoparticles and have shown these products to generate aerosols in the nanoparticle range, and the differing methods of application to have a large effect on particle concentration [32]. 3.2.3.

Size Distribution

The size distribution of the individual particles within the nanomaterial is associated with its uptake and behavior during treatment and aggregation and accumulation within the environment. Information on shape may also be provided here as this factor may prove important in inhalation exposure, where length and bio-persistency are thought to determine inflammatory potential [8]. 3.2.4.

Aggregate Size

The initial aggregate size the particles within the nanomaterial occur is associated with its uptake and behavior during treatment and aggregation and accumulation within the environment. Initial particle size should be taken into account along with aggregate size as studies with agglomerations of nano-sized and fine TiO2 particles with similar aerodynamic diameters showed the nano-sized agglomerations to produce more adverse lung effects on a mass basis [37]. It must also be noted that large nano-sized aggregates have a large physical diameter but a low density, and so have a small aerodynamic diameter and therefore be respirable [7]. This state of aggregation and resulting available surface area of nanomaterials may change once introduced into biological media as a result of surface-tension-mediated disaggregation of electrostatically or loosely agglomerated particulates [34]. 3.2.5.

Surface Area

The surface area of nanoparticles is generally larger than that for the same material in greater than nano-size on a mass or volume basis. This larger surface area correlates to more potential reactive sites on a mass or volume basis which in turn is associated with a greater redox and photoactivity potential, adsorption potential and aggregation potential, affecting transport properties within the environment and behavior during treatment. This high number of potential reactive sites may also be associated with potential pulmonary inflammation upon inhalation [28]. 3.2.6.

Surface Charge

The initial surface charge of the particles within the nanomaterial may affect the aggregation state of nanoparticles, which in turn is associated with the transport, accumulation and further agglomeration states of the nanomaterial once released into the environment and during treatment. Surface charge may also play an important role in adsorption and potential inflammatory effects once inhaled or

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ingested. Studies by Veronesi et al. [36] have shown PM negative surface charge to correlate with PM induced pulmonary inflammation. A review by Hoet et al. [19] into nanoparticle health risks highlighted the poor bioavailability of ingested positively charged particles through electro static repulsion and (negatively charged) mucus entrapment. 3.2.7.

Solubility/Persistence

The solubility or degrading ability of a material is associated with its persistence in ecological and biological systems. The rate of dissolution may be considered proportional to particle surface area, therefore nanoparticulate materials should dissolve faster than larger-sized bulk materials, for the same mass, on surface area considerations alone [12]. The dissolution of soluble metal ions from the surface metal-based nanoparticles, and perhaps the eventual complete dissolution of the particle upon entry into ecological systems, is of concern. Even with solubility of a few percent, a 1 mg l−1 solution of a metal oxide NP might generate l µg l−1 concentrations of metal ions in solution, and so there are concerns that some nanoparticles will act as delivery vehicles for free metal ions [17]. Active functionalization of the nanomaterial surface or the addition of a surfactant may alter the degradability of a material. 3.2.8.

Life Cycle Stage

The life cycle stage of a particular product or process will be associated with the form the material is associated with and its potential environment exposure targets, quantities and treatment. The life cycle stages of note include nanomaterial manufacture, use as an ingredient in production, application of nano-containing product/ process and disposal. 3.2.9. Quantities/Concentrations The quantities (t/year, g/p/day) and concentrations (ppm, µg/m3) in which a nanoproduct or process occurs is associated with its likelihood of release, treatment, transport and accumulation within the environment. A study of Swiss industry by Schmid and Riediker [31] found that several types of nanoparticles were found to be used in quantities of more than 1,000 kg/year per company, but the majority of nanoparticle applications were of a much smaller production scale. An ICON workplace report highlighted the scale in which nanoparticles are produced in various sectors, varying from bench or laboratory scale to full commercial scale. Remediation technologies typically use nanoparticles in the region of g/l [24]. A report into nanoparticle exposure modelling [4] highlighted the concentrations of engineered nanoparticles currently found in a range of consumer products, ranging from 0.001 to 100 mg/g.

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3.2.10.

Frequency

The frequency (daily, single treatment) and location (rural, urban) in which a nanoproduct or process occurs is associated with its likelihood of release, treatment, accumulation and transport within the environment. A report into nanoparticle exposure modelling [4] highlighted the current usage frequencies for consumer products likely to contain nanoparticles in the future and the potential subsequent nanoparticle release assuming different market penetrations. These products ranged from personal care products to paints and cleaning products. 3.3.

LEVEL 2: TREATMENT MODULE

3.3.1.

Disposal Methods

The methods of disposal of a nano-product (wastewater, nano-specific, incineration and landfill) are associated with its likelihood of release into the environment, the media into which it is released (soil, water, air) and its accumulation, transport and ultimate fate within the environment. An ICON report [20] highlighted industrial disposal of nanomaterials as hazardous waste through a waste management company and the incineration, agglomeration, storage or recycling of nanomaterials. However, most companies did not separate nano-waste into separate containers and did not label it as “nanomaterial,” but rather classified it by the bulk material. 3.3.2.

Waste-Water Treatment

Where nanomaterials are released intentionally into the environment or are released unintentionally from industrial facilities and domestic use, these materials are likely to enter wastewater treatment facilities before direct human exposure through ingestion and dermal exposure. The aggregation, surface charge and surface area of the nanomaterials as well as the treatment method employed will affect their removal efficiency and fate. Wastewater may be subjected to many different types of treatment, including physical, chemical and biological processes. Nanosized particles are most likely to be affected by sorption processes and chemical reactions. Nanomaterials that escape sorption in primary treatment may be removed from wastewater after biological treatment via settling in the secondary clarifier. The rate of gravitational settling of particles in water is dependent on particle diameter, and while nanoparticles may settle more slowly, their large surface to mass ratio will encourage entrapment in larger sludge flocs, enhancing removal [35]. 3.3.2.1. Treated Water Release Many wastewater treatment processes are expected to remove nanomaterials very efficiently, such as activated sludge [4], due to Brownian motion and their affinity to organic colloid binding. Due to high removal efficiencies, along with significant dilution factors upon release, it is expected that nanomaterials shall not be found in significant amounts in the released, treated waters.

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3.3.2.2. Sludge Release Where large quantities of nanomaterials are removed in the wastewater treatment process, this nanomaterial may be applied to soil within the treatment sludge. Silver mass flows have shown a significant percentage of released silver may be applied to agricultural soils, with nanomaterials likely to be removed in a similar fashion [3]. The transport and fate of this soil applied sludge, and thus nanomaterials, is an exposure route with potential effects on accumulation and secondary effects on the food chain as well as cross-media contamination into water and subsequent human exposure. A report into modelling exposure to engineered nanoparticles has attempted to apply traditional equations, used for pesticide drift and wastewater treatment amongst others, to potential intentional and unintentional nanoparticle release scenarios [4]. These models attempt to predict nanomaterial application to soils and release into waterways; however, the report concedes that much more data is needed in order to refine these models. 3.3.3.

Filter/Converter Efficiencies

Filter and catalytic converter efficiencies may have a large bearing on the amount of nanomaterial released into the environment from processes such as fuel additive and industrial manufacturing. Initial investigations into the efficiencies of filters with a cerium additive show a slight chance of cerium release into the environment, though simulations with worst case scenarios (all vehicles employing high levels of cerium additive; 92% efficient filter) indicate a very low risk of cerium inhalation [18]. Cerium levels in the air and soil in the vicinity of major transport systems would increase, although this must be assessed in a risk-benefit framework as cerium additives have also been shown to reduce the overall particle mass level released from vehicles [18]. Fibrious filtration techniques, such as HEPA standard filters used in industrial environments, have been shown to be even more efficient with nanosized particles (<100 nm), due to these particles being subject to Brownian motion enhancing collision probability with fibers. The maximum particle penetrating size was observed at approximately 150–300 nm [26]. 3.3.4.

Transformation of Characteristics

Treatment of nanomaterials may result in a transformation of their characteristics such aggregation state and surface charge. This transformation may affect their treatment removal efficiencies and subsequent environmental behavior such as adsorption and transport. An example of transformation in the environment is that of iron nanoparticles used for the dechlorination of organic pollutants. These particles are oxidized to iron oxide during this reaction and other metal particles are also converted to oxides in the presence of air and water. The resulting oxides may even be more reactive then the original free metals. Metal compounds in the environment may also be converted to more mobile compounds [35]. The effects of environmental release of particles on surface charge will depend on the media into which the nanoparticles are released. It has been noted in studies by

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Mahmoodi et al. [25] that their TiO2 surfaces were positively charged in acidic media (pH < 6.8), and as the pH of the system increased, the number of negatively charged sites increased, increasing the adsorption potential to negatively charged species. 3.4.

LEVEL 2: BEHAVIOR MODULE

Table 1 lists the particle and process characteristics that may affect some typical material behavior in the environment that may be of relevance in assessing the human exposure risk posed by a nanomaterial according to available literature. The exact theory of nanomaterial behavior in the environment has not yet been elucidated so the relationships listed in Table 1 may be seen as subjective. The actual characteristics considered shall change depending on which exposure media is being considered. The characteristics indicated will have different effects on the final behavior of the material, such as transport or adsorption, and in the final assessment these different characteristics must be weighted in accordance to their perceived relevance to specific nanomaterial behavior. The listed characteristics and behaviors will have inter-relationships and layers of complexity, although this strategy only considers those behaviors and characteristics which are reasonably easy to define and have a potentially significant effect on the nanomaterials final exposure risk. TABLE 1. Nanomaterial characteristics and environmental behavior. Behavior Material Character.

Transpt/Mob.

Aggreg.

Accum.

Adsorp.

Redox/Ptact

B_trpt

B_agg

B_acc

B_abs

B_rd/pt

C_mat

X

C_form

X

C_sd

X

X

X

C_agg

X

X

X

X

C_sa

X

X

X

C_sc

X

X

X

X

X

C_sol

X

X

X

C_con

X

X

X

C_freq

X

T_dis

X

X

X

T_ww

X

X

X

X

T_wat

X

X

X

X

T_slg

X

X

X

X

T_fil

X

T_car

X

X

X

X

C_lcs X

X

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Exposure Media

The exposure media relates to the environmental media into which the nanomaterial is released or is transported within; air, water or soil. This will affect the fate, aggregation, accumulation and human exposure probability of the material in question. Release of nanomaterials into the environment may be direct or through treatment facilities such as treated wastewater and sludge, as can be seen in the two-way exposure pathways in Figure 1. 3.4.2.

Transport/Mobility

The transport or mobility properties of a material will affect the potential area exposed to a nanomaterial and thus the potential human exposure. The differing characteristics of a material in different environmental media will affect its transport potential. Fate and transport of nanomaterials in aqueous environments, for example, is limited by the materials aqueous solubility, interactions between the nanomaterial and natural and anthropogenic chemicals in the system, and biological processes. Nanoparticles generally settle more slowly than larger particles of the same material in aqueous systems, though nanosized particles have a greater potential to be adsorbed onto soil and sediment particles, due to their larger surface to mass ratio, thus affecting their transport potential [35]. Fate and transport of nanoparticles in soil systems is affected by particle characteristics such as particle concentration, surface area and aggregate size and system characteristics such as pH and ionic strength [24]. A review by Nowack and Bucheli [27] into surface modified nanoparticles concluded that these particles were likely to be mobile under natural conditions, indicating the importance of determining exact surface properties of nanomaterials and particles, as indicated in this strategy, in order to assess their potential mobility in the environment. 3.4.3.

Adsorption

The adsorptive properties or potential of a nanomaterial may relate to the potential of materials to adsorb onto the nanomaterial or the potential of nanomaterials to adsorb onto larger particles or materials. The adsorptive potential of a nanomaterial is influenced by its surface area, surface charge, aggregation state and surface treatments. Adsorption of nanomaterials onto organic and soil particles will influence their treatment removal potential and their transport potentials in environmental media. Adsorption of materials such as transition metals and organic compounds may result in secondary exposure scenarios such as the socalled “Piggy-backing effect”, where a potentially harmful compound attaches to a nanomaterial, resulting in a bioavailability that may not have been previously available [9, 11]. A study by Zhang et al. [38] showed a much greater uptake of cadmium in Carp in the presence of TiO2 nanoparticles than in the presence of cadmium alone, highlighting this potential for enhanced bioavailability.

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3.4.4.

Aggregation

Aggregation of nanomaterials will affect their transport, redox, adsorption, treatment and persistence potential. Particle aggregation will be affected by the ionic strength of natural systems, which vary considerably, and this will thus affect transport, as these aggregates are mobile. This must be taken into consideration in nanoparticle-based environmental remediation systems, analyzing life cycles of nanoparticles used in commercial products, and determining potential exposure to nanoparticles for health and impact studies [10]. The chemistry of engineered nanoparticles suggests they will aggregate in many types of natural waters (e.g., hard freshwater and seawater), and ecotoxicologists have found it virtually impossible to disperse these particles in pure water by physical means alone [17]. Phenrat et al. [29] has suggested that, given the rapid aggregation of nano-scale zero valent iron into micrometer-sized fractal aggregates in NaHCO3 at pH 7.4 they observed, it may be more appropriate to specify the aggregate size for use in any filtration models since the choice of particle size greatly affects the estimated effective mobility of the particles. In a study focusing on actual nanomaterial emissions into the environment, Kaegi et al. [21] traced TiO2 nanoparticles from their source, painted facade, to their sinks, such as storm drains and rivers. These particles were not found in aggregates but mostly isolated or in organic binds. 3.4.5.

Accumulation

Accumulation of nanomaterials in the environment will affect their transport potential and exposure concentrations and frequencies, with aggregation and accumulation likely to result in fewer, but more extreme, exposure events. Accumulation of nanomaterials in media such as sediment and soil applied sludge may have secondary effects on the food chain, such as organisms in the lower trophic levels such as benthic worms and daphnia [17]. A cautionary tale into secondary affects on the food chain is the introduction of a veterinary drug into cattle in the 1980s in India leading to a 99–97% reduction in vulture numbers, with resultant rapid escalation of scavenger populations such as feral dogs, rats and crows, which in turn increased the risk of spreading disease amongst humans [16]. 3.4.6.

Redox/Photo-Activity

The redox or photo-activity of a nanomaterial may be seen as a potential indicator of toxic potential upon human exposure, where behavioral characteristics may be linked to cell toxicity mechanisms. Studies by Gojova et al. [13] on the inflammatory effects of metal oxide particles on human aortic endothelial cells following acute exposure showed that these effects depend on particle composition. Studies specifically on nano-TiO2 have lead to different proposals as to the particular characteristics that drive reactive oxygen species production and subsequent inflammatory effects, depending on exposure routes. Singh et al. [33] have shown these particles, even as aggregates/agglomerates, to have inflammatory properties in lung epithelial cells that appear driven by their specific surface area. However,

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Grassian et al. [15] found engineered nanoparticles, with the highest commercially available surface area and smallest particle size for TiO2 used in the study, did not show particularly toxic effects to rat lungs in a sub-acute inhalation study. These results are in conflict with the notion that inflammatory response is expected to be high with high surface area powders composed primarily of nanoparticles in the lower size range. While any inflammatory effects in these studies were concluded to be produced by oxidative stress, the responsible mechanism(s) could not be elucidated. TiO2 nanoparticles may undergo surface treatments, such as alumina or silica/alumina coatings that limit their chemical and photo-chemical activity. Particles having undergone such a treatment would be expected to have a low risk potential for producing adverse pulmonary health effects [37]. 3.5.

LEVEL 3: EXPOSURE SCENARIOS

The exposure scenarios examined in Level 3 relate to those primary questions posed in Level 1 of the risk assessment strategy. These exposure scenarios typically address exposure concentrations, frequencies and routes. Resultant exposure scenarios are a result of the combination of process and treatment characteristic elements and behavioral conclusions of the strategy in Level 2. Some typical exposure scenario questions, such as those highlighted in Figure 1, are discussed below. 3.5.1.

Environmentally Relevant Concentrations

The concentrations of a nanomaterial found in the environment will determine whether this material poses a realistic environmental and subsequent human health hazard. Level 2 strategy elements relevant to the concentrations of a nanomaterial released into the environment include the life cycle stages considered, concentrations or quantities of a product or process in circulation, the material disposal methods and the treatment and filtration methods employed. A study by Handy et al. [17] into lethal dose values on the ecotoxicity of nanoparticles found very few published studies, but studies on fish and invertebrates have suggested that C60 fullerenes and 10–20 nm TiO2 particles are toxic in the milligram per liter range, but that the specific LC50 values were dependent on the preparation of the material and the use of dispersants. 3.5.2.

Local vs. Widespread Exposure

The extent to which an environmentally released nanomaterial is transported will determine whether this material poses a realistic human exposure hazard. Level 2 strategy elements relevant to the extent of penetration of a nanomaterial released into the environment include the life cycle stages considered, concentrations or quantities of a product or process in circulation, the material disposal methods, the treatment methods employed and the transport, aggregation and accumulation behavior.

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3.5.3.

Exposure Frequency

The frequency of exposure to a nanomaterial is an important factor in accumulation and fatigue effects through repeated exposure. Level 2 strategy elements relevant to the likely frequency of exposure to a nanomaterial released into the environment include the life cycle stages considered, concentrations or quantities of a product or process in circulation, the material disposal methods, the treatment methods employed and the transport, aggregation and accumulation behavior. 3.5.4.

Primary Routes of Human Exposure – Inhalation, Ingestion, Dermal Exposure

The route of exposure to a nanomaterial is an important factor in determining characteristics, frequencies and concentrations of concern to human health. Level 2 strategy elements relevant to the likely routes of exposure to a nanomaterial released into the environment include the transport, aggregation and accumulation behavior. 4. 4.1.

Model Application UNCERTAINTY, VARIABILITY AND ASSUMPTIONS

In the case of nanomaterials, and nanoparticles in particular, there is great uncertainty as to their fate in the environment, the quantities these particles may be present in at each exposure point and the potential ecotoxicological hazards and transformations that may take place such as disaggregation and adsorption of potentially harmful materials. Because of a lack of exposure and toxicological data concerning nanoparticles, qualitative risk assessments employing probability distributions, substitutions and even simulation in tandem with expert opinion and critical literature reviews are required to fill these data gaps [14]. The case for eliciting expert opinion or critically analyzing literature in order to overcome uncertainty and data gaps in risk assessment modelling is one which has been examined in an assessment by Cooke et al. [6] on campylobacter transmission in chicken processing lines. In this assessment, expert judgment on predicted observable quantities in combination with probabilistic inversion was used for validation and criticism of a general mathematical chicken processing model. Study of the experts’ rationales led to a revision of the model and a good fit between the experts’ and the re-predicted distributions. A qualitative model derived from the strategy presented here may employ a critical analysis of literature, in which the intrusion of subjectivity would be unavoidable, although once critical exposure points such as fate during treatment processes and transport in different environmental media are better understood and studies with universal reference materials undertaken, this strategy may be converted to a quantitative basis where a common risk ranking structure for nanomaterials may be developed.

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Distributions allow us to account for the full spectrum of possible events in the particles lifetime. For example, carbon nanotubes may adsorb significant amounts of the catalytic metals used to produce them and particles in the environment may adsorb bio-molecules. Both scenarios may result in inflammatory effects in the human body [11]. Iterative simulations employing these distributions relating to the various release and behavioral possibilities allow a true picture of the potential exposure scenarios to be assembled. Any model using this strategy may tackle the problem of deficiencies in initiating data by employing predefined distributions for the particular entry derived from data sets according to the known initiating parameters and their inter-relationships. These data sets may be derived from literature, manufacturers’ information and expert opinion. One of the major assumptions made in this three-level strategy is that the material, process, treatment and behavioral characteristics presented alone are involved in the exposure scenarios. The second is that any relationships employed in a model derived from this strategy would by independent of all other physical variables. Many of the potential model relationships employed may not be derived from any firm underlying physical laws, nor may they as yet be verified by direct observation or by experiment. Indeed, studies into compartmentalized models for hazardous materials, such as exposure models concerning mass transfers over time, have shown that the types of arguments leading to a choice of a specific model depend entirely on the material in question [23]. Once a compartmental model is chosen, the method for determining the relationships involved and values of the underlying transfer coefficients is also highly specific to the problem at hand and involves a great deal of qualitative reasoning. The absence of direct physical measurements of these inter-relationships and transfer coefficients means that relevant uncertainty inherent in a qualitative model derived from this strategy could not be determined by objective statistical methods, but by the subjective uncertainty of experts. 5.

Discussion and Conclusions

The strategy presented here does not cover every material, process and environmental characteristic that may be relevant to human exposure to nanomaterials, though it does provide an overview of the principle factors, their inter-relationships and effects on nanomaterial environmental behavior that need to be taken into account before developing a nanomaterial or process for wide scale release, or before developing regulatory frameworks for these materials. Due to its largely qualitative basis, any model derived from this strategy would be of more use in comparing two nanomaterials, or comparing the effects of changing one or more material or process characteristics. As more information is generated on critical exposure points such as fate during treatment processes and transport in different environmental media, models with a quantitative basis may be constructed on this basis, where nanomaterials may be compared on a common risk ranking structure, while also removing the subjectivity associated with qualitative risk analyses. This

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model strategy could find application in regulatory forecasting, where future exposure scenarios may be explored and controls set where appropriate. Another avenue of research that may be undertaken as part of this vein of research is that of potential ecotoxicity, as alluded to in discussions on effects of accumulation of nanomaterials in the environment, such as critical damage to vital links in the food chain. The anti-bacterial effects of nano-silver are well reported [2], but research by Adams et al. [1] into the ecotoxic potential of various nanoscale metal oxides in water suspensions indicated varying degrees of antibacterial activity to test organisms, highlighting the importance of nanomaterial environmental exposure control until more is known about material characterisation and potential toxic mechanisms. Models assessing potential ecotoxicity may incorporate information on the characteristics of the ecological systems into which the specific nanomaterial is to be introduced, such as salinity/ionic strength, pH, hardness, dissolved organic matter, etc. [17]. Secondary effects of nanomaterials that may need to be taken into account in undertaking a full human health impact analysis of nanomaterials is that of raw material extraction and potential recyclability. The functionalization of nanomaterials at the nanoscale has opened up new avenues of exploitation for many materials, and the extraction of the raw mineral materials that form these nanomaterials may have secondary effects on the environment and subsequently human health [22, 30]. This functionalization enhances traditional material characteristics, such as strength, melting temperature, etc. but also limit the traditional recycling routes and methods available for these enhanced material and products [22]. The risk assessment of nanomaterials may ultimately be an exercise of measuring risk vs. benefit of a potential new enabling nanoproduct, process or technology. Acknowledgements The authors would like to acknowledge the financial support from the Irish Environmental Protection Agency for this work. References 1. Adams, L.K., Lyon, D.Y., Alvarez, P.J., 2006, Comparitive eco-toxicity of nanoscale TiO2, SiO2, and ZnO water suspensions, Water Res 40:3527–3532. 2. Benn, T.M., Westerhoff, P., 2008, Nanoparticle silver released into water from commercially available sock fabrics, Environ Sci Technol DOI: 10.1021/es7032718. 3. Blaser, S.A., Scheringer, M.A., MacLeod, M., Hungerbühler, K., 2008, Estimation of cumulative aquatic exposure and risk due to silver: contribution of nano-functionalized plastics and textiles, Sci Total Environ 390:396–409. 4. Boxall, A.B.A., Chaudhry, Q., Sinclair, C., Jones, A., Aitken, R., Jefferson, B., Watts, C., 2007, Current and future predicted exposure to engineered nanoparticles (March 28, 2008); http://www.defra.gov.uk/science/Project_Data/DocumentLibrary/CB01098/CB01098_6 270_FRP.pdf. 5. Conti, J.A., Killpack, K., Gerritzen, G., Huang, L., Mircheva, M., Delmas, M., Herr Harthorn, B., Appelbaum, R.P., Holden, P.A., 2008, Health and safety practices in the

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22. Karn, B., 2008, US research on nanotechnology applications: green nanotechnology for past, present and preventing future problems, March 2008, Ascona, Switzerland, nanoEco conference book of abstracts, p 77. 23. Krann, B.C.P., Cooke, R.M., 2000, Uncertainty in compartmental models for hazardous materials - a case study, J Hazard Mater 71:253–268. 24. Lowry, G.V., Phenrat, T., Kim, H.J., Saleh, N., Tilton, R.D., 2008, Polyelectrolyte surface modifications optimise emplacement and mitigate ecological risk of reactive nanoparticles for in situ groundwater remediation, March 2008, Ascona, Switzerland, nanoEco conference book of abstracts, p 81. 25. Mahmoodi, N.M., Arami, M., Limaee, N.Y., Gharanjig, K., Nourmohammadian, F., 2007, Nanophotocatalysis using immobilized titanium dioxide nanoparticle. Degradation and mineralization of water containing organic pollutant: case study of Butachlor, Mater Res Bull 42:797–806. 26. NanoSafe, 2008, Efficiency of fibrous filters and personal protective equipments against nanoaerosols (March 28, 2008); http://www.nanosafe.org/node/907. 27. Nowack, B., Bucheli, T.D., 2007, Occurance, behavior and effects of nanoparticles in the environment, Environ Pollut 150:5–22. 28. Oberdorster, G., Maynard, A., Donaldson, K., Castranova, V., Fitzpatrick, J., Ausman, K., Carter, J., Karn, B., Kreyling, W., Lai, D., Olin, S., Monteiro-Riviere, N., Warheit, D., Yang, H., 2005, Principles for characterizing the potential human health effects from exposure to nanomaterials: elements of a screening strategy, Part Fibre Toxicol 2:8. 29. Phenrat, T., Saleh, N., Sirk, K., Tildon, R.D., Lowry, G.V., 2007, Aggregation and sedimentation of aqueous nanoscale zerovalent iron dispersions, Envrion Sci Technol 41:284–290. 30. Rickerby, D.G., Morrison, M., 2007, Nanotechnology and the environment: a European perspective, Sci Tech Adv Mater 8:19–24. 31. Schmid, K., Riediker, M., 2008, Use of nanoparticles in Swiss industry: a targeted survey, Environ Sci Technol 42:2253–2260. 32. Schneider, T., 2007, Evaluation and control of occupational health risks from nanoparticles (March 28, 2008); http://norden.org/pub/velfaerd/arbetsmiljo/uk/TN2007581. pdf. 33. Singh, S., Shi, T., Duffin, R., Albrecht, C., van Berlo, D., Höhr, D., Fubini, B., Martra, G., Fenoglio, I., Borm, P.J.A., Schins, R.P.F., 2007, Endocytosis, oxidative stress and IL-8 expression in human lung epithelial cells upon treatment with fine and ultrafine TiO2: role of the specific surface area and of surface methylation of the particles, Toxicol Appl Pharmacol 222:141–151. 34. Soto, K., Garza, L.E., Murr, L.E., 2007, Cytotoxic effects of aggregated nanomaterials, Acta Biomater 3:351–358. 35. United States Environmental Protection Agency (USEPA), 2007, Nanotechnology white paper (March 28, 2008); http://es.epa.gov/ncer/nano/publications/whitepaper 12022005.pdf. 36. Veronesi, B., de Haar, C., Lee, L., Oortgiesen, M., 2002, The surface charge of visible particulate matter predicts biological activation in human bronchial epithelial cells (BEAS-2B), Toxicol Appl Pharmacol 178:144–154. 37. Warheit, D.B., Webb, T.R., Sayes, C.M., Colvin, V.L., Reed, K.L., 2006, Pulmonary instillation studies with nanoscale TiO2 rods and dots in rats: toxicity is not dependent upon particle size and surface area, Toxicol Sci 91:227–236. 38. Zhang, X., Sun, H., Zhang, Z., Niu, Q., Chen, Y., Crittenden, J.C., 2007, Enhanced bioaccumulation of cadmium in carp in the presence of titanium dioxide nanoparticles, Chemosphere 67:160–166.

CLASSIFYING NANOMATERIAL RISKS USING MULTI-CRITERIA DECISION ANALYSIS

I. LINKOV, J. STEEVENS, M. CHAPPELL US Army Research and Development Center, CEERD-EP-R Vicksburg, MS 39180, USA [email protected] T. TERVONEN Faculty of Economics and Business University of Groningen P.O. Box 800, 9700 AV Groningen, The Netherlands [email protected] J.R. FIGUEIRA CEG-IST, Centre for Management Studies, Instituto Superior Técnico, Technical University of Lisbon 2780-990 Porto Salvo, Portugal [email protected] M. MERAD Societal Management of Risks Unit/Accidental Risks Division – INERIS BP 2 - F60550 Verneuil-en-Halatte, France [email protected]

Abstract. There is rapidly growing interest by regulatory agencies and stakeholders in the potential toxicity and other risks associated with nanomaterials throughout the different stages of the product life cycle (e.g., development, production, use and disposal). Risk assessment methods and tools developed and applied to chemical and biological material may not be readily adaptable for nanomaterials because of the current uncertainty in identifying the relevant physico-chemical and biological properties that adequately describe the materials. Such uncertainty is further driven by the substantial variations in the properties of the original material because of the variable manufacturing processes employed in nanomaterial production. To guide scientists and engineers in nanomaterial research and application as well as promote the safe use/handling of these materials, we propose a decision support system for classifying nanomaterials into different risk categories. The classification system is based on a set of performance metrics that measure both the toxicity and physico-chemical characteristics of the original materials, as well as the expected environmental impacts through the product life cycle. The stochastic I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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multicriteria acceptability analysis (SMAA-TRI), a formal decision analysis method, was used as the foundation for this task. This method allowed us to cluster various nanomaterials in different risk categories based on our current knowledge of nanomaterial’s physico-chemical characteristics, variation in produced material, and best professional judgement. SMAA-TRI uses Monte Carlo simulations to explore all feasible values for weights, criteria measurements, and other model parameters to assess the robustness of nanomaterial grouping for risk management purposes.1,2 1.

Introduction

Nanotechnology is a rapidly growing field of research that is already demonstrating a great impact on consumer products. The field of nanotechnology can be defined as the production and use of materials at the nano-scale, normally characterized as smaller than 100 nm in one dimension [28]. Nanomaterials are formed through both natural (e.g., combustion by-products) and synthetic processes. For the purposes of this paper, we focus our discussion solely on engineered nanomaterials, which are currently used in more than 600 different consumer products (Woodrow Wilson Institute http://www.nanotechproject.org/inventories/ consumer/). In spite of their potential commercial benefits, some nanomaterials have been identified as toxic in in vivo and in vitro tests. Clearly, our knowledge of the potential toxicity of these materials is far from comprehensive [28, 35]. The potential environmental fate and toxicity (as well as potential for exposure and risk) of nanomaterials may be strongly impacted by the material’s physicochemical characteristics. For example, potentially toxic nanoparticles that tightly bind to soil surfaces may exhibit limited movement through the environment. In this case, such materials may be deemed relatively safe for certain specific uses. Such information is important as a lack of understanding of nanomaterial toxicity and risks may delay full-scale industrial application of nano-enabled technologies. Nanomaterial research and regulations could be guided by a systematic characterization of factors leading to toxicity and risks in the absence of definitive data. In this paper, we propose a risk-based classification system for nanomaterials that takes into account several parameters commonly associated with nanoparticle toxicity and risk. These parameters vary from nanomaterial physico-chemical characteristics to expected environmental concentrations to fate and transport mechanisms. In this work, we consider risk to both humans and to the environment in a broad ecological sense. This work does not attempt to draw exact conclusions about the environmental risks associated with different nanomaterials, but rather to provide reasonable recommendations about which nanomaterials may need more precise measurements and testing to be safely deployed in consumer products. 1

This paper is based on material submitted for publication in the Journal of Nanoparticle Research. The views and opinions expressed in this paper are those of the individual authors and not those of the US Army, NATO, or other sponsor agencies.

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2.

MCDA Approaches to Classification

Clustering nanomaterials into ordered risk categories can be treated as a sorting problem in the context of multi-criteria decision analysis (MCDA). MCDA refers to a group of methods used to impart structure to the decision-making process. Generally, the MCDA process consists of four steps: (1) structuring the problem by identifying stakeholders and criteria (nanomaterial properties in this case) relevant to the decision at hand, (2) eliciting the parameters of the model (weights, thresholds, etc.), and assigning measurements for each alternative (e.g., nanomaterial risk group), (3) executing the model through computer software, and (4) interpreting results of the model and possibly re-iterating the process from step 1 or 2 by re-evaluating the model. The goal of this MCDA process was not to select a single best alternative, but to rank or group alternatives through a structured process. A detailed analysis of the theoretical foundations for different MCDA methods and their comparative strengths and weaknesses is presented in [2]. A review of MCDA applications to environmental management can be found in [22]. The SMAA-TRI sorting method [32] is well suited for the proposed classification system given the uncertain physico-chemical characteristics of nanomaterials. Many of the characteristics attributed to nanomaterials are limited to a solely qualitative assessment (see [14] for a review of other MCDA sorting methods). We used SMAA-TRI, an outranking model based on ELECTRE TRI (see e.g. [15]) for the assignment procedure. If an alternative outranked another, then the alternative was considered at least as good or better than another alternative. We preferred SMAA-TRI as it extends the capabilities of ELECTRE TRI by allowing the use of imprecise parameter values. ELECTRE TRI assigns the alternatives (different nanomaterials in this study) to ordered categories (risk classes). Three types of thresholds are used to construct the outranking relationships by defining preferences with respect to a single criterion. The indifference threshold defines the difference in a criterion that is deemed insignificant. The preference threshold is the smallest difference that would change the expert preference. Between these two lay a zone of “hesitation” of indifference. The veto threshold is the smallest difference that completely nullifies (raises a “veto” against) the outranking relation. The assignment procedure involves comparing the properties associated with a specific nanomaterial (g1, g2, …, gm) against a profile that includes ranges of criteria metric values corresponding to several risk classes. Comparisons are performed with respect to each criterion, taking into account the specified thresholds. The final classification decision is based on the profile criteria weights and specified cutoff level (lambda). For example, Class 4 represents the highest risk while Class 1 is the lowest risk (Figure 1). The assigned criteria weights represent the subjective importance of the criteria. For this reason, ELECTRE TRI was particularly attractive for these classifications because the weights represent “votes” for each criteria which are not affected by criteria scales. The lambda cutting level represents the minimum weighted sum of criteria that have to be in concordance with the outranking relation for it to hold: the lambda cutting level is used to transform the “fuzzy”

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gm gm-1

s Cla

s4

3 ss Cla

2 ss Cla

1 ss Cla

g3 g2 g1 Figure 1. Example measurements of profiles for each criterion gj. Profiles are marked with horizontal lines. (Adapted from [25])

outranking relation into an exact one (whether an alternative outranks a profile or not). For example, a lambda cutting level of 0.6 means that 60% of the weighted criteria have to be “at least as good” for the outranking relation to hold. Alternatives were compared by accounting for the three thresholds. An alternative and profile with scores of 0.4 and 0.6 (for the same criterion) respectively, and an indifference threshold of at least 0.2, demonstrates that this criterion fully supports the conclusion that the alternative outranks the profile. Sometimes the support is not binary, but is further affected by linear interpolation in the hesitation zone of both veto and preference thresholds (see e.g. [31]). In this case the support can have real values between 0 (no support) and 1 (full support). All the parameters of ELECTRE TRI can be imprecise and represented by arbitrary joint distributions in SMAA-TRI. This feature allows us to make conclusions about risks related to different nanomaterials even though the information about their characteristics is limited. Monte Carlo simulations were used in SMAA-TRI to compute acceptability indices for alternative categorizations (i.e., for assigning nanomaterials in different risk classes). Output of SMAA-TRI comes as a set of category acceptability indices which describes the share of feasible parameter values that assign alternatives to each category. The category acceptability indices are measures indicating the stability of the parameters, i.e., if the parameters are too uncertain to make informed decisions. A high index (>95%) signals a reasonably safe assignment of the alternative into the corresponding category. With lower indices, the risk attitude of the decision maker defines the final assignment. For example, if an alternative has a 80% acceptability for the lowest risk category, and a 20% acceptability for the second lowest risk category, a risk-averse decision maker could assign the alternative to the higher risk category. SMAA-TRI conducts the numerical simulation by comparing the effect of changing parameter values and criteria evaluations on the modeling outcomes. Parameter imprecision can be quantified by Monte Carlo simulations using different

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probability distributions (uniform, normal, log-normal, etc.). Gaussian or uniform distributions are typically used (for more information about SMAA methods, see [34]). 3.

Criteria

Recent articles, as well as the frameworks reviewed in this study, generally use several different characteristics in their assessment of nanomaterial risk. These characteristics are generally based on extrinsic particle characteristics (size, agglomeration, surface reactivity, number of critical function groups, dissociation abilities) [3, 5, 6, 17, 21, 23, 27, 35]. Summary descriptions of five basic extrinsic nanomaterial properties, agglomeration, reactivity/charge, critical functional groups, particle size, and contaminant dissociation are presented below: ƒ Agglomeration is an important criterion of risk because it includes a description of the physical state of nanoparticles (NP) in the system. In aqueous solutions, NP agglomeration generally occurs by two mechanisms: colloid settling and flocculation. Flocculation occurs when Brownian-driven collisions bind unassociated particles together through van der Waals forces by dehydrating the interacting surfaces. Consequently, the particle separates out of solution containing the mass of the previously unassociated particles. Settling, on the other hand, occurs due to the pull of gravity, as described by Stokes law relationships. Particles may settle but remain non-flocculated, settling at interparticle distances with the lowest free energies. In the absence of surfactive agents, particle flocculation is fairly predictable by particle charge. Charged functional groups give way to the development of a surface electrostatic potential which extends out a few nanometers at the solid-liquid interface forming a diffuse double layer or DDL [8, 36]. Classical DLVO theory predicts that repulsive forces between particles (arising from overlapping DDLs) increase with increasing ion concentrations (or increasing ionic strength, I) because of rising osmotic pressures at the solid-solution interface force the DDL to swell ([13] and references therein). Yet, classical Debeye–Huckel theory predicts a competing case where increasing ion concentration decreases DDL thickness, throwing a system into flocculation. Thus, at a fundamental level, the process of agglomeration represents the balance of these two competing charge interactions. ƒ Reactivity/Charge. Charge may be expressed on NP either by design (such as through functionalization) or by spontaneous degradative reactions. NPs may be functionalized with various types of groups, such as COOH, NH2, and SH2 through standard organic synthesis methods. Such functionalizations may be useful for manufacturing processes. For example, single-walled carbon nanotubes (SWNTs) are typically carboxylated at their ends as part of the isolation/ purification process (Anita Lewin, RTI International, personal communication, 2007). The type of charge occurring on functionalized NPs is called variable charge, which means that the magnitude of the surface electrostatic potential varies with solution pH [36]. Variably charged groups characteristically exhibit a surface pKa. Thus, variably charged surface groups may be speciated (e.g.,

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protonated vs. deprotonated) by the classical Henderson-Hasselbauch equation. Furthermore, the magnitude of the surface electrical potential may be suppressed by increasing I, as described previously. Thus, the reactivity of variably charged functional groups varies with the difference in solution pH from the surface pKa and the magnitude of I. ƒ Critical functional groups: Related to the reactivity/charge, critical functional groups make up an important criterion given the fact that nanomaterial functionality and bioavailability is directly related to chemical species. Basing risk criteria on elemental speciation is superior to elemental composition alone because it identifies the unique set of reactions available to each species. For example, suspended zero-valent Fe nanoparticles have been shown to catalyze reductive degradations of aqueous organic contaminants [19]. The same degradative ability has been shown for structural Fe2+ (higher oxidation state than zero-valent Fe but different speciation in terms of its complexation environment) domains at clay-edge and -interlayer nano-sites in soil [18]. The Cd2+ cation in quantum dots exhibits no toxicity to organisms as long as it remains complexed with Se [11]. Speciation also determines solubility or potential dissociation of nanomaterials. ƒ Contaminant dissociation: This criterion describes risk associated with residual impurities contained within the NP. For example, Fe oxide NP may contain S impurities depending on whether FeCl3 or Fe2(SO4)3 was used in manufacturing. Carbon nanotubes may contain Ni, Y, or Rb metal cation impurities [7, 10], which may either be entrained within or adsorbed onto the surface of the tubes. However, little is actually known about the extent in which metallic and organic contaminants remain with the manufactured product. Thus, the assignment of this risk criterion could change depending on better information. ƒ Size: Particle size is a criterion related to the agglomeration and reactivity criteria. Obviously, smaller particles agglomerate at slower rates. However, agglomeration is also related to the particle size distribution or polydispersivity. For example, greater monodispersivity of particles sizes appears to promote more stable dispersions [9]. Also, nanoparticle reactivity is also impacted by the size of NP surface relative to the bulk of the solid. While the surface is the reactive portion of solids, the bulk component may suppress the surface reactivity through internal reorganizations, etc. NPs are essentially surfaces with limited bulk. Thus, the smaller particle size, the lower bulk to potentially limit surface reactivity. Surfaces with low accompanying bulk have been shown to possess enhanced reactivities, such as high-affinity adsorption of metals or unique structures of assembly during agglomeration [1, 12]. Particle size is particularly important in terms of distinguishing the unique size-dependent chemistry of nanoparticles from classical colloid chemistry. Processes that may influence the potential hazards of engineered nanomaterials include bioavailability potential, bioaccumulation and translocation potential, and potential for toxicity. These processes have been described in empirical studies and are dependent on the characteristics of the particles as described above. It is

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difficult to predict the behavior of these materials, however, in the future computational approaches are expected to provide additional tools to estimate these processes from the physical and chemical parameters. ƒ Bioavailability potential: Bioavailability describes the amount of material absorbed across cell membranes from the various exposure routes (e.g., dermal, inhalation, and oral exposures) into system circulation in an organism [24]. This process is controlled by the characteristics described above. For example, charge of the particles may influence the agglomeration of the particles and hence limit the ability of the particle to cross the gastrointestinal membranes after oral ingestion. There are however, several pathways which nanoparticles may cross cell membranes ranging from pinocytosis, endocytosis, and diffusion as summarized in [37]. The mechanisms by which these particles are absorbed are highly dependent on the particle composition, surface modification, size, shape, and agglomeration. ƒ Bioaccumulation potential: Bioaccumulation is the net accumulation of particles absorbed from all sources (soil, water, air, and food) and exposure routes listed above into an organism. Accumulation must consider the temporal aspects of exposure and include kinetic factors such as exposure concentration, duration of exposure, clearance, biotransformation, and degradation. Most studies to date have focused on the potential for uptake and translocation in specific tissues [20, 30] and have not addressed the toxicokinetics of nanoparticles. ƒ Toxic potential: Toxicity of engineered nanomaterials and particles in mammalian and other animal systems has been assessed primarily through cytotoxicity screening assays; although some in vivo studies have been completed. Effects of nanomaterials occurs through oxidative stress, inflammation from physical irritation, dissolution of free metal from metal nanoparticles, and from impurities in nanomaterials (e.g., catalysts) [28]. The characteristics of nanoparticles that influence toxicity include the size, surface area, morphology, and dissolution. To date, screening studies using in vitro approaches have observed toxicity from metal nanoparticles at lower concentrations [4] than toxicity from carbon-based nanoparticles [16, 26]. 4.

Proposed Classification Framework

The purpose of the proposed classification system is to preliminarily group nanomaterials in risk classes for screening level risk assessments. Such groupings should aid in prioritizing materials for further study. In this paper, we considered five risk categories: extreme, high, medium, low, and very low risk. In order to assign particular nanomaterials to these categories, we need to define criteria scales, thresholds, and measurements. The quantitative criterion, particle size, was evaluated as the mean size of the material in units of nanometers as obtained from literature review and expert estimates. Bioavailability, bioaccumulation, and toxic potential were measured through subjective probabilities that the nanomaterial has significant potential in

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the criterion. These, as well as rest of the criteria (agglomeration, reactivity/charge, critical function groups) were measures based on expert judgments. The qualitative criteria, agglomeration, reactivity/charge, and critical function groups, were measured in terms of ordinal classes: 1 was the most favorable (least risk) value class, while 5 the least favorable (highest risk). For the qualitative criteria, we encoded the classes with integers. The indifference thresholds were set to 0 and the preference thresholds to 1. This choice of thresholds represented an ordinal scale: a smaller number was preferred to a larger one, but the intervals did not carry any information (e.g. 1 is as much preferred to 2 as 1 is to 3). If there were multiple possible classes for an alternative, the measurement was modeled with a uniform distribution, meaning that the integers corresponding to these classes were equiprobable within specified range. Veto thresholds were not used in this phase of the framework, but will be added later when more information about the criteria becomes available. Size is a criterion that should have some veto associated with it, so that very small materials cannot be assigned to the safer (lower risk) categories. Even though nanomaterial size is believed to be a factor influencing toxicity, there is little specific information available characterizing toxic effects relative to the 1–100 nm size range [29]. More research is needed to define the thresholds in a more exact manner. If a “smaller”-sized nanoparticle represents higher risk, it follows that a larger size is “more preferable” because of its inherently lower risk. Due to these knowledge gaps, imprecise thresholds were used for nanomaterial size with indifference threshold of 10 ± 5% and preference threshold of 25 ± 5%. Bioavailability, bioaccumulation, and toxic potential were all measured using a cardinal but subjective scale as described in the previous section. Because of the subjectivity of this scale, we applied imprecise thresholds. Indifference thresholds were set to vary uniformly from 0 to 10, and preference thresholds from 10 to 20. The SMAA-TRI model separated the risk categories using profiles formed from measurements of the same criteria as the alternatives. In our framework, the profile measurements were all exact (Table 1). Our model applied imprecise preference information in the form of weight bounds. For more information on how these were implemented, see [33]. We judged the toxic potential to be the most important criterion, and thus it was assigned weight bounds of 0.3–0.5. Bioavailability and bioaccumulation potentials were deemed the least important criteria, and as a result, we were undecided on their relative importance. Both of these criteria were given weight bounds ranging from 0.02–0.08. The rest of the criteria were assigned weight bounds of 0.05–0.15. We used imprecise values for the lambda cutting level within the range of 0.65–0.85. Lambda defines the minimum sum of weights for the criteria that must be in concordance with the outranking relation to hold. The classification was performed according to the pessimistic assignment rule, which in risk assessment applications represents a more conservative approach.

3

2

1

Highmedium

Mediumlow

Low-very low

1

2

3

4

Reactivity/ charge

1

2

3

4

Crit. function groups

1

2

3

4

Contaminant dissociation

60

70

80

100

Bioavailability potential

60

70

80

100

Bioaccumulation pot.

60

70

80

100

Toxic pot.

200

100

50

5

Size

4

4

3

5

MWCNT

CdSe

Ag NP

Al NP

4

C60

Agglomeration

1 1

4,5

1,2

4 1

2,3

4,5

3

Crit. function groups

2,3

Reactivity /charge

1

4

4

3

2

Contaminant dissociation

25

50

50

25

25

Bioavailability pot. (±10)

75

75

75

50

50

Bioaccumulation pot. (±10)

10

75

75

25

10

(±10)

Toxic pot.

50

50

20

50

100

(±10%)

Size

TABLE 2. Criteria measurements. The first four criteria are measured as ordinal classes. Measurements of reactivity/charge have associated uncertainty in that the materials can belong to either of the indicated classes. The following three criteria have linear imprecision of 10 in both directions from the indicated mean value. Size has uncertainty of 10% of the shown mean value.

4

Profile

Extremehigh

Agglomeration

TABLE 1. Profile measurements. Each row corresponds to a profile differentiating the categories presented in the first column.

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5.

Example

We demonstrated application of the framework by classifying five nanomaterials: nC60 (a fullerene), MWCNT (Multi-Walled Carbon Nanotube), CdSe (quantum dot), Ag NP (Silver-Nanoparticles), and Al NP (Aluminum Nanoparticles). Typical size ranges for these materials were estimated based on in situ measurements from the available literature. Other properties were assessed using authors expert judgments, taking into account the characteristics for each criterion described in Section 3. Metrics for the five materials used in our case study (Table 2) were input into the SMAA-III software. Category acceptability indices obtained from the simulation are presented in Figure 2. These indices show that the data was too imprecise to make definite decisions about the risks related to the different nanomaterials. However, there was sufficient data to make preliminary classifications. For example, CdSe exhibited a very high index in the high risk-class. On the other hand, Al NP may be considered relatively safe, its category acceptability indices for low and very low risk were 34 and 34, respectively. Summing these indices gave the material an estimated 68% probability of being classified as “low to very low risk”. C60 showed a reasonable acceptability index (49%) for the low risk category. In terms of making riskaware decisions for C60 and Al NPs, we feel that further studies into expanding the potential applications of Al NP and C60 (as opposed to CdSe) are justified. It is important to point out that in spite of the high uncertainty of the above results, this work represents a reasonable starting point for a more thorough followup analysis. And indeed, more data is required to improve our estimates. Risk estimates based on acceptability indices below 80% should be viewed with caution.

Extreme risk High risk Medium risk Low risk Very low risk C60

0

0

51

49

0

MWCNT

0

26

73

1

0

CdSe

0

98

1

1

0

Ag NP

0

29

71

1

0

AI NP

0

0

33

34

34

Figure 2. Category acceptability indices of the example. A high index means, that the material is assigned to that category with a large share of possible parameter values (weights, measurements,...).

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For example, should C60 be deemed viable for further research and application, additional measurements will be required to further refine the risk estimates. In spite of its limitations, the quantified risk values determined from our simulations are helpful in characterizing the risk and uncertainty for limited and variable data. 6.

Concluding Remarks

Nanotechnology is a fast growing research field with an increasing impact on our everyday lives. Although nanomaterials are used in common consumer products, the lack of information about human health and environmental risks may hamper the full-scale implementation of this technology. We presented in this paper a systematic multi-criteria approach that allows for assigning nanomaterials into ordered risk classes. Materials assigned to the highest risk class potentially represent areas of important future toxicological studies while materials exhibiting low risk may be recommended for direct commercial use. The proposed framework takes into account measurements and expert estimates for multiple criteria that are known to impact the toxicity of the material. The use of SMAA-TRI approach allows for the explicit incorporation of uncertainty parameters in the model. An appealing characteristic of the outranking model applied in SMAA-TRI is that it allows veto effect to be modeled, meaning that a nanomaterial’s poor performance in one criterion cannot be compensated by good performance in other criteria (as is the case for compensatory MCDA models, e.g. utility theory). This convention prevents decisions about the risk of a particular nanomaterial being unduly based on one particular criterion (such as size vs. surface reactivity relationships) as the material may have other physicochemical characteristics related to size that exhibit a greater impact on its toxicity. Acknowledgements The studies described and the resulting data presented herein were obtained from research supported by the Environmental Quality Technology Program of the US Army Engineer Research and Development Center (Dr. John Cullinane, Technical Director). References 1. Auffan, M., J. Rose, T. Orsiere, M. De Meo, W. Achouak, C. Chaneac, J.-P. Joliver, A. Thill, O. Spalla, O. Zeyons, A. Maison, J. Labille, J.-L. Hazeman, O. Proux, V. Briois, A.-M. Flank, A. Botta, M.R. Wiesner, and J.-Y. Bottero, 2008. Surface Reactivity of Nano-Oxides and Biological Impacts Nanoparticles in the Environment: Implications and Applications. Centro Stefano Fracnscini, Monte Verita, Ascona, Switzerland. 2. Belton, V., and T.J. Stewart, 2002. Multiple Criteria Decision Analysis – An Integrated Approach. Kluwer, Dordrecht. 3. Biswas, P., and C.-Y. Wu, 2005. Nanoparticles and the environment. Journal of the Air & Waste Management Association 55, 708–746.

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4. Braydich-Stolle, L., S. Hussain, J.J. Schlager, and M. Hofmann, 2007. In vitro cytotoxicity of nanoparticles in mammalian germline stem cells. Toxicological Sciences 88(2), 412–419. 5. Borm, P., and D . Müller-Schulte, 2006. Nanoparticles in drug delivery and environmental exposure: same size, same risks? Nanomedicine 1(2), 235–249. 6. Borm, P., D. Robbins, S. Haubold, T. Kuhlbusch, H. Fissan, K. Donaldson, R. Schins, V . Stone, W . Kreyling, J . Lademann, J . Krutmann, D . Warheit, and E. Oberdorster, 2006. The potential risks of nanomaterials: a review carried out for ECETOC. Particle and Fibre Toxicology 3(11). 7. Bortoleto, G.G., S.S.O. Borges, and M.I.M.S. Bueno, 2007. X-ray scattering and multivariate analysis for classification of organic samples: a comparitive study using Rh tube and synchroton radiation. Analytica Chimica Acta 595(1-2), 38–42. 8. Bowden, J.W., A.M. Posner, and J.P. Quirk, 1977. Ionic adsorption on variable charge mineral surfaces. Theoretical-charge development and titration curves. Australian Journal of Soil Research 15, 121. 9. Chappell, M.A., A.J. George, B.E. Porter, C.L. Price, K.M. Dontsova, A.J. Kennedy, and J.A. Steevens. 2008. Surfactive Properties of Dissolved Soil Humic Substances for Stabilizing Multi-Walled Carbon Nanotubes Dispersions Nanoparticles in the Environment: Implications and Applications. Centro Stefano Franscini, Monte Verita, Ascona, Switzerland. 10. Chen, Q., C. Saltiel, S. Manickavasagam, L.S. Schadler, R.W. Siegel, and H. Yang. 2004. Aggregation behavior of single-walled carbon nanotubes in dilute aqueous suspension. Journal of Colloid Interface Science 280, 91–97. 11. Derfus, A.M., W.C. Chan, and S.N. Bhatia, 2004. Probing the cytotoxicity of semiconductor quantum dots. Nano Letters 4, 11–18. 12. Erbs, J.J., T.S. Berquo, B. Gilbert, T.L. Jentzsch, S.K. Banerjee, and R.L. Penn, 2008. Reactivity of Iron and Iron Oxide Nanoparticles in the Environment: Implications and Applications. Centro Stefano Franscini, Monte Verita, Ascona, Switzerland. 13. Evangelou, V.P., 1998. Environmental Soil and Water Chemistry: Principles and Applications. Wiley, New York. 14. Figueira, J., S. Greco, and M. Ehrgott (Eds.), 2005a. Multiple Criteria Decision Analysis: State of the Art Surveys. Springer Science+Business Media, New York. 15. Figueira, J., V. Mousseau, a n d B. Roy, 2005b. ELECTRE methods. In: J. Figueira, S. Greco, and M. Ehrgott (Eds.), Multiple Criteria Decision Analysis: State of the Art Surveys. Springer Science+Business Media, New York, Ch. 4. 16. Grabinski, C., S. Hussain, K. Lafdi, L. Braydich-Stolle, and J. Schlager. 2007. Effect of particle dimension on biocompatibility of carbon nanomaterials. Carbon 45, 2828– 2835. 17. Gwinn, M., and V. Vallyathan, 2006. Nanoparticles: health effects – pros and cons. Environmental Health Perspectives 114(2), 1818–1825. 18. Hofstetter, T.B., R.P. Schwarzenbach, and S.B. Haderlein, 2003. Reactivity of Fe(II) species associated with clay minerals. Environmental Science & Technology 37, 519– 528. 19. Joo, S.H., A.J. Feitz, and T.D. Waite, 2004. Oxidative degradation of the carbothioate herbicide, monlinate, using nanoscale zero-valent iron. Environmental Science & Technology 38, 2242–2247.

NANOMATERIAL RISKS USING MULTI-CRITERIA DECISION ANALYSIS 191 20. Kashiwada, S., 2006. Distribution of nanoparticles in the see-through medaka (Oryzias latipes). Environmental Health Perspectives 114, 1697–1702. 21. Kreyling, W., M. Semmler-Behnke, and W. Möller, 2006. Health implications of nanoparticles. Journal of Nanomaterial Research 8, 543–562. 22. Linkov, I., K. Satterstrom, G. Kiker, C. Batchelor, and T. Bridges, 2006. From comparative risk assessment to multi-criteria decision analysis and adaptive management: recent developments and applications. Environment International 32, 1072–1093. 23. Medina, C., M. Santos-Martinez, A. Radomski, O. Corrigan, and M. Radomski, 2007. Nanoparticles: pharmacological and toxicological significance. British Journal of Pharmacology 150, 552–558. 24. Medinsky, M.A., and J.L. Valentine, 2001. Chapter 7. Toxicokinetics. In Casarett and Doull’s Toxicology, 6th Edition. Klaassen, C.D. Ed.; McGraw-Hill. New York. 230 pp. 25. Merad, M.M., T. Verdel, B. Roy, and S. Kouniali, 2004. Use of multi-criteria decisionaids for risk zoning and management of large area subjected to mining-induced hazards. Tunnelling and Underground Space Technology 19(2), 125–138. 26. Murr, L.E., K.M. Garza, K.F. Soto, A. Carrasco, T.G. Powell, D.A. Ramirez, P.A. Guerero, D.A. Lopez, and J. Venzor, 2005. Cytotoxicity assessment of some carbon nanotubes and related carbon nanoparticle aggregates and the implications for anthropogenic carbon nanotube aggregates in the environment. International Journal of Environmental Research and Public Health 2(1), 31–42. 27. Nel, A., T. Xia, L. M¨adler, and N. Li, 2006. Toxic potential of materials at the nanolevel. Science 311, 622–627. 28. Oberdörster, G., V. Stone, and K. Donaldson, 2007. Toxicology of nanoparticles: a historical perspective. Nanotoxicology 1(1), 2–25. 29. Powers, K., M . Palazuelos, B . Moudgil, and S . Roberts, 2007. Characterization of the size, shape, and state dispersion of nanoparticles for toxicological studies. Nanotoxicology 1(1), 42–51. 30. Ryman-Rasmussen, J.P., J.E. Riviere, and N.A. Monterio-Riviere, 2006. Penetration of intact skin by quantum dots with diverse physicochemical properties. Toxicological Sciences 91, 159–165. 31. Tervonen, T., 2007. New directions in stochastic multicriteria acceptability analysis. Ph.D. thesis, Annales Universitatis Turkuensis AI:376, University of Turku, Finland. 32. Tervonen, T., J.R. Figueira, R. Lahdelma, J. Almeida Dias, and P. Salminen, 2009. A stochastic method for robustness analysis in sorting problems. European Journal of Operational Research 191(1), 236–242. 33. Tervonen, T., and R. Lahdelma, 2007. Implementing stochastic multicriteria acceptability analysis. European Journal of Operational Research 178 (2), 500–513. 34. Tervonen, T., and J.R. Figueira, 2008. A survey on stochastic multicriteria acceptability analysis methods. Journal of Multi-Criteria Decision Analysis 15(1-2), 1–14. 35. Thomas, K., and P. Sayre, 2005. Research strategies for safety evaluation of nanomaterials, part I: evaluating the human health implications of exposure to nanoscale materials. Toxicological Sciences 87(2), 316–321. 36. Uehara, G., and G. Gillman, 1981. The Mineralogy, Chemistry, and Physics of Tropical Soils with Variable Charged Clays. Westview Press, Boulder, CO. 37. Unfried, K., C. Albrecht, L. Klotz, A. Von Mikecz, S. Grether-Beck, and R.P.F. Shins, 2007. Cellular responses to nanoparticles: target structures and mechanisms. Nanotoxicology 1, 52–71.

NANOMATERIALS, NANOTECHNOLOGY Applications, Consumer Products, and Benefits

G. ADLAKHA-HUTCHEON Defence R&D Canada Ottawa, Ontario, Canada [email protected] R. KHAYDAROV INP, Uzbekistan Academy of Sciences Tashkent, Uzbekistan R. KORENSTEIN Faculty of Medicine, Tel-Aviv University Tel-Aviv, Israel R. VARMA United States Environmental Protection Agency Cincinnati, Ohio, USA A. VASEASHTA Nanomaterials Laboratories & Characterization Labs Marshall University One John Marshall Drive Huntington, WV 25575, USA H. STAMM Joint Research Centre European Commission Ispra, Italy M. ABDEL-MOTTALEB Department of Chemistry, Faculty of Science Ain Shams University 11566 Abbassia Cairo, Egypt

Abstract. Nanotechnology is a platform technology that is finding more and more applications daily. Today over 600 consumer products are available globally that utilize nanomaterials. This chapter explores the use of nanomaterials and I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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nanotechnology in three areas, namely Medicine, Environment and Energy. Given the large number of applications being designed that utilize nanomaterials and nanotechnologies, and the perception that nanotechnology can (or will) provide the ultimate solution for the world’s problems; questions arise regarding who benefits from these technological advances. Additionally, within the popular press all nanotechnology products are generally portrayed as being beneficial to society without necessarily distinguishing between real and potential benefits of the technology. Lastly, the benefits and implications of these technological advancements in society are explored.1 1.

Introduction

The NATO Advanced Research Workshop titled “Risk, Uncertainty and Decision Analysis for Nanomaterials: Environmental Risks and Benefits and Emerging Consumer Products” had five primary objectives. The Working Group (WG) on “Nanotechnology and its benefits” discussed two off the five, namely: “The potential benefits of nanotechnology enabled commercial products”; and “Identifying strategies for users in developing countries to best manage this rapidly developing technology and its associated risks, as well as to realize its benefits”. The subject of the WG’s deliberations primarily revolved around the former and the latter only to the extent that it pertained to benefits. 2.

Definition of Nanotechnology

The late Dr. Richard Smalley defined Nanotechnology as the art and science of building stuff that does stuff at the nanometer scale. This definition is therefore inclusive of science in speaking of nanotechnologies; for our purposes here reference to nanotechnology included science in its fold. 3.

Nanotechnology: New Name for Old Products?

Nanomaterials have been used for centuries – from the use of nanometer-size gold particles for red stained glass to soot from candles in inks. Nanoparticles can be both man-made and naturally occurring. What is different today is that technological advancements have enabled us to produce and detect these materials and begin to understand how their shape and size can be used to good effect, and with this ability, we can begin to change them so that they are more exploitable. This

1

Summary of the NATO ARW Technology Working Group discussions. Co-chairs – Gitanjali Adlakha-Hutcheon and Rafi Korenstein; Members – Mohamed Abdel-Mottaleb, Azad Bayramov, John Cullinane, Oleg Figovsky, Nava Haruvy, Renat Khaydarov, Mikhail Kondratyev, Hermann Stamm, Rajender Varma, Ashok Vaseashta, Teresa Vieira.

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development is best summed up by The Royal Society and the Royal Academy of Engineering, UK – they define Nanotechnology as the ability to measure, see, manipulate and manufacture things between 1 and 100 nm (1 billionth of a meter) – is seen as the driver of a new industrial revolution emerging with the development of materials that exhibit new properties and potential new risks and benefits at this tiny scale [27]. 4.

Applications

Nanotechnology is a platform technology that utilizes the inherently unique properties of matter that arise at the nanoscale. Applications of this technology can be found in areas of material sciences, medicine, energy, environment, communications and electronics among others. The enormous international S&T investment in nanotechnology research has evolving, and potentially endless possibilities. Researchers continue to find new applications for nanomaterials. Whether it is using carbon nanotubes to make vehicle composites stronger than steel, but lighter (thereby improving fuel economy), or creating medicines that can target and treat specific cells in the body, or purifying water at point of use – nanotechnology could revolutionize some of these sectors. One of the challenges is to garner benefits without risk. In this section applications of nanotechnology in the fields of nanomedicine, energy and environment will be elaborated. 5.

Nanomedicine – Answering Clinical Needs

The European Technology Platform (ETP) group has defined nanomedicine as the application of nanotechnology to achieve breakthroughs in healthcare [8]. Nanomedicine consists of several subdomains including diagnostics and imaging; drug delivery; and regenerative medicine. An important subdomain of nanomedicine is the field of in-vivo diagnosis based on imaging technologies. One of the most promising applications is molecular imaging, which refers to the characterization and measurement of biological processes at the cellular and/or molecular levels, and has emerged as a powerful tool to visualize molecular events of an underlying disease. The merging of nanotechnology with molecular imaging provides a versatile platform for novel design of nano-probes that will have tremendous potential to enhance the sensitivity, specificity, and signaling capabilities of various biomarkers in human diseases. Nanoengineered platforms possess unprecedented potential for early detection, accurate diagnosis, and personalized treatment of diseases. Such platforms have been employed in many biomedical imaging modalities, namely, optical imaging, computed tomography, ultrasound, magnetic resonance imaging, single-photon-emission computed tomography, and positron emission tomography [4]. Multifunctionality is the key advantage of nanoplatforms over traditional approaches. Targeting ligands, imaging labels, therapeutic drugs, and many other agents can all be integrated into the nanoplatform to allow for targeted molecular imaging and molecular therapy by encompassing many biological and biophysical

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barriers [4]. Moreover, the technological advancement in miniaturizing medical devices in conjunction with microelectromechanical systems (MEMS) technology provides foundations for the nanoelectromechanical systems (NEMS). The application of medical devices in nanomedicine can be envisioned in four areas of applications consisting of minimally invasive surgery, heart assisting devices, drug delivery on demand and finally pain therapy. Drug delivery aims to employ nanoscale carrier particles or molecules developed to improve the bioavailability and pharmacokinetics of therapeutics. Drug-delivery systems can be synthesized with controlled composition, shape, size and morphology as demonstrated by examples such as programmable fusogenic vesicles [1]. The surface properties of nanocarriers can be manipulated to increase solubility, immunocompatibility and cellular uptake. The limitations of current drug delivery systems include suboptimal bioavailability, limited effective targeting and potential cytotoxicity. Examples of drug delivery systems include liposomes, polymer nanoparticles, nano-suspensions and polymer therapeutics. The pharmaceutical industry is interested in these delivery systems owing to their unique properties: (1) Nanoparticles can be used for passive tumor targeting; (2) They have the potential to improve penetration through biological barriers, such as the blood brain barrier, for drug delivery; (3) They can be used to increase the solubility of drugs; and (4) They can even possess characteristics of contrast agents for improved imaging (e.g., the use of nanometer-sized superparamagnetic iron oxide particles as cellular contrast agents allows the non-invasive detection of labeled cells on high-resolution magnetic resonance images). Thus, the production of multifunctional targeted drug carriers, also possessing imaging characteristics enables the possibility of combining the diagnostic properties with the therapeutic ones (“theranostics”) [8]. Today, our surgical tools are large and crude at the molecular scale, yet the cellular and molecular machinery in our tissue is small and precise. The only reason that modern surgery works is the remarkable ability of cells to regroup, bury their dead, and heal over the wound. However, the possibility of spontaneous tissue regeneration is limited. Recent advances in stem cell research, opens promising pathways towards regeneration of injured organs. There are two major strategies for inducing regeneration in the damaged tissue: (i) activation of the endogenous regenerative capacity, and (ii) cell transplantation therapy. Cell transplantation is approaching clinical reality. To continue to enhance the benefits of cell transplantation it has been proposed that nanobiotechnology possesses a unique potential that will aid considerably in overcoming obstacles including: identifying a universal cell source that can be differentiated into specific cellular phenotypes, developing techniques to enhance integration of the transplant within the host tissue, improving strategies for in vivo detection and monitoring of the cellular implants, and developing new techniques to deliver genes to cells [6]. These enhancements will benefit considerably from understanding, visualizing, and controlling cellular interactions through the manipulation of materials, tissues, cells, and DNA at the level of and within the individual cell. As such, nanobiotechnology is well suited to optimize the generally encouraging results already achieved in cell transplantation.

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Nanomedicine therefore has the potential, by enabling earlier diagnosis, for better therapy and improved follow-up care, to make healthcare more effective in terms of clinical outcome and more affordable for the society in general. 6.

Nanotechnology and the Environment

Two types of applications of nanotechnology are possible with respect to the environment, environmental technology applications that help solve environmental problems like pollution: and those that support sustainability. According to the US Environmental Protection Agency’s (US EPA) White Paper [28], nanotechnology presents new opportunities to improve how contaminants in the environment are measured, monitored, managed, and minimized [28]. This paper discusses the potential environmental benefits of nanotechnology, describing environmental technologies as well as other applications that can foster sustainable use of resources. It further encourages the US EPA to engage resources and expertise to encourage, support, and develop approaches that promote pollution prevention, sustainable resource use, and good product stewardship in the production, use and end of life management of nanomaterials. Additionally, it asks the Agency to draw on new, “next generation” nanotechnologies to identify ways to support environmentally beneficial approaches such as green energy, green design, green chemistry, and green manufacturing. Responsible manufacturing which incorporates principles of green chemistry and environmentally responsible production of nanomaterials (such as making use of reusable and recyclable materials, restricting the use of chemicals or other harmful materials) is now being referred to as “Green Nanotechnology” [30, 31]. In this area there has also been increasing interest in identifying environmentally friendly materials such as reducing agents, capping agents and dispersants etc. that are multifunctional. Examples of green manufacturing range from processes employing environmentally friendly chemicals with minimum energy requirements to producing silver and gold nanoparticles, among other noble nanometals, using benign reagents such as vitamin B2, [19], vitamin C [20] and tea and coffee extract [21]. 7.

Energy

Energy security is the largest challenge facing humankind in the twenty-first century. Eighty-five percent (85%) of energy consumption worldwide is provided by fossil fuels, while the current rate of discovery of fossil fuels is almost half the rate of consumption. Further, for every oil field, either new or in use, only ca. 60% of the oil is recovered [33]. These facts clearly indicate the urgent need for systematically addressing this challenge. The energy issue can be generally divided into two main sectors, namely, securing new sustainable energy sources, and an effective, clean and rational use of existing energy resources. Nanotechnology (NT) has the potential to revolutionize the entire energy sector both in terms of finding new resources and maximizing the utilization of existing ones [31].

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In terms of maximizing current energy resources, NT offers two main approaches. First, an ability to secure more resources at a cheaper cost for example, the possibility of retrieving more than 95% of the oil out of the well. Several examples of how NT achieves this goal include subsurface sensors that can be used to improve both the discovery and the recovery of hydrocarbons; better materials to make it easier, cheaper and faster to extract oil. Corrosion problems caused by bacteria during oil production can be solved with the help of selfassembled layers that contain silver nanoparticles which in turn inhibit or kill the corrosive bacteria. Nanotechnology also offers alloys and additives that increase material performance, making drilling bits and pipes stronger, more wearresistant, and lighter, thus decreasing drilling costs. Additionally, NT can produce smart materials able to respond to external conditions (e.g. poreholes that can respond to water presence by changing the diameter of the hole, thus stopping a “lifting response”, or smart pipelines that detect leaks and self-heal [18]). Secondly, NT can enable more efficient use of the existing energy resources. Huge energy savings can be obtained by lowering the operational temperature of industrial chemical reactions or by increasing the selectivity of such reactions. Since catalysis mainly depends on maximizing surface area per volume (S/V [7, 26]), nanomaterials are good sources to achieve high S/V and to study catalytic processes [10]. For a long time the fundamental study of catalysis in the laboratory was carried out using much idealized model systems far removed from the complex three-dimensional (3D) systems in real applications [14, 23]. NT offers the tools and mechanisms to build controlled 3D catalytic systems mimicking real application conditions while still providing the conditional control necessary for laboratory studies [15, 34]. NT’s impact on the field of catalysis goes beyond fundamental studies; it can provide completely new catalysts – for example, gold which is an inert material in bulk conditions is found to have a high catalytic activity when applied in nanometer sized structures [13, 29]. In terms of finding new resources, Filipponi and Sutherland ([9]) present an overview of the applications of nanotechnology that may have the potential to help within the Energy sector. Nanotechnology will cut cost both of the solar cells and the equipment needed to produce and deploy them, making solar power economical and hence a more useable alternative to fossil fuels. For this application one needs to able to make solar cells inexpensively – NT has such a potential and could therefore help move solar power into the mainstream. There is also the potential for nanotechnology to contribute to reductions in energy demand through lighter materials for vehicles; materials and geometries that contribute to more effective temperature control; technologies that improve manufacturing process efficiency; materials that increase the efficiency of electrical components and transmission lines; and materials that could contribute to a new generation of fuel cells (FC) and a step closer towards a hydrogen economy. Fuel cells represent an important research direction for clean energy production. These devices convert fuel such as hydrogen directly into electricity through an electro-catalytic process rather than by combustion, which yields higher energy efficiency. In such devices, the electrodes play a very important

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role. Thus the stability of the electrodes against electrochemical processes and impurity poisoning, and high-charge carrier mobility are important [12]. The structure of such electrodes is very complex, which makes fundamental studies of structure/performance relationship very difficult. NT offers the tools to systematically study this problem. Further, the precise positioning capabilities offered by NT allow the construction and manipulation of such complex electrodes [5, 11]. In summary, NT offers more diverse approaches to the pressing energy issue than any other technology to date. Not just in terms of actual energy production, but even in terms of energy savings on every level, for example, smart-windows that can control the amount of light transmitted into the building thus controlling the temperature. Furthermore, industrial processes with high energy consumption are being modified using NT to lower the energy demand. Thus, nanotechnology may indeed offer mankind hope towards energy security. 8.

Nanotechnology and Emerging Consumer Products

Nanotechnology is a growing global enterprise that will have large economic and social impacts as can be observed with the ever emerging products that utilize some form of nanotechnological application whether it is a coating on cars to selfcleaning windows. Consumer products containing nanomaterials are entering the marketplace at a rapid pace. “Nanotechnology is no longer simply a science of the future, but it is a way of producing and using materials at a tiny scale that is rapidly entering our everyday lives in cosmetics, medicine, food, sports equipment, computers, automobiles, and many other consumer products”. Nanoscale materials are in some sunscreens, house paints, clothing, and computers being sold in stores around the world (Project on emerging nanotechnologies [25]). 9.

Consumer Products

As cited in the sections above, nanotechnology heralds a world of better and more durable consumer products. In 2006, nanotechnology was incorporated into more than $50 billion worth of manufactured goods. The Project on Emerging Nanotechnologies maintains an inventory of consumer products that utilize nanomaterials. As of May 15, 2008, this inventory contained 610 products or product lines produced by 322 companies located in 20 countries. This online list of companyidentified nanotechnology consumer products includes merchandise from such well known brands as Samsung, Black & Decker, Eddie Bauer, and others [25]. Since this list relies on manufacturers self-identifying products that may contain nanomaterials or use nanotechnologies in the manufacturing process, it is not an all-inclusive inventory. Other inventories are maintained, for instance, in Japan, although these cannot be easily or completely accessed due to language differences (e.g. [2]).

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10. Benefits of Nanotechnology Rapid advances in material sciences and technology that enable manipulation of matter at the nanometer scale will continue to allow the realization of many benefits of this technology. Foremost among these will be a new manufacturing paradigm. Present day activity for manufacturing and use of nanomaterials is 49% in the United States, 30% in the European Union, and 21% in other parts of the world [3]. Although techniques for manufacturing nanomaterials are as varied as the materials themselves, they can be divided into two main types of approaches: “bottom-up” and “top-down” procedures. Bottom-up manufacturing is based on the building of structures, atom-by-atom or molecule-by-molecule and can be split into three categories: chemical synthesis, self-assembly, and positional assembly [27]. Bottom-up methods are widely used for manufacturing of metal nanoparticles, nanofilms, fullerenes, nanotubes, quantum dots etc. Top-down manufacturing involves starting with a micrometer- to millimeter-sized piece of material and etching, milling or machining fine, nanosized structures from it by removing material using for instance, precision engineering or lithography techniques. Topdown manufacturing can be used for obtaining computer chips, precisionengineered surfaces, metal oxanes etc. [32]. 11. Paradigm Shift for Manufacturing What would it mean if one could inexpensively make things with every atom in the right place? For starters, one could continue the revolution in computer hardware right down to molecular gates and wires – something that today’s lithographic methods (used to make computer chips) could never hope to do. One could inexpensively make very strong and very light materials: shatterproof diamond in precisely the shapes one wants, in large volumes, and over 50 times lighter than steel of the same strength. One could make a Cadillac that weighed 50 kg, or a full-sized sofa you could pick up with one hand. One could make surgical instruments of such precision and deftness that they could operate on the cells and even molecules from which one is made – something well beyond today’s medical technology. The list goes on – it is projected that almost every manufactured product could be improved, often by orders of magnitude. 11.1.

THE ADVANTAGES OF POSITIONAL CONTROL

The reason that such revolutionary changes in manufacturing would be possible is due to positional control – a basic principle of nanotechnology. At the macroscopic scale, the idea that one can hold parts in our hands and assemble them by properly positioning them with respect to one another goes back to prehistory: we celebrate ourselves as the tool using species. At the molecular scale, the idea of holding and positioning molecules is new and almost outrageous.

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Nanotechnology, employing positional control, will dramatically reduce the costs and increase the capabilities of spacecrafts and space flight. The strength-toweight ratio and the cost of components are absolutely critical to the performance and economy of space ships: with nanotechnology, both of these parameters will be improved by one to two orders of magnitude. Improvements in these two parameters alone should improve the overall cost/performance ratio by over three orders of magnitude. This has led NASA to support nanotechnology by initiating projects examining molecular manufacturing systems and molecular machines using computational models. Beyond inexpensively providing remarkably lighter and stronger materials for spacecrafts, nanotechnology will also provide extremely powerful computers that are small relative to their computing powers with which to guide both those ships and a wide range of other activities in space. 12. Quantum Computing Nanotechnology will take us to the post-lithographic era. In futuristic computers each logic element will be made from just a few atoms. One would be able to economically build and interconnect trillions upon trillions of small and precise devices in a complex three dimensional pattern. Further enabling us to build mass storage devices that can store more than a 1020 bytes in a volume the size of a sugar cube; RAM that can store a mere 1018 bytes in such a volume; and massively parallel computers of the same size that can deliver a1018 instructions per second. Such enhanced computing could open up areas for innovation within the defence and security domains such as: secure messaging through quantum encryption; intelligent and completely autonomous short and long-range weapons; selfrepairing military equipment; global information networks through quantum computing; miniature high energy battery and power supplies; and highly sensitive miniature biological and chemical sensors among others. According to Merkle [17] today, “smart” weapons are fairly big – we have the “smart bomb” but not the “smart bullet.” In the future, even weapons as small as a single bullet could pack more computer power than the largest supercomputer in existence today, allowing them to perform real-time image analysis of their surroundings and communicate with weapons tracking systems to acquire and navigate to targets with greater precision and control. We’ll also be able to build weapons both inexpensively and much more rapidly. Rapid and inexpensive manufacture of great quantities of stronger more precise weapons guided by massively increased computational power will alter the way wars are fought. Changes of this magnitude could destabilize existing power structures in unpredictable ways. While molecular manufacturing will not arrive for many years to come, it’s obvious that military potential will increasingly attract the interest of planners. One can now see the fundamental shape of a molecular manufacturing technology. Self replicating assemblers, operating under computer control, let us inexpensively build more assemblers. The assemblers can be reprogrammed to build other products. The assemblers use programmable positional control to

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position molecular tools and molecular components, permitting the inexpensive fabrication of most structures consistent with physical law. Diamondoid materials in particular have become inexpensive and its remarkable properties usher the technology in what has been called the Diamond Age [17]. The obvious leap in our manufacturing capabilities will come from positional control leading to faster miniaturization and precision. Along with all the obvious manufacturing benefits, there are also many potential medical and environmental benefits. 13. Global Implications Benefits through nanotechnology for the environment as was eluded to earlier, will include: reduction of waste products generated, and energy used, during manufacturing of conventional materials as well as nanomaterials; research applications of nanomaterials in areas of green energy approaches, including solar energy, hydrogen, power transmission, diesel, pollution control devices, and lighting; environmental remediation/treatment research supporting improvement of pollutant capture or destruction by exploiting novel nanoscale structureproperty relations for nanomaterials used in environmental control and remediation applications; development of nanotechnology-enabled devices for measuring and monitoring contaminants and other compounds of interest, including nanomaterials. Examples of the latter would involve development of new nanoscale sensors for the rapid detection of virulent bacteria, viruses, and protozoa in aquatic environments [28]. Nanotechnology could let us make almost every manufactured product better (faster, lighter, stronger, smarter, safer and cleaner). One can already see many of the possibilities as the examples above illustrate. New products that solve new problems in new ways are more difficult to foresee, yet their impact is likely to be even greater. Could Edison have foreseen the computer, or Newton the communications satellite? The development of higher quality materials, more efficient energy storage, better water quality, and more effective delivery of pharmaceuticals all have the potential to improve everyday life for many people. Product development using nanotechnology today far exceeds the body of knowledge concerning the safety of nanomaterials or the implications for human or environmental health. New generations of nanomaterials will evolve, and with them new and possibly unforeseen health and environmental issues. It will be crucial that the regulatory bodies while leveraging the benefits of nanomaterials continue to evolve in parallel with the expansion of and advance in these new technologies. Given the large number of applications being designed that utilize nanomaterials and nanotechnologies, and the perception that nanotechnology is (or will be) a panacea for the world’s problems, questions about who benefits from these technological advances arise. The popular press generally touts all nanotechnology products as beneficial to society, while not necessarily distinguishing between real and potential benefits of the technology. On economic grounds, current projections

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put the global market for nanotechnology and nanomaterial-containing products at an estimated $2.6 trillion by 2014 [16]. Consequently, a very significant challenge is ensuring an even distribution of benefits throughout the world community. These implications led to the Technology and Benefits WG at the NATO ARW discussing the potential for nanotechnology to sustain world resources as another benefit. 14. Conclusions and Future Recommendations The WG acknowledged that technological advances are largely being driven by the promise of economic benefits. Taking three examples, namely: applications of nanotechnology in medicine, environment and energy the risks to health and environment; total investment; health and environmental benefits; return on investment; and the size of population impacted were evaluated. Preliminary predictions, based on arbitrary economic numbers, showed that benefits were not evenly distributed across the world. The Advanced Research Workshop at large felt that concurrent advances in methods to protect human and environmental health will be essential so that asymmetric benefits to society are not created. There was a clear recognition among all workshop participants that resolving the question of who benefits from nanotechnology lies in pulling together multidisciplinary expertise from multiple nations. Probably the most significant strength of Nanotechnology is that the approach is crossdisciplinary. Simply put, ideas and products originally developed for medical and biological purposes find applications in electronics or energy industries. This has in turn pushed scientists, medical doctors and engineers to significantly revise and modify their approach to problem solving to rapidly adopt new ideas and techniques. The ultimate beneficiary of such a paradigm shift will be humanity. For the first time in history, a new technology holds forth the promise of providing inexpensive energy, food and clean water for everyone on the planet thereby it could also be used in innovative ways to encourage political stability and responsibility [24]. Acknowledgements We acknowledge the NATO ARW on “Nanomaterials: Environmental Risks and Benefits and Emerging Consumer Products” held in Faro, Portugal from 27–30 April 2008 and the Participants of the Working Group on Nanotechnology and its benefits.

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19. Nadagouda, M.N., and Varma, R.S. (2006) Green and controlled synthesis of gold and platinum nanomaterials using vitamin B2: density-assisted self-assembly of nanospheres, wires and rods, Green Chem. 8, 516–518. 20. Nadagouda, M.N., and Varma, R.S. (2007) A greener synthesis of core (Fe, Cu)-shell (Au, Pt, Pd and Ag) nanocrystals using aqueous vitamin C, Cryst. Growth Design 7, 2582–2587. 21. Nadagouda, M.N. and Varma, R.S. (2008) Green synthesis of silver and palladium nanoparticles at room temperature using coffee and tea extract, Green Chem. 10, 859–862. 22. National Nanotechnology Initiative (2004) Nanoscience Research for Energy Needs, Report of the National Nanotechnology Initiative Grand Challenge Workshop. 23. Österlund, L., Grant, A.W., and Kasemo, B. (2007) Lithographic techniques in nanocatalysis. In: Heiz, U., Landman, U. (eds.) Nanocatalysis, vol. 1, Springer Verlag GmbH, Berlin, p. 269. 24. Petersen, J.L., and Egan, D.M. (2002) Small security: Nanotechnology and future defense, Defense Horizons 8, 1–6. 25. Project on Emerging Nanotechnologies (PEN) (2008) A Nanotechnology Consumer Products Inventory, Woodrow Wilson International Center for Scholars. Available via DIALOG, http://www.nanotechproject.org/inventories/consumer/ (last accessed 27 July 2008). 26. Somorjai, G.A. (1994) Introduction to Surface Chemistry, Wiley, New York. 27. The Royal Society and Royal Academy of Engineering, UK (2004) Nanoscience and Nanotechnologies: Opportunities and Uncertainties. Available online at http://www. nanotec.org.uk/finalreport.htm (last accessed 27 July 2008). 28. United States Environmental Protection Agency (US EPA) (2007) Nanotechnology White Paper. Prepared for the US EPA by members of the Nanotechnology Workgroup, a group of EPA’s Science Policy Council, US Food and Drug Administration (US FDA). Nanotechnology: A Report of the U.S. Food and Drug Administration. Nanotechnology Task Force. Available online at http://www.fda.gov/nanotechnology/taskforce/ report2007. html (last accessed 27 July 2008). 29. Valden, M., Lai, X., and Goodman, D.W. (1998) Onset of catalytic activity of gold clusters on Titania with the appearance of nonmetallic properties, Science 281, 1647– 1650. 30. Vaseashta, A., Riesfeld, R., and Mihailescu, I.N. (2008) “Green Nanotechnologies for Responsible Manufacturing” in The Business of Nanotechnology, edited by Gandhi, A., Giordani, S., Merhari, L., Tsakalakos, L., and Tsamis, C., in Materials Research Society Spring meeting. Proc. 1106E, #1106-PP03-05. Warrendale, PA. 31. Vaseashta, A., and Mihailescu, I.N. (2008) Functionalized Nanoscale Materials, Devices, and Systems, Springer, Dordrecht, The Netherlands. 32. Wiesner, M.R., Lowry, G.V., Alvarez, P., Dionysiou, D., and Biswas, P. (2006) Assessing the risks of manufactured nanomaterials, Environ. Sci. Technol. 40(14), 4336–4345. 33. Wikipedia.org. (2008) Peak oil, reference 39. Available online at http://Wikipedia.org/ wiki/Peak_oil#cite_note-nyt08212005-38 (last accessed 27 July 2008). 34. Zhdanov, V.P., and Kasemo, B. (2000) Simulations of the reaction kinetics on nanometer supported catalyst particles, Surf. Sci. Rep. 39, 25–104.

RISK REDUCTION VIA GREENER SYNTHESIS OF NOBLE METAL NANOSTRUCTURES AND NANOCOMPOSITES

M.N. NADAGOUDA, R.S. VARMA Sustainable Technology Division, US Environmental Protection Agency National Risk Management Research Laboratory 26 West Martin Luther King Drive, MS 443 Cincinnati, OH 45268, USA [email protected]

Abstract. Aqueous preparation of nanoparticles using vitamins B2 and C which can function both as reducing and capping agents are described. Bulk and shapecontrolled synthesis of noble nanostructures via microwave (MW)-assisted spontaneous reduction of noble metal salts using α-D-glucose, sucrose, and maltose has been achieved. The MW method also accomplishes the cross-linking reaction of poly (vinyl alcohol) (PVA) with metallic systems such as Pt, Cu, and In; bimetallic systems, namely Pt-In, Ag-Pt, Pt-Fe, Cu-Pd, Pt-Pd and Pd-Fe; and single-walled nanotubes (SWNT), multi-walled nanotubes (MWNT), and Buckminsterfullerene (C-60). The strategy is extended to the formation of biodegradable carboxymethyl cellulose (CMC) composite films with noble nanometals; such metal decoration and alignment of carbon nanotubes in CMC is possible using a MW approach. The MW approach also enables the shape-controlled bulk synthesis of Ag and Fe nanorods in poly (ethylene glycol) (PEG). 1.

Introduction

Lately, much effort has been devoted to the controlled synthesis of nanostructured materials because of their unique chemical and physical properties. Metal nanomaterials have attracted considerable attention because of their unique magnetic, optical, electrical, and catalytic properties and their potential applications in nanoelectronics. Hierarchical assembly of solution-based nanocrystals as building blocks is of great interest because of their potential in controlling morphologies of nanostructures and, hence, their properties wherein structured nanoparticle assemblies such as wires, rings, and superlattices, have been prepared. However, the challenge of synthetically controlling particle shape had limited success. Nevertheless, some physical and solid state chemical methods have been developed for making semiconductor, metal nanowires, nanobelts, and nanodots in addition to wet chemical methods.

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Herein, we report a simple and general strategy using a wide variety of relatively benign solvents under which noble metal nanoparticles effectively self assemble into spheres, nanowires, and nanorods in presence of vitamin B2 (Riboflavin), vitamin B1 and vitamin C. The approach also serves the need for a greener protocol as there is a renewed interest in using green chemistry to synthesize metal nanoparticles [1]. Green chemistry is the design, development, and implementation of chemical products and the process to reduce or eliminate the use and generation of substances hazardous to human health and the environment. A primary driver for newer synthetic endeavors is the development of efficient and environmentally benign protocols for the synthesis of a variety of materials. Strategies to address mounting environmental concerns with current approaches include the use of environmentally benign solvents, biodegradable polymers, and non-toxic chemicals. In the synthesis of metal nanoparticles by reduction of the corresponding metal ion salt solutions, there are at least three areas of opportunity to engage in green chemistry: (i) choice of solvent, (ii) the reducing agent employed, and (iii) the capping agent (or dispersing agent). In this area there has also been increasing interest in identifying environmentally friendly materials that are multifunctional. For example, vitamin B2 functions both as a reducing and capping agent for metal nanostructures in addition to its high water solubility, low toxicity and biodegradability [2]. As the pressure to produce materials in a rapid and benign fashion has continued to increase, so microwave (MW)-assisted chemistry has emerged as a valuable tool that permeates various aspects of chemistry including material synthesis. The major objectives are to maximize the efficient use of safer raw materials and to reduce waste. The use of emerging MW-assisted chemistry techniques in conjunction with greener reaction media is dramatically reducing chemical waste and reaction times in several chemical syntheses and chemical transformations [3]. MW irradiation provides rapid and uniform heating of reagents, solvents, and intermediates and this homogeneous heating also provides uniform nucleation and growth conditions, resulting in the formation of homogeneous nanomaterials with small sizes. Power dissipation is fairly uniform throughout with ‘deep’ inside-out heating of the solvent, which leads to better crystallinity. 2.

MW-Assisted Shape-Controlled Bulk Synthesis of Ag and Fe Nanorods in PEG Solutions

Recently, bulk syntheses of Ag and Fe nanorods using PEG under MW irradiation conditions have been accomplished [4]. Favorable conditions to make Ag nanorods were established and the process was extended to make Fe nanorods with uniform size and shape. The nanorods formation depended upon the concentration of PEG used in the reaction with metal salts. Ag and Fe nanorods crystallized in face centered cubic symmetry. The method uses no surfactant or reducing agent and is greener in nature which could open a myriad of applications. In a typical procedure, aqueous silver nitrate (AgNO3) solution (0.1 M) and different mol ratio

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of PEG (molecular weight 300) were mixed in a 10 ml test tube at room temperature to form a clear solution. The reaction mixture was irradiated in a CEM Discover focused MW synthesis system maintaining a temperature of 100°C (monitored by a built-in infrared sensor) for 1 h with a maximum pressure of 280 psi. The resulting precipitated Ag nanorods were then washed several times with water to remove excess PEG. The obtained Ag nanorods are shown in Figure 1. In summary, bulk synthesis of silver and iron nanorods can be achieved in PEG medium under MW irradiation conditions. The results clearly demonstrate that the concentration of PEG controls the final shape and size of the nanostructures which act as reducing agent as well as capping agent. The nanorod formation depends upon the concentration of PEG used in the reaction with respect to the silver or iron salts.

Figure 1. SEM images of Ag nanorods obtained via MW irradiation for 1 h using (a) 4 ml PEG + 4 ml AgNO3 , (b) 5 ml PEG + 3 ml AgNO3, and (c) 3 ml PEG + 5 ml AgNO3.

3.

MW-Assisted Synthesis of Noble Metals Using Natural Polymers

Bulk and shape-controlled synthesis of gold (Au) nanostructures with various shapes such as prisms, cubes, and hexagons was accomplished via MW-assisted spontaneous reduction of noble metal salts using an aqueous solution of α-Dglucose, sucrose, and maltose [5]. The expeditious reaction was completed under

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MW irradiation in 30–60 s and can be applied to the generation of nanospheres of Ag, Pd, and Pt (see Figure 2 for TEM images). The noble nanocrystals underwent catalytic oxidation with monomers such as pyrrole to generate noble nanocomposites, which have potential functions in catalysis, biosensors, energy storage systems, nanodevices, and other ever-expanding technological applications. In a typical experiment, an aqueous solution of HAuCl4 (0.01 N) was placed in a 20 ml glass vessel and mixed with an appropriate amount of α-D-glucose. The reaction mixture was exposed to high-intensity MW irradiation (1,000 W, Panasonic MW oven equipped with invertor technology) for 30–45 s. Similarly, experiments were conducted using 0.01 N PtCl4, 0.01 N PdCl2 and 0.1 N AgNO3.

Figure 2. TEM images of Au nanostructures synthesized (low concentration of sugar) using MW irradiation with natural polymers such as (a) sucrose, (b) α-D-glucose, or (c, d) maltose. The insets show corresponding electron diffraction patterns.

4.

MW-Assisted Synthesis of CMC/Metal Biodegradable Nanocomposites

A green approach was established that generates bulk quantities of nanocomposites containing transition metals such as Cu, Ag, In, and Fe at room temperature using a biodegradable polymer, carboxymethyl cellulose (CMC), by reacting respective metal salts with the sodium salt of CMC in aqueous media [6]. These nanocomposites exhibit broader decomposition temperatures when compared with control CMC, and Ag-based CMC nanocomposites exhibit a luminescent property at longer wavelengths. The noble metals such as Au, Pt, and Pd do not react at room temperature with aqueous solutions of CMC, but do so rapidly under MW irradiation conditions at 100°C. This environmentally benign approach, which provides facile entry to the production of multiple shaped noble nanostructures (see Figure 3) without using any toxic reducing agent such as sodium borohydride (NaBH4), hydroxylamine hydrochloride, and so forth, and/or a capping/surfactant agent, and which uses a benign biodegradable polymer CMC, could find widespread technological and medicinal applications.

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Figure 3. Photographic image of CMC reduced Au, Pt and Pd (from left to right) synthesized using MW at 100 °C for 5 min.

5.

Preparation of Novel Metallic and Bimetallic Cross-Linked PVA Nanocomposites Under MW Irradiation

A facile method utilizing MW irradiation was achieved that accomplishes the crosslinking reaction of PVA with metallic and bimetallic systems [7]. Nanocomposites of PVA cross-linked metallic systems such as Pt, Cu, and In, and bimetallic systems such as Pt-In, Ag-Pt, Pt-Fe, Cu-Pd, Pt-Pd and Pd-Fe were prepared expeditiously by reacting the respective metal salts with 3 wt% PVA under MW irradiation and maintaining the temperature at 100°C, a radical improvement over the methods for preparing cross-linked PVA described in the literature. The general preparative procedure is versatile and provides a simple route to manufacturing useful metallic and bimetallic nanocomposites (see Figure 4) with various shapes, such as nanospheres, nanodendrites and nanocubes.

Figure 4. Photographic image of cross-linked PVA with various metallic and bimetallic systems: (a) Pt, (b) Pt-In, (c) Ag-Pt, (d) Cu, (e) Pt-Fe, (f) Pt with higher concentration ratio, (g) Cu-Pd, (h) In, (i) Pt-Pd and (j) Pd-Fe.

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MW-Assisted Synthesis of Noble Metal Decoration and Alignment of Carbon Nanotubes in CMC

A facile MW method that accomplishes alignment and decoration of noble metals on carbon nanotubes (CNT) wrapped with CMC was achieved. CNT’s such as SWNT, MWNT, and C-60 were well dispersed using the sodium salt of CMC under sonication [8]. Addition of respective noble metal salts then generated noble metal-decorated CNT composites at room temperature.

Figure 5. Aligned CNT’s in CMC polymer matrix upon MW irradiation.

However, aligned nanocomposites of CNTs could only be generated by exposing the above nanocomposites to MW irradiation. The general preparative procedure is versatile and provides a simple route to manufacturing useful metal coated CNT nanocomposites (see Figure 5). 7.

MW-Assisted Synthesis of Cross-Linked PVA Nanocomposites Comprising SWNT’s, MWNT’s, and C-60

The cross-linking reaction of PVA with SWNTs, MWNTs, and C-60 using MW irradiation afforded nanocomposites of PVA cross-linked with SWNT, MWNT and C-60 expeditiously by reacting the respective CNT’s with 3 wt% PVA under MW irradiation and maintaining a temperature of 100°C, representing a radical improvement over literature methods to prepare such cross-linked PVA composites (see Figure 6 for SEM image) [9]. This general preparative procedure is versatile and provides a simple route to the manufacture of useful SWNT, MWNT and C-60 nanocomposites.

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Figure 6. SEM images of SWNT cross-linked PVA nanocomposites.

8.

A Greener Synthesis of Core (FE, CU)-Shell (AU, PT, PD, and AG) Nanocrystals Using Aqueous Vitamin C

A greener method to fabricate novel core (Fe and Cu)-shell (noble metals) metal nanocrystals using aqueous ascorbic acid (vitamin C) is described [10]. Transition metal salts such as Cu and Fe were reduced using ascorbic acid, a benign naturally available antioxidant; addition of noble metal salts then resulted in the formation of the core–shell structure depending on the core and shell material used for the preparation (see Figure 7). Pt yielded a tennis ball kind of structure with a Cu core, whereas Pd and Au formed regular spherical nanoparticles. Au, Pt, and Pd formed cube-shaped structures with Fe as the core. Inversely, transition metals

Figure 7. TEM images of core (Fe)-shell with (a) Au, (b) SAED of Au, (c) Pd, and (d) Pt core–shell bimetallic nanostructures.

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with noble metals, such as Pd, as the core also formed interesting structures; these structures were brushlike with indium as the shell and needle-like when Cu was employed as the shell. The method is general uses no surfactant or capping agent and can be extended to noble metals as cores and transition metals as shells. The core–shell nanocrystals were characterized using transmission electron microscopy (TEM) and selected area electron diffraction (SAED). These nanocrystals have unique properties that are not originally present in either the core or shell materials and may have potential functions in catalysis, biosensors, energy storage systems, nanodevices, and ever-expanding other technological applications. 9.

Green Synthesis of Noble Nanospheres, Nanowires, and Nanorods Using Vitamin B2: Catalytic Polymerisation of Aniline and Pyrrole

For the first time, a new green chemistry approach is described that uses vitamin B2 in the synthesis of silver (Ag) and palladium (Pd) nanospheres, nanowires, and

Figure 8. TEM image of Ag and Pd nanoparticles synthesized using vitamin B2. (a) Ag (average size 6.1 ± 0.1 nm) in ethylene glycol, (b) Pd (average size 4.1 ± 0.1 nm) nanoparticles in ethylene glycol, and (c), (d) Ag (average size 5.9 ± 0.1 nm, and average size 6.1 ± 0.1) nanoparticles in acetic acid and NMP, respectively. Inset shows corresponding particle size distribution, electron diffraction, and UV excitation.

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nanorods at room temperature without using any harmful reducing agents, such as sodium borohydride (NaBH4) or hydroxylamine hydrochloride, or any special capping or dispersing agent [2]. In ethylene glycol, the average particle size of Ag nanoparticles was found to be 6.1 ± 0.1 nm; the average particle size of Pd nanoparticles was found to be 4.1 ± 0.1 nm. In acetic acid and NMP, average sizes of Ag nanoparticles were 5.9 ± 0.1 and 6.1 ± 0.1 nm, respectively (see Figure 8). 10. Conclusion We have demonstrated the use of various environmentally benign reagents such as sugars, vitamins and renewable polymers for the greener production of a wide variety of metal nanoparticles as well as nanocomposites. The use of MW energy coupled with the use of eco-friendly solvents enables the expeditious generation of nanomaterials and their nanocomposite forms with utmost ease. References 1. M. N. Nadagouda and R. S. Varma, “Green and controlled synthesis of gold and platinum nanomaterials using vitamin B2: density-assisted self-assembly of nanospheres, wires and rods,” Green Chem., 8, 516–518 (2006). 2. M. N. Nadagouda and R. S. Varma “Green synthesis of Ag and Pd nanospheres, nanowires and nanorods using vitamin B2: catalytic polymerisation of aniline and pyrrole,” J. Nanomater., 1–8 Article ID 782358, doi:10.1155/2008/782358 (2008). 3. V. Polshettiwar and R. S. Varma, “Microwave-assisted organic synthesis and transformations using benign reaction media,” Acc. Chem. Res., 41, 629–639 (2008). 4. M. N. Nadagouda and R. S. Varma “Microwave-assisted bulk synthesis of silver and Fe nanorods in poly (ethylene glycol) solutions” Cryst. Growth Design, 8, 291–295 (2008). 5. M. N. Nadagouda and R. S. Varma “Microwave-assisted shape-controlled bulk synthesis of noble nanocrystals and their catalytic properties” Cryst. Growth Design, 4, 686–690 (2007). 6. M. N. Nadagouda and R. S. Varma “Synthesis of thermally stable carboxymethyl cellulose/metal biodegradable nanocomposite films for potential biological applications” Biomacromolecules, 8, 2762–2767 (2007). 7. M. N. Nadagouda and R. S. Varma “Preparation of novel metallic and bimetallic crosslinked poly(vinyl alcohol) nanocomposites under microwave irradiation” Macromol. Rapid Commun., 28, 465–472 (2007). 8. M. N. Nadagouda and R. S. Varma “Noble metal decoration and alignment of carbon nanotubes in carboxymethyl cellulose” Macromol. Rapid Commun., 29, 155–159 (2008). 9. M. N. Nadagouda and R. S. Varma “Microwave-assisted synthesis of cross-linked poly (vinyl alcohol) nanocomposites comprising single-wall carbon nanotubes (SWNT), multi-wall carbon nanotubes (MWNT) and Buckminsterfullerene (C-60)” Macromol. Rapid Commun., 28, 842–847 (2007). 10. M. N. Nadagouda and R. S.Varma “Green synthesis of core (Fe, Cu)-shell (Au, Pt, Pd and Ag) nanocrystals using aqueous vitamin C” Cryst. Growth Design, 7, 2582–2587 (2007).

REMEDIATION OF CONTAMINATED GROUNDWATER USING NANO-CARBON COLLOIDS R.R. KHAYDAROV Institute of Nuclear Physics Ulugbek, 100214 Tashkent, Uzbekistan [email protected] R.A. KHAYDAROV, O. GAPUROVA Institute of Nuclear Physics Tashkent, Uzbekistan

Abstract. The paper deals with a novel method of obtaining nano-carbon colloids (NCC). The method allows synthesizing aqueous dispersions of NCC with the sizes in the range of 1–100 nm, concentration of 150–400 ppm and pH of 2.8–3.1. Due to functional carboxyl groups the ion exchange capacity of carbon colloids obtained is very high – 7.4 mmol/g for a monovalent cation. NCC can be used for effective removal of metal ions (Zn, Ni, Cu, Sb, Co, Cd, Cr, etc.) from contaminated water. 1.

Introduction

Using metals and chemicals in process industries has resulted in the generation of large quantities of effluent containing high levels of toxic heavy metals, meanwhile mining and mineral processing operations also generate toxic liquid wastes [2]. The presence of different organic and heavy metal contaminants in groundwater has a large environmental, public health and economic impact. Most of the traditional technologies such as solvent extraction, activated carbon adsorption, biological degradation and common chemical oxidation, whilst effective, very often are costly and/or time-consuming [3]. Over the last decade usage of nanoparticles, structures from 1 to 100 nm in size, have been studied in this regard due to their large surface areas and high surface reactivity [1]. For instance, nanoscale iron particles have been considered as a new generation of environmental remediation technologies that could provide cost-effective solutions to some of the most challenging environmental cleanup problems [4]. This paper deals with synthesizing nano-carbon colloids (NCC), it also discusses their usage for the extraction of pollutants from industrial wastes. The colloidal carbon with functional groups such as carboxyl, hydroxyl and keto-groups can be particularly useful being applied jointly with micro and ultra-filtration processes for conducting separations not achievable by microporous activated carbons. The

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commercially available activated carbons are heterogeneous in nature; hence new carbons with well defined chemical groups are required. Although it is not possible to form colloids of unoxidized carbon, colloids of oxidized graphite or graphite oxide are widely known [5]. Nitric acid, hypochlorite and ammonia are usually used for surface modification of carbon. Here, we describe an electrochemical oxidation method to produce the water-based NCC with sufficient stability without mixing the nitric acid with a surfactant. The capability of NCC in removing metal ions and radionuclides from water is also discussed.

2. Materials and Methods High-density isotropic graphites are used as an anode and a cathode. The dimensions of electrodes are chosen as follows: 65 mm (W) × 30 mm (H) x 15 mm (Th). The distance between electrodes immersed in a distilled water bath is able to be varied from 10 to 120 mm in the current density range 0.1–3 mA/cm2. The electric power applied to the electrodes is 60 V (DC). Two anodes and one cathode between anodes are used to increase the surface of working electrodes and to decrease dimensions of the device. Total working area of the anodes is 24 cm2. The constructed apparatus includes an electrolytic cell 120 mm (W) × 140 mm (H) × 105 mm (Th) made of plastic. The cell contains distilled water as an electrolyte and three carbon electrodes immersed into the electrolyte. The deionized water is most preferable for cost-effective production of pure carbon colloids. The electrolytic cell is installed on the magnetic stirrer. The electrolyte is passed between the electrodes to provide the electrolyte with carbon particles and discharge the gas generated via electrolysis from the electrodes. The process of the device operation consists of two stages. The first stage is the electrolysis during 10 min. The second stage is the electrolyte stirring during 60 s. This process is executed automatically. Twin timer ST-T (Korea) is used to control the process. Radionuclides used as the label of ions during the study of water purification process are given in Table 1. Radionuclides were produced by irradiating salts of ions in nuclear reactor of the Institute of Nuclear Physics (Tashkent, Uzbekistan). Ge(Li) detector with a resolution of about 1.9 keV at 1.33 MeV and the 4096channel multichannel analyzer were used to detect γ-quantum from radionuclides. Areas under γ-peaks of radionuclides were measured to calculate the amount of ions. The exchange capacity Q, mmol/g, was calculated as follows: Q = (A0 – Ae )/(A0 – AB) . B/W,

(1)

where B is amount of carrier, mmol; W is weight of exchanger, g; A0 is a count rate of the original solution, Ae is a count rate of the solution at equilibrium, AB is a background count. The distribution coefficient Kd and the percent adsorption P were calculated by Eqs. 2 and 3:

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P = 100 (1 - (Ae – AB) /(A0 – AB)),

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(2) (3)

where V is a total volume of the solution, ml. TABLE 1. Radionuclides used as labels (T1/2 is the half-life of the radionuclides, Eγ is the energy of the γ-peaks).

3.

Elements

Radionuclides

T1/2

Cr(VI) Co(II) Ni(II) Cu(II) Zn(II) Sr(II) Cd(II) Sb(II) Cs(I)

51

27.73 days 5.27 years 2.5 h 12.7 h 244.1 days 50.5 days 53.5 h 60.2 days 2.07 years

Cr 60 Co 65 Ni 64 Cu 65 Zn 89 Sr 115 Cd 124 Sb 134 Cs

Eγ, MeV 0.320 1.17, 1.33 1.480 0.511 1.115 0.909 0.336 1.691 0.605

Mechanism of NCC Formation

In the graphite structure, each carbon atom is covalently bonded with other carbon atoms so that they form flat sheet-like sequential hexagonal structures. However, the parallel flat sheets of hexagonal-structured carbon atoms are weakly bonded together due to attractive van der Waals forces. Thus the parallel carbon flat sheets are easy to split by relatively weak external forces; other functional groups can also easily enter between the graphite flat sheets. During the electrochemical oxidization in the water, an anion (OH−) formed from the cathode with the excess of electrons moves toward the anode with the deficit of electrons. At the anode, the electrons are removed at the surface of carbon nanoparticles, and simultaneously, the oxidation process was occurred. Since the oxidation is imposed on the surface of carbon in the electrochemical process, the magnitude of repulsion forces formed between the stacked layers get larger than that of van der Waals attraction forces between the layers. Carbon nanoparticles are charged negatively and after switching off the electric power the oxidized particles come away from the anode and the functional groups such as carbonyl (>C=O) , hydroxyl (-OH), and carboxyl (-COOH) group are formed on the surface of carbon particles. Thus the resulting NCC nanofluid is able to maintain its stability as long as the hydrophilic functional groups exist. 4.

NCC Preparation Technique

The electrolysis is executed by two stages: activation of the anode and the carbon nanoparticles generation. At the first stage the electrolyte has low conductivity, value of electric current is small, about 0.1–0.2 mA/cm2 and the oxidization reaction is slow. Duration of

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this stage is about 50 h and depends on the quality (density) of graphite. At this stage a voltage between electrodes can be high, about 60–100 V. As the reaction proceeds, the conductivity of the electrolyte is abruptly increased, electric current can increase up to 10 mA/cm2 and higher and the oxidization reaction is activated. As a result, the carbon is finely split, and then is covered by the carboxyl group. At the second stage the electric current between electrodes must be about 3–4 mA/cm2. If current density values greater than 8–10 mA/cm2, the rate of oxygen evolution is greater than the rate of its diffusion through the electrode; hence there is a pressure build-up within the electrode causing the electrode to disintegrate. NCC is not stable, in 2–3 weeks the precipitation of NCC is to be observed. Similarly, at current density less than 3–4 mA/cm2 the rate of oxygen evolution is such that, although some pressure builds up in the electrode, the gas is able to diffuse out of the electrode before disintegration occurred, small pieces of carbon broke off in the process to form colloidal carbon and very small amount of slurry. The NCC is stable during 150 days at least. The rate of diffusion of hydrogen at the cathode is such that little or no pressure built up within the electrode and therefore no colloid is produced at this electrode. The colloidal carbon is produced only at the anode and remains within the vicinity of the electrode, indicating that the carbon is negatively charged. Reversal of the electrode polarity results in the surrounding carbon migrating slowly to the new anode. Carbon nanoparticles are removed from the anode during the electrolyte stirring stage. Figure 1 demonstrates the process of carbon nanoparticles splitting. pH of the NCC is 2.8–3.1 and depends on the concentration of carbon nanoparticles; concentration of carbon nanoparticles is 150–400 ppm and depends on duration of the process; ion exchange capacity is 7.4 mmol/g for a monovalent cation. The typical TEM image for NCC obtained is shown on Figure 2.

Figure 1. Process of carbon colloids splitting.

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Figure 2. Typical TEM image of carbon colloids obtained (the scale is 200 nm).

5.

Water Decontamination by Carbon Nanoparticles

Removing heavy metal ions (Zn, Ni, Cu, Sb, Co, Cd, Cr, etc.) from water was studied. pH of the NCC was 2.8, concentration of carbon nanoparticles was 250 ppm Dependence of the distribution coefficient Kd for different ions at pH = 7.1 of the solutions is presented in Table 2. TABLE 2. Distribution coefficient Kd (ml/g) and percent adsorption P (%) for different ions (concentration of ions C0 = 10 mg/l, V = 50 ml, W = 0.5 g, pH = 7.1, contact time 1 h). Elements Cr(III) Co(II) Ni(II) Cu(II) Zn(II) Sr(II) Cd(II) Sb(II) Cs(I)

P >99 >99 >99 >99 >99 >99 >99 >99 60

Kd, 105 140 170 1,300 1,400 4,000 3,800 100 400 0.6

The results given in Table 2 demonstrate high ion-exchange potential of the colloidal carbons. In real water which contains different ions, the colloidal particles are coagulated within some time depending on the concentration of salts. Before and during coagulation process the nanoparticles as the ion exchangers react with

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cations. After coagulation water can be easily filtered from particles with attached cations. This means that the colloidal particles are quite effective for removal of the metal cations and may provide a useful alternative for example to method of flocculation of metal hydroxides and oxides. 6.

Conclusion

The described method allows producing NCC with concentration of carbon nanoparticles of 150–400 ppm and pH of 2.8–3.1. The concentration of nanoparticles depends on duration of the process and pH of NCC depends on concentration of carbon nanoparticles. The ion exchange capacity of carbon nanoparticles due to functional carboxyl groups is very high, 7.4 mmol/g for a monovalent cation. NCC can be used for effective removing metal ions (Zn, Ni, Cu, Sb, Co, Cd, Cr, etc.) from contaminated water. References 1. Bönnemann, H., and Richards, R. (2001) Nanoscopic metal particles – synthetic methods and potential applications, Eur. J. Inorg. Chem. 10, 2455 and 2480. 2. Coetser, S.E., Heath, R.G., and Ndombe, N. (2007) Diffuse pollution associated with the mining sectors in South Africa: A first-order assessment. Water Sci. Technol. 55: 9–16. 3. Theron, J., Walker, J.A, and Cloete, T.E. (2008) Nanotechnology and water treatment: applications and emerging opportunities, Crit. Rev. Microbiol. 34, 43–69. 4. Zhang, W. (2003) Nanoscale iron particles for environmental remediation: an overview, J. Nanopart. Res. 5, 323–332. 5. Peckett et al. (2000) Electrochemically oxidised graphite. Characterisation and some ion exchange properties. Carbon 38, 345–353.

A NOVEL SIZE-SELECTIVE AIRBORNE PARTICLE SAMPLING INSTRUMENT (WRAS) FOR HEALTH RISK EVALUATION

H. GNEWUCH, R. MUIR, B. GORBUNOV Naneum Limited, CEH, University of Kent Canterbury, Kent CT2 7NJ, UK [email protected] N.D. PRIEST Urban Pollution Research Centre, Middlesex University Queensway, Enfield, Middlesex EN3 4SA, UK P.R. JACKSON CERAM Queens Road, Penkhull Stoke-on-Trent, Staffordshire ST4 7LQ, UK

Abstract. Health risks associated with inhalation of airborne particles are known to be influenced by particle sizes. A reliable, size resolving sampler, classifying particles in size ranges from 2 nm–30 µm and suitable for use in the field would be beneficial in investigating health risks associated with inhalation of airborne particles. A review of current aerosol samplers highlighted a number of limitations. These could be overcome by combining an inertial deposition impactor with a diffusion collector in a single device. The instrument was designed for analysing mass size distributions. Calibration was carried out using a number of recognised techniques. The instrument was tested in the field by collecting size resolved samples of lead containing aerosols present at workplaces in factories producing crystal glass. The mass deposited on each substrate proved sufficient to be detected and measured using atomic absorption spectroscopy. Mass size distributions of lead were produced and the proportion of lead present in the aerosol nanofraction calculated and varied from 10% to 70% by weight. 1.

Introduction

The high health risk associated with the inhalation of airborne particles has been recognised and documented, see e.g. Brown et al. [1]; Pope et al. [15]. Many epidemiological studies have shown associations between exposure to particulate matter in the air and increases in morbidity and mortality [4]. There is a growing concern that health risk associated with airborne particles is influenced by size. Some studies indicate that nanoparticles (less than 100 nm in diameter) having I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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increased toxicity relative to larger particles composed of the same materials [5–7, 14]. Size-resolved sampling of airborne particles often requires various techniques to be employed [11]. There would be a significant benefit in a sampler that could reliably collect size resolved samples across the entire size range which is considered to be relevant to health effects. There are many technical difficulties in sizeresolved sampling of particles smaller than 100 nm – especially under real conditions of variable and/or high humidity. Pressure drop in low-pressure cascade impactors corrupts size distributions and causes condensation of water as well as other atmospheric constituents on substrates, e.g., Hart and Pankow [9] have estimated that the gas-particle mass exchange for PAHs could cause errors in measurements of up to 40%. Large mass changes were directly observed by Moor et al. [13] in experiments where atmospheric aerosol particles collected onto substrates of a cascade impactor were exposed to conditions with lowered partial pressures of semi-volatile compounds. 2.

Methods

In this paper, we describe a novel size-selective aerosol sampling instrument, WRAS (Wide Range Aerosol Sampler), based upon diffusion deposition coupled with inertial deposition in a single apparatus (www.naneum.com). This enables the size-selective sampling of aerosol particles in a wide range of airborne particle sizes without employing low-pressure cascade impactor technology. The WRAS instrument comprises an inertial unit similar to a May [12] cascade impactor having the lowest stage cut off diameter 0.25 μm and a specially designed diffusion deposition unit (nano-selector) for smaller particles. Operating flow rate is 20 l/min. First, aerosol particles are drawn into an isokinetic inlet of the cascade impactor where those greater than 0.25 μm in aerodynamic diameter are collected according to their aerodynamic diameter. Collection efficiency of particles in an inertial cascade impactor increases with size, therefore, the largest particles are removed from the flow by the first stage and the smaller particles are deposited onto following stages, stages 6–12 (Table 1). TABLE 1. The characteristics of the stages of the WRAS sampler.* Stage 1 2 3 4 5 6 7 8 9 10 11 12

Min. size (µm) 0.001 0.0015 0.005 0.015 0.06 0.25 0.5 1.0 2.0 4.0 8.1 20

Max. size (µm) 0.0015 0.005 0.015 0.06 0.25 0.5 1.0 2.0 4.0 8.1 20 ~35

Unit Nano-selector Nano-selector Nano-selector Nano-selector Nano-selector Cascade impactor Cascade impactor Cascade impactor Cascade impactor Cascade impactor Cascade impactor Cascade impactor

*Latest model of the WRAS sampler

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The flow emerging out of the cascade impactor contains particles smaller than 0.25 μm. These particles are collected by sets of Nylon nets. Collection efficiency of particles in a diffusion unit decreases with the size, therefore, the smallest particles are collected at the first net and the larger particles are deposited onto following nets according to cut off diameters shown in Table 1 (Sections 1–5). Nano-selector units have been designed to collect particles sequentially in the size range from 1 nm to 0.25 μm. In practice, this is achieved by selecting nets with differing fibre diameters, fibre densities and by varying the number of nets per stage and the flow velocity. The nano-selector deployed in the WRAS sampler has a cylindrical cross-section (ID = 4.7 cm) and contains five stages. From Table 1 the cut off diameters of the WRAS sampler covers the size range from 1 nm to 35 μm. Thus it is the first universal size-selective sampling apparatus which enables airborne particles to be collected in the entire aerosol size range that is of concern with respect to health risks. Artificial lead and tungsten aerosols were employed to calibrate the WRAS sampler according to the approach described by Sinclair et al. [16] and Cheng et al. [2]. The cut off diameters in the nanoparticle size range were calculated according to Cheng and Yeh [3] and were compared with the cut-off diameters found from the size distributions measured (with SMPS) before and after a net. The calculated and measured cut-off diameters were in good agreement (Table 2). TABLE 2. Calculated/measured cut off diameters of WRAS diffusion collector stages.* Stage

Di (nm) calculated

Di (nm) measured

2

17

16.5 + 1

3

80

80+ 5

4

120

110 + 10

*Previous model of WRAS sampler

A case study is presented here to illustrate the potential of the novel sampling system. The developed WRAS sampling unit (previous model) was employed to sample airborne particles at various working places in the crystal glass industry. Aerosol particles were collected in a range of sizes from 2 nm to 20 μm (11 size fractions) at a flow rate 20 l/min and at a controlled relative humidity of 80%. The sampling time employed varied from 2 to 24 h (according to aerosol concentration levels). The mass of lead collected was determined by atomic absorption spectroscopy [8]. Aerosol mass size distributions of lead were obtained from the samples collected. Size distributions are crucial for the evaluation of health risk. It is known that particle deposition efficiency in the human respiratory system is influenced by the size of particles. An example compiled from experimental and theoretical data is shown in Figure 4 [10]. The efficiency is a V-shaped function with a high degree of deposition for nanoparticles and for particles in micro-range (close to 100%). In

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the sub-micron range, the efficiency falls to about 10–20 %. Therefore, when the mass of airborne particles is concentrated in the sub-micron range (as in Figure 3) the dose of deposited particles is proportionally less than from an aerosol with a maximum positioned towards the nano size range (Figure 2). This shows the importance of size-resolved sampling for correct evaluation of health risk. 3.

Results

The total mass concentration of lead aerosols determined at working places ranged from 0.6 to 50 μg/m3. The nanoparticle mass fraction of aerosols (sizes less than 100 nm) was found to vary from 10% to 70%. A typical aerosol size distribution of lead (sampled at the glass smelting area at plant A) is shown in Figure 1. The size distribution has a maximum at about 0.35 μm. but there is a noticeable amount of Pb associated with nanoparticles in the range below 0.1 μm. Even more nanoparticle mass fraction was observed at plant B where melting of lead compounds also takes place (Figure 2). In contrast, at plant C, involved in glass polishing, airborne particle size distributions contain much less mass fraction in the nanoparticle range (Figure 3). Thus, size distribution of lead at workplaces may vary considerably depending on production processes.

Figure 1. Airborne lead particle size distribution obtained at a plant A involved in hot lead processing.

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Figure 2. Airborne lead particle size distribution obtained at a plant B involved into hot lead processing.

Figure 3. Airborne lead particle size distribution obtained at a plant C involved into hot lead processing.

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The size distribution of the number of particles deposited in the respiratory system Nl(D) is a product of the ventilation rate Q, exposure time t, airborne particle size distribution fa(D) and the deposition efficiency of particles E(D)

N l ( D) = Q t f a ( D) E ( D)

(1)

Nl(D), therefore, represents the mass distribution of particles that were deposited in the respiratory system. The fraction of particles captured by the respiratory tract calculated for distributions shown in Figures 1–3, and for the efficiency presented in Figure 4 showed that the fraction of deposited total particle mass varied from 16% (Figure 3) to 37% (Figure 1) to 51% (Figure 2). 100% 90%

Efficiency

80% 70% 60% 50% 40% 30% 20% 10% 0% 0

1

2

3

4

LogD, D - nm

Figure 4. Efficiency E(D) of airborne particles deposition in the human respiratory tract.

4.

Conclusions

The principles of inertial and diffusion deposition have been employed in the design and construction of a new instrument (WRAS) that was developed to sizeselectively collect aerosol particles across a wide aerosol size range relevant to health effects. The instrument developed does not require low pressure to collect nanoparticles and, therefore, can be employed to sample size-selectively aerosol particles across the entire aerosol size range down to nanometer-sized particles with minimal sampling artefacts caused by evaporation/condensation of volatile and semi-volatile compounds. Data shows that the size distributions of lead containing particles in the aerosol at workplaces are influenced by manufacturing processes in the crystal glass industry. The nanoparticle mass fraction of aerosols (sizes less than 100 nm) was found to vary from 10% to 60%. It was found that the fraction of mass of lead deposited in the respiratory system depends on the mass distribution of lead and

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varies from 16% to 51%. This result is important for air quality assessment and health risk evaluation. It shows that standard, non-size-resolving OH sampling techniques, used by the crystal glass industry and others will overestimate the total health risk considerably. References 1. Brown J. S., Kirby L. Z. and William D. B. (2002) Ultrafine particle deposition and clearance in the healthy and obstructed lung. Am J Resp Crit Care Med, 166:1240– 1247. 2. Cheng Y. S., Keating J. A. and Kanapilly G. M. (1980) Theory and calibration of a screen-type diffusion battery, J Aerosol Sci., 11:549–556. 3. Cheng Y. S. and Yeh H. C. (1980) Theory of a screen-type diffusion battery. J. Aerosol Sci. 11:313–320. 4. Dockery D. W., Pope C. A., Xu X., Spengler J. D., Ware J. H., Fay M. E., Ferris B. G. and Speizer F. E. (1993) An association between air pollution and mortality in six US cities. N Engl J Med 329:1753–1759. 5. Donaldson K., Li X. Y. and MacNee W. (1998) Ultrafine (nanometer) particlemediated lung injury. J Aerosol Sci 29:553–60. 6. Ferin J. (1994) Pulmonary retention and clearance of particles. Toxicol Lett 72:121– 125. 7. Ferin J., Oberdorster G. and Penny D. P. (1992) Pulmonary retention of ultrafine and fine particle in rats. Am J Resp Cell Mol Biol 6:535–542. 8. Gorbunov B., Priest N., Jackson P. R. and Cartlidge D. (2000) Aerosol size distribution of lead at working places. J Aerosol Sci 31(Suppl. 1):S520–521. 9. Hart K. M. and Pankow J. F. (1994) High-volume air sampler for particle and gas sampling. 2. Use of backup filters to correct for the adsorption of gas-phase polycyclic aromatic hydrocarbons to the front filter. Environ Sci Technol 28:655–661. 10. Hinds W. C. (1999) Aerosol technology. Properties, Behaviour and Measurement of Airborne Particles. New York: Wiley, pp. 233–259. 11. John W. (2001) Size Distribution Characteristics of Aerosols. In: Aerosol Measurement. Principles, Techniques and Applications. Ed. PA Baron and K Willeke. New York: Wiley, pp. 99–116. 12. May K. R. (1982) A personal note on the history of the cascade impactor. J Aerosol Sci 13:37–47. 13. Moore M., Gorbunov B. and Williams I. (1998) A new method to study interaction of semi-volatile compounds with aerosol particles. J Aerosol Sci 29(Suppl. 1):S887–888. 14. Oberdorster G., Ferin J. and Lehnert B. E. (1994) Correlation between particle-size, invivo particle persistence, and lung injury. Environ Health Perspect 102(Suppl. 5):173– 179. 15. Pope C. A., Dockery D. W. and Schwartz J. (1995) Review of epidemiological evidence of health effects of particulate air pollution. Inhal Toxicol 7:1–18. 16. Sinclair D., Countess R. J., Liu B. Y. H. and Pui D. Y. H. (1976) Experimental verification of diffusion battery theory. J Air Poll Control Assoc 26:661–663.

NANOTECHNOLOGIES AND ENVIRONMENTAL RISKS Measurement Technologies and Strategies

T.A.J. KUHLBUSCH, H. FISSAN, C. ASBACH Air Quality & Sustainable Nanotechnology Unit Institute for Energy and Environmental Technology (IUTA) e. V. Bliersheimerstr. 60 47229 Duisburg, Germany [email protected]

Abstract. Assessments of nanoparticle exposure are needed to enable risk assessments which are needed to achieve a sustainable development of nanotechnology including public perception. Therefore an overview of measurement techniques, needed data quality, comparability, and measurement strategies is given. Additionally some results of exposure related studies are summarized. Overall it is demonstrated that an integrated approach towards nanoparticle exposure assessments in workplaces, but also in the environment is needed, despite the current published results indicating mainly release of nanoparticle agglomerates in the size range larger than 100 nm. 1.

Introduction

Nanoparticles and nanoobjects, intentionally produced particles of nanoscale in three or two dimensions, have specific properties possibly altering the (eco-) toxicological potential when compared to larger particles or the corresponding bulk material. The detailed assessment of this potential risk is a prerequisite to accomplish sustainable nanotechnology since it directly influences the public perception. The risk is generally a function of potential hazard and exposure. The importance of the latter is given by (a) that no risk exists if no exposure, (b) the dose, leading to possible health effects, is directly linked to the exposure, and (c) correct exposure determination is also of importance for e.g. epidemiological studies. To assess exposure it is also necessary to clarify the areas (e.g. workplace, environment), subjects (e.g. humans, animals, ecosystems) and exposure media (air, liquid, solid) of interest. This paper focuses on the human exposure mainly in workplace environments since highest exposure can be expected in these areas. Also, measurement technologies and strategies can be evaluated and tested in workplace environments since possible sources and hence particle material is known and can be differentiated from ambient nanoscale particles.

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The currently discussed main exposure route of nanoparticles is via the airborne state by inhalation. Other discussed routes of exposure such as via the skin or gastrointestinal tract possibly leading to an uptake are currently seen as of minor importance [4] but still have to be investigated. Two major pieces of information are necessary for the assessment of exposure and possible nanoparticle implications: ƒ The exposure leading to a dose ƒ The hazard, influenced by the particle properties Hence, assessments of exposure to nanoparticles have a twofold task. One task is the general determination of an exposure and to quantify the ‘relevant’ aerosol property. The second task is the characterization of the nanoparticle properties since these may have been influenced or changed during the transport period after release. Any changes in these particle properties may have a significant influence on the possible hazard of nanoparticles. Spatial and time resolution of the measurements can therefore play a crucial role in the exposure determination and its evaluation. This background puts certain demands onto the measurement techniques for airborne nanoparticles as well as the measurement strategies. 2.

Measurement Techniques

Basically, various physical and/or chemical properties of nanoparticles and aerosols can be determined with especially particle size and concentration being physical properties of importance in the case of nanoparticles (<100 nm in three dimensions) and nanoobjects (<100 nm in two dimensions). For a decision on the instrumentation to be used for exposure measurement the scheme shown in Figure 1 was introduced in Borm et al. [2]: This scheme indicates the different steps of possibilities when choosing the instrumentation for exposure assessment. Certainly, the ideal sampling for exposure assessment would be a personal sampler measuring and reporting continuously the physical and chemical characteristics of all single particles (agglomerates or primary particles) as well as their concentrations entering the measurement system. Since this is not possible, decisions have to be made based on the task to perform and

Figure 1. Scheme of particle characterization for exposure measurements [2].

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the corresponding availability of adequate measurement technology. If e.g. the question is limited to whether primary particles of a specific nanoparticle product are present in the work area it may be sufficient to use a device determining particle number concentration or particle number size distributions. If, on the other hand, exposure should be determined in the framework of epidemiological studies, possibly certain particle properties such as lung deposited particle surface area become important. Hence, currently an array of stationary instruments and measurement technologies are employed to study exposure and possible effects of nanoparticles. To assess particle properties such as morphology or chemical composition, mainly offline methods, namely single particle analysis following particle deposition, commonly by electrostatic precipitation [7], are usually required. The analytical techniques may comprise electron microscopic (SEM, TEM), atomic force microscopic analysis for physical properties and energy-dispersive x-ray spectroscopy (EDX) for single particle or total reflection x-ray fluorescence spectrometry (TXRF) [10] for total chemical analysis. While the determination of particle concentrations and size distributions from the sample deposits is generally possible by electron microscopy, this method is very limited in its concentration range and also very time consuming. Technically mature online instrumentation for the determination of various aerosol properties is commercially available. The aerosol properties of interest include particle number and surface area concentration and their size distributions. Mass concentration determination is of minor importance for nanoparticle detection due to the low sensitivity and low mass involved. Total particle number concentrations are commonly determined with a Condensation Particle Counter (CPC), sometimes also called Condensation Nucleus Counter (CNC). In a CPC, particles get exposed to an atmosphere supersaturated with vapour of its working fluid, commonly butanol, isopropyl alcohol or water. The vapour condenses on the particle surface and causes the particles to grow to a size that can scatter a laser beam downstream of the condensation chamber. The number of impulses from the scattering of the laser beam is counted in order to determine the particle number concentration. [17]. The lower detection limit for these devices reaches down to 3 nm [9] and below. There are no instruments available that can determine airborne concentrations of geometric particle surface area. In electrical diffusion chargers such as the LQ1DC (Matter Engineering) particles are exposed to a unipolar ionic atmosphere and ions are attached to the particle surface due to Brownian diffusion. The current, measured upon deposition of the charged particles, is proportional to the so-called Fuchs surface area [11], i.e. the surface area of particles available for ion attachment. This “surface area” is proportional to dp1.39 and therefore smaller than the geometric surface area, being proportional to dp2. Another instrument, called Nanoparticle Surface Area Monitor, NSAM (TSI) also uses an electrical diffusion charger but manipulates the size distribution such that the measured current is proportional to the geometric particle surface area concentration that gets deposited in either the alveolar or tracheobronchial region of the lung [8, 19].

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Number size distributions of airborne particles with diameters down to a few nanometers can be determined using electrical mobility analysis. Particles are initially brought to a known charge distribution (equilibrium) in a neutralizer which can be based on radioactive decay or corona discharge. The particles then enter a Differential Mobility Analyzer (DMA), a concentric, cylindrical set up, near the outer electrode. Charged particles are deflected in the electric field between the two electrodes. The electrical mobility is a function of particle size and charge. Particles of high electric mobility, i.e. small and/or highly charged particles move faster towards the inner electrode than particles of low electrical mobility, i.e. the location where they hit the inner electrode is a function of their electrical mobility. At the other end of the inner electrode, particles of certain mobility are withdrawn through an outlet slit. The withdrawn mobility is determined by the voltage applied to the electrodes. In a Scanning Mobility Particle Sizer, SMPS [20], the voltage is continuously ramped and the particle concentration in the sample flow through the slit measured with a CPC. An algorithm is used to relate the measured concentrations to the corresponding electrical mobilities and along with the known charge distribution to determine the number size distribution as a function of electrical mobility diameter. If the relationship between particle mobility diameter and particle surface area is know, the number size distribution can easily be converted into surface area size distribution. Integration over a desired size range can also provide total number or surface area concentration. Another, for work related exposure interesting measurement technique is also based on the electrical mobility of charged particles. It is implemented in the Fast Mobility Particle Sizer (FMPS, TSI) which is based on work conducted by Mirme et al. [18]. The main difference to the SMPS described above is that the particle detection is based on an array of 22 electrometers, placed along the outer electrode in a DMA. Simultaneous detection of particles within the entire size range covered (5.6–560 nm) allows for a time of resolution of 1 s. For comparison, a comparable size scan by an SMPS would take at least 2 min, because the different sizes are measured sequentially. The downside of the FMPS is the lower size resolution, 16 channels per decade, compared to e.g. possible 64 channels per decade for the SMPS. Nevertheless, the FMPS may be preferred if size distribution have to be determined in work areas with quickly varying work processes and therefore size distribution fluctuations shorter than the time resolution of the SMPS. Extended information on measurement techniques may also be found in Kuhlbusch et al. [14]. 3.

Comparability and Data Quality

Measurements to assess exposure of e.g. humans should be comparable to actually allow for comparisons between different work environments, different work processes, to enable the evaluation of exposure reduction measures etc. Still, the comparability between different instruments, instruments from different manufacturers, or even between two similar instruments but two different users is not

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always sufficient. Comparison studies as e.g. reported by Dahman et al. [5] clearly showed the differences between various instruments and the need of ‘understanding’ the equipment.

Fitted Size Distributions SMPS-T1 (0.3/3 lpm) SMPS-T2 (0.6/6 lpm) SMPS-G1 (L-DMA) SMPS-G1 (M-DMA) FMPS

3.5x105

dN/dlog(dp) [nm]

3.0x105 2.5x105 2.0x105 1.5x105 1.0x105 5.0x104 0.0

10

100 Particle Diameter dp [nm]

Figure 2. Example of NaCl particle size distribution determined with various SMPS (different providers, volume flow, and type of DMA) and FMPS. (Adapted from Asbach et al. [1].)

An example of a comparison for sodium chloride test particles is given in Figure 2. This figure clearly shows the comparability of (a) number concentration <100 nm, (b) modal diameter, and (c) width of the size distribution. This comparability for the ideal test condition is general in the range of around 40% and better. More detailed analysis of the comparability will soon be published. Nevertheless, it has to be stated that comparability and reproducibility are currently more in an infant state and that standardization as well as good understanding of the measurement devices are still needed. 4.

Measurement Strategies

The difficulties in the determination of nanoparticles in air, water or soils are manifold. In all three matrices the problems of the specific nanoparticles have to be overcome. In all cases single particle analyses are necessary to enable identification. The problem may be reduced if nanoparticles with very specific and robust properties or specific chemical components, not or only rarely present in the corresponding matrix, are used. Nevertheless, in some cases clear differentiation of the source of the nanoscale particle, natural or manmade, may not be possible as e.g. for iron particles. ƒ ƒ ƒ

Identification (and differentiation from natural nanoscale particles) Characterization And quantification

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Another problem, difficult to be covered with “normal” measurement methods is the alteration of surfaces of nanoparticles. Surfaces of nanoparticles are altered after the production to achieve specific particle properties and to enhance e.g. dispersion of nanoparticles during certain production steps. These surface properties are currently discussed to be of possible importance for toxicological effects. No study, to the knowledge of the authors, has so far been conducted to investigate whether particle surface properties are stable after e.g. accidental release to the environment. The above two paragraphs briefly explain the difficulties in the measurements and hence in the set up of measurement strategies for nanoparticles exposure. While the latter case (persistence of particle surface properties) is only of interest if particles are released we may first focus on the task of the general assessment whether nanoparticle exposure exists or not. This is of importance since no risk exists when no exposure is given. To allow for first tests and evaluations of measurement strategies as well as measurement techniques we first focus on exposure related measurements in work areas since there we know which kind of nanoparticle to determine and we can expect the highest exposure concentrations compared to e.g. in the environment. Two of the first questions to tackle in the case of exposure measurements are the questions of measurement metric and necessary lower detection limit. Table 1 gives an overview of possible particle metrics and concentration ranges of interest. TABLE 1. Particle metrics and concentrations of interest for exposure measurements. Number (N/cm³) <1,000 1,000–100,000 >100,000

Surface (µm²/cm³) <10 10–1,000 >1,000

The concentrations given in the first row of Table 1 (<1,000 N/cm³ or <10 µm²/cm³) are in our view concentration ranges with no or only little effects unless particle specific toxicity as e.g. for asbestos is given. The latter may be assessed in toxicological screening tests. In those cases where such low limits of detection are needed only single particle analysis by microscopes coupled with e.g. EDX can currently be employed as is already used for asbestos. Due to this detection technique it is normally possible to discriminate environmental nanoscale particles from engineered ones. Nevertheless, this method is very time consuming, expensive, and can hardly be employed in routine monitoring. In cases of particle concentrations exceeding 100,000 N/cm³ (or 1,000 µm²/µm³) a source has to be close to the measurement point and should be identifiable by simple aerial particle number concentration measurements with a CPC. The most difficult and maybe most important case for exposure assessments is the intermediate concentration range of 1,000–100,000 N/cm³ (or 10–1,000 µm²/cm³). This concentration range covers the usual ambient particle number concentrations which may range from a few hundreds particles per cm³ in clean air conditions, e.g. mountainous regions or sea sides, around 10,000–30,000 N/cm³ in urban

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background situations, up to possibly 100,000 N/cm³ close to high traffic areas (e.g. Dingenen et al. [6]). Hence, to assess nanoparticle exposure in this concentrations range neither microscopic single particle analysis nor simple number or surface area concentration measurements are really an option due to potentially high background contributions and variability. A measurement strategy is therefore needed to overcome this problem but still to allow for a relatively practicable assessment of possible nanoparticle exposure. The following approach briefly summarized here is described in detail in Kuhlbusch et al. [15] and is based on the strategy used in studies at several carbon black production facilities [12, 13]. One of the basic assumptions of this strategy is that the intrusion of ambient particles into a work area can be calculated by a constant, but size dependent ‘penetration factor’. This factor is determined by e.g. measuring with an SMPS concurrently at a comparison site and in the work area when no work activity is taking place. By calculating the ratio of the two measured size distributions a size dependent ‘penetration factor’ is derived.

80,000

Number concentration / #/cm

3

70,000 60,000 50,000 40,000

Outside area

30,000 20,000 10,000

16:00

15:00

14:00

13:00

12:00

11:00

10:00

09:00

Inside area 08:00

0

Time

Outside area Environment

Working area (Inside area)

Traffic subtract

Other workings

?

Production process

Figure 3. Penetration of particles from outside area into the work area. (Adapted from Kuhlbusch et al. [15].)

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The same measurements are performed when the work activity of interest is ongoing. Now, the measurements conducted in the work area show the particle size distribution with work activity. The size distribution to be present in the work area when no work activity would have been ongoing can be calculated based on the measurement at the comparison site and the ‘penetration factor’ determined before. The comparison of the two values, in this example particle size distribution, show (a) whether nanoscale particles were released by the work activity and (b) the size distribution emitted by the process. So far, this value is only indicative, whether nanoparticles may have been released. No nanoparticles have been released by the process if no increased particle concentration is determined. If increased particle concentrations are determined further investigations based on e.g. single particle analysis or time of release (does it correlate with the specific work activity?) are needed. This basic idea is sketched in Figure 3. 5.

Results from Previous Studies

Several studies have now been conducted to assess possible exposure to particles below 100 nm. Most of these studies however deal with unintentionally produced particles such as welding and soldering fumes (e.g. Brouwer et al. [3]). Only a limited number of measurements have so far been conducted determining possible exposure to nanoparticles or nanoobjects in real nanotechnology work areas [12, 13, 15]. The results of the measurements conducted at three different industrial plants are summarized in Table 2. TABLE 2. Summary of particle release below 100 nm at three different carbon black plants. (Adapted from Kuhlbusch and Fissan [13].) Observed increases Plant 1

Plant 2

Plant 3

Likely origin

Reactor

No

Pelletizer

No

Bagging

No

Reactor

Yes

Nearby traffic

Pelletizer

Yes

Nearby traffic

Bagging

Yes

Propane fork lifts

Reactor

Yes

condensed oil vapors

Pelletizer

Yes

Flue gas–leak

Bagging

Yes

Diesel fork lifts, gas heater

Measurements to determine possible nanoparticle exposure were conducted at overall nine sites. Six of these sites showed elevated concentrations of nanoscale particles. In two cases this could be attributed to nearby traffic by e.g. analyzing

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the wind direction dependency, in further two cases other sources than the nanoparticle production were the reason for the elevated concentrations, namely forklifts and gas heater. Finally in two cases the reason for the higher concentrations was found to be related with the production facility. One time it was condensed oil vapors coming from maintenance work. These particles were nanoscale particles but no nanoparticles. In the last case a leak in the production facility was the reason for the very high concentrations. In this case true nanoparticles were present. Another study which investigated the possible exposure to carbon nanotubes was conducted by Maynard et al. [16]. This study showed that there was no evidence of an increase in particle number concentration during the handling of carbon nanotube material. Rather, in all cases, the field number concentration decreased during the periods when the material was handled. But they also state that laboratory investigation showed that nanoparticles, or better here nanoobjects can become airborne when vigorously agitated. Yeganeh et al. [21] on the other hand reported significant increases of sub-100 nm particle number concentrations during the handling of carbonaceous nanomaterials including fullerenes. Anyhow, no quantification of release was done due to the highly variable background and hence the actual contribution of engineered nanoparticles to the determined number concentration is not known. Wake et al. [22] investigated nanoscale particles at different workplaces in various industries, including workplaces with nanoparticle production. They conclude that there was no evidence of significant ultrafine particle release in unagglomerated form when working with nanoscale powders. In contrast, processes involving heat, such as welding, released high levels of nanoscale particles. The examples above show that nearly no or little exposure was determined in the field. This may well be due to the materials being produced and the safe work conditions at the investigated work places. It now becomes necessary to get comparable measurement technologies and measurement strategies in place to investigate the various work places in nanoparticle production facilities. Exposure to nanoparticles and nanoobjects has to be carefully screened to ensure a safe and sustainable development of this technology. 6.

Summary

An array of measurement techniques for the determination of airborne nanoscale particles exists. Still, the demand on these techniques, namely measurements of all possibly health relevant particle parameters online as personal dose (personal sampler) is extremely high and currently not fulfilled. Only few devices exist for personal sampling (only offline and use of imaging techniques) and measurements of the dose. Especially the latter may vary significantly since particle uptake is size dependent (even within the size range below 100 nm) but also dependent of physiochemical characteristics such as solubility and hygroscopicity. The main techniques currently used are stationary systems such as the SMPS. First assessments of comparability and reproducibility of size distribution

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measurement devices show discrepancies in e.g. number concentrations, modal size in the range of 30–40%. Uncertainties can be expected to be larger since no protocols on data correction (e.g. diffusion losses, multiple charge correction), and only limited information on influence of state of agglomeration on the measurement results exist. Measurement strategies are currently needed beside reproducible and comparable measurement techniques to allow for a first assessment if product nanoparticles/ nanoobjects were released. The measurement strategy is crucial to allow for an assessment of uncertainty and of lower detection limits. Despite all the above problems, which still have to be dealt with, first measurement results indicate that 1. 2. 3.

Measurements are currently feasible Monitoring on a routine base can also be done and No or only limited release of nanoscale particles or objects has been detected

Nevertheless, it has to be kept in mind that the information base for exposure assessment is currently built on an uncertain and limited data base which has to be improved in size, comparability, reproducibility. This can be achieved by working on the feasibility for routine assessments, development of reliable measurement techniques, standardization of measurement techniques, measurement strategies, and implementation of screening/monitoring of nanoscale particles in sensitive work areas. Future challenges are currently especially seen in the detection of product nanoparticles in the environment, which we believe to be currently nearly impossible for airborne particles. References 1. Asbach, C., H. Kaminski, H. Fissan, C. Monz, D. Dahmann, S. Mülhopt, H.R. Paur, H.J. Kiesling, F. Herrmann, M. Voetz, T.A.J. Kuhlbusch, Intercomparability of continuous particle number based measurement techniques for nanotechnology workplaces, Proceedings Euronanoforum 2007, European Commission, EUR 22833, 344–345, 2007 2. Borm, P.J.A., D. Robbins, S. Haubold, T.A.J. Kuhlbusch, H. Fissan, K. Donaldson, R. Schins, V. Stone, W. Kreyling, J. Lademann, J. Krutmann, D. Warheit, E. Oberdorster, The Potential Risk of Nanomaterials: A review carried out for ECETOC, Particle and Fibre Toxicology 3:11, 2006 3. Brouwer, D.H., J.H.J. Gijsbers, M.W.M. Lurvink, Personal exposure to ultrafine particles in the workplace: Exploring sampling techniques and strategies, Annals of Occupational Hygiene 48(5):439–453, 2004 4. Butz, T. et al. Quality of Skin as a Barrier to ultra-fine Particles. http://www.unileipzig.de/%7Enanoderm/Downloads/Nanoderm_Final_Report.pdf, in Nanoderm Final Report to the EU, 2007 5. Dahman, D. et al. (16 authors) Intercomparison of mobility particle sizers, Gefahrstoffe Reinhaltung der Luft 61(10):423–428, 2001

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6. Dingenen, R.V. et al. (27 authors) A European aerosol phenomenology - 1. Physical characteristics of particulate matter at kerbside, urban, rural and background sites in Europe, Atmospheric Environment 38:2561–2577, 2004 7. Dixkens, H., H. Fissan Development of an electrostatic precipitator for off-line analysis, Aerosol Science & Technology 30:438–453, 1999 8. Fissan, H., S. Neumann, A. Trampe, D.Y.H. Pui, W.G. Shin Rationale and principle of an instrument measuring lung deposited nanoparticle surface area, Journal of Nanoparticle Research 9:53–59, 2007 9. Hermann, M., B. Wehner, O. Bischof, H.-S. Han, T. Krinke, W. Liu, A. Zerrath, A. Wiedensholer Particle counting efficiencies of new TSI condensation particle counters, Journal of Aerosol Science 38:674–682, 2007 10. John, A.C., T.A.J. Kuhlbusch, H. Fissan, K.-G. Schmidt, H.-U. Pfeffer, D. Gladke New sampling unit for size dependent chemical analyses of airborne dust using total reflection x-ray fluorescence spectrometry, Journal of Aerosol Science 31:149, 2000 11. Jung, H., D. Kittelson, Characterization of aerosol surface instruments in transition regime, Aerosol Science & Technology 39:902–911, 2005 12. Kuhlbusch, T.A.J., S. Neumann, H. Fissan, Number size distribution, mass concentration, and particle composition of PM1, PM2.5 and PM10 in bagging areas of carbon black production, JOEH 1:660–671, 2004 13. Kuhlbusch, T.A.J., H. Fissan, Particle characteristics in the reactor and pelletizing areas of carbon black production, JOEH 3(10):558–567, 2006 14. Kuhlbusch, T.A.J., H. Fissan, C. Asbach, Measurement and detection of nanoparticles in the environment, in Nanotechnology, Volume 2: Environmental Aspects, Ed. H. Krug, ISBN 978-3-527-31735-6, Wiley-VCH, Weinheim, p. 229–266, 2008a 15. Kuhlbusch, T.A.J., H. Kaminski, M. Beyer, D. Jarzyna, H. Fissan, and C. Asbach, Measurement of nanoscale TiO2 in workplace environments - method and results, in preparations, 2008b 16. Maynard A. D., P. A. Baron, M. Foley, A. A. Shvedova, E. R. Kisin, V. Castranova, Exposure to carbon nanotube material: aerosol release during the handling of unrefined single-walled carbon nanotube material, Journal of Toxicology Environmental Health Part A 67(1):87–107, 2004 17. McMurry, P. The history of condensation nucleus counters, Aerosol Science & Technology 33:297–322, 2000 18. Mirme, A., M. Noppel, I. Peil, J. Salm, E. Tamm, H. Tammet, Multi-channel electric aerosol spectrometer. In 11th International Conference on Atmospheric Aerosols, Condensation and Ice Nuclei, Budapest 2, 155–159, 1984 19. Shin, W. G., D. Y. H. Pui, H. Fissan, S. Neumann, A. Trampe, Calibration and numerical simulation of nanoparticle surface area monitor (TSI model 3550 NSAM), Journal of Nanoparticle Research 9:61–69, 2007 20. Wang, S. C., R. Flagan, Scanning electrical mobility spectrometer. Aerosol Science and Technology 13:230–240, 1990 21. Yeganeh, B., C. M. Kull, M. S. Hull, L. C. Marr, Characterization of airborne particles during production of carbonaceous nanomaterials, Environmental Science & Technology, accepted, 2008 22. Wake, D., D. Mark, C. Northage, Ultrafine aerosols in the workplace. Annals of Occupational Hygiene 46(Suppl. 1):235–238, 2002

PROCESSING OF POLYMER NANOFIBERS THROUGH ELECTROSPINNING AS DRUG DELIVERY SYSTEMS

E. KENAWY, F.I. ABDEL-HAY, M.H. EL-NEWEHY Chemistry Department, Polymer Research Group Faculty of Science, Tanta University Tanta 31527, Egypt [email protected] G.E. WNEK Department of Chemical Engineering Case Western Reserve University Cleveland, OH 44106-7217, USA

Abstract. The use of electrospun fibers as drug carriers could be promising in the future for biomedical applications, especially postoperative local chemotherapy. In this research, electrospun fibers were developed as a new system for the delivery of ketoprofen as non-steroidal anti-inflammatory drug (NSAID). The fibers were made either from polycaprolactone (PCL) as a biodegradable polymer or polyurethane (PU) as a non-biodegradable polymer, or from the blends of the two. The release of the ketoprofen was followed by UV–VIS spectroscopy in phosphate buffer of pH 7.4 at 37°C and 20°C. The results showed that the release rates from the polycaprolactone, polyurethane and their blend were similar. However, the blend of the polycaprolactone with polyurethane improved its visual mechanical properties. Release profiles from the electrospun mats were compared to cast films of the various formulations. 1.

Introduction

Controlled drug delivery systems have gained much attention in the last few decades. This is due to the many advantages compared with the conventional dosage forms such as improving therapeutic efficacy, reducing toxicity by delivering them at a controlled rate. Recently, electrospun fibers were explored as new device for drug delivery [1–5]. The main advantages of the fibrous carriers are that they offer site-specific delivery of drugs to the body. Also, more than one drug can be encapsulated directly into the fibers. Due to the high surface area and porous structure of the electrospun fibers, they find applications in many fields such as medicine [6–18], biosensors, catalysts, photonic, sensitized solar cells, tissue engineering, nanocomposites, antimicrobial materials and membranes [9–31].

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Recently, we reported the first drug delivery system for the antibiotic tetracycline hydrochloride from nanofibrous membranes based on poly(ethyleneco-vinyl acetate), poly(lactic acid) and their blends [1]. Kim et al. incorporated a hydrophilic antibiotic into poly (lactide-co-glycolide) to produce nanofibrous scaffolds [32], while Brewster et al. used polymer based electrospun nanofibers containing dispersions of poorly water-soluble pharmaceuticals as delivery systems [33]. Biodegradable polymers are good candidates for applications in the biomedical field due to their biocompatibility, their degradation and mechanical properties. Polycaprolactone (PCL) (Figure 11) is a rather hydrophobic semi-crystalline polymer with a high molecular weight. It may be used in diffusion-controlled delivery systems. The main mode of degradation for caprolactone polymers is hydrolysis. This degradation proceeds first by diffusion of water into the material, followed by random hydrolysis fragmentation of the material, and finally more extensive hydrolysis accompanied by phagocytosis, diffusion, and metabolism. The hydrolysis is affected by the size, hydrophilicity, and crystallinity of the polymer and the pH and temperature of the environment [34].

[O(CH2)5CO]n Figure 1. Chemical structure of polycaprolactone (PCL).

On the other hand, polyurethanes, as non-biodegradable polymer, have many medical applications. The applications includes external devices such as wound dressing to many types of catheters and feeding tubes to long term implants such as pacemakers. Generally, polyurethanes are made of hard and soft domains (Figure 22). O (O CH2CH2)x O C NH Polyol

O CH2 Isocyanate

NH C O CH2CH2CH2CH2 O Extender

Figure 2. Chemical structure of polyurethane (PU) (Tecophilic Resin HP-60D-60).

The diisocyanate and extender make up the hard domains and the macrodiol makes the soft domain. Tecophilic is a reaction product synthesized from hydrogenated methylene diisocyanate (HMDI) (diisocyanates), poly (ethylene glycol) (macrodiols) and 1, 4-butanediol (chain extenders). In this work, fibrous membranes containing ketoprofen based on polycaprolactone (PCL), polyurethanes and their blends were prepared from electrospinning. Various blends were prepared and the release of the ketoprofen from the various

PROCESSING OF POLYMER NANOFIBERS THROUGH ELECTROSPINNING 249

membranes was investigated at body temperature (37°C) and at room temperature (20°C). 2.

Experimental

2.1.

GENERAL EXPERIMENTAL PROCEDURE

2.1.1.

Materials

Polycaprolactone (PCL) (average Mw 80,000k g/mole), methanol, chloroform, sodium phosphate dibasic (Na2HPO4) and potassium phosphate monobasic (KH2PO4) were purchased from Aldrich (USA). Polyurethane (PU) (Mw 120,000k g/mole, was measured by GPC using PMMA or PS standard) was purchased from Thermedics Polymers Products, a division of VIASYS Healthcare (USA). Ketoprofen was purchased from Sigma (USA). All these materials were used as received without further purification. 2.1.2.

Characterization Techniques

The morphology of a dried mats and films were investigated with a JSM-820 scanning electron microscope (SEM) (JEOL Ltd., USA). The thickness of electrospun mats and films was measured using a Precision Micrometer, Model No. 49-61, Range: 0–1.270 mm, Testing Machines, INC. AMITVILLE N.Y. (USA). UV spectra were recorded using GENESYS™ 6 Spectrophotometer (USA). 2.1.3.

Preparation of Phosphate Buffer Solution (PB)

The phosphate buffer solution (pH 9.0) was prepared as described previously [35] by dissolving sodium phosphate dibasic (Na2HPO4) (35.49 g) in 1 l deionized water and the pH was adjusted to 9.0 using 0.1N sodium hydroxide and 0.1N hydrochloric acid solutions. The phosphate buffer solution (pH 7.4) was prepared by dissolving sodium phosphate dibasic (Na2HPO4) (21.70 g) and potassium phosphate monobasic (KH2PO4) (2.60 g) in 1 l deionized water and the pH was adjusted to 7.4 using 0.1N sodium hydroxide and 0.1N hydrochloric acid solutions. The pH 2.0 buffer solutions were adjusted with 0.1N hydrochloric acid and the pH was adjusted to 2.0 using 0.1N sodium hydroxide and 0.1N hydrochloric acid solutions. 2.2.

ELECTROSPINNING

2.2.1.

Preparation of Polymer Solution and Fiber Aggregates

2.2.1.1. Polyurethane (PU) Polyurethane (PU) solution was prepared by dissolving PU in chloroform by heating at 65–70°C for 3–4 h with stirring to obtain a concentration of 10%

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solution by weight (w/w). Ketoprofen in concentration of 5% w/w PU was dissolved in a small amount of methanol and was added to PU solution and was stirred for 20–30 min before electrospinning. 2.2.1.2. Polycaprolacton (PCL) Polycaprolactone (PCL) solution was prepared by dissolving PCL in chloroform at room temperature overnight with vigorous stirring to obtain a concentration of 10% w/w. Ketoprofen in concentration of 5% w/w PU was dissolved in a small amount of methanol and was added to PCL solution and was stirred for 20–30 min before electrospinning. 2.2.1.3.

Polyurethane/Polycaprolactone) Blend

Blend of PU/PCL with different ratio (PU/PCL: 75/25, 50/50 and 25/75) was prepared as following: Polyurethane (PU) solution was prepared by dissolving PU in chloroform on heating at 65–70°C for 3–4 h with stirring. The solution was cooled to room temperature and then polycaprolactone (PCL) was added and the solution was stirred at room temperature overnight to give a total concentration of 10% w/w. Ketoprofen in concentration of 5% w/w PU/PCL blend was dissolved in a small amount of methanol and was added to the solution and was stirred for 20–30 min before electrospinning. 2.3.

GENERAL PROCEDURE FOR ELECTROSPINNING PROCESS

A schematic diagram of the electrospinning process is shown in (Figure 3). It consists of a syringe with a flat-end metal needle cut, a syringe pump (model 100 KD scientific Inc., New Hope, PA) for controlled feeding rates, a grounded cylindrical stainless steel mandrel, and a high voltage DC power supply (Spellman, CZE1000R, Spellman High voltage Electronics Corp., Hauppauge, NY). The solution was placed in a syringe; positive or negative voltage was applied to initiate the jet. The feeding rate was controlled by the syringe pump and the tip-to-collector distance (TCD) was adjusted. The electrospun mats was dried in a hood at room temperature overnight. For the purpose of comparison, casting film containing the same materials was made onto Petri dish.

Figure 3. Schematic of electrospinning system.

PROCESSING OF POLYMER NANOFIBERS THROUGH ELECTROSPINNING 251

2.4.

IN VITRO DRUG RELEASE TESTS

2.4.1.

Determination of Total Ketoprofen Content

Ten milligram of mat or film were suspended in 10 ml basic solution of pH 9.0 (sodium hydroxide solution). The mixture was maintained at 60°C and the amount of ketoprofen released by hydrolysis was determined by UV spectrophotometer at λmax = 260 nm. 2.4.2.

In Vitro Drug Release

The release of ketoprofen was determined by UV spectrophotometer at λmax = 260 nm as a function of time. The procedure used was as following: 10 mg of electrospun mat or film was placed in 10 ml phosphate buffer (PB) of pH 7.4 and was shacked in a shaking water bath (Shaker Water bath, Model #25, USA) at 37°C and 20°C. 3.

Results and Discussions

Non-steroidal anti-inflammatory drugs (NSAIDs) are used for controlling pain and inflammation in rheumatic diseases. Administration of acidic NSAIDs to arthritic patients relieves pain and inflammatory swelling [36]. While NSAIDs have many advantages, one of their few disadvantages is a relatively short plasma half-life. This results in short activity duration, and a pronounced ulcerogenic potency [37-38]. Ketoprofen (Figure 4), our drug model, is one of NSAIDs group. It is effective as anti-inflammatory agent in humans with floristic diseases.

=

O

CH3 CHCOOH

Figure 4. Chemical structure of ketoprofen.

In the current work, new systems of controlled drug release via electrospinning technique were developed. Electrospun polycaprolactone as biodegradable system and polyurethane as non-biodegradable system for drug delivery were prepared. Polycaprolactone has poor mechanical properties; therefore, it was blended with polyurethane to improve its mechanical properties. 3.1.

PREPARATION OF FIBER AGGREGATES

3.1.1.

Polyurethane (PU)

Polyurethane with ketoprofen entrapped on it was electrospun from 10% w/w solution with feeding rate 5–11 ml/h when 20 kV was applied with TCD 20 cm. A

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(a)

(b)

(c)

(d)

(e) Figure 5. SEM micrograph of electrospun PU, PCL and their blends containing ketoprofen drug, (a): PU; (b): PCL; (c): PU/PCL 75/25, (d): PU/PCL 50/50 and (e): PU/PCL 25/75.

rotating metal drum was used to collect the resulting fiber to give a white sheet of non-woven fiber. The non-woven fiber diameters ranged from 3.12 to 6.25 μm. The sheet thickness ranged from 104 to 143 μm. The SEM of electrospun fiber is shown in (Figure 5). The electrospun mat is opaque due to light scattering from

PROCESSING OF POLYMER NANOFIBERS THROUGH ELECTROSPINNING 253

the fibrous structure. Casting film was prepared and the film thickness ranged from 200 to 269 μm. 3.1.2.

Polycaprolactone (PCL)

Polycaprolactone with ketoprofen entrapped on it was electrospun from 10% w/w solution with feeding rate 6–7 ml/h when 20 kV was applied with TCD 15 cm. A rotating metal drum was used to collect the resulting fiber to give a white sheet of non-woven fiber. The non-woven fiber diameters ranged from 2 to 6.66 nm and the sheet thickness ranged from 113 to 120 μm. The SEM of electrospun fiber is shown in Figure 5. The electrospun mat is opaque due to light scattering from the fibrous structure. SEM detected no ketoprofen crystals on the surface of the fibers, indicating this indicated that ketoprofen was perfectly embedded in the fibers. Casting film was prepared and the film thickness ranged from 196 to 204 μm. 3.1.3.

Polyurethane/Polycaprolactone (PU/PCL) Blend

Blends of polyurethane and polycaprolactone with different ratios (PU/PCL: 75/25, 50/50 and 25/75) with ketoprofen entrapped on it were electrospun from 10% w/w solution. Generally, the electrospun mat is opaque due to light scattering from the fibrous structure. 3.1.3.1. PU/PCL (75/25) Blend PU/PCL (75/25) blend with ketoprofen entrapped on it was electrospun with feeding rate 6 ml/h when 20 kV was applied with TCD 15 cm. The produced nonwoven fiber diameters ranged from 1 to 7 μm. The sheet thickness range was 65– 88 μm. The SEM of electrospun fiber before and is as shown in Figure 5. This indicated that there ketoprofen was perfectly embedded in the fibers. For comparison studies, casting film was prepared and the film thickness ranged from 200 to 255 μm. 3.1.3.2. PU/PCL (50/50) Blend When voltage of 22 kV was applied to solution of PU/PCL: 50/50 with ketoprofen entrapped on it with feeding rate 6–8 ml/h and TCD 15 cm, non-woven fiber of diameters ranged from 1.75 to 6.45 μm were obtained. The sheet thickness ranged from 85 to 106 μm. The SEM of electrospun fiber is as shown in Figure 5. The film thickness ranged from 238 to 297 μm. 3.1.3.3. PU/PCL (25/75) Blend Non-woven fiber of (PU/PCL: 25/75) with ketoprofen entrapped on it from 10 wt% solution was obtained when a voltage of 21 kV was applied, with feeding rate 6 ml/h and TCD 15 cm. The non-woven fiber diameters ranged from 1 to 4.25 μm. The sheet thickness ranged from 74 to 112 μm. The SEM image of electrospun fiber is shown in Figure 5. The cast film thickness ranged from 160 to 179 μm.

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3.2.

DETERMINATION OF TOTAL KETOPROFEN CONTENT

To evaluate the total content of ketoprofen in the samples, they were hydrolyzed by heating or sonication of a known amount of the mat or film in alkaline solution of pH 9.0. The amount released of ketoprofen from the sample was determined by UV spectrophotometer at λmax = 260 nm, at room temperature within 30 min. Then, the samples were heated at 60°C. The drug concentration was monitored by UV spectrophotometer until it reaches a constant concentration for the drug. 3.2.1.

Polyurethane (PU)

The fast release studies of ketoprofen trapped in the polyurethane (PU) in the alkaline solution of pH 9.0 at 60°C showed that, the total ketoprofen content of PU-spun was 49.97 (mg ketoprofen)/(g polymer) and for PU-film was 51.12 (mg ketoprofen)/(g polymer) (TABLE 1). 3.2.2.

Polycaprolactone (PCL)

Based on the fast release of ketoprofen studies from polycaprolactone in the alkaline solution of pH 9.0 at 60°C, the ketoprofen content for electrospun PCL was 52.30 (mg ketoprofen)/(g polymer) and 48.21 (mg ketoprofen)/(g polymer) for PCL-film (TABLE 1). 3.2.3.

PU/PCL (75/25)

The fast release studies of PU/PCL (75/25) blend with ketoprofen entrapped on it in alkaline solution of pH 9.0 at 60°C, showed that the total ketoprofen content for PU/PCL (75/25)-mat was 46.94 (mg ketoprofen)/(g polymer) and 48.62 (mg ketoprofen)/(g polymer) for PU/PCL (75/25)-film (TABLE 1). 3.2.4.

PU/PCL (50/50)

The studies of PU/PCL (50/50) blend in alkaline solution of pH 9.0 at 60°C showed a total ketoprofen content of 50.44 (mg ketoprofen)/(g polymer) for PU/PCL (50/50)-mat and 48.67 (mg ketoprofen)/(g polymer) for PU/PCL (50/50)film (TABLE 1). 3.2.5.

PU/PCL (25/75)

PU/PCL (25/75) blend with ketoprofen entrapped on it in alkaline solution of pH 9.0 at 60°C, showed a total ketoprofen content for electrospoun PU/PCL (25/75) of 49.68 (mg ketoprofen)/(g polymer) and 48.79 (mg ketoprofen)/(g polymer) for PU/PCL (25/75)-film (TABLE 1).

PROCESSING OF POLYMER NANOFIBERS THROUGH ELECTROSPINNING 255 TABLE 1. Ketoprofen content for electrospun mat and film made from PU, PCL and their blends after sonication for 24 h at 60°C. Polymer code

PU-spun

(mg ketoprofen)/(g polymer) Found from hydrolysis Calculated 49.97 50.08

PU-film

51.12

51.78

PCL-spun

52.30

52.69

PCL-film

48.21

53.58

PU/PCL:75/25 spun PU/PCL:75/25 film

46.94 48.62

49.03 49.03

PU/PCL:50/50 spun

50.44

50.86

PU/PCL:50/50 film

48.67

51.45

PU/PCL:25/75 spun

49.68

49.75

PU/PCL:25/75 film

48.79

49.95

3.3.

IN VITRO DRUG RELEASE

The rate of ketoprofen released from electrospun fibers was studied at pH 7.4 and various temperatures. The rate of release is likely to depend on the temperature. The electrospinning technique is newly utilized in the field of drug delivery [1–5]. It provides a unique and simple technique for the drug delivery. The advantages of this technique are that it could be applied for wide range of pharmaceutical compounds either functionalized or non-functionalized. It could be used for more than one drug at the same time; in addition, more than one polymer could be used to be electrospun at one jet at the same time. Also, it is possible to be electrospun as layers. It could be applied directly for transdermal drug delivery, used as a nerve guide or as a bag for the biohemostate devices. 3.3.1.

Drug Release from Electrospun Fiber and Film Made from Polyurethane (PU)

The release rates of ketoprofen from electrospun fiber and cast film made from polyurethane were studied in pH 7.4 at 37°C and at 20°C. In general, the trend of release from both electrospun mat and cast film showed initial fast release in the first few hours followed by slower release rates as shown in (Figure 6). Investigation of the release profiles showed that the electrospun polyurethane exhibited initial burst release even at 20°C. However, the release rate of the ketoprofen drug from the electrospun polyurethane mat showed relatively higher release rate at 37°C than that at 20°C as shown in (Figure 6). It released a total amount of 47.61 (mg drug)/(g polymer) which represents 95.28% of its drug content at 37°C. Whereas, it released 43.80 (mg drug)/(g polymer) which represents 87.64% of its drug content at 20°C. For comparison, film was cast from polyurethane containing the same amount of ketoprofen. The release profile of the

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drug from the cast film is as shown in (Figure 6). It also showed initial fast release within the first few hours followed by a slower release rate. At 37°C, the total amount released of ketoprofen from cast film was 44.96 (mg drug)/(g polymer) which represents 87.96% of its drug content. At 20°C, the total amount released of ketoprofen from cast film was 38.59 (mg drug)/(g polymer) which represents 75.51% of its drug content. Again, the effect of temperature here was clear. As it increased, the amount of ketoprofen released from the cast polyurethane film increased from 75.51% to 87.96% of its drug content. This is expected because the release from the film is diffusion dependent and the temperature increases the diffusion rate. Comparison between the amount released of ketoprofen from the electrospun PU mat and the PU cast film is as shown in (Figure 6). At 37°C, the difference between the amount released from both electrospun mat and cast film was not high. This could be due to the effect of temperature on the diffusion from the film, which increases the release rate. This increment due to temperature effect diminishes the effect of high surface area of the electrospun fibers. While at lower temperature, 20°C, the diffusion rate is lower. Consequently, the high surface area of the electrospun fibers showed high release rate compared to the cast film.

Cumulative drug released (%)

100 80 60

spun-20°C

40

film-20°C film-37°C

spun-37°C

20 0 0

40

80

120

160

200

240 280

320

360

Time (h) Figure 6. In vitro release profile of ketoprofen from electrospun mat and film made from PU in phosphate buffer pH 7.4 at the 37°C and 20°C.

3.3.2.

Drug Release from Electrospun Fiber and Film Made from Polycaprolactone (PCL)

The ketoprofen released from the PCL mat and film was studied at 37°C (approximate body temperature) and at 20°C in phosphate buffer of pH 7.4. The

PROCESSING OF POLYMER NANOFIBERS THROUGH ELECTROSPINNING 257

release profiles are shown in Figure 7. The release from electrospun PCL at 20°C was slower than that released at 37°C. It showed an initial fast release at both temperatures. It released about 39.61% of its drug content within the first 2 h at 37°C, and then the release rate was slower as shown in Figure 7. It released 44.18 (mg drug)/(g polymer) which represents 84.48% of its drug content within 2 weeks at 20°C, whereas 50.65 (mg drug)/(g polymer) which represents 96.85% of its drug content at 37°C was released within the same period. Cast film from PCL showed a total release of 38.66 (mg drug)/(g polymer) which represents 80.36% of its drug content at 37°C while it showed 36.64 (mg drug)/(g polymer) which represents 76.16% of its drug content at 20°C. Comparison between the electrospun mat and cast film showed initial fast release at both 20°C and 37°C within the first few hours. After about 2 h, the profile showed a faster release from the electrospun mat than the film. It showed a total release of 50.65 (mg drug)/(g polymer) which represents 96.84% of its drug content after 2 weeks at 37°C and 44.18 (mg drug)/(g polymer) which represents 84.47% of its drug content at 20°C after the same period. The same phenomenon was observed at 20°C for both PCL mat and film.

Cumulative drug released (%)

100 80 spun-20°C spun-37°C film-20°C film-37°C

60 40 20 0 0

40

80

120

160 200

240

280

320

360

Time (h) Figure 7. In vitro release profile of ketoprofen from electrospun mat and film made from PCL in phosphate buffer pH 7.4 at 37°C and 20°C.

3.3.3.

Drug Release from Electrospun Fibers and Films Made from Polyurethane/Polycaprolactone (PU/PCL) Blends

3.3.3.1. Polyurethane/Polycaprolactone (PU/PCL: 75/25) Blend. The ketoprofen release profiles from electrospun fiber and film made from (PU/PCL: 75/25) are shown in Figure 8. The ketoprofen release was studied at

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37°C and at 20°C in phosphate buffer of pH 7.4. At 37°C, the amount released of ketoprofen from electrospun fiber within the first 2 h was 29.46 (mg drug)/(g polymer) which represents 62.76% of its drug content as shown in Figure 8, while it released 42.68 (mg drug)/(g polymer) which represents 90.93% of its drug content after 2 weeks. At 20°C, it released 23.94 (mg drug)/(g polymer) which represents 51.01% of its drug content within the first 2 h. After 2 weeks, a slight increase in the amount released of ketoprofen was observed, it released 36.33 (mg drug)/(g polymer) which represents 77.40% of its drug content. Cast film of (PU/PCL: 75/25) showed a total release of 79.88% of its drug content at 37°C while it showed 59.35% of its drug content at 20°C. Comparison between the amounts released of ketoprofen from the electrospun fiber and cast film. Both of the electrospun fiber and cast film showed initial fast release at both 37°C and at 20°C within the first few hours. After 2 h, the release profile showed a faster release for the electrospun mat than the film. Electrospun fiber showed a total release of 42.68 (mg drug)/(g polymer) which represents 90.93% of its drug content after 2 weeks at 37°C and cast film showed a total release of 38.84 (mg drug)/(g polymer) which represents 79.88% of its drug content after the same period. The initial fast release was also observed at 20°C for both electrospun mat and film.

Cumulative drug released (%)

100 80 spun-20°C spun-37°C film-20°C

60 40

film-37°C

20 0 0

40

80

120

160

200

240

280

320

360

Time (h) Figure 8. In vitro release profile of ketoprofen from electrospun mat and film made from (PU/PCL: 75/25) blend in phosphate buffer (pH 7.4) at 37°C and 20°C.

3.3.3.2. Polyurethane/Polycaprolactone Blend (PU/PCL: 50/50). The ketoprofen release profiles from electrospun fiber and cast film of (PU/PCL: 50/50) are shown in (Figure 9). The release was studied at 37°C and 20°C in phosphate buffer of pH 7.4. At 37°C, the amount released of ketoprofen from

PROCESSING OF POLYMER NANOFIBERS THROUGH ELECTROSPINNING 259

electrospun fiber within the first 2 h was 30.24 (mg drug)/(g polymer) which represents 59.95% of its drug content, while it released 44.63 (mg drug)/(g polymer) which represents 88.49% of its drug content after 2 weeks. At 20°C, it released 27.59 (mg drug)/(g polymer) within the first 2 h which represents 54.69% of its drug content, while it showed a total release of 41.51 (mg drug)/(g polymer) which represents 82.30% of its drug content after 2 weeks. The in vitro drug released from (PU/PCL: 50/50) cast film was also investigated. The total amount released of ketoprofen was 34.87 (mg drug)/(g polymer) which represents 71.66% of its drug content after 2 weeks at 37°C and 24.12 (mg drug)/(g polymer) which represents 49.57% of its drug content at 20°C. Comparison between the electrospun fiber and cast film, showed initial fast release at both 37°C and 20°C within the first 2 h. After about 2 h, the profile showed a faster release from the electrospun mat than the film. This is due to the high surface area of the electrospun fibers compared to the cast films. Electrospun fiber showed a total release of 30.24 (mg drug)/(g polymer) which represents 59.95% of its drug content after 2 weeks at 37°C and cast film showed a total release of 21.48 (mg drug)/(g polymer) which represents 44.14% of its drug content after the same period. The initial fast release phenomenon was also observed for electrospun mat and the cast film of (PU/PCL: 50/50) at 20°C. The total amount released of ketoprofen from the blend 50:50 was higher in case of electrospun mat than the film. This is again attributed to the high surface area of the very fine fibers.

Cumulative drug released (%)

100 80 60

spun-20°C

40

film-20°C film-37°C

spun-37°C

20 0 0

40

80

120

160 200

240

280

320

360

Time (h) Figure 9. In vitro release profile of ketoprofen from electrospun mat and cast film made from (PU/PCL: 50/50) blend in phosphate buffer pH 7.4 at 37°C and 20°C.

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3.3.3.3. Polyurethane/Polycaprolactone Blend (PU/PCL: 25/75). The ketoprofen release profiles from electrospun fiber and cast film of (PU/PCL: 25/75) are shown in (Figure 10). The ketoprofen release was studied at 37°C and 20°C in phosphate buffer pH 7.4. At 37°C, the amount released of ketoprofen from electrospun fiber within the first 2 h was 33.09 (mg drug)/(g polymer) which represents 66.61% of its drug content, while it showed a total release of 44.19 (mg drug)/(g polymer) which represents 88.96% of its drug content after 2 weeks. At 20°C, it released 29.90 (mg drug)/(g polymer) within the first 2 h which represents 60.18% of its drug content, while it showed a total release of 40.73 (mg drug)/(g polymer) which represents 81.99% of its drug content after 2 weeks. The in vitro release profiles of ketoprofen from (PU/PCL: 25/75) cast film. The total amount released of ketoprofen from cast film after 2 weeks at 37°C was 36.92 (mg drug)/(g polymer) which represents 75.67% of its drug content and 33.73 (mg drug)/(g polymer) released at 20°C which represents 69.15% of its drug content. Comparison between the electrospun fiber and cast film, showed initial fast release at both 37°C and 20°C within the first 2 h. After about 2 h, the profile showed a faster release from the electrospun mat than the film. Electrospun fiber showed a total release of 44.19 (mg drug)/(g polymer) which represents 88.96% of its drug content after 2 weeks at 37°C and cast film showed a total release of 36.92 (mg drug)/(g polymer) which represents 75.67% of its drug content at 20°C after the same period. The same effect for the device shape was explored; it was found that electrospun mat showed faster release rate than the film, however, both showed initial release.

Cumulative drug released (%)

100 80 spun-20°C spun-37°C film-20°C film-37°C

60 40 20 0 0

40

80

120

160

200

240 280

320

360

Time (h) Figure 10. In vitro release profile of ketoprofen from electrospun mat and film made from (PU/PCL: 25/75) blend in phosphate buffer pH 7.4 at the body temperature 37°C and 20°C.

PROCESSING OF POLYMER NANOFIBERS THROUGH ELECTROSPINNING 261

4.

Conclusion

New drug delivery systems for ketoprofen as non-steroidal anti-inflammatory drug (NSAID) were developed. These systems were based on the encapsulation of ketoprofen in the electrospun fibers. These fibers were either biodegradable, such as polycaprolactone (PCL), or non-biodegradable polymers, such as polyurethane (PU), or their blends. The ketoprofen release was monitored in phosphate buffer of pH 7.4 at 37°C and 20°C. Generally, as the temperature increased, the amount released of ketoprofen increased. The release rates from the polycaprolactone, polyurethane and their blend are almost similar. However, the blend of the polycaprolactone with polyurethane improved its visual mechanical properties. References 1. Kenawy, E.-R., Bowlin, G.L., Mansfield, K., Layman, J., Simpson, D.G., Sanders, E.H., and Wnek, G.E. (2002) Release of tetracycline hydrochloride from electrospun poly(ethylene-co-vinylacetate), poly(lactic acid), and a blend, Journal of Controlled Release, 81(1–2), 57–64. 2. Zong, X., Kim, K., Fang, D., Ran, S., Hsiao, B.S., and Chu, B. (2002) Structure and process relationship of electrospun bioabsorbable nanofiber membranes, Polymer 43(16), 4403–4412. 3. Zeng, J., Xu, X., Chen, X., Liang, Q., Bian, X., Yang, L., and Jing, X. (2003) Biodegradable electrospun fibers for drug delivery, Journal of Controlled Release 92(3), 227–231. 4. Jiang, H., Fang, D., Hsiao, B.S., Chu, B., and Chen, W. (2004) Optimization and characterization of dextran membranes prepared by electrospinning, Biomacromolecules 5(2), 326–333. 5. Kenawy, E.-R., Abdel-Hay, F.I., El-Newehy, M.H., and Wnek, G.E. (2007) Controlled release of ketoprofen from electrospun poly (vinyl alcohol) nanofibers, Materials Science and Engineering A 459 (1–2), 390–396. 6. He, C.-L., Huang, Z.-M., Han, X.-J., Liu, L., Zhang, H.-S., and Chen, L.-S. (2006) Coaxial electrospun poly(L-lactic acid) ultrafine fibers for sustained drug delivery, Journal of Macromolecular Science, Part B: Physics 45 B (4), 515–524. 7. Taepaiboon, P., Rungsardthong, U., and Supaphol, P. (2006) Drug-loaded electrospun mats of poly (vinyl alcohol) fibres and their release characteristics of four model drugs, Nanotechnology 17, 2317–2329. 8. Cui, W., Li, X., Zhu, X., Yu, G., Zhou, S., and Weng, J. (2006) Investigation of drug release and matrix degradation of electrospun poly (DL-lactide) fibers with paracetanol inoculation, Biomacromolecules 7(5), 1623–1629. 9. Luong-Van, E., Grøndahl, L., Chua, K.N., Leong, K.W., Nurcombe, V., and Cool, S.M. (2006) Controlled release of heparin from poly (ε-caprolactone) electrospun fibers, Biomaterials 27(9), 2042–2050. 10. Lee, L.J. (2006) Polymer nanoengineering for biomedical applications, Annals of Biomedical Engineering 34(1), 75–88. 11. Jiang, H., Hu, Y., Li, Y., Zhao, P., Zhu, K., and Chenm, W. (2005) A facile technique to prepare biodegradable coaxial electrospun nanofibers for controlled release of bioactive agents, Journal of Controlled Release 108(2–3), 237–243. 12. Zhang, C., Yuan, X., Wu, L., and Sheng, J. (2005) Drug-loaded ultrafine poly(vinyl alcohol) fibre mats prepared by electrospinning, E-Polymers 19 October 2005, 9.

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AIR POLLUTION MONITORING AND USE OF NANOTECHNOLOGY BASED SOLID STATE GAS SENSORS IN GREATER CAIRO AREA, EGYPT

A.B.A. RAMADAN National Center for Nuclear Safety and Radiation Control 3 Ahmed El-Zomor Street, Nasr City 11762, P.O. Box 7551 Cairo, Egypt [email protected]

Abstract. Air pollution is a serious problem in thickly populated and industrialized areas in Egypt, especially in greater Cairo area. Economic growth and industrialization are proceeding at a rapid pace, accompanied by increasing emissions of air polluting sources. Furthermore, though the variety and quantities of polluting sources have increased dramatically, the development of a suitable method for monitoring the pollution causing sources has not followed at the same pace. Environmental impacts of air pollutants have impact on public health, vegetation, material deterioration etc. To prevent or minimize the damage caused by atmospheric pollution, suitable monitoring systems are urgently needed that can rapidly and reliably detect and quantify polluting sources for monitoring by regulating authorities in order to prevent further deterioration of the current pollution levels. Consequently, it is important that the current real-time air quality monitoring system, controlled by the Egyptian Environmental Affairs Agency (EEAA), should be adapted or extended to aid in alleviating this problem. Nanotechnology has been applied to several industrial and domestic fields, for example, applications for gas monitoring systems, gas leak detectors in factories, fire and toxic gas detectors, ventilation control, breath alcohol detectors, and the like. Here we report an application example of studying air quality monitoring based on nanotechnology ‘solid state gas sensors’. So as to carry out air pollution monitoring over an extensive area, a combination of ground measurements through inexpensive sensors and wireless GIS will be used for this purpose. This portable device, comprising solid state gas sensors integrated to a Personal Digital Assistant (PDA) linked through Bluetooth communication tools and Global Positioning System (GPS), will allow rapid dissemination of information on pollution levels at multiple sites simultaneously.

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1.

Introduction

Most of industrial and nuclear activities, involving the use of energy and transportation prominently among them, are accompanied by emission of air pollutants. Urban air pollution, in turn, is the source of range of problems, including health risks with inhalation of gases and particles, accelerated corrosion and deterioration of materials. Greater Cairo is considered the most important city in Egypt from demographical point of view. It encompasses 27% of the Egyptian population, 64% of the industry and 45% of motor vehicles. Greater Cairo area lies in a sub-tropical region with a dry climate, warm summers and mild winters. It rarely gets rain. There are fairly substantial variations between daytime and nighttime temperatures. The average summer temperature is 31°C, while that of winter is 16°C with an average difference between day and night of 10°C. This great temperature difference promotes the formation of dew at dawn as the relative humidity of the air becomes generally high, especially during the winter season. The prevailing wind velocity with an average of 3 m s−1, but gusts of up to 4–5 m s−1 may be experienced in early morning and late afternoon. Dust storms also occur during April and May when the Khamasin winds blow over the Egyptian western desert with a wind speed of the order of 10 m s−1. Relative humidity fluctuates between 59% in June and 71% in December, with visibility of about 5 km. This restricted visibility is the result of the presence of solid particles in the atmosphere. The strong emissions of trace gases and aerosol particles by vehicles traveling on the city’s narrow roads, industry and resuspended soil dust, together with secondary aerosol, coupled with the unfavourable natural conditions of dispersion, are responsible for the high concentrations of pollutants observed in the greater Cairo metropolitan area. Greater Cairo areas suffers from high ambient concentrations of atmospheric pollutants [1–3], including particulates (PM), carbon monoxide (CO), oxides of nitrogen (NOx), ozone (O3) and sulfur dioxide (SO2). Nasralla [1] reported particulate lead concentrations ranged from 0.5 µg/m3 in a residential area to 0.3 µg/m3 at the city centre. Sturchio et al. [2] measured total suspended particulate (TSP) and lead concentrations using stable isotopic ratios (207Pb/204Pb and 208Pb/204Pb) at 11 sites in Cairo. Lead and TSP concentrations ranged from 0.08 to 25 µg/m3, respectively at Helwan to over 3 and 1,100 µg/m3, respectively, at the city centre. Rodes et al. [4] measured fine (PM2.5) and coarse (PM10-PM2.5) concentrations as a part of a source apportionment study in Cairo from December 1994 to November 1995. The annual average PM10 concentrations exceeded the 24 h average US standard of 150 µg/m3 at all sites except Ma’adi and the background site. In general, one can see that air pollution level is high during winter months and create winter syndrome due to low temperature, low mixing depth, pollution inversion, traffic density, driving habits or due to ratio of automobiles to trucks. In recent years there has been considerable concern about the many adverse effects of elevated air pollutants levels in the atmosphere, which are associated with various anthropogenic and natural processes. In the meantime, photochemical smog formation has been observed in Cairo metropolitan areas [2]. Photochemical

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smog is a complex mixture of atmospheric pollutants termed photo-oxidants, which are rapidly formed on warm sunny days through reactions of volatile hydrocarbons and other oxidisable organic compounds with nitrogen oxides under the influence of sunlight [5]. The aims and objectives of this paper approach include: (1) To apply a suitable gas sensing device coupled to a personal digital assistant for continuous monitoring of urban air pollution and disseminate the information in real time through wireless GIS. (2) To build up a simple monitoring system using low cost portable gas sensing systems. (3) To assist in establishing priorities, measurements of air pollution in greater Cairo area and increasing public awareness and enhanced public participation. 2.

Air Pollution in Greater Cairo Area

Greater Cairo area’s geographic location and its industrial and population development make it vulnerable to the problems caused by atmospheric particulate matter and ozone. Because of the situation outlined above and Egypt’s location at latitude 30o N with more than 340 days of sunshine per year, it is expected that high levels of photochemical smog occur in Egypt, especially greater Cairo area today, with higher levels predicated for the near future. Air quality in the streets of greater Cairo area has become critical and the predominant cause of air pollution in downtown street is vehicle emission. Crowded traffic density and flow conditions in Cairo city have become worse and ambient air quality has deteriorated as a result. A decade ago the health costs of exposure to lead (Pb), particulate matter (PM), and carbon monoxide (CO) in Cairo were estimated to be equivalent to between 8% and 12% of urban annual income. These pollutants are mostly emitted by the transport sector. During the last years the ambient levels of key pollutants – Pb, particulates, SO2 and CO-in Cairo and other urban centers have fallen dramatically. Using as an example of visibility measurements at Helwan area, air quality has improved since 2001, and even improvements are reported in PM10 levels. Concentration levels of NOx and CO are stable and declining respectively. SO2 concentrations are not so high but it can exceed the Air Quality Limit value under certain conditions. Also SO2 levels have declined substantially as new technology has been established at the country’s power plants. Ozone (O3) levels are still causing concern with Maximum levels exceeding the standard [6]. Downwind transport of ozone precursors from heavily populated areas in Cairo causes the high ozone concentrations at locations to the south. Diurnal variation of ozone exhibits a seasonal variability, with the maximum diurnal variation during summer. PM10 is still the most critical problem facing Egypt. It still giving very high concentrations which can reach six times the Air Quality limit value as daily average this may be due to the high background in Egypt which is mainly generated by wind blown dust. Highest concentrations of PM10 are found in industrial and traffic areas. PM10 exhibits two maxima during the year, each forced by a different mechanism. The first occurs during the spring, is sharp and of shorter duration, and is forced by the sand storms during Khamseen conditions.

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The second peak is during the fall, with longer duration and less amplitude, and is due to pollution episodes associated with the more local meteorological conditions of the season. All VOC group-totals are indoors higher than outdoors but only the concentrations of alkanes and terpenes are statistically significant higher indoors than outdoors [7]. The concentration of the group of aromatic hydrocarbons is in Cairo indoors and outdoors nearly identical. 3.

Air Quality Monitoring System

The EEAA has been measuring air quality levels through the automatic monitoring system and reporting real time air quality levels through the Internet as air quality index (AQI) maps (Figure 1). Air quality monitors comprise 40 permanent stations and are set up at roadside and general sites. Unfortunately, the cost of establishing and implementing traditional monitoring systems is extremely high. This air quality monitoring system can measure and report air quality levels in real time; nevertheless there is still a huge disadvantage that this monitoring system cannot be implemented at many sites to monitor air pollution over an extensive area

Figure 1. Location of air quality monitoring stations in the greater Cairo area.

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because of high costs. To substitute the typical analytical tools and adapt or extend the air quality monitoring system of EEAA with a new generation of detectors, nanotechnology based metal oxide semiconductors such as ZnO semiconductor used in this study are a viable alternative. In fact these solid state gas sensors offer an excellent opportunity for implementation in environmental monitoring due to light weight, extremely small size, robustness, low cost and also as they can be installed anywhere to collect data covering extensive areas. The air quality data can eventually be transmitted through a Wireless GIS network system to the general public. 4.

Nanotechnology

The nanotechnology realm has traditionally been defined as lying dimensions between 0.1 and 100 nm. Nanotechnology has been applied to industry for example in textile, medicine and health, computing, transportation, aeronautics and space exploration, environment, and so on. In the last decade the specific demand for gas detection and monitoring has emerged especially as the awareness of need to protect the environment has grown [8]. Gas sensors are applied in numerous fields of applications [9]. In the present case, a nanotechnology based gas sensors application for studying air pollution is described. The answer to why use nanotechnology based solid-state gas sensor is that increasing the surface to bulk atom ratio increases grain size dependence, meaning increasing gas adsorption and more sensitivity [10]. 4.1.

SOLID STATE GAS SENSORS FOR AIR POLLUTION

Gas sensors for detecting air pollutants must be able to operate stably under deleterious conditions, including chemical and/or thermal attack. Therefore, solid state gas sensors appear to be the most appropriate in terms of their practical robustness. The sensors used for detecting air pollutants are usually produced simply by coating a sensing (metal oxide) layer on a substrate with two electrodes. Typical materials are tin oxide (SnO2), zinc oxide (ZnO), titanium oxide (TiO2) and tungsten oxide (WO3) with typical operating temperatures of 200–400°C [11]. The general mechanism for a metal oxide sensor is a change in the resistance (or conductance) of the sensor when it is exposed to pollutant gas, relative to the sensor resistance in background air. The sensor resistance is the best-known sensor output signal and is in most cases determined at constant operation temperature and by DC-measurement [11]. AC measurements have also been reported [12] but are more frequently used in impedance spectroscopy [13] at a modeling level. Figure 2 explains how metal oxide semiconductor detects pollutant gases. The depletion zone at the surface of metal oxide sensor is due to absorption of atmospheric oxygen. When the metal oxide sensor absorbs a reducing gas (CO, H2), depletion area at the surface will be decreased, meaning increasing conductivity. On the other hand, if a metal oxide sensor absorbs an oxidizing gas (NO2), the depletion zone at the surface will be increased, meaning

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decreasing conductivity. In conclusion, a change of conductivity/resistance is related to gas concentration. In the case of a ZnO sensor, conductivity decreases that means resistance increases when the sensor absorbs NOx, dependent on NOx concentration [11].

Figure 2. Schematic diagram of a metal oxide semiconductor following [11].

5.

Internet GIS

Internet GIS is a relationship between GIS and Internet. Users will be able to access GIS applications without purchasing GIS software by using a web browser. Detailed maps can be generated from huge databases of spatial information and distributed all over the world. The Web is a cost effective way to share or provide public access to data worldwide on the Internet. As shown in Figure 3, the wireless GIS Data Logging System being developed in this study is composed of two parts, i.e. hardware and software. On the hardware side, a Mandrake 9.1 Server provides the back-end support. A user has in hand a Personal Digital Assistant operated on Pocket PC. So as to be complete, a Global Position Receiver (GPS) and Digital camera can be also integrated through proper extensions. On the software side, a Minnesota Map server 4.4.0 ensures Web Map Service (WMS), which is an Open Source Common Gateway Interface (CGI) based development environment for building spatially enabled Internet applications. The server setup is made up of Postgre SQL, Post GIS and PHP, configured with each other to execute the client’s request and manage the database. The client setup is composed of interfaces, developed using JavaScript and Hyper Text Markup Language (HTML) [14]. For wireless Data Updating System, it is composed of three tiers, including Front-End Tier, Middle-Tier and Back-End Tier. On the Front-Tier is the client, making a request, Minnesota Map Server in the Middle Tier passes the CGI-request over to the Back-End Tier where PHP and PostgreSQL with PostGIS read the data and execute the request.

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Figure 3. Flow chart showing Internet GIS set up.

6.

NOx Observation Using the ZnO Sensor

The data used for this study are composed of measured NOx concentration from ten stationary air quality monitoring sites as shown in Figure 4. A limited number of observation sites were taken to test the method at locations which are critical for automobile pollution. The data were collected every hour from 0700 h until 1900 h, which were fed to the GIS for further processing. It is supposed that more air sampling points are needed for more accurate interpolation techniques, or interpolation by creating a buffer at each point is supposed to be more suitable method for this study as shown in Figure 4. 7.

Integrating GIS with Nanosensors

The solid-state gas sensor gives out electric signals, related to NOx concentration. An A/D circuit converter converts the NOx concentration values from an analog to digital signal. NOx concentration levels, acquired from monitoring sites, GIS base maps and attributes were input into Personal Digital Assistant linked with GPS. The results were utilized for air quality level modeling of the study area. The model developed were used for acquiring and monitoring real time air quality levels and also updating information through wireless GIS using WMS. The information on the resulting air quality levels can operate as a monitoring system and be displayed in the form of GIS database. The air quality levels were

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categorized into five classes, overlaid with Cairo GIS base maps. The five classes of air quality level reported include hazardous, very unhealthy, unhealthy, moderate and good. Hence, Internet users can browse and query air quality interpolated maps, relating to geographic information, including districts, roads, urban settlement, and historical air quality level. The Internet based GIS is useful real time interaction on air quality levels and increases public awareness and participation. Nanosensors and Evaluation Kit

Ambient air smapling

A /D converter GIS base map of BKK - Admin. boundary - Population - Road - Urban settlement

Digital NOx Concentration

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Report real time AQ data through wireless GIS Figure 4. Conceptual framework for NOx monitoring using nanosensors integrated with internet GIS.

8.

Conclusion and Discussion

Current air quality of greater Cairo area is better than a decade ago. However, greater Cairo area still has been facing serious air pollution problems. As seen in central Cairo, black and white smoke from truck and public bus exhaust still occurs. This is attributed to the rapid economic and industrial growth, combined with a lack of strict implementation of air quality and requires the EEAA to adapt or extend the current EEAA’s air quality monitoring systems and also facilitate the problem of analyzing and monitoring air pollution in greater Cairo area. The traditional air quality monitoring system, controlled by the EEAA, is extremely expensive. Analytical measuring equipment is costly and time consuming, and can seldom be used for air quality reporting in real time. The EEAA has been forecasting and reporting real time air quality levels through the Internet in the form of maps. However, the air quality index of each monitoring site is just shown by rather coarse levels; good, moderate, unhealthy, very unhealthy and hazardous. The air quality report should be more in detail, including information such as air quality interpolated maps, relating to other information for better understanding the air quality level. For these reasons, this work is aimed to build up an easy monitoring system using low cost portable gas sensing systems ‘solid state gas sensors’ so as to carry out air pollution monitoring over an extensive area and to be able to report real time air quality data through Wireless Internet GIS.

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References 1. Nasralla, M.M. (1994) Air Pollution in Greater Cairo, Comparing the health risk in Cairo, Egypt, Vol. 3, Annex G, submitted to USAID/Egypt project, 398-0365. 2. Sturchio, N., Sultan, M., Sharkaway, M.E., and Maghraby, A. (1997) Concentration and isotopic composition of lead in urban particulate air, Cairo, Egypt, 1996, Argonne National Laboratory/Center for Environmental Hazard Mitigation, Cairo University, Argonne, IL/Cairo, Egypt. 3. Elminir, H. (2005) Dependence of urban air pollutants on meteorology, Science of the Total Environment 359 (1–3), 231. 4. Rodes, C.E., Nasralla, M.M., and Lawless, P.A. (1996) An assessment and source apportionment of airborne particulate matter in Cairo, Egypt, Activity Report No. 22, prepared for the USAID Mission to Egypt under EHP Activity No. 133-RCm Delivery Order No. 7. 5. Gusten, H. (1986) Formation, transport and control of photochemical smog, in Hutzinger, O. (ed.), The Handbook of Environmental Chemistry, Vol. 4, Part A, p. 53, Springer, Berlin/Heidelberg, Germany. 6. Ramadan, A., and Alian, A. (2007) Environmental Radiation Monitoring in the Egyptian Territories, Report No. 460 in NCNSRC, AEA, Cairo, Egypt. 7. Schlink, U., Rehwagen, M., Ramadan, A., Richer, M., and Herbarth, O. (2006) Comparison of environmental security in Cairo and Berlin: Exposure of volatile organic compounds, in Risk Management Tools for Port Security, Critical Infrastructure and Sustainability, NATO Advanced Research Workshop, 16–19 March 2006, Venice, Italy. 8. Capone, S., Forleo, A., Francioso, L., Rella, R., Siciliano, P., Spadavecchia, J., Presicce, D.S., and Taurino, A.M. (2003) Solid state gas sensors: state of the art and future activities, Journal of Optoelectronics and Advanced Materials 5, 1335–1348. 9. Sberveglieri, G. (1992) Gas Sensors—Principles, Operation and Development, Kluwer, Dordrecht/Germany. 10. Hauptmann, P. (1993) Sensors: Principles and Applications, Prentice-Hall, Hertfordshire, UK. 11. Simon, I., Barsan, N., Bauer, M., and Weimar, U. (2001) Micromachined metal oxide gas sensors: opportunities to improve sensor performance, Sensors Actuators B 73, 1– 26. 12. Weimar, U., and Gopel, W. (1995) AC measurements on tin oxide sensors to improve selectivities and sensitivities, Sensors Actuators B 26/27, 13–18. 13. Gopel, W., and Schierbaum, K. (1995) SnO2 sensors: current status and future prospects, Sensors Actuators B 26/27, 1–12. 14. Marshall, J. (2002) Developing internet-based GIS applications, GIS India 11, 16–19.

ADVANCED MATERIAL NANOTECHNOLOGY IN ISRAEL

O. FIGOVSKY, D. BEILIN, N. BLANK Polymate, Ltd. International Nanotechnology Research Center Migdal Ha’Emek, Israel [email protected]

Abstract. One of the most interesting directions in material engineering during the past few years is the technical development of nanocomposite materials consisting from two or more phases with precise interphase border and nanostructured materials based on interpenetrated polymer network. Israel is one of world leaders in fundamental and industrial nanotechnology research, including fostering of start-up companies. Some important developments in the field of nanotechnology material engineering in Israel are summarized in the paper. 1.

Introduction [1–6]

The economic, security, military, and environmental implications of molecular manufacturing are diverse. Unfortunately, conflicting definitions of nanotechnology and blurry distinctions between significantly different fields have complicated the effort to understand those differences and to develop sensible, effective policy for each. The risks of today’s nanoscale technologies cannot be treated the same as the risks of longer-term molecular manufacturing. It is a mistake to group them in policy considerations – each is important to address, but they offer different problems and will require far different solutions. The field of nanotechnology usually involves a broad collection of diverse fields. Essentially, anything sufficiently small and interesting can be called nanotechnology. It has been projected that many of these materials are benign. Molecular manufacturing, by contrast, will bring unfamiliar risks and new types of problems. Desktop nanofactories will use vast arrays of tiny machines to fasten single molecules together quickly and precisely, allowing engineers, designers, and potentially anyone else to make powerful products at the touch of a button. Although such a contraption has been envisioned in some detail for almost two decades, with the basic concept dating back to 1959 when the physicist R. Feynman first described it, it’s only in recent years that technology has advanced to the point where we can begin to see the practical steps that might bring it into reality.

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The essence of nanotechnology is the ability to work at the molecular level to create large structures with fundamentally new molecular organization. Materials with features on the scale of nanometers often have different properties from their macroscale counterparts. The prospect of a new materials technology that can function as a low-cost alternative to high-performance composites has, thus, become irresistible around the world. By this means nanotechnology presents a new approach to material science and engineering as well as for design of new devices and processes. Figures 1–3 provide perspective on the global momentum of nanotechnology development. Composite materials are two- or multiphased with a well defined interphase border. Such materials contain the reinforcing elements immersed into a polymeric, ceramic or metal matrix. Mechanical properties of composites depend on structure and properties of the interphase border. Phases of usual composite materials have micron and submicron sizes. Important among these nanoscale materials are nanocomposites in which the constituents are mixed on a nanometer-length scale. They often have properties that are superior to conventional microscale composites and can be synthesized using surprisingly simple and inexpensive techniques. The tendency to reduce the phase’s sizes of a filler (a strengthening element) is attributable to a decrease in its microscopic deficiency (the size of one of nanocomposite phase is less than 100 nm). The reinforced polymer remains transparent since to the nanometer size of the particles is smaller than the wavelength range of visible light. Other characteristics of the composites include high barrier performance and improved thermal stability, which make these compounds suitable for many applications. This nanocomposite technology is one of the most promising directions in a material engineering, applicable to a wide range of polymers including thermoplastics, thermosets and elastomers. Israel is a world leader in Nanotechnology, that is involved in fundamental academic research but focuses most on fostering industrial research and start-up companies (Figure 4).

Figure 1. Global nanotechnology market 2007.

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Revenue (Million USS)

Figure 2. Nanotechnology market evolution 2006–2012.

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In the paper we present new developments within one of the lead Israeli companies: Polymate Ltd., International Nanotechnology Research Center (Polymate Ltd., INRC) which includes a branch in Berlin, Germany. Polymate Ltd., INRC specializes in providing applied and fundamental research and development (R&D) in the scientific and technological fields of material, chemical and environmental engineering, with a focus on the development, marketing, and commercialization of advanced nanocomposites. Polymate Ltd., INRC successfully operates on the basis of multi-sided partnerships in many regions around the world, such as Europe, Japan, Canada, the Former Soviet Union among others. Polymate Ltd., INRC’s latest Network Nanostructured Polymer System has been named a winner in the third annual NASA Nanotech Briefs®’ Nano 50™ Awards (2007) in the Technology category.

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Figure 4. Nanotechnology material engineering companies in Israel.

2.

General Comment

Nanostructured composite materials can be categorized depending on the location of the nanoscale structure in the system (Figure 5). After an initial literature review, and when considering the information needed in order to describe a nanomaterial from a physical and chemical perspective when estimating the hazard of nanomaterials, we propose the following nine properties as being important: ƒ Chemical composition ƒ Size ƒ Shape ƒ Crystal structure ƒ Surface area ƒ Surface chemistry ƒ Surface charge ƒ Solubility ƒ Adhesion, defined as “the force by which the nanoparticles and its components are held together”

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Figure 5. Classification of nanomaterials.

3.

Nanostructured Composites Based on Interpenetrated Polymer Network [7–11]

This project is oriented to prepare nanocomposites based on an interpenetrated polymer network (IPN), such as polyurethanes, epoxies and acrylate by way of creating nanoparticles of SiO2, TiO2 and other metal oxides during a technological stage from a liquid phase. Using an interpenetrating polymer network principle in production of composite materials provides a unique possibility to regulate both micro- and nano-structured properties. Formulation of a new class of nanocomposite materials is characterized by the absence of contaminants for a network polymers technology. As a main component of such technology we are using branched (dendro)-aminosilanes that at the first stage are curing agents for many oligomers. The proposed dendro-aminosilane hardeners provide potential to introduce the siloxane fragments into aromatic structure of diphenylolpropane based epoxyamine network polymers. Additional hydrolysis of aminosilane oligomer creates the secondary nano-structured network polymer that improves the service properties of the compound. Branched (dendro) polyamine hardeners are a novel direction in epoxy and cyclocarbonate and acryl resins chemistry.

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The new hardeners give rise to formation of IPN of a polymerized resin with a polysiloxane network by the hydrolytic polycondensation of silane groups. The IPN network may be formed on the base of epoxy-cyclocarbonate oligomers. It was found that at least 0.1 equivalent weight of silane per epoxy resin equivalent weight may result in IPN formation. Epoxy resin has a low resistance to acetone and methanol attack. Novel hybrid nonisocyanate polyurethane based nanocomposites (HNIPU) were produced by the following reaction.

Pilot production of two component paints, top coatings, adhesives and floorings are obtained. Figure 6 illustrates industrial application of the IPN flooring. The two-component compounds have unique properties that combine the best mechanical properties of polyurethane and chemical resistance of epoxy binders. 4.

Nanocomposites Based on Hybrid Organo-Silicate Matrix [12–17]

Important among nanoscale materials are hybrids or nanocomposites. They often exhibit properties superior to conventional composites. Organic-inorganic hybrid

Figure 6. IPN flooring (Tosaf Compounding Co., Israel).

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nanostructures have generated great interest by combining optical, magnetic or electronic properties of inorganic crystals with mechanical properties and functionality of organic compounds. They suggest a variety of potential applications such as electrical, optical and medical markers. By using a principle of forming nanostructure by creating nanoparticles during a technological process from a liquid phase, Polymate Ltd., INRC has elaborated a few composites based on different kinds of soluble silicates. Significant increases in silicate matrix strength and durability were reached by incorporation of special liquid additives, such as TFS, which serve as a microcrystallizing nucleator on the technological stage and later deposit into the pores of silicate matrix. Our last developments are mainly applying a novel type of soluble silicate contained organic cations, for example, the DABCO (shown below)-based organic alkali soluble silicate. 5.

Polymer Nanocompsites with Very Low Permeability and High Resistance to Adverse Environments [18–22]

Novel chemically resistant polymer materials were developed by adding nano-size inorganic active fillers that react with aggressive media into which they are introduced, forming a new phase of high-strength hydrate complexes. This enhanced bonding occurs upon penetration of aggressive media into active nano-fillers containing polymer material. The chemical resistant properties of the forming polymer materials are activated by harsh environmental conditions where polymer systems without additives remain susceptible to corrosion. Figure 7 illustrates the effect of special powdered additives on chemical resistance of nonisocyanate polyurethane covering. 12 1 0.8 0.6 0.4 0.2 0 With additives Without additives

0

6

12 Time. months

Figure 7. Chemical resistance of nonisocyanate polyurethane covering to 25% H2SO4 at 25°C.

Polymate Ltd., INRC has developed an extensive product range of such active nano-fillers for upgrading the most common polymers against a wide variety of aggressive media including acids, sea water, fluorine, alkalis and more.

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6.

Novel Metallic Matrix of Nanoreinforced Materials Produced by Superdeep Penetration [23]

Technological process on the basis of new physical effect “superdeep penetration” (SDP) allows applications ranging from the steel tools (for example, HSS) to new composite materials (Figure 8).

100− 180 mm

Detonation

High-energy flow

200 mm

The Steel bush Steel intermediates

Figure 8. Principal scheme of superdeep penetration of micro particles into metal body.

These materials can be used for replacement base steels in metal-cutting and stamp tools. In some cases new materials can be used for replacement of a hard metal (on the basis of WC) in the tools for mining (e.g., cutters of coal and mining machines, Figure 9). The application of the new SDP technology allows an increase in the service life of the tools up to 1.5–5.0 times compared to currently used tools. The technology can be applied for the volume strengthening of practically any type of instrumental steel.

Figure 9. The tools for coal cracking strengthened by SDP method.

Use of new physical effect SDP allows acquisition of special composite materials on the basis of aluminum, with the set anisotropy of physical and chemical properties. In micro-sized volumes of the aluminum matrix, the electrical conductivity in mutually perpendicular directions of an aluminum matrix can differ by a factor of two. The new technology of volumetric reorganization of aluminum will find wide application in the manufacturing of electric installations and electronic devices.

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Water-Dispersion Paint Composition with Biocide Properties Based on Silver Nano-Powder [24]

We have developed an advanced bioactive coating using silver nanoparticles. As found in numerous studies during the past 2 decades, particles with dimensions in nanometer scale (10−9 to 10−8 m) possess unique properties that differ from those of atoms and ions on the one hand and bulk substances on the other hand. These silver nanoparticles were produced by the novel BAR-synthesis. The biological activity of varnish-paint materials modified by silver nanoparticles was estimated on the following microorganisms: ƒ Escherichia coli (E. coli 1257) as a conventional device. Due to reduction in cost of expensive materials, the use of these novel aluminum materials in electric installations and control systems will save millions of U.S. dollars. The preparation cost of aluminum structure rearrangement does not exceed US$40/kg, a two- to threefold reduction in industrial production cost. An individual preparation may lead to manufacture of tens to thousands of electronic devices. Process SDP is high-efficiency and does not require expensive equipment. The new technology of volumetric reorganization of aluminum, creation zones of nano-structures, the materials received on this basis, will find wide manufacturing applications for electric installations and electronic devices. ƒ Other applicable model species ƒ Coliphage (RNA-phage MS-2) as a model of viral infection, including influenza A and B, hepatitis A ƒ Mold fungi (Penicillinum chrysogenum) as a typical representative of microflora of the dwellings and a model of fungicidal contamination ƒ Spores and other microflora The test data confirms the significant advantages of elaborated water-born acrylic bioactive coatings. 8.

Nanocellulose and Biodegrable Composite Materials [25, 26]

Nanocellulose (NanoCell) with CI crystalline modification was prepared using an advanced, environmentally friendly, efficient and cheap technology. The developed technology permits producing NanoCell in bench scale and industrial amounts. The NanoCell product can be manufactured in the form of dispersions, high solid paste and dry powder. The FDA-approved nanostructured aqueous polymer, GreenCoat, is applied for protective covering of paper and wood. The coating layer imparts material barrier properties against permeation of water, grease, oxygen and some other substances (Figure 10). Waste of coated material can be re-pulped and used in paper industry or decomposed in nature due to its biodegradability.

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GreenCoat Layer Cellulose base

Figure 10. The new nano-scale cellulose product.

The GreenCoat emulsion is coated on a cardboard surface by means of bar – coater and dried at 150–170oC for 30–60 s. The GreenCoat W glazing hot melt composition is then coated on the first layer by means of bar-coater at 130–135oC and air cooled. The waste of the coated material can be re-pulped and used in paper industry or decomposed in nature due to its biodegradability (Figure 11).

Figure 11. Recycling of the biodegradable coatings.

References 1. http://cientifica.eu 2. http://search.dainfo.com/inni/Template1/Pages/ShowMap.aspx?isDebug=true&initLoad Vars=true&showcategory=230 3. http://www.researchandmarkets.com/reportinfo.asp?report_id=586187 4. http://www.knowledgefoundation.com/events/2130931.htm 5. http://www.ccmr.cornell.edu/images/pdf/CCMR-2003-IRG-B.pdf

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6. Y. Chvalun: Polymeric nanocomposires, J. “Pripoda”, No7, 2007 7. O. Figovsky: Active Fillers for Composite Materials: Interaction with Penetrated Media Encyclopedia of surface and colloid science/edited by P. Somasundaran. N.Y. 2006, volume 1, pp. 94–96. 8. O. Figovsky, L. Shapovalov, O. Axenov: Advanced Coatings Based Upon NonIsocyanate Polyurethanes for Industrial Application. Surface Coatings International, Part B: Coatings Transactions, vol. 82, B2, 2004, pp. 83–90. 9. O. Figovsky, L. Shapovalov: Nanostructured Hybrid Nonisocyanate Polyurethane Coatings. Paint and Coatings Industry, no. 6, 2005, pp. 36–44. 10. O. Figovsky, L. Shapovalov: Organic-Inorganic Nanohybrids Materials for Coatings. Book of Abstract of E-MRS Conference (Symposium E), Warsaw, Poland, 5–9 September, 2005, p. 124. 11. V. Ferreiro, G. Schmidt, C. Han, A. Karim: Dispersion and Nucleating Effects of Clay Fillers in Nanocomposite Polymer, Polymer Nanocomposittes. Synthesis, Characterization and Modeling, ACS Symposium, Series 804, Washington DC, 2000, pp. 177–193. 12. O. Figovsky. US patents: 6,120,905; 6,960,619 13. O. Figovsky, E. Gutman: Carbon Fiber Reinforced Silicate-Polymer Composite Materials. Proceedings of International Conference on Composite Materials and Energy (ENERCOMP - 95), Montreal, Canada, May 8–10, 1995, pp. 499–502. 14. O. Figovsky: New Polymer and Silicate Matrix for Composite Materials. Proceedings of Ninth Annual International Conference on Composite Engineering. July 1–6, San Diego, CA, USA, pp. 205–206. 15. O. Figovsky: Nanocomposite Bonding Composition Based on Hybrid Organic-Silicate Matrix. Abstracts of the International Symposium on Bond Behaviour of FRP in Structures, Hong Kong, China, 7–9 December, 2005, No. BBC S0064. 16. F. Buslov, L. Shapovalov, O. Figovsky: Advanced Synthesis of Organo-Inorganic Nanohybrid Materials for Coatings. Proceedings of Third World Congress “Nanocomposites 2003”, 10–12 November, 2003, San Francisco, CA, USA, pp. 32/1–7. 17. O. Figovsky, L. Shapovalov: Nanocomposite Coatings Based on Nonisocyanate Polyurethanes and Hybrid Binder. Proceedings of the 80th JSCM Anniversary Conference “New Fields in Colour and Coatings”, September 12–14, 2007, Tokyo, Japan, pp. 34–37. 18. O. Figovsky: Composite Materials with a Microstructure which Gives the Possibility Increasing Service Properties During Exploitation. The Structural Integrity of Composite Materials & Structures, A Residential Meeting & Workshop, Isle of Capri, Italy, 20–25 May, 2001. 19. O. Figovsky, L. Sklyarsky, O. Sklyarsky: Polyurethane Adhesives for Electronic Devices. Journal of Adhesion Science and Technology, vol. 14, no. 7, 2000, pp. 915– 924. 20. R. Potashnikov, O. Birukov, O. Figovsky, A. De Shrijver: Nanostructured Acrylic Uvcurable Foam - Sealant. Abstract of the 11th Israel Materials Engineering Conference, December 24–25, 2003, Haifa, Israel, p. 134. 21. O. Figovsky, N. Blank: Novel active nanofillers for increasing chemical resistance and durability of polymer composite materials. The 15th International Conference “Additives 2006”, Las Vegas, Nevada, USA, 30 January–1 February 2006, pp. 9/1– 9/12. 22. O. Figovsky, N. Blank: Nanocomposite Based on Polymer Matrixes with Increasing Durability. Abstracts of the 12th Israel Materials Engineering Conference, Beer-Sheva, Israel, 1–2 March, 2006, p. 102.

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23. S. Usherenko, O. Figovsky, Yu. Usherenko: Receiving of Nanomaterials in Volume of Metals and Alloys in a Mode of Superdeep Penetration. Book of abstracts of First International Conference RAR-2006, Voronezh, Russia, November 9–10, 2006. pp. 73–77. 24. B. Kudryavtzev, O. Figovsky, E. Egorova, A. Revina, F. Buslov, D. Beilin: The Use of Nanotechnology in Production of Bioactive Paints and Coatings. Journal of Scientific Israel-Trchnology Advantages, vol. 5, no. 1–2, pp. 209–215. 25. M. Ioelovich, O. Figovsky: Porous Structure and Barrier Properties on Polymer Materials. Proceedings of Ninth Annual International Conference on Composite Engineering, July 1–6, San Diego, CA, USA, pp. 321–322. 26. M. Ioelovich, O. Figovsky: Study of Nanoplastics Contained Fillers of Various Types. Abstracts of ECCM-11, May 31–June 3, 2004, Rhoges, Greece, B-039.

SILVER NANOPARTICLES Environmental and Human Health Impacts

R.R. KHAYDAROV Institute of Nuclear Physics Ulugbek, 100214 Tashkent, Uzbekistan [email protected] R.A. KHAYDAROV Institute of Nuclear Physics Tashkent, Uzbekistan Y. ESTRIN ARC Centre of Excellence for Design in Light Metals Department of Materials Engineering, Monash University CSIRO Division of Materials Science and Engineering Clayton, Victoria, Australia S. EVGRAFOVA V.N. Sukachev Institute of Forest SB RAS Krasnoyarsk, Russia T. SCHEPER, C. ENDRES Institute of Technical Chemistry Leibniz University Hannover, Germany S.Y. CHO Yonsei University Seoul, South Korea

Abstract. The bactericidal effect of silver nanoparticles obtained by a novel electrochemical method on Escherichia coli, Staphylococcus aureus, Aspergillus niger and Penicillium phoeniceum cultures has been studied. The tests conducted have demonstrated that synthesized silver nanoparticles – when added to water paints or cotton fabrics – show a pronounced antibacterial/antifungal effect. It was shown that smaller silver nanoparticles have a greater antibacterial/antifungal efficacy. The paper also provides a review of scientific literature with regard to

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recent developments in the field of toxicity of silver nanoparticles and its effect on environment and human health. 1.

Introduction

Medicinal and preservative properties of silver have been known for over 2,000 years. The ancient Greek and Roman civilizations used silver vessels to keep water potable. Since the nineteenth century, silver-based compounds have been widely used in bactericidal applications, in burns and in wound therapy, etc. [11]. Over the last decades silver has been engineered into nanoparticles, structures from 1 to 100 nm in size. Owing to their small size, the total surface area of the nanoparticles is maximized, leading to the highest values of the activity to weight ratio. Due to this property being distinctly different from that of the bulk metal, silver nanoparticles have attracted much attention and have found applications in diverse areas, including medicine [26], catalysis [14], textile engineering [14], biotechnology and bioengineering [23], water treatment [30], electronics [12] and optics [21]. Furthermore, currently silver nanoparticles are widely used as antibacterial/antifungal agents in a diverse range of consumer products: air sanitizer sprays, socks, pillows, slippers, respirators, wet wipes, detergents, soaps, shampoos, toothpastes, air filters, coatings of refrigerators, vacuum cleaners, washing machines, food storage containers, cellular phones, etc. [6]. Numerous synthesis approaches were developed to obtain silver nanoparticles of various shapes and sizes, including laser ablation [13], gamma irradiation [18], electron irradiation [3], chemical reduction by inorganic and organic reducing agents [4], photochemical methods [19], microwave processing [31], and thermal decomposition of silver oxalate in water and in ethylene glycol [22]. Having compared minimum inhibitory concentration (MIC) values for bacterial cultures, one can see that the antimicrobial activity of silver nanoparticles strongly depends on the method of their synthesis. This paper deals with the authors’ research in the field of antimicrobial properties of silver nanoparticles obtained by our recently suggested electrochemical technique [10], which provides extremely low minimum inhibitory concentration (MIC) values as well as a high efficacy of nanosilver as antimicrobial agent against a range of microbes on the surface of paints and fabrics [7]. This paper also provides a review of the most recent scientific publications regarding the possible toxic effects of silver nanoparticles to the environment and human health.

2. Materials and Methods The process of electrochemical synthesis of silver nanoparticles [10] is based on using an inexpensive two-electrode setup in which the anode and the cathode made from the bulk Ag are placed vertically, face-to-face, 10 mm apart. The electrodes are immersed into an electrochemical cell filled with 500 ml of distilled water obtained with water distiller (DE-25, Russia). In the tests reported here, the

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electrolysis was performed during 1 h at the temperature range of 325–340 K with a constant voltage of 20 V. Periodical changing the polarity of the direct current between the electrodes with a period of 4 min and vigorous stirring during the process of electrolysis were applied in order to reduce the agglomeration of particles. Synthesized silver nanoparticle solutions were stored under ambient conditions in glass containers. The morphology of the silver nanoparticles/ powders obtained was studied using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and dynamic light scattering (DLS) measurements. The concentration of silver nanoparticles in solutions was determined by neutron activation analysis [29]. To evaluate the antibacterial and fungicidal properties of Ag nanoparticles Escherichia coli was used as a representative Gram-negative bacterium; Staphylococcus aureus was used as a Gram-positive bacterium; Aspergillus niger and Penicillium phoeniceum were used to represent cosmopolitan saprotrophic fungi. To assay the antimicrobial activity of silver nanoparticles in aqueous solution against E. coli on solid media, the agar disk diffusion method was used. Bacteria inocula were prepared from a log-phase culture of E. coli K12 grown in LB-media on a rotary shaker (120 rpm) at 37°C. The inocula were diluted with 0.9% NaCl to the 0.5 McFarland standard and 100 μl were applied onto 9 cm Mueller-Hinton agar plates with a depth of approximately 5 mm. Disks of absorbent paper (5 mm in diameter) were impregnated with 10 μl of silver nanoparticle solutions (47.5, 42.5, 22.6 and 11.3 ppm). For comparison, disks of the same diameter with 10 μl Tetracycline, Penicillin G and Ampicillin (1 g/l each) were used, leading to a concentration of the respective substance of 10 μg/disk. The freshly prepared disks were placed on the surface of the inoculated agar plates. After incubation at 37°C for 18 h the zones of bacterial inhibition were measured optically. In order to impregnate a cotton fabric with silver nanoparticles, the simple padding procedure [12] was used. In a separate exercise, commercially available water paint was mixed with silver nanoparticles solutions in a ratio of 7:1 in order to impart antimicrobial properties to the paint. To evaluate the antibacterial and fungicidal properties of Ag nanoparticles added to a cotton fabric and a water paint, samples (1.5 × 1.5 cm) treated by different compositions of Ag nanoparticles as well as control samples were immersed in a thin layer of beef-extract agar. A 1 ml of suspension of approximately 105 CFU/ml density of the microorganisms to be tested were distributed uniformly on agar surface and incubated at 28°C (CFU = colony forming units). Antimicrobial activity was evaluated according to the presence or absence of microbial growth just above the sample after a 24-h incubation for bacteria and a 72-h incubation for fungi. All microbiological tests were performed in triplicate. MICs of silver nanoparticle solutions for various microbes were determined using the macrodilution broth susceptibility test. Nutrient broth used in the macrodilution method contained peptic digest of animal tissue 50.00 g/l; beef extract 1.5 g/l; sodium chloride 5.00 g/l; glucose 5 g/l; pH 7.4 ± 0.2. A standardized suspension of approximately 106 CFU/ml density was obtained by inoculating the culture in nutrient broth (Hi-Media) and incubating the tubes at 37°C for 3 h. A serial dilution of our silver nanoparticles solution was prepared

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within a desired range. Ten milliliter of the standardized culture suspension was then inoculated and tubes were incubated at 37°C for 24 h. MIC was defined as the lowest concentration of the inhibiting agent that completely inhibited bacterial growth, the unit for MIC was chosen as mg(Ag)/l. MIC was examined visually, by checking the turbidity of the tubes. 3. 3.1.

Results and Discussion MORPHOLOGY OF THE SYNTHESIZED Ag NANOPARTICLES

It was shown by DLS measurements that a typical sample of silver nanoparticles solution obtained by the two-electrode setup described above contains not only nanoparticles, but also a small amount of large (>100 nm) colloidal silver particles. In order to remove these coarse particles and to provide reduction of silver ions present in the solution, we used filtration of the solution through a 3-μm pore size paper filter. The filter narrows the range of size distributions of synthesized silver nanoparticles while providing additional reduction of Ag ions according to the following reaction: Ag+1 + e → Ag0. As a result, the ratio of the concentrations of silver ions and silver nanoparticles suspended in the solution is reduced. A final stage of Ag nanoparticle synthesis involves additional treatment of the smallest-size fraction of silver nanoparticles remaining in solution after the filtering stage. It consists of adding hydrogen peroxide to a level of up to 0.005% concentration of H2O2 to the solution. Due to the reaction Ag2O + H2O2 → 2Ag + H2O + O2 silver oxide is reduced to Ag which is released in the solution. By this process the size of the silver nanoparticles is reduced, while new Ag nanoparticles may be forming as well. Examination of TEM images taken 2 weeks after the addition of H2O2 revealed that silver nanoparticles suspended in water solution were nearly spherical and that their size distribution fell in the range of 2–20 nm, the average size being about 7 nm, cf. Figure 1.

Figure 1. Typical TEM image and size distribution of silver nanoparticles obtained by electrochemical synthesis.

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ANTIBACTERIAL ACTIVITY OF SILVER NANOPARTICLES

In Figure 2 the antibacterial effect of silver colloids with the concentrations of 47.5, 42.5, 22.6 and 11.3 ppm is presented vis-à-vis to that of known antibiotics. The concentrations of silver were selected in such a way as to correspond to maximum Ag concentrations used in consumer nanoproducts which are currently available on the market. Comparing zones of growth inhibition around the disks impregnated with various antibiotics and Ag nanoparticles, one can see that silver nanoparticle solution demonstrates a certain antimicrobial effect. The intensity of the effect is increased with the concentration of the solution. Figure 3 demonstrates zones of growth inhibition around the disks impregnated with various antibiotics and the disk with the largest Ag nanoparticles concentrations that we have used. Considering that the Ag concentration used in the experiment was approximately 20 times lower than that of the antibiotics, one can expect that silver nanoparticles would outperform Ampicillin, Penicillin and Tetracycline antibiotics of the same concentration. 20 18 16

zone of inhibition diameter [mm]

14 12 10 8 6 4 2 0 Am picillin

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0.425 μ g/disk

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Figure 2. Antibacterial activity of silver nanoparticles in aqueous solution against E. coli K12 determined by the agar disk diffusion method.

In order to reveal an effect of the size of silver nanoparticles on their bactericidal efficiency the minimum inhibitory concentration (MIC) assays were conducted against the gram-negative bacterium E. coli and the gram-positive bacteria S. aureus and B. subtilis. The results for MIC assays shown in Table 1 demonstrate that smaller silver nanoparticles had a greater antibacterial efficacy. The conducted MIC assays have also shown clearly that the proposed electrochemical technique

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Figure 3. Zones of growth inhibition around disks impregnated with silver nanoparticles and various antibiotics.

provides very high antimicrobial activity of synthesized silver nanoparticles. For example, Sarkar et al. [27] have recently proposed a method of synthesis of Ag nanoparticles that provided the same MIC values for E. coli and S. aureus varieties as in the present study. Sarkar and coauthors claimed that “such a low value of MIC showed by silver nano particles is unprecedented”. The results obtained for larger nanoparticles (with a mean size of 70 nm) are in good agreement with MIC assays for E. coli for colloidal silver (32.2 mg/l in case of average Ag-particle size of 63 nm) stabilized by sodium oleate (cf. [32]). On the other hand, MIC values for the same bacteria obtained by Rupareli et al. [25] are higher than those presented in Table 1, although they studied smaller silver nanoparticles (3.32 ± 1.129 nm). We suppose that it is mainly connected with the high purity of nanoparticles obtained by our electrochemical technique without surfactants. Unfortunately, existing studies on nanotoxicity were concentrated on empirical evaluation of the toxicity of various nanoparticles, with less regard Table 1. Minimum inhibitory concentration (MIC) assay results for silver nanoparticles. Bacterium E. coli S. aureus B. subtilis

MIC (mg(Ag)/l) (average particle size of 7 nm) 3 2 19

MIC (mg(Ag)/l) (average particle size of 70 nm) 34 25 no data

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given to the relationship between nanoparticle properties and toxicity [6]. Thus, there is an obvious need for further studies on the development of a database of bactericidal efficacy of silver nanoparticles as a function of their size and composition. 3.3.

ANTIMICROBIAL EFFECT OF COTTON AND PAINT SAMPLES MODIFIED WITH SILVER NANOPARTICLES

Bactericidal activity has become a significant property of textiles and paints used in applications such as medicine, clothing, and household products. We have impregnated cotton fabrics and water paints with our nanosized silver colloids. As one can see from Figure 4, most of initial silver nanoparticles had agglomerated into clusters because of attractive interaction forces between them (6-month old samples).

Figure 4. Samples of water paint (left) and cotton fabric (right) with immobilized silver nanoparticles.

The bactericidal action of the cotton fabric with immobilized silver nanoparticles on S. aureus was also studied. Experiments with agar plates demonstrated that the modified fabric (1 µg/cm2) can inhibit the growth of S. aureus on beef extract agar (Figure 5). Similar tests were conducted on S. aureus using pasteboard covered with water paint modified with silver nanoparticles. These tests demonstrated that the modified paint with the area concentration of Ag of 0.001 mg/cm2 could inhibit the growth of S. aureus on beef extract agar. Our recent microbiological tests [7] confirmed antifungal effect of the water paint modified with silver nanoparticles on Aspergillus niger and Penicillium phoeniceum cultures. It was shown in particular that a 20 ppm concentration of Ag nanoparticles (mean size of 50 nm) and a 3 ppm concentration (mean size of 15 nm) have similar antifungal effects, i.e. smaller silver nanoparticles had a greater antifungal efficacy. Tests on nanosilver-modified cotton fabrics, in which a 20 ppm solution of Ag nanoparticles with the mean size of 50 nm was used, also confirmed their antibacterial/antifungal effect: growth of these species of fungi in the vicinity of samples treated with a colloidal solution of Ag nanoparticles was suppressed.

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Figure 5. Growth of S. aureus culture on a cotton fabric sample modified by silver nanoparticles on the first and the next day. (Note the white spots corresponding to S. aureus colonies.) The sample #1 is a control sample, i.e. non-modified; other samples are modified with silver nanoparticles having various average sizes.

4.

Environmental and Human Health Impacts

Silver-based materials have been widely used over the last decades in medical organizations, photographic laboratories etc. Not long ago, the annual silver release into the environment from industrial wastes and emissions was estimated at approximately 2,500 t, of which 150 t ended up in the sludge of wastewater treatment plants with 80 t being released into surface waters [28, 24]. The maximum concentrations of silver released into the environment are regulated at various levels in different countries by their appropriate environmental protection agencies. It was well documented in studies conducted in the twentieth century that the toxicity of silver in the environment occurred mainly in the aqueous phase and depended on the concentration of active, free Ag+ ions. [24]. As for the impact on human health, the scientific literature of the last century cited mainly cases of permanent bluish-gray discoloration of the skin (argyria) or eyes (argyrosis) occurring when the accepted threshold values for silver and its compounds were exceeded [1]. In the twenty-first century the significant growth of applications of nanosilver in various branches of industry as well as its use in consumer products has caused new concerns that silver nanoparticles may have a toxic effect on the environment and human health. There is a public perception that silver nanoparticles do not discriminate between different strains of bacteria and are likely to destroy microbes beneficial to other organisms and ecological processes [2]. Unfortunately, only a few scientific investigations on cytotoxicity of nanosilver have been conducted to date. For example, in vitro toxicity assays of silver nanoparticles in rat liver cells by Hussain et al. [9] have shown that low level exposure resulted in oxidative stress, cellular shrinkage and impaired mitochondrial function. Silver nanoparticles also turned out [5] to be highly toxic to in vitro mouse germline stem cells, as they drastically reduce mitochondrial function and cause increased leakage of ions through cell membranes. According to studies conducted by Soto [31], nanoparticulate

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silver aggregates were more cytotoxic than asbestos. There is also an impact of nanosilver exposure on development of the lymphatic system of embryos of chickens, although the entire embryo development was not influenced by silver nanoparticles [8]. Considering the studies on cytotoxicity of nanoparticles, it is important to keep in mind that in vitro results can differ from what is found in vivo and are not necessarily clinically relevant [15]. It should also be noted that some reported silver cytotoxicity studies were performed using unrealistically high concentrations of nanosilver. It would be fair to say that the mechanism of the bactericidal effect of silver nanoparticles is not well understood as yet. Lok et al. [17] have recently reported that “Nanosilver represents a special physicochemical system which confers their antimicrobial activities via Ag+”. If this conclusion is verified then most bioaccumulation and toxicity issues relating to silver nanoparticles can be considered from the point of view of the toxic potential of ionic silver, which is documented sufficiently well. As under natural environmental conditions the ionic silver is readily transformed to nonreactive compounds [24], this would mean that the environmental risks of nanosilver toxicity is not as severe as the popular perception may suggest. By contrast, according to Morones et al. [20] the bactericidal effect of silver nanoparticles on micro-organisms is connected not merely with the release of silver ions in solution. Following their report, silver nanoparticles can also be attached to the surface of the cell membrane and disturb its proper function drastically. They are also able to penetrate inside the bacteria and cause further damage by possibly interacting with sulfur- and phosphorus-containing compounds such as DNA. It is interesting to note that silver nanoparticles have also demonstrated synergistic effects with known antibiotics, such as amoxicillin [16]. Thus, there is an urgent need for further studies on the bactericidal mechanism of silver nanoparticles, which will be a step forward to better understanding of their environmental and human health impacts. As silver-based materials have a great commercialization potential, we anticipate a large amount of reports from various scientific groups in the field of nanosilver toxicity in near future. To quote a recent review: “A full understanding of the hazards of nanoparticles will make a major contribution to the risk assessment that is so urgently needed to ensure that products that utilize nanoparticles are made safely, are exploited to their full potential and then disposed of safely” [15]. 5.

Conclusion

An electrochemical technique for synthesis of silver nanoparticles with high antimicrobial activity has been developed. Our studies have revealed that silver nanoparticles suspended in water solution are nearly spherical, their average diameter being 7 ± 3 nm. Due to their high purity, very low inhibitory concentration (MIC) values for Escherichia coli (3 mg/l), Staphylococcus aureus (2 mg/l) and Bacillus subtilis (19 mg/l) cultures have been obtained. The tests

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conducted have demonstrated that synthesized silver nanoparticles added to water paints or cotton fabrics show a pronounced antibacterial/antifungal effect, despite the fact that they tend to be agglomerated into clusters. It has been shown that smaller silver nanoparticles have a greater antibacterial/antifungal efficacy. A brief review of the scientific literature on recent studies into the impact of silver nanoparticles on environment and human health has been provided. Acknowledgments R. R. Khaydarov acknowledges partial support of this work through the INTAS Fellowship Grant No. 5973 for Young Scientists under the “Uzbekistan – INTAS 2006” program. References 1. ACGIH (1991) Documentation of the Threshold Limit Values and Biological Exposure Indices, 6th edn, American Conference of Governmental Industrial Hygienists, Cincinnati, OH. 2. Allsopp, M., Walters, A., and Santillo, D. (2007) Nanotechnologies and Nanomaterials in Electrical and Electronic goods: A Review of Uses and Health Concerns, Greenpeace Research Laboratories Technical Note 09/2007 (December 2007). 3. Bogle, K.A., Dhole, S.D., and Bhoraskar, V.N. (2006) Silver nanoparticles: synthesis and size control by electron irradiation, Nanotechnology 17, 3204–3208. 4. Bönnemann, H., and Richards, R. (2001) Nanoscopic metal particles – synthetic methods and potential applications, Eur J Inorg Chem 10, 2455–2480. 5. Braydich-Stolle, L., Hussain, S., Schlager, J., and Hofmann M.-C. (2005) In vitro cytotoxicity of nanoparticles in mammalian germline stem cells, Toxicol Sci 88(2), 412–419. 6. Buzea, C. et al. (2007) Nanomaterials and nanoparticles: sources and toxicity. Biointerphases 2(4), MR17–MR71. 7. Estrin, Y., Khaydarov, R.R., Khaydarov, R.A, Gapurova, O., Cho, S., Scheper, T., and Endres, C. (2008) Antimicrobial and antibacterial effects of silver nanoparticles synthesized by novel electrochemical method. Nanoscience and Nanotechnology, ICONN 2008, Proceedings of 2008 International Conference on Nanoscience and Nanotechnology, 25–29 February 2008, Melbourne, Victoria, Australia, 44–47. 8. Grodzik, M., and Sawosz, E. (2006) The influence of silver nanoparticles on chicken embryo development and bursa of Fabricius morphology, J Anim Feed Sci 15(Suppl 1), 111–114. 9. Hussain, S.M., Hess, K.L., Gearhart, J.M., Geiss, K.T., and Schlager, J.J. (2005) In vitro toxicity of nanoparticles in BRL 3A rat liver cells, Toxicol In Vitro 19, 975–983. 10. Khaydarov, R.R., Khaydarov, R.A., Gapurova, O., Estrin, Y., and Scheper, T. (2008) Electrochemical method of synthesis of silver nanoparticles. J Nanopart Res. Doi:10.1007/ s11051-008-9513-x. 11. Klasen H. (2000) A historical review of the use of silver in the treatment of burns. II. Renewed interest for silver. Burns 26(2), 131–138. 12. Lee, H.J., and Jeong, S.H. (2005) Bacteriostasis and skin innoxiousness of nanosize silver colloids on textile fabrics, Text Res J 75, 551–556. 13. Lee, I., Han, S.W., and Kim, K. (2001) Simultaneous preparation of SERS-active metal colloids and plates by laser ablation, J Raman Spectrosc 32, 947–952.

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14. Lewis, L.N. (1993) Chemical catalysis by colloids and clusters, Chem Rev 93, 2693– 2730. 15. Lewinski, N., Colvin, V., and Drezek, R. (2008) Cytotoxicity of nanoparticles, Small 4(1), 26–49. 16. Li, Y., Wu, X., and Ong, B.S. (2005) Facile synthesis of silver nanoparticles useful for fabrication of high-conductivity elements for printed electronics, J Am Chem Soc 127, 3266–3267 17. Lok, C.N. et al. (2007) Silver nanoparticles: partial oxidation and antibacterial activities. J Biol Inorg Chem 12(4), 527–534. 18. Long, D., Wu, G., and Chen, S. (2007) Preparation of oligochitosan stabilized silver nanoparticles by gamma irradiation, Radiat Phys Chem 76(7), 1126–1131. 19. Mallick, K., Witcomb, M.J., and Scurrell, M.S. (2004) Polymer stabilized silver nanoparticles: a photochemical synthesis route, J Mater Sci 39, 4459–4463. 20. Morones, J.R. et al. (2005) The bactericidal effect of silver nanoparticles. Nanotechnology 16, 2346–2353. 21. Murphy, C.J., Sau, T.K., Gole, A.M., et al. (2005) Anisotropic metal nanoparticles: synthesis, assembly, and optical applications, J Phys Chem B 109, 13857–13870. 22. Navaladian, S., Viswanathan, B., Viswanath, R.P., et al. (2007) Thermal decomposition as route for silver nanoparticles, Nanoscale Res Lett 2, 44–48. 23. Niemeyer, C.M. (2001) Nanoparticles, proteins, and nucleic acids: biotechnology meets materials science, Angew Chem Int Ed 40(22), 4128–4158. 24. Ratte, H.T. (1999) Bioaccumulation and toxicity of silver compounds: a review. Environ Toxicol Chem 18(1), 89–108. 25. Ruparelia, J.P. et al. (2008) Strain specificity in antimicrobial activity of silver and copper nanoparticles. Acta Biomater 4:707–716. 26. Salata, O.V. (2004) Application of nanoparticles in biology and medicine, J Nanobiotechnol 2, 1–12. 27. Sarkar, S. et al. (2007) Facile synthesis of silver nano particles with highly efficient anti-microbial property, Polyhedron 26, 4419–4426. 28. Smith, I.C., and Carson, B.L. (1977) Trace Metals in the Environment, Vol 2—Silver, Ann Arbor Science, Ann Arbor, MI. 29. Soete, D.D., Gijbels, R., and Hoste, J. (1972) Neutron Activation Analysis, Wiley Interscience, New York. 30. Solov’ev, A.Y., Potekhina, T.S., Chernova, I.A., et al. (2007) Track membrane with immobilized colloid silver particles, Russ J Appl Chem 80(3), 438–442. 31. Soto, K.F. et al.(2005) Comparative in vitro cytotoxicity assessment of some manufacturednanoparticulate materials characterized by transmissionelectron microscopy. J Nanopart Res 7, 145–169. 32. Zeng, F., Hou, C., Wu, S., Liu, X., Tong, Z., and Yu, S. (2007) Silver nanoparticles directly formed on natural macroporous matrix and their anti-microbial activities, Nanotechnology 18(5), 055605, 1–8.

DEVELOPING STRATEGIES IN BRAZIL TO MANAGE THE EMERGING NANOTECHNOLOGY AND ITS ASSOCIATED RISKS

A.S.A. ARCURI, M.G.L. GROSSI, V.R.S. PINTO, A. RINALDI Foundation on Occupational Safety and Health Researches and Studies – FUNDACENTRO – Ministry of Labour and Employment Rua Capote Valente 710 San Paolo 05409-002, Brazil [email protected] A.C. PINTO IIEP – Intercâmbio, Informações, Estudos e Pesquisas Rua Pedro Américo, 52, 13º andar San Paolo, Brazil P.R. MARTINS RENANOSOMA, IPT – Instituto de Pesquisas tecnológicas do estado de São Paulo Av. Prof. Almeida Prado 532 Cid. Universitária. 05508-901 São Paulo, Brazil P.A. MAIA FUNDACENTRO – Ministry of Labour and Employment Rua Marcelino Velez, 43 Campinas – 13020-200, Brazil

Abstract. Emerging countries, such as Brazil, are beginning to feel the impact of nanomaterial production occurring in further developed countries. It is important to identify strategies for the risk management of these products. For this reason, Fundacentro, a Ministry of Labor and Employment institution, in Brazil is currently working to develop management strategies for nanotechnology and its associated risk. One of Brazil’s first efforts to develop a nanotechnology management and risk assessment plan occurred at the “Nanotechnology, Environment and Society for a Possible New World” workshop held on January 25, 2004 at the 5th World Social Forum in Porto Alegre. Within the same year, there was also the creation of Renanosoma, a Brazilian research network involved in nanotechnology, sociological issues, and environmental matters. The aim of Renanosoma is to research potential effects of nanotechnology and increase public awareness of the social, I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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economical, environmental, and ethical impacts. This network has also been responsible for four international seminars related to nanotechnology, and coordinated a federally funded project titled “Public Engagement in nanotechnology”. Through this project, conferences are held three times a week via the internet (http://www. meebo.com/room/nanotecnologia/). In each conference, debates involving a main speaker (a previously invited researcher), researchers from all over the country, social scientist, and the interested public discuss different views and aspects of nanotechnology’s implementations and impacts. Since 2006, many other organizations have joined the Renanosoma network, some of which include the IIEP (Information Exchange, Studies and Research), DIESAT (Inter Union Department of Studies and Research on Health and Workplace), DIEESE (Inter Union Department of Statistics and Socio-Economical Studies), and FUNDACENTRO (Foundation on Occupational Safety and Health Researches and Studies). The interest and participation of these organizations in the Renanosoma network drove the momentum for two additional seminars to be held on occupational safety and health. Additionally, FUNDACENTRO is funding a project that is being developed to propose feasible controlling measures for nanomaterial and identify impacts that nanotechnology may have on the general working public and the environment. Several additional projects and activities are planned for the year 2008 that may become developments of groups recently added to Renanosoma. 1.

Introduction

FUNDACENTRO is a foundation, created in 1966, that produces and disseminates research studies in many different occupational fields. Since the foundation’s creation, FUNDACENTRO main objective has been to foster a safe and healthy work environment for industry employees by identifying main items of risk that occur in the workplace. Currently, the foundation develops projects and activities in the construction industry, chemical safety, small enterprises, the rural sector, ergonomics, ionizing and non-ionizing radiations (mainly at the telecommunications field), machinery protection, fishing, silicosis elimination, and many others. The creation of regulative norms for the safety and health of Brazilian workers requires a great deal of research. In 1995, a legislation agreement was enacted to prohibit the use of Benzene in anhydrous alcohol production and to admit only 0.1% (v/v) of benzene in products such as solvents, paints, and varnishes. The development of this agreement was based on FUNDACENTRO’s intervention in the sectors where Benzene was present. It was introduced a technological reference value parameter for measuring the environmental concentration of the benzene found in workplace air. This agreement was able to engage industry workers, employers, and branches of the government. In addition to Benzene, FUNDACENTRO developed studies that established awareness of the carcinogenic effects of Asbestos, which helped drive the banishment of this highly toxic substance.

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Nanotechnology is still considered an emerging field. Currently, several nanoproducts available on the market but additional technology remain to be introduced into product manufacturing and distribution. The production of these materials can represent risks, even unknown ones, to society and exposed workers. Risk can occur at any stage of the product’s life cycle such as the development, production, and disposal/destruction of the material. Due to the extensive potential for risk, FUNDACENTRO has the opportunity to intervene not only in facilities where workers are currently being exposed to hazards, but also by implementing effective prevention measurements. Research is currently being conducted to identify the risk of new production methods and how the launch of these new products could negatively impact exposed workers. From this preliminary knowledge, FUNDACENTRO is in the process of developing information and communication about nanomaterial risk that are typical actions of risk management. This process is developing despite the fact that the foundation’s researchers have just recently become aware of nanotechnology. FUNDACENTRO realizes that precautions must be taken to establish risk management strategies in protecting exposed workers and the general public. In the workshop “Risk, uncertainty and decision analysis for nanomaterials: environmental risks and benefits and emerging consumer products” one of the statements of purpose is defined as “Identify strategies for users in developing countries to best manage this emerging technology and its associated risks”. This statement gives a clear insight to the intentions and actions developing in Brazil by FUNDACENTRO and its stakeholders to try and manage possible associated risks from these technologies. 2.

Risk Management

A classic model for risk management begins from hazard identification. NIOSH (2006) NIOSH (2006a) published a figure with steps to protect workers involved with nanotechnology. The NIOSH figure below depicts hazard identification as the first step, hazard characterization as the second, exposure assessment as the third, and risk characterization as the fourth. All of these sequential steps lead to the end objective of the model that is to predict risk management. When the topic is nanotechnology, it is difficult to follow the steps outlined in this model. There are many unknown elements regarding the first step of the model, which is hazard identification of nanostructured materials. Many references exist that discuss issues pertaining to the lack of knowledge relative to nanotechnology [1, 2, 6, 9–11, 13, 14, 16, 20, 21, 23, 24]. In the field of nanotechnology there remains an abundance of material to be studied and revealed. Despite the fact that there are currently wide gaps of knowledge, enough information has already been produced to understand that there is a need in minimizing or eliminating a person’s exposure to nanomaterial substances. It is also important to point out that traditional protocols established in occupational health may not be efficient for nanomaterial exposure due to their novel properties and the questionable efficiency of past protocols.

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Steps to protect workers involved with nanotechnology Hazard identification “Is there reason to believe this could be harmful?” Hazard identification “How and under what conditions could be harmful?” Exposure assessment “Will there be exposure in real-world conditions?” Risk characterization “is substance hazardous and will there be exposure?” Risk management “Develop procedures to minimize exposures?”

Recent information of nanoparticles and their potential effects was stated below by NIOSH [17]: ƒ “Nanomaterials have the greatest potential to enter the body if they are in the form of nanoparticles, agglomerates of nanoparticles, and particles from nanostructures materials that become airborne or come into contact with the skin. ƒ Based on results from human and animals studies, airborne nanomaterials can be inhaled and deposit in the respiratory tract; and based on animal studies, nanoparticles can enter the blood stream and translocate to others organs. ƒ Experimental studies in rats show that equivalent mass doses of insoluble ultrafine particles (smaller than 100 nm) are more potent than large particles of similar composition in causing pulmonary inflammation and lung tumors in those laboratory animals. However, toxicity may be mitigated by surface characteristics and other factors. Results from in vitro cell culture studies with similar materials are generally supportive of biological responses observed in animals. ƒ Cytotoxicity and experimental animal studies shown that changes in the chemical composition, structure of molecules, or surface properties of certain nanomaterials can influence their potential toxicity. ƒ Studies in workers exposed to aerosols of manufactured microscopic (fine) and nanoscale (ultra fine) particles have reported lung function decrements and adverse respiratory symptoms; however, uncertainty exists about the role of ultra fine particles relative to other airborne contaminants (e.g., chemicals, fine particles) in these work environments in causing adverse health effects.”

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This reference concludes that “Engineered nanoparticles whose physical and chemical characteristics are like those ultra fine particles need to be studied to determine if they pose health risks similar to those that have been associated with ultra fine particles” [17]. In addition to the issues reported by NIOSH, many additional reports have been published that address potential health concerns relative to nanoparticles [3, 4, 5, 7, 8, 12, 15, 18, 19]. As we can see, engineered nanomaterials pose many new questions for risk assessment that are not yet completely answered. Swiss researchers lead a study [9] that gives an overview of the general properties of nanomaterial products in the market. The study reveals that in general, industries working with nanomaterials in Germany and Switzerland have approached the issue of risk and safety through written surveys collected from over 40 companies. The characterization of particles and safety measures returned in the surveys from each company was so diverse that no categorization relative to risk and material specification could be determined. Twenty-six companies (65%) indicated that they did not perform any risk assessment of their nanomaterials and 13 companies (32.5%) performed risk assessments sometimes or always. Fate of nanomaterials in the use and disposal stage received little attention by industry, and the majority of companies did not foresee any unintentional release of nanomaterials throughout the life cycle. The development of risk and safety decision framework in nanotechnology industry is necessary to ensure that the potential risks of engineered nanomaterials are taken into consideration. The Helland study reveals that the majority of companies surveyed did not perform any form of risk assessment or proactive risk assessment strategies. As revealed in cases such as this, it is becoming more apparent that risk management strategies need to be implemented in industries involved with nanotechnology manufacturing and development. Management strategies need to be developed urgently not only to protect public and environmental health, but also to protect the industry workers being exposed to the materials. 3.

Risk Management in Brazil

New technologies, especially in the nano field, are becoming instruments of life style change in society. Therefore, before and after public acceptance, information about nanomaterials has been released through the media in Brazil in addition to many other countries. The media is describing nanotechnology as a science that will improve human life and society at large. This publicity has played a large role in propagating the potential impact that amplification and improvement of nanomaterial products will have on the general public. An additional drive behind nanotechnology may be the increase in wealth for most companies involved with production of materials. Although there is much universal discussion concerning the potential impacts of nanomaterials, very few discussions lead to the topic of whether these materials should actually be available through the public market. This universal discussion rarely stamps some negative point that leads the society to a better decision.

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On the other side, many research centres and universities conduct studies solely for the purpose of determining the potential positive impacts of nanomaterials. Consequently, some facilities will study the potential harmful effects of their materials only after the receiving results for their initial studies, which may occur after products have already been released onto the market. This is the case of many nano research facilities in Brazil founded by CNPq (Brazilian National Council for the Scientific and Technological Development). Through the Microelectronic Laboratory of Polytechnic School of USP (University of San Paolo), nanomaterial research will be conducted for developments in fields of medicine and industry. In total, this lab will gather about 20 Brazilian researchers in the next 2 years The Laboratory of Nanotechnology integrated with Synchrotron Light (located in Campinas, South Brazil) is currently developing research focusing on nanomaterial properties and characterizations. The fact that this laboratory is focusing on material research and characterization sets it apart from other facilities conducting nanomaterial research in Brazil. Research in the field of nanotechnology may have the ability to promote the technological development of Brazil; consequently this may exclude the public from debates concerning economic and social implications as well as potential risks of such advancements. Many teaching institutions, such as technical and high schools, are offering nanotechnology classes that explore how the present pioneering initiative is aimed at contributing knowledge to the scientific community and other graduate professionals faced with technological challenges. One institution developing programs aimed at gaining student interest in the field of nanotechnology is the Multidisciplinary Centre for Ceramic Material, which gathers researchers from the Federal University of San Carlos (UFSCar) and from Paulista State University (UNESP). This institution has developed a game that gets players familiar with the nanoscopic world. The participants are given games pieces that must be joined together as quickly as possible to form a realistic scientific image. Companies, even more than universities, are willing to develop new products at nanometric scale based on profit. Products are often released into the public market well before any research investigating the potential effects of these products on man and the environment has been conducted. For instance, in May 2008, a symposium on automotive materials and nanotechnology was conducted by SAE BRASIL, the theme of which was “The Re-invention of the Automobile and New Components”. During this symposium they discussed replacing steel with other materials, some of which may include materials from a new field such as nanomaterial. Nanotechnology is stepping ahead in the car industry, especially in plastics, paints, and electronic component fields. Although there are potential new developments using nanotechnology in the automotive industry, the symposium program does not plan to cover relevant damages that may be caused to workers or the environment after exposure to materials used in production. Additionally, products such as washing-machines, refrigerators, and hair dryers bearing nanosilver particles can be currently found in use at several Brazilian residences. Owners of these products often do not know enough information to

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ask questions regarding the possible negative impacts that these particles could have if released into the environment. There is a national program created by the Ministry of Science and Technology, “Nanotechnology and Nanoscience Development”. Among its priority actions, are politics on ethical and social impact subjects. Unfortunately, budgets that would normally fund the program have been allocated nearly 100% toward industrial research and growth. What can be concluded from this report is that there are not enough agents to provide society knowledge of possible impacts from these new technologies. RENANOSOMA projects, alongside with “Public Engagement on Nanotechnology” and “FUNDACENTRO” have been exceptions. From 2006 on, Fundacentro has studied as well as publicized the impacts of nanotechnology on workers and the environment. Though significant, such efforts are too little to make the all of the Brazilian population aware of the problems and possible risks from nanotechnology. The lack of knowledge may result, if persistent, to a scenario of unrepairable damages and losses to the environment and human health, especially to industry workers exposed to the materials. Many difficulties are encountered when well established countries attempt to follow the steps outlined for risk management due to the lack of knowledge about the materials, but the risk management process is even more difficult to follow in developing countries. Despites the difficulties, scientific researchers, the NGO, and social representatives have put forth an effort to discuss problems that may be encountered by nanomaterial production with public and industry workers. This initiative is being considered the beginning of a risk management process in Brazil, which has benefited from learning the challenges faced by classical risk assessment actions. 4.

FUNDACENTRO Project on Nanotechnology

In 2007, FUNDACENTRO began a project that took a preliminary survey about nanotechnology and its potential impact to worker health and safety. Surveys were taken in areas that conducted the greatest amount of nanotechnology work. As a result of this project, many other areas on interest in nanotechnology were developed. The seminar entitled “Nanotechnology, workers health, foods and social and environmental impacts” consisted of lectures concerning nanotechnology. Along with the seminar was also the production of a website, http://blog.iiep. org.br/nanotecnologia/, which distributed related press material. This project is continuing in 2008. This year we intend to prepare field research in nanomaterial product development laboratories and enterprises. The target is assessment of workplace conditions. Similar surveys had already been done by other researchers [6, 9]. Through this project we will try to compare if the risk and safety decision frameworks in Brazilian industry and laboratories are, or not, similar to those in other countries. We plan to continue propagating awareness about the impacts and information associated with nanotechnology. Scheufele et al. [22] conducted research studies

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concluding that scientists expressed more concerns than the general public about two areas of potential risks of nanotechnology: more pollution and new health problems. Due to these impending concerns, we believe it is important to inform the public as well as nanomaterial industry workers about the potential impacts that these products could have. The action items of this year are to produce events, educational material, videos, and a website discussing the potential impacts of nanotechnology. All information will be posted on the FUNDACENTRO website and available to the public. References 1. ACC – American Chemistry Council (2006) “ACC nanotechnology Panel: Engineered Nanomaterials Survey”. Summary Discussion (September, 2007). Available at http:// www.americanchemistry.com/s_acc/bin.asp?CID=654&DID=5945&DOC=FILE.PDF 2. ASCC – Australian safety and Compensation Council (2006) “A review of the Potential Occupational Health and Safety Implications of Nanotechnology for the Department of Employment and Workplace Relations”. Final Report, July, 2006 (April 9, 2008). Available at: http://www.ascc.gov.au/ascc/AboutUs/Publications/ResearchReports/ AReviewofthePotentialOccupationalHealthandSafetyImplicationsofNanotechnology.htm 3. BAFU/BAG – Bundes für Umwelt/Bundesamt für Gesundheit (2007) “Synthetische Nanomaterialien. Risikobeurteilung und Risikomanagement. Grundlagenbericht zum Aktionsplan”. Available at http://www.bafu.admin.ch/publikationen/index.html?lang= en&action=show_publ&id_thema=30&series=UW&nr_publ=0721 4. BAUA – German Federal Institute for Occupational Safety and Health e VCI - German Chemical Industry Association (2007) “Guidance for Handling and Use of Nanomaterials in the Workplace”. Available at http://www.baua.de/nn_49456/en/Topicsfrom-A-to-Z/Hazardous-Substances/Nanotechnology/pdf/guidance.pdf 5. Borm, P.J.A. and Kreyling, W. (2004) Toxicological Hazards of Inhaled Nanoparticles– Potential Implications for Drug Delivery. J. Nanosci. Nanotechnol. 4(6):1–11 6. Conti, J.A., Killpack, K., Gerritzen, G., Huang, L., Mircheva, M., Delmas, M., Harthorn, B.H., Appelbaum, R. and Holden, P.A. (2008) Health and Safety Practices in the Nanomaterials Workplace: Results from an International Survey. ASAP Environ. Sci. Technol. 10.1021/es702158q, published on Web 04/01/2008. Available at http:// pubs.acs.org/cgi-bin/abstract.cgi/esthag/asap/abs/es702158q.html 7. Donaldson, K., Aitken, R., Tran, L., Stone, V., Duffin, R., Forrest, G. and Alexander, A. (2006) Carbon Nanotubes: A Review of Their Properties in Relation to Pulmonary Toxicology and Workplace Safety. Toxicol. Sci. 92(1):5–22 8. Drobne, D. (2007) Nanotoxicolgy for Safe and Sustainable Nanotechnology. Arh. Hig. Rada Toksikol. 58:471–478 9. Helland, A., Scheringer, M., Siegrist, M., Kastenholz, H.G., Wiek, A. and Scholz, R.W. (2008) Risk Assessment of Engineered Nanomaterials: A Survey of Industrial Approaches. Environ. Sci. Technol. 42(2):640–646. 10.1021/es062807i 10. ICON – International Council on Nanotechnology (2006a) “Review of Current Practices in Nanotechnology. Phase One Report: Current Knowledge and Practices Regarding Environmental Health and Safety in the Nanotechnology Workplace” (Issued October 18, 2006). Available at http://cohesion.rice.edu/CentersAndInst/ ICON/emplibrary/ Phase%20I%20Report_UCSB_ICON%20Final.pdf

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11. ICON – International Council on Nanotechnology (2006b) “Phase Two Report: A Survey of Current Practices in the Nanotechnology Workplace” (Issued November 13, 2006). Available at http://cohesion.rice.edu/CentersAndInst/ICON/emplibrary/ ICONNanotechSurveyFullReduced.pdf 12. Lam C.W. James, J.T., MaCluskey, R., Arepalli, S. and Hunter, R.L. (2006) A Review of Carbon Nanotube Toxicity and Assessment of Potential Occupational and Environmental Health Risks. Crit. Rev. Toxicol. 36:189–217 13. Lindberg, J.E. and Quinn, M.M. (2007) “A Survey of Environmental, Health and Safety Risk Management Information Needs and Practices among Nanotechnology Firms in the Massachusetts Region”. Available at http://www.nanotechproject.org/process/ assets/files/5921/file.pdf 14. Maynard, A.D. (2006) Nanotechnology: A Research Strategy for Addressing Risks, Woodrow Wilson International Center for Scholars, Washington, DC, 41pp. (April 9, 2008). http://www.nanotechproject.org/file_download/files/PEN3_Risk.pdf 15. Nel, A., Xia, T., Mädler, L. and Li, N. (2006) Toxic Potential of Materials at the Nanolevel. Science 311:622–627 16. NIOSH – National Institute of Occupational Safety and Health (2006a) Progress Towards Safe Nanotechnology in the Workplace (April 9, 2008). http://www.cdc.gov/ niosh/docs/2007-123/pdfs/2007-123.pdf 17. NIOSH – National Institute of Occupational Safety and Health (2006b) Approaches to Safe Nanotechnology: An Information Exchange with NIOSH (April 9, 2008). http://www.cdc.gov/niosh/topics/nanotech/safenano/pdfs/approaches_to_safe_nanotech nology_28november2006_updated.pdf 18. Oberdörster, G., Oberdorster, E. and Oberdorster, J. (2005) Nanotoxicology: An Emerging Discipline Evolving from Studies of Ultrafine Particles. Environ. Health Perspect. 113(7):823–837 19. Oberdörster, G., Stone, V. and Donaldson, K. (2007) Toxicology of Nanoparticles: A Historical Perspective. Nanotoxicoloy 1(1):2–25 20. ORC – Worldwide. “Nanotechnology Consensus Workplace Safety Guidelines”. Available at http://www.orc-dc.com/Nano.Guidelines.Matrix.htm 21. Schmid, K. and Riediker, M. (2008) Use of Nanoparticles in Swiss Industry: A Targeted Survey. Environ. Sci. Technol. 42(7) 2253–2260. 10.1021/es071818o. Available at http://pubs.acs.org/cgi-bin/abstract.cgi/esthag/2008/42/i07/abs/es071818o.html 22. Scheufele, D.A., Corley, E.A., Dunwoody, S., Shih, T., Hillback, E. and Guston, D.H. (2007) Scientists Worry About Some Risks More Than the Public. Nat. Nanotechnol. 2:732–734 23. Schulte, P.A. and Salamanca-Buentello, F. (2007) Ethical and Scientific Issues of Nanotechnology in the Workplace. Environ. Health Perspect. 115(1):6–11 24. USEPA – US Environmental Protection Agency (2007) “Nanotechnology White Paper, EPA 100/B-07/001/” (February). Available at: http://www.epa.gov/osa/pdfs/nanotech/ epa-nanotechnology-whitepaper-0207.pdf

THE CURRENT STATE-OF-THE ART IN THE AREA OF NANOTECHNOLOGY RISK ASSESSMENT IN RUSSIA

M. MELKONYAN A.V. Shubnikov Institute of Crystallography of RAS 59 Leninsky pr 119333 Moscow, Russia [email protected] S. KOZYREV Center for Advanced Studies of the Saint-Petersburg State Polytechnical University 29 Polytekhnicheskaya ul St. Petersburg 195251, Russia

Abstract. The purpose of this paper is to describe the first steps in the area of Nanotechnology risk studies in Russia, to discuss the importance of joining Russia to the bodies responsible for international cooperation on environmental, health and safety impacts of N&N. 1.

Introduction

In June 2004 an “International dialog on responsible research and development of Nanotechnology” meeting took place in Alexandria (VA), USA. The meeting discussed a wide range of topics, such as: benefits and risks of Nanosciences and Nanotechnologies (N&N) to environment, human health and safety (EHS); socioeconomic and ethical implication; special consideration of N&N in developing countries. It was highlighted that there is need and opportunity to address the possible societal, health and environmental impact of N&N at an international level. This event was the very positive starting point. Since that time many important steps have been made and the real results were achieved in the further discussions of the interested parties within OECD and some other international organizations. They were related to exchange of information and best practices, address issues of common interest, such as: nomenclature, methodologies for risk assessment, toxicological and ecotoxicological studies. The OECD Working Party of Manufactured Nanomaterials established in 2006 has developed some projects, among them there is the development of OECD database on (EHS) research. Some years ago the evaluation of Nanotechnology risks for the environment and human health, the associated need to consider preventive measures was not a priority in Russia. This was mainly due to the lack of scientific information, I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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relatively limited use of nanomaterials, and no apparent evidence of adverse impacts on the environment and human health. Currently the understanding of the importance of this problem has become the key issue in Russia and the first steps have been undertaken. The goal of this paper is to describe these steps in the area of Nanotechnology risks studies in Russia, to discuss the importance of joining Russia to the bodies responsible for international cooperation on environmental, health and safety impacts of N&N. 2.

The Brief History of N&N in Modern Russia

The history of N&N in modern Russia can be divided into two periods: since 1991 until 2007 and since 2007 – till our days and beyond. During the first period the main governmental investments in N&N were relatively small, however some state programmes were launched: 1. State Programme of the Ministry of Education and Science (1992): “Prospective technologies and devices for micro- and nanoelectronics” 2. Interdepartmental Programmes coordinated by the Ministry of Education and Science (1993): “Fullerenes and atomic clusters” “The Physics of Solid State Nanostructures” 3. Programmes of Russian Academy of Sciences: “Fullerenes and atomic clusters” (1998) “Low-dimensional quantum structures” (2001) “Fundamental problems of physico-chemistry of nanomaterials” (2002) 4. Federal Targeted Programme (FTP) 2002–2006 “Research & Development in priority fields of Russia’s S&T Complex”, Priority “Industry of Nanosystems and Materials” (since 2004) 5. Enterprising Projects funded by Russian Foundation for Basic Research (since 1992) We note that the Interdepartmental Programme “Fullerenes and atomic clusters” devoted to complex problem of nanocarbon was the first interdisciplinary nanoprogram of modern Russia. In program section “Biological activity and medical application of fullerenes” have been carried out toxicological researches of fullerenes and fullerene soot, which were very important in that period of becoming of fullerene technology. On April 26, 2007 Vladimir Putin, the former President of Russia, announced a national initiative on the development of nanoindustry in Russia in his address to Parliament. The golden age of Russia N&N has started. The investments in this area will be ~$7.5 billion by 2015. The strategic goal of this initiative is to create the Russian nanoindustrial sector in national high-tech, which would be able to compete with those of economically developed countries on the internal and international markets of nanoproducts in key fields of State security and defensive capacity, technological security and economical independence, as well as improving people’s life quality (http://www.spbcas.ru/nanobio/Nanobio08/Abstracts_ all.pdf).

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Main tools of the state support of investigations and developments of nanoindustry are the following programmes (http://www.fasi.gov.ru/fcp; S. Ostapyuk in http://www.spbcas.ru/nanobio/Nanobio08/Abstracts_all.pdf): ƒ Federal Targeted Programme “Research & Development in priority fields of Russia’s S&T Complex 2007–2012”, priority “Industry of Nanosystems and Materials” ƒ Federal Targeted Programme “National technological base 2007–2011” ƒ Federal Targeted Programme “Development of electronic component base and electronics 2008–2015” ƒ Federal Space Program of Russia for 2006–2015 ƒ Federal Program for the development of nanoindustry up to 2015 ƒ Specialized NanoProgramme of the Russian Academy of Sciences ƒ Programme of the Russian Academy of Medical Sciences “Nanotechnologies and Nanomaterials in Medicine” for 2008–2015 ƒ Specialized Projects of the Russian Foundation for Basic Research Main tool for the development of the experimental and technological basis in nanoindustry is the Federal Target Program “Development of the Infrastructure of Nanoindustry in the Russian Federation for 2008–2010” (http://www.government. ru/government/governmentactivity/rfgovernmentdecisions/archive/2007/08/09/86 03022.htm). In 2007 the State Corporation “Russian nanotechnologies” was founded for the support of the emerging high-tech companies in national nanoindustry (http://www. rusnano.com). The tool ensuring the effective scientific personnel training for the national nanoindustry, the social protection of scientific personnel, attracting and keeping young people in science, education, and high-tech technologies is the Federal Target Program “Scientific and Pedagogical Personnel of the Innovative Russia” for 2009–2013. The main effect of the realization of the above-listed tools for nanoindustry development will be formation of the competitive national sector of investigations and developments in nanoindustry and ensuring conditions for the gradual raising of the rate of production of new types of goods. And, as a result, the profile Russian companies should get on in the world high-tech markets. 3.

First Steps in Nanotechnology Risks Studies in Russia

In Russia there is not currently research Programme underway to address human health and/or environmental safety aspects of Nanomaterials. But a number of R&T projects on impacts of nanoparticles are funded by Russian Foundation for Basic Research; by Federal Agency for Science and Innovation within the thematic priority “The industry of nanosystems and materials” of the Federal Target-oriented Programme “Research and Development in Priority Fields of S&T Complex of Russia for 2007–2012”. Studies of physico-chemical properties of Nanomaterials (in particular, nanoparticles) have been carried out within Russian

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Academy of Sciences (RAS), especially in the frame of “Fundamental problems of physico-chemistry of nanomaterials” Programme launched in 2002. Some researchers are including toxicological, ecotoxicological and metrological aspects on Nanotechnology in their research, but there is no official network for these areas. A number of Russian organizations are the partners of projects on analysis of toxicity of nanomaterials that have been funded by ISTC (http://search.istc.ru/index. jsp?v=7 ). Consideration of projects funded by Russian Foundation for Basic Research has demonstrated the interesting results (http://www.rfbr.ru/pics/22366ref/file. pdf). First of all, the number of scientific papers in the area of nanosciences was increased rapidly during 2003–2007 period (see Figure 1). The distribution of papers among different areas of knowledge has shown that in 2003 the most studies were accomplished in the area of physics (Figure 2a). In 2006 the situation radically changed, and 3% of projects were devoted to problems of medicine and biology (see Figure 2b). We can recognize that some of these projects were relevant to studies of nanotechnology impacts on human health and environment. The first event in Russia, devoted to the risks and benefits of Nanotechnology, was organized by National contact point “Nanotech” (FP7-NMP NCP) in October 2006. It was the round table on risks of Nanotechnology for human health and environment under the title “Nanomaterials may be reactive, but nanoscientists should be proactive”. This event demonstrated that Russian scientific community has recognized the importance of studies of Nanotechnology potential impacts on human health and environment. The similar thematic workshop “Impact of nanomaterials on (EHS)” was organized within the SCOPE-EAST Conference in Moscow, December 3–4, 2007 (http://scope-east.net/?p=conference_w_nano).

Figure 1. The increase in the number of research projects in the area of N&N during the period 2003-2007.

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Figure 2a. Distribution of nanoprojects among the different subject areas in 2003.

Figure 2b. Distribution of nanoprojects among the different subject areas in 2006.

In 2007 Federal Consumer Rights and Human well being Department (Rospotrebnadzor; http://www.rospotrebnadzor.ru) issued the regulations concerning the inspection of new products containing Nanomaterials (№ 53, 23.07. 2007); regarding the approval and implementation of methodological recommendations on the assessment of Nanomaterials safety (№ 280, 12.10.2007); regarding the Conception of the toxicological studies, risk assessment methodology, methods of identification and quantitative description of Nanomaterials (№ 79, 31.10.2007).

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Nanotechnology Action Plan for Russia – 2015 will contain the special subprogramme covering issues of nanosafety and potential impacts of Nanomaterials on health and environment. Representatives of Russia participate in the work of ISO/229-Nanotechnology. For last year the specialized working groups with focus on the development of different aspects of Nanotechnology impacts on human health and environment have been established in governmental structures and research organizations. For example, the expert analytical group for nanosafety and nanorisks at the Center for Advanced Studies of the Saint-Petersburg State Polytechnical University (http:// www.spbcas.ru). «National Nanoindustry Association» (NCO «NNA»), a non-commercial organization was established in Russia, January 2008 (http://www.nanotech. ru/nan/). One of the critical directions of the work is to promote studies of Manufactured Materials impacts on EHS. NCO NNA organized two relevant workshops “Waste Management using Nanotechnologies” (March 2008), “Nanotechnology in Chemical industry” (April 2008). According to its informal character the special session was not expected to produce any formal conclusions, however it was highlighted that there is the need and opportunity for Russia to join the international forum on the possible societal, health and environmental impacts of nanotechnology. Russia is at the start point in development of studies on Nanotechnology risks. Coordinating systematic comparisons of research results and sharing of information between Russia and other countries, laboratories across the world is of the great importance. The expert analytical group at the Center for Advanced Studies and Russian NCP “Nanotech” organized the special session “The international dialog on Nanotechnology risk assessment and management: opportunities for Russia” in the frame of the Second International Conference on Nanobiotechnologies” “NanoBio’2008” in Saint-Petersburg (June 16–18, 2008) (http://www.spbcas. ru/nanobio). The main objectives of the special session are: ƒ ƒ ƒ

To present European and international activities in the area of nanotechnology risk studies To discuss how to promote joining of Russia to the bodies responsible for international cooperation on impacts of nanotechnology to environment, health safety (EHS) To consider how to establish the national network for the area of nanotechnology risk studies and assessment, how to coordinate and manage different activities in this area at national level

The summary of the special session has included the following points: ƒ ƒ

To establish the national forum for the area of impacts of Nanotechnologies on environment, human health safety (EHS) in the frame of national network for Nanotechnologies The national forum will include scientific institutions experienced in risk assessment, companies, innovative small and middle enterprises

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This forum could support national coordination and participation of Russia in international organizations, such as OECD, ISO, UNESKO, in relation to risk assessment and risk management

The inventory of research studies in the area of Nanotechnology risks in Russia will be reflected in the public report “the state-of-the-art”. This report could help the further development of research strategies to investigate the EHS impacts of manufactured nanomaterials: on one hand – fundamental studies of different physico-chemical properties of nanomaterials and development of new methods in predictive toxicology; on the other hand – targeted research is needed to ensure adequate understanding of nanomaterials that are close to market. A very important achievement could be the creation of national data base on results of studies of toxicity, physico-chemical properties of nanoparticles, manufactured nanomaterials. This database should be with easy access and structured. Detailed studies of Nanotechnology risks have suggested active dissemination of information on European, national, international activities in this area (special web-site, newsletters, publishing of booklet); wide dissemination of knowledge about impacts of Nanotechnologies on EHS in Russia, covering the social aspects of N&N, boosting the responsible and safe approach to development of this area in the country; informing of all stakeholders in this area on international efforts and activities in this area; launch of special; identifying knowledge gaps, facilitate collaboration between projects, network and communicate; public consultations, on-line survey on different aspects of Nanotechnology risks and benefits. More actively participate in FP7 EU projects, calls dedicated to the problems of Nanotechnology impacts on EHS.

ENVIRONMENTAL RISK ASSESSMENT OF NANOMATERIALS

A.A. BAYRAMOV Institute of Physics National Academy of Sciences of Azerbaijan G.Javid 33 AZ1143 Baku, Azerbaijan [email protected]

Abstract. In this paper, various aspects of modern nanotechnologies and, as a result, risks of nanomaterials impact on an environment are considered. This very brief review of the First International Conference on Material and Information Sciences in High Technologies (2007, Baku, Azerbaijan) is given. The conference presented many reports that were devoted to nanotechnology in biology and business for the developing World, formation of charged nanoparticles for creation of functional nanostructures, nanoprocessing of carbon nanotubes, magnetic and optical properties of manganese-phosphorus nanowires, ultra-nanocrystalline diamond films, and nanophotonics communications in Azerbaijan. The mathematical methods of simulation of the group, individual and social risks are considered for the purpose of nanomaterials risk reduction and remediation. Lastly, we have conducted studies at a plant of polymeric materials (and nanomaterials), located near Baku. Assessments have been conducted on the individual risk of person affection and constructed the map of equal isolines and zones of individual risk for a plant of polymeric materials (and nanomaterials). 1.

Introduction

Nanotechnology can be defined as the control and restructuring of matter below 100 nm in size in order to create materials, devices, structures and functional systems. Simply put, nanotechnology is the direct manipulation of matter at the level of atoms and molecules [1]. Restructuring nature at the nanoscale leads to materials with novel and exotic properties. For existing substances and materials remade at the nanoscale, these properties are significantly different to their larger equivalents. The novel properties of nanomaterials make them attractive for use in industrial processes. Many reports were devoted to nanotechnology in biology and business for the developing World, formation of charged nanoparticles for creation of functional nanostructures, nanoprocessing of carbon nanotubes, magnetic and optical properties of manganese-phosphorus nanowires, ultra-nanocrystalline diamond films, and

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nanophotonics communications in Azerbaijan (2007, Baku, Azerbaijan) [2]. Several are mentioned below. Firstly, N. Mamedov from Institute of Physics National Academy of Sciences of Azerbaijan has made the report, “Photonics (nanophotonics) and optical communications in Azerbaijan: horizons for development”. He noted that current optical research is directed towards the advanced design and fabrication of optical fibers, integrated optics, optical amplifiers, optoelectronic devices and nanostructures, which are all photonic devices. Although research, education, and training on photonics and nanophotonics in Azerbaijan can hardly be taken for fully adequate to the word standards, the forecast given by the Ministry of Communications and Information Technologies with regard to optical communications is optimistic with a significant increase in the nearest future. Secondly, Y. Nakavama from Osaka University (Japan) has made the report “Preparation and nanoprocessing of carbon nanotubes”. He noted that because of their structural perfection, tiny size, low density, excellent mechanical property and unique electronic property, carbon nanotubes (CN‘I’s) have been placed in the research and development of various applications such as reinforcement with electric conductance for functionalized composites and building blocks for future nanoscale electronic or electromechanical devices In his report he reviewed recent works on the synthesis toward millimeter-long blush-like (vertically aligned) CNTs and nanoscale-engineering of CNTs. Finally, S. Habib from Nanotechnology Center King Abdul Aziz University Saudi Arabia has made the report “Nanotechnology for the Developing World”. He noted that the sheer size of global expenditure on research and development on nanotechnology is a sure indicator attesting to the very promising economical viability of nanotechnology worldwide. Presently, the private sector spends over 10 billion annually and the figure is projected to reach 12 billion in 2008, while global governmental funding on nanotechnology research and development is about 4 billion and rising. By no means this expenditure is evenly distributed among the different countries and as a matter of fact the different regions and contents of the world. A fact indicating how is the possible prime winners of exploiting the emerging trillion dollar nanotechnology market. Competing for market shares on the nanotechnology products projected to reach a trillion dollar size, some countries are spending around €10 per capita annually to develop such products. In Azerbaijan, roughly US$10 million is spent each year on the research and development of nanotechnology and nanomaterials. Nanomaterials in the form of nanoscale powders and fibres are already being used in sunscreens, cosmetics, food additives, packaging, scratch-proof and self-cleaning paints and glass, clothing, sports equipment, disinfectants, fuel additives, batteries and a range of other products. Table 1 below outlines the applications for nanomaterials that are currently in use in Azerbaijan or close to commercialization.

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Table 1. Nanomaterials currently in use in Azerbaijan. Energy and environment

Electronic Manufacturing Mining and agribusiness Health and medical

Industrial catalysts Fuel additives Membrane separation Water/air purification, fuel cells technologies Semiconductors Memory applications Flexible displays Coatings; catalysts Coatings for food protection Zinc oxide (ZnO) in paints, sunscreens Alumina platelets Mineral Separation Bioextraction; applications for particles, oxide powders Diagnostic markers Particle engineering Biosilicates for tissue engineering

Let us consider some common nanomaterials and their uses. 2.

Some Common Nanomaterials and Their Uses

Zinc oxide and titanium dioxide powder have been used in sunscreens extensively since their inception, lending them their distinctive thick white appearance [3]. While these conventional powders are opaque, nanoscale zinc oxide and titanium dioxide particles in the order of (40–50) nm are transparent while still retaining the ability to block UV rays. By substituting conventional powders of zinc oxide and titanium dioxide with nanoparticles, manufacturers are able to produce a sunscreen that is transparent when applied. In 2003 in Azerbaijan, the initial use of nanoscale titanium dioxide and zinc oxide began. Carbon nanotubes consist of carbon atoms arranged in a lattice and rolled into a tube of variable length, but only a few nm in diameter. They are needle-like in shape and have a structure similar to that of asbestos [2]. Carbon nanotubes are extremely strong, up to ten times that of steel, while remaining very light. Their high strength to weight ratio makes them especially suitable for reinforcing materials ranging from tennis rackets and car tires, to military tanks. Carbon nanotubes also exhibit novel electrical conductivity, and they are being developed for use in high performance circuits and displays. Catalytic nanomaterials are used in many different industrial processes ranging from mineral refinement, chemicals production and the manufacture of polymers (e.g. Chemical Plant of Polymer in Baku). Researchers at Rutgers University in the United States have been developing nanoscale iron and cobalt particles for use in the chemical conversion of coal to diesel [4]. With these new catalysts, researchers hope to continue transport fuel production through the conversion of coal. During the manufacture, transport, use and disposal of nanomaterials and those products containing nanomaterials, the release of these materials into the environment is inevitable. As the use of nanomaterials increases, presence in the environment will also. While pathways such as the waste stream from industrial processes or

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product disposal are similar to those for other substances, the use of nanomaterials in sunscreens and cosmetics can also lead to the environmental presence of nanomaterials. In Europe, ecologists are detecting the active ingredients of sunscreens and skin care products in inland lakes at levels that are starting to have an impact on wildlife [5]. This suggests that even the use of these consumer products, which are not traditionally seen as entering the environment after use, will likely lead to the environmental release of nanomaterials. Since nanomaterials are, can and will enter into the environment, it is crucial to assess the potential risk these materials may have for human health and environmental harm. 3.

The Risk Assessment of Nanomaterials

The unique properties and extremely small size of nanomaterials are such that even determining the full extent of the risks to human health and environment is currently beyond the means of existing risk assessment frameworks [3]. Given that nanomaterials can be more toxic than their conventional equivalents, it is clear that the risks associated with nanomaterials cannot be inferred from the relative risk or safety of their bulk equivalents. That is, although some nanomaterials are made of substances that have long been used in other forms, their very different physical and chemical properties mean they may pose different risks than conventional materials. The toxicity of a nanomaterial cannot be assumed by comparison with another nanomaterial since toxicological properties arise from a variety of features, such as their surface characteristics, size, shape, overall composition and chemical reactivity. There are in essence several independent and interdependent variables that dictate toxicity. The dedicated testing of each individual nanomaterial will be particularly pertinent when next-generation nanotechnology develops complex nanostructures and devices those themselves actively interact and manipulate molecules and organic compounds. The level of interactions possible with living organisms and the wider environment will be so broad and complex that the data derived from testing one next-generation nanomaterial cannot be used to determine the safety or risk of any other next-generation nanomaterial due to the inordinate number of variables in play. While there is an established methodology for assessing the toxicity of conventional substances, the report into the risks associated with Nanomaterials by Britain’s Royal Society notes that current testing regimes are not entirely suitable for nanomaterials [6]. For example, the European Commission’s Scientific Committee on Emerging and Newly Identified Health Risks has suggested that any determination of the critical dose of nanomaterials must also take into account the number of particles and total surface area, rather than just the exposure mass of a substance, which is the current practice [3]. In addition, the effects of surface characteristics and coatings, their size and shape, physical composition and chemical reactivity, and the potential for aggregation (clumping) all need to be specifically tested to develop a comprehensive assessment of the risks of nanomaterials. The Royal Society flags as a priority the need to establish a standardized set of methodologies to

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effectively assess the contribution of all these factors to nanotoxicity in both the environment and in humans [6]. Current toxicological methodologies express toxicity with respect to a critical mass concentration beyond which harm occurs. Yet hazardous dosages expressed in mass concentrations do not give an accurate indication of the exposure amount for nanomaterials above which harm is induced. The minimum toxic dose for nanomaterials is also affected by the total surface area available for biological reaction and the number of particles present. The risk assessment of nanomaterials is further complicated by a lack of established standardized indicators for nanotoxicity. While factors such as surface characteristics and coatings, shape, physical composition and chemical reactivity, and the potential for aggregation may all play a role in nanotoxicity, their exact contribution is not known. Researchers are still clarifying the way nanomaterials are transported within living organisms and the regions and organs in which they concentrate. This information is essential in establishing the risk of nanomaterials as it gives an indication of which organs and processes are most vulnerable to toxic effects. The extremely small size of nanomaterials puts them completely beyond the ability of optical microscopes to detect and analyse. The instruments required to track and observe nanomaterials, such as scanning tunneling microscopes and atomic force microscopes, are extremely expensive machines that are confined to the laboratory. Even for toxicological studies conducted within the lab using cell cultures or test animals, these instruments are unsuitable for tracking and analyzing nanomaterials within individual organisms or single cells. This makes it difficult to study the behaviour of nanomaterials in living organisms and is one of the reasons why this area of knowledge is so limited. And so, without a coherent testing regime within which the risks of nanomaterials can be appropriately assessed, it is currently impossible to make informed decisions regarding their handling and use. Not only is there not enough information about the actual hazards of nanomaterials currently in use to effectively manage these risks, but there are no established risk assessment regimes capable of considering the unique characteristics and properties of these new materials. 4.

Simulation of Risk Assessment of Nanomaterials

At normal functioning, the analysis of nanomaterials manufacture shows, the influence of such objects on an environment is connected both to social– psychological influence on people and with the potential danger of pollution of an atmosphere and territory dangerous substances [8–12]. Therefore, the model of risk should reflect all essential factors on which functioning system to the greatest degree depends should be taken into account. Output parameters of mathematical model of risk determine a mathematical expectation of amount of the affected people living in area of industrial object [13]. We shall consider possible analytical approaches to the decision of a

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problem. The mathematical expectation (risk R) of amounts of affected people can be determined dependence. 2π

R =

∞

∫ ∫ r (ϕ , l ) ⋅ P(ϕ , l )dϕ ⋅ dl ,

ϕ =0 l =0

Where: r(ϕ,l) is a distance from a plant up to the person in polar coordinates (the beginning of coordinates is superposed with plant); P(ϕ,l) is a probability of affection of the person in a point with (ϕ,l) coordinates. The probability of affection P(ϕ,l) is defined as follows: P(ϕ,l) = P0(ϕ)⋅Pl(l,ϕ0), Where: P0(ϕ) is a probability of that at the moment of emission the direction of wind ϕ = ϕ0 will be realized; Pl(l,ϕ0) is a probability of affection on distance l from a place of emission in direction ϕ0. As a pollution is equiprobable at any moment then P0(ϕ) should be defined on the basis of a wind rose in the given zone or region. If to neglect differences in characteristics of an underlying surface on each of directions of possible distribution of harmful emission and to enter concept of the average characteristic, it is possible to simplify essentially a problem, having divided variables:

R =

l =∞

ϕ = 2π

l =0

ϕ =0

∫ P(l )

∫ r (ϕ , l ) ⋅ P(ϕ )dϕ ⋅ dl

This approach to calculation of risk criterion is one of possible variants of an analytical method of assessment. In practice of risk assessment, the following approaches to mathematical modelling risk are considered. Modeling of individual risk. Individual risk is the probability of the person affection in the course of year from the certain reasons in the certain point of space. Results of the analysis of individual risk are displayed on a map of the plant as the closed lines of equal values (isolines). The construction of isolines of individual risk is carried out under the formula (1)

Ri ( x, y ) =

∑ ∑P (

m∈M

l∈L

Q x, y )

F ( Am )

(1)

Where: PQ(x,y) is a probability of influence on the person in a point with coordinates (х, у) of the damaging factor Q with the intensity corresponding to affection of the person (healthy man of 40 years) under condition of realization of Ат event (pollution); F (Am) is frequency of occurrence of Ат event per year; M is a set of indexes which corresponds to considered events; L is a set of indexes which correspond to the list of all damaging factors arising at considered events.

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We have carried out researches at a plant of polymeric materials (and nanomaterials), located near to Baku. Isolines of equal risk and zones of individual risk are resulted on Figure 1 for this factory. We can see from Figure 1, that near of plant (zone 1) the individual risk of person affection is high, R = 10−4. In zone 2 R = 10−5 (the individual risk of person affection is acceptable). Lastly, in zone 3 R = 10−6, i.e. the individual risk of person affection is low.

Figure 1. Construction isolines of equal risk and zones of individual risk for a plant of polymeric materials (and nanomaterials): 1, 2, 3 are zones of accordingly high, acceptable and low risk.

Modeling of social risk. The social risk is a dependence of occurrence frequency of the events causing affection of people, on this number of people. Social risk R F (N) characterizes scale of possible extreme situations. The social risk can be designed under the formula (2)

Rs ( N ) =

⎛ N ⎞ ⎛ Qm ⎞ ⎟⎟ P⎜⎜ ⎟⎟ F ( Al ) , ⎝ m ⎠ ⎝ Al ⎠

∑ ∑ P⎜⎜ Q

m∈M

l∈L

(2)

⎛ N ⎞ ⎟⎟ is a probability of N people affection from the damaging factor P⎜⎜ ⎝ Qm ⎠ ⎛Q ⎞ Qm; P⎜⎜ m ⎟⎟ is a probability of occurrence the damaging factor Qm at realization ⎝ Al ⎠

Here:

events Al. Modeling of risk at accidents on chemically dangerous plants manufacturing of nanomaterials. On known toxic dose D in a point with coordinates (х, у) a mathematical expectation of losses among population M (N) is determined under the formula

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M (N ) =

∫ ∫ P[D(x, y )]⋅ψ (x, y )dxdy

(3)

Sr

Where: Sr is an integration domain, i.e. the area of a part of city within the limits of which people affection is possible at accidents on the set plant; ψ(x,y) is a density of people location in vicinities of a point with coordinates (x, y); P[D(x,у)] is a probability of people affection depending on amount of a toxic doze in a point of city with coordinates (х, у), determined from the parametrical law of people affection harmful substances; D (x, у) is the toxic doze chemically dangerous substance for a point with coordinates (х, у) under the formula tk

D(x, y ) = ∫ Ω(x, y, t )dt tn

Where: tn..........tk are intervals of time; Ω(х,у,t) is a concentration of chemically dangerous substance in an atmosphere for a point with coordinates (х, у) during the set moment of time (t). Under the formula (3), mathematical expectation of losses is determined for a case when the initial data are known. It is necessary to take into account variability of a direction (θ) and speeds of a wind (v) within 1 year. Then losses can be determined under the formula M (N ) =

2π Vmax

∫ ∫ ∫ ∫ f (θ ,V )P[D(x, y )]ψ (x, y )dVdθdxdy

Sr

0

(4)

Vmin

Where: f(θv) is a function of density of distribution of a direction 0 and speed v a wind; vmin and vmax are minimal and maximal possible values of speed of a wind; Sr is an integration domain. Other designations are same, as in the formula (3). Taking into account expression (4), the assessment of individual risk at a plant can be carried out under the formula

Re =

H N

2π Vmax

∫ ∫ ∫ ∫ f (θ ,V )P[D(x, y )]ψ (x, y )dVdθdxdy

Sr

0

Vmin

Where: H is a probability of pollution in the course of year; N is population size. 5.

Conclusion

Various aspects of modern nanotechnologies and risks of nanomaterials impact on an environment are considered. The mathematical methods of simulation of the group, individual and social risks are considered for the purpose of nanomaterials

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risk reduction and remediation. We have carried out researches at a plant of polymeric materials (and nanomaterials), which is located near Baku. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

M.M. Nordan and M.W. Holman (2005) A prudent approach to nanotechnology environmental, health and safety risks. Industrial Biotechnology 1(3): 146. Book of Abstracts (2007) First International Conference on Material and Information Sciences in High Technologies, Baku, Azerbaijan. A. Tolstoshev (2003) Nanotechnology: Assessing the Environmental Risks for Australia, Earth Policy Centre, Melbourne, Australia. K. Bullis (2006) Clean Diesel from Coal, MIT Technology Review, 26 April 2006. P.J. Borm et al. (2006) The potential risks of nanomaterials - a review carried out for ECETOC. Particle and Fibre Toxicology 3(11): 41. Royal Society (2004) Nanoscience and Nanotechnologies, The Royal Society, London, p. 46. EPA (2005) Nanotechnology and the Environment: Applications and Implications Progress Review Workshop/// p.88. V.F. Martinuk et al. (1995) Risk analysis and its supply of standard. Industrial Safety 11: 55–62. Kandlikar, M., Ramachandran, G., Maynard, A., Murdock, B., and Toscano, W.A. (January 2007) Health risk assessment for nanoparticles: a case for using expert judgment. Journal of Nanoparticle Research 9(1): 137–156. Owen, R. and Handy, R. (August 2007) Formulating the problems for environmental risk assessment of nanomaterials. Environmental Science & Technology, 41(16): 5582– 5588. Sweet, L. and Strohm, B. (June 2006) Nanotechnology - life-cycle risk management. Human and Ecological Risk Assessment, 12(3): 528–551. Tyshenko, M.G. and Krewski, D. (2008) A risk management framework for the regulation of nanomaterials. International Journal of Nanotechnology, 5(1): 143–160. Roy L. (February 1994) Smith Use of Monte Carlo Simulation in Risk Assessments. US Environmental Protection Agency. EPA903-F-94-001.

CONSIDERATIONS FOR IMPLEMENTATION OF MANUFACTURED NANOMATERIAL POLICY AND GOVERNANCE

F.K. SATTERSTROM Harvard University School of Engineering and Applied Sciences Cambridge, MA 02138, USA [email protected] A.S.A. ARCURI Foundation on Occupational Safety and Health Researches and Studies (FUNDACENTRO) Ministry of Labour and Employment Rua Capote Valente 710 São Paolo 05409-002, Brazil T.A. DAVIS Department of Chemistry, University of Montreal C.P. 6128, succursale Centre-Ville Montreal (QC) H3C 3J7, Canada W. GULLEDGE American Chemistry Council 1300 Wilson Blvd., Arlington, VA 22209, USA S. FOSS HANSEN Department of Environmental Engineering, Nano DTU Technical University of Denmark Building 113 Kgs. Lyngby DK-2800, Denmark M.A. SHAFY HARAZA Quality Assurance, Quality Control Department National Center of Nuclear Safety and Radiation Control Atomic Energy Authority Ahmed El Zomor Street Nasr City 11672 Box 7551 Cairo, Egypt L. KAPUSTKA LK Consultancy 8 Coach Gate Place SW Calgary, AB T3H 1G2 Canada [email protected] I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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D. KARKAN Nanotechnology Health Products and Food Branch A.L. 2005A, Graham Spry Building Ottawa, Ontario K1A 0K9, Canada I. LINKOV US Army Engineer Research and Development Center Concord, MA 01742, USA M. MELKONYAN Institute of Crystallography of RAS Leninsky pr., 59 Moscow 119333, Russia J. MONICA Porter Wright Morris & Arthur LLP 1919 Pennsylvania Avenue NW, Suite 500 Washington, DC 20006-3434, USA R. OWEN Department for Environment, Food and Rural Affairs (DEFRA) Environment and Human Health Programme, UK Environment Agency Block 1 Government Buildings Burghill Road Bristol BS10 6BF, UK J.M. PALMA-OLIVEIRA Faculty of Psychology and Sciences of Education (FPCE) University of Lisbon, Alameda da Universidade 1100 Lisboa, Portugal B. SRDJEVIC Faculty of Agriculture, University of Novi Sad Trg D. Obradovica 8 Novi Sad 21000, Serbia

Abstract. Many policy frameworks for risk assessment of manufactured nanomaterials have been developed worldwide. These frameworks range from voluntary methods and self-regulation to prescriptive regulation. In our view, the regulatory policies ideally need to include consideration of the risks and benefits of nanotechnology, as well as risk perception and risk communication efforts. Further, the policies should: (a) take a holistic viewpoint, considering the entire lifecycle of a manufactured nanomaterial, including use, production, transport, and disposal, and

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(b) consider the ecological and human health effects for all of the reasonably foreseeable exposures. There is a need for adaptive management to allow reaction to new developments (e.g., new toxicology information) and to gain additional information through policy.1– 2 1.

Introduction

The authors of this chapter were members of the Considerations for Implementation of Manufactured Nanomaterial Policy and Governance Working Group at the NATO Workshop on Nanomaterials Risks and Benefits (Faro, Portugal, April 2008). The working group (WG) focused on risk assessment and policy frameworks. This chapter includes the original focus and also discusses guidance on methods for policy development based on the best available science, as well as the information and tools (e.g., databases, modeling software, and web portals) that (a) support the development of policies by regulators, industry, and others, and (b) efficiently disseminate information to the public and others. The foundation for the WG’s efforts was a recent book chapter [24] that reviewed current nanomaterial risk management frameworks and related documents developed by regulatory agencies, trade associations, not-for-profit organizations, academics, and companies, including an in-depth review of 13 such documents. Table 1 lists 11 documents reviewed by Linkov and Satterstrom, and the WG added one additional recently published U.S. government multi-agency framework (National Nanotechnology Initiative, NNI) and the European Union’s recently enacted Registration, Evaluation, Authorisation, and restriction of CHemicals (REACH) legislation. In all, the models and frameworks include comprehensive state-of-thescience regulation framework documents, voluntary programs, documents on the regulation and ethics of nanomaterials, and position statements. The Linkov and Satterstrom chapter developed a list of criteria based on work being undertaken by Health Canada on nanotechnology, with the categories being: (1) Science and Research Aspects; (2) Legal and Regulatory Aspects; (3) Social Engagement and Partnerships; and (4) Leadership and Governance. Within each category, Linkov and Satterstrom modified Health Canada’s specific criteria to fit their categories. For example, the “Science and Research Aspects” are adapted from the US Nanotechnology Environmental and Health Implications Working Group’s research needs categories, and the Legal and Regulatory Aspects are adapted from the Woodrow Wilson Center. The WG also reviewed the NNI and REACH in the same manner, with the results included in Table 1.

1 2

Summary of the NATO ARW Working Group discussions.

The views and opinions expressed in this paper are those of the individual authors and not those of the US Army, NATO, or other sponsor agencies.

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TABLE 1. Overview of papers discussing different aspects of the nanomaterial risk assessment process in Linkov and Satterstrom [24], with information added by the Working Group for the NNI and REACH. Elements of nanomaterial regulation frameworks discussed in each document (criteria are numbered 1–4 under each category; for each document and criterion, ■ = document discussed the criterion, ▪ = document mentioned the criterion, and (blank) = document did not address the criterion).

Sub-criteria for the table are as follows: Science and research aspects 1. Development of methods for detection/characterization/data collection 2. Assessment of environmental fate & transport/impacts 3. Assessment of toxicology/human health impacts 4. Assessment of health and environmental exposure Legal and regulatory aspects 1. Voluntary regulatory and best-practices measures 2. Information-based regulatory tools (e.g., labeling) 3. Economic-based regulatory tools (e.g., tax or fee for safety testing) 4. Liability-based regulatory tools (e.g., penalty for pollution)

Category 3: Social engagement and partnerships 1. Promotion of education and distribution of information/use of risk communication tools 2. Use of stakeholder engagement tools 3. Development of partnerships with academia, industry, public organizations, provinces, and international regulators 4. Emphasis of ethical conduct Category 4: Leadership and Governance 1. Transparency in nanotechnology-related decisions 2. Consideration of benefits of nanotechnology 3. Adaptive modification of existing or development of new legislation 4. Consideration of precautionary principle

The WG agreed with the conclusion from the Linkov and Satterstrom chapter that regulatory tools should be further assessed to ensure availability of the methodology and knowledge base necessary to regulate manufactured nanomaterials. Further, the WG agreed that the starting point for further development of these tools is the set of risk assessment and risk management policies and procedures already developed by regulatory agencies and industry for traditional industrial materials, such as surfactants and other chemical substances. 2.

Regulatory Gaps and Review of the Current Landscape

This section presents a summary of current regulatory frameworks and trends reported and discussed at the NATO Workshop.

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EU PERSPECTIVE

The identification of limitations of the current regulation of nanomaterials has been subject to intense international scrutiny. European legislation covers nanomaterials in principle [14, 15], and four areas are especially relevant to nanomaterial regulation: (1) the new chemical legislation termed Registration, Evaluation and Authorisation and restriction of CHemicals (REACH); (2) food laws; (3) the safety at workplace directives, and, finally, (4) waste management directives [19]. REACH went into force in early 2007, establishing an authorizing system that requires the registration and evaluation of existing and new chemical substances marketed in the EU [17]. Under REACH, a chemical substance is defined as: a chemical element and its compounds in the natural state or obtained by any manufacturing process, including any additive necessary to preserve its stability and any impurity deriving from the process used, but excluding any solvent which may be separated without affecting the stability of the substance or changing its composition [17]. In theory, the wide definition of a chemical substance under REACH covers nanoscale substances [5]. However, REACH has at least two major limitations of its potential application to nanoparticles. First, registration is based on chemical composition, which means that, for instance, C60 and carbon nanotubes could in theory be included under the same registration as carbon black, and nano-sized TiO2 could be included under the same registration as micron-sized TiO2, despite the fact that it is well-known that these have vastly different chemical and biological properties [8, 19]. Another potential limitation of REACH is that requirements for producers and importers to provide toxicological data and requirements for assessing environmental exposure are based on mass thresholds. Data sets are not required until production or imported volumes are above the threshold of 1 t/year of substance. For many nanoparticles, this threshold would hardly be reached in the short term [5, 19] low concentration of nanoparticles in a final product article is likely to exclude many nanoengineered articles from the REACH legislation, since no registration is required when the concentrations of a substance is lower than 0.1% w/w [19]. Just as REACH in theory covers nanomaterials, so do EU food laws, since the EU Food Law Regulation requires all food to be safe [18]. This in theory applies to all foods and food packaging containing nanomaterials as well; however, the laws have been criticized for being too loose [20]. None of the existing EU regulations applicable to agriculture, food, or food packaging currently consider or mention nanoscale products or materials, nor do they require new safety assessment or labeling due to particle size [20]. Future regulation may include nanomaterials more explicitly. The European Parliament’s Committee on the Environment, Public Health and Food Safety stated last year that it wanted separate limit values for nanotechnologies and that the permitted limits for a nanoparticle additives should not be the same as for traditional food additives [21]. Additionally, in a recent proposal adopted by the

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European Commission to revise the EU Novel Foods Regulation, the definition of novel food includes foods modified by new production processes, such as nanotechnology and nanoscience, which might have an impact on the food itself [9]. The European Food Safety Authority (EFSA) is also currently preparing an initial scientific opinion on the potential risks arising from the use of nanotechnology in food, expected by 31 March, 2008 [20]. The Safety at Workplace Directives include no direct reference to workers’ potential exposure to engineered nanoparticles, nor does the communitarian and national legislation on the protection of workers’ health at workplaces [19]. The Framework Directive 89/31 and Directive 98/24 on the risks associated with chemical substances set guidelines to establish Occupational Exposure Limits (OELs) for workers [10, 11]. However, there are three main problems associated with the establishment of OELs for workers at this point: 1. The establishment of OELs is typically based on a complete risk assessment procedure which is presently not possible for engineered nanoparticles. 2. OELs are based on mass concentration being a proper metric for toxicity, but the most optimal parameter(s) to determine nanoparticle toxicity is still undefined. 3. Nanoparticles are not easily detected and monitored in the workplace and it is unclear whether existing personal protective equipment is adequate [19]. Just as with the safety at workplace directives, there are no specific references to engineered nanoparticles in existing laws. Hence, nanomaterial-including wastes are tackled by waste management regulations in a non-specific way [19]. In some cases, the nano-waste can fall within a particular waste category; for example, C60 in oil lubricants is specifically regulated [19]. If a certain nano-waste falls within the scope of Council Directive 1991/689 on the management of hazardous waste [12], more severe obligations would apply. Again, the lack of (eco)toxicological data makes it difficult to state if nanoparticles meet the criteria of hazardousness [19]. 2.2.

U.S. PERSPECTIVE

The regulation of engineered nanoscale materials at the federal level in the United States is currently accomplished through the application of existing environmental, health, safety, food, drug, and workplace laws. Engineered nanoscale materials are primarily subject to the regulatory authorities enforced by the Environmental Protection Agency (EPA), Food and Drug Administration (FDA), Occupational Safety and Health Administration (OSHA), and the Consumer Product Safety Commission (CPSC). Whether new nano-specific laws, regulations, and/or guidance documents are needed is the subject of vigorous research, analysis, and debate. 2.2.1.

EPA

The EPA currently uses existing laws and regulations to guard against any potential nano-related environmental health and safety (EHS) risks. The most prominent

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laws in this scheme are the Clean Air Act, Clean Water Act, Safe Drinking Water Act, Resource Conservation and Recovery Act, Comprehensive Environmental Response Compensation and Liability Act, Federal Insecticide, Fungicide, and Rodenticide Act, and the Toxic Substances Control Act (“TSCA”). The EPA has primarily relied upon TSCA thus far. The EPA has comprehensive authority to regulate the production and use of all chemical substances under TSCA, including engineered nanoscale materials. If the EPA makes the requisite findings that a specific chemical substance poses a substantial EHS risk, it has full power to limit or ban that substance. No such findings have been made (or asserted) for any engineered nanoscale material. Further, any new chemical substance or significant new use of an existing chemical substance requires premanufacturing review and approval by the EPA under TSCA. The EPA determines whether an engineered nanoscale material is a new chemical substance or significant new use of an existing chemical substance based on the case-by-case approach that the Agency has historically applied in determining the TSCA inventory status of chemical substances. Under its TSCA powers, the EPA initiated a voluntary information collection program for engineered nanoscale materials in January 2008. The EPA’s Nanoscale Materials Stewardship Program (NMSP) is intended to provide a firm scientific foundation for any future regulatory action by encouraging submission of hazard and other information including risk management practices for nanoscale materials. The EPA worked extensively with interested stakeholders on the NMSP’s design, which has two levels: a “basic” and an “in-depth” program. ƒ Basic program: Participants were invited to voluntarily report available information (including material characterization, hazard, use, potential exposures, and risk management practices) on any engineered nanoscale materials they manufacture, import, process, or use. The EPA developed a data form for submitting this information, but participants were asked to provide available data in any convenient format. Additionally, the EPA did not ask participants to develop any new information, only to submit existing data. Participants who had already developed a risk management plan were invited to include the plan as part of their submission under the basic program. The EPA further encouraged participants who do not have a risk management plan to consider developing one and provide it with their basic submission. ƒ In-depth program: Participants are invited to voluntarily develop data (including testing if needed) over a longer timeframe. Entities or consortia with an interest in developing data for a specific nanoscale material(s) were requested to notify the EPA at any time. Once potential participants are identified, the EPA will facilitate a process leading to data development. The EPA states: “The data and experience generated by the basic program, including input from the interim program evaluation, will help to inform the types of in-depth data that need to be developed.” As of late July 2008, the EPA has received submissions under the Basic Program from 19 companies covering 90 nanomaterials. An additional 11 companies committed to the EPA to provide

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information, also under the basic program. Three companies volunteered to participate in the in-depth program. 2.2.2.

FDA

Because it is already accustomed to dealing with products that interact with the body at the nanoscale level, the FDA believes existing laws, regulations, and product review and approval processes should be sufficient to ensure against any potential EHS risks posed by the use of nanoscale materials in food, drugs, medical devices, biologics, blood & vaccines, animal & veterinary products, cosmetics, radiation-emitting products, and combination products. To this end, FDA employs a “product-by-product” approach that may include one or more of the following: ƒ Premarket Approval: Prior to introduction into the marketplace, new pharmaceuticals, high-risk medical devices, food additives, colors, and biological substances require prior approval by the FDA. Typically, the producer/sponsor of the product identifies and assesses the risks presented by the product and addresses each risk and how it will be minimized in a product application. FDA staff then reviews these documents, often with the assistance of an Advisory Committee. A pre-approval inspection of the manufacturing plant is often required. ƒ Premarket “Acceptance”: These products are often similar to products that were approved previously or are products prepared in accordance with approved specifications, such as pharmaceuticals manufactured to existing USP Monographs and medical devices marketed with 510(k) Premarket Notifications. The review process of these products is significantly more rapid than Pre-Market Approval. ƒ Post-Market Surveillance: In this third category, the FDA manages the risks of products like foods, cosmetics, radiation-emitting electronic products, and materials such as food additives and food packaging that are “generally recognized as safe” (GRAS). For these products, market entry and distribution are at the discretion of the manufacturer/producer. All of these products are generally regulated by the application of Good Manufacturing Practices. FDA monitors the behavior of these products and takes regulatory action if adverse events occur that threaten public or individual health. 2.2.3.

OSHA

Potential workplace exposure risks are regulated under existing OSHA standards. No nano-specific workplace exposure standards have been deemed necessary as of the date of this paper. Additionally, the National Institute for Occupation Health and Safety informs and advises OSHA regarding workplace exposure issues and has published a strategic research plan and workplace handling guidance documents specifically addressing the use of engineered nanoscale materials in the workplace.

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CSPC

Certain widely-used consumer products containing engineered nanoscale materials are regulated by the CPSC under existing laws. The CSPC’s resources are stretched, although its FY 2009 budget contains its first ever nano-specific funding for research and study. While the CSPS believes its existing laws are sufficient to cover nanoscale materials, it also notes that the nanoscale products it regulates are not subject to premarket approval; thus, the CPSC may not become aware of some potential EHS risks involving these products until reported after the fact. 2.2.5.

Municipalities and States

Finally, two American municipalities have created registries for engineered nanoscale materials – Berkeley, California and Cambridge, Massachusetts. Several states are contemplating similar initiatives. Berkeley’s hazardous materials handling ordinance was amended in December 2006 to encompass engineered nanoscale materials. The ordinance requires: All facilities that manufacture or use manufactured nanoparticles shall submit a separate written disclosure of the current toxicology of the materials reported, to the extent known, and how the facility will safely handle, monitor, contain, dispose, track inventory, prevent release and mitigate such material3 […] All manufactured nanoparticles defined as a particle with one axis less than 100 nanometers in length, shall be 4 reported in the disclosure plan. So far, only a handful of companies have submitted information responsive to Berkeley’s ordinance. Further, Cambridge, Massachusetts studied the same issue during 2008 and determined that: [i]n the absence of acceptable exposure standards, the Cambridge Public Health Department, with the invaluable guidance offered by the Nanomaterials Advisory Committee, has concluded that active and constructive collaboration with firms and institutions in Cambridge that currently manufacture, process, or conduct research on engineered nanoscale materials is the most reasonable and effective strategy at this time for reducing health risks to workers, students, and residents. In keeping with this conclusion, in July 2008, Cambridge’s City Council adopted a six-part plan for dealing with possible EHS risks related to engineered nanoscale materials: 3 Berkeley, California, Municipal Code, Chapter 15.12, Hazardous Materials and Waste Management, Section 15.12.040(I), Filing of disclosure information. 4 Berkeley, California, Municipal Code, Chapter 15.12, Hazardous Materials and Waste Management, Section 15.12.050(C)(7), Quantities requiring disclosure.

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1. Have the Cambridge Fire Department and the Local Emergency Planning Committee establish an inventory of engineered nanoscale materials being manufactured, handled, processed, or stored in the city 2. Work with academia and industry to offer assistance to companies to help evaluate and limit potential workplace exposure to nanoscale materials 3. Educate the public concerning products containing nanoscale materials 4. Track nano-related EHS science and studies as they develop 5. Track the status of regulations and best practices concerning nanoscale materials as they develop and 6. Report back to the City Council every 2 years on any new development in these areas 2.3.

CANADIAN PERSPECTIVE

The Canadian Environmental Protection Act, 1999 [7] is in place to contribute to sustainable development through pollution prevention and the protection of environment and human health. Under the Act, provisions are outlined for both new and existing substances as well as establishing a legal regime for information gathering and assessment powers. The Domestic Substance List (DSL) is the sole basis for determining whether a substance is new in Canada, and any substance not listed on the DSL is considered to be new, and thereby subject to New Substances Notification Regulations (NSNR). These regulations ensure that any new substance undergoes a risk assessment of its potential effects on the environment and human health. Currently in Canada, the Act and the Regulations apply to new nanomaterials in the same way as any other substance, as outlined in the New Substances Program Advisory Note 2007–06. Although there is no internationally recognized definition of a nanomaterial, they can be described as substances having one or more dimensions in a nanoscale range. Accordingly, nanomaterials which are manufactured in or imported into Canada are subject to the same regulatory requirements as chemicals and polymers. In this framework, nanomaterials which are manufactured in or imported into Canada that are not listed on the Domestic Substance List are considered new and thereby subject to the Regulations. The nanoscale form of a substance on the DSL is viewed to be new if it has “unique structures or molecular arrangements.” As an example, the nanomaterial fullerene (CAS No. 99685-96-8) is not listed on the DSL and is therefore considered as a new substance in Canada. Under the “Proposed Regulatory Framework for Nanomaterials Under the Canadian Environmental Protection Act, 1999” [6], Environment Canada and Health Canada propose a two-phase approach for a regulatory framework for nanomaterials. The proposal emphasizes the importance of being scientifically robust as well as harmonized with international efforts. The two-phase approach is based on short- and long-term objectives. Phase 1 (2006) consists mainly of working with international partners to develop scientific and research capacities, informing potential notifiers of their regulatory responsibilities under the current framework, developing information-gathering initiatives, and considering whether

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amendments to CEPA [7] or the New Substances Notification Regulations will be needed. Phase 2 (beginning 2008) consists of a focus on terminology and nomenclature by ISO TC229, consideration of data requirements under NSNR, and consideration of the Significant New Activity (SNAc) provision of CEPA [7] to require notification of nanoscale forms of substances already on the DSL. 2.4.

OTHER GLOBAL PERSPECTIVES

The United Kingdom has been in the forefront of developing and implementing voluntary environmental programs for nanomaterials, including one run by the UK Department for Environment, Food and Rural Affairs (DEFRA). The DEFRA voluntary reporting scheme is intended to: develop a better understanding of what types of engineered nanoscale materials are likely to be produced in the UK, and to build up an understanding of their properties and characteristics so that the potential hazard, exposure and risks associated with these materials may be determined [28]. The program is intended to run for 2 years. Industry is asked to submit existing data on the characteristics of engineered nanoscale materials, including information on material characterization, hazard, use and exposure potential, and risk management practices. Submission of all available information is encouraged and lack of a complete package of data should not keep companies from reporting under the scheme [28]. However, DEFRA does not request that industry develop new data and even discourages industry from generating any additional data that would require animal testing [28]. After 6 months of implementation, only nine submissions have been received by DEFRA, two from academia and seven from industry [30]. The Brazilian co-author of this chapter, an occupational exposure expert, noted potential special considerations regarding worker exposures when developing and implementing policies and regulations for manufactured nanomaterials. Workers may present the main exposure risk potential among humans, and they may be involved in the entire product life cycle. These activities imply that workers may be exposed to these products for a much longer time than the general population, and to potentially much higher concentrations as well. This situation is of special concern when there is the possibility of nanomaterial release to the atmosphere, especially in the form of nanoparticles. It is also of special concern when activities involve possible dermal contact with the nanoparticles. These possible workplace exposures require specific regulations concerning the production and use of the manufactured nanomaterials, aimed at eliminating or at least minimizing the possibility of occupational exposures to these products. It is also important to remember that the workers have the right to know the type of agents to which they may be exposed. Recommendations about regulations should thus include consideration of the workplace. Additionally, the WG notes that developing countries may be affected by the nanotechnology products manufactured in developed countries [1], that Russia has

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taken initial steps in nanotechnology risk assessment, and that Israel is active in nanotechnology research as well. 3.

Considerations for Development and Implementation of Policy and Governance

In addition to the prescriptive regulation discussed above, voluntary and other programs have also been initiated to regulate nanomaterials. 3.1.

VOLUNTARY ENVIRONMENTAL PROGRAMS

Given the gaps and limitations of the current regulation, the questions as to whether or not or how to regulate the manufacture and commercialization of nanomaterials have become the subject of heated debate internationally. Several governments have opted to implement voluntary environmental programs (VEPs), arguing that this is the only viable proportional option for the time being [22, 28, 29, 31, 33]. Two such VEPs, both already discussed, are the voluntary Nanoscale Material Stewardship Program implemented in the US in 2008 and the voluntary reporting scheme for engineered nanoscale materials implemented in the UK in 2006. It remains to be seen whether voluntary measures will be enough to generate up-to-date and relevant health and safety information to ensure protection of health, safety, and the environment. It is generally known that key elements of any successful VEP are incentives to participate for various stakeholders, agency guidance and technical assistance, signed commitments and periodical reporting, quality of information, and transparency in design, reporting, and evaluation. However, Hansen and Tickner [22] recently found that many of these elements have not been fully addressed in VEPs currently implemented on nanomaterials in the UK and the US. After 2 years of the DEFRA program implementation and 6 months of implementation in the US, the number of submissions received remains small [13, 30]. 3.2.

INTEGRATION OF RISK ASSESSMENT, COST-BENEFIT ANALYSIS, AND MULTI-CRITERIA DECISION ANALYSIS

Conventional methods and decision-support tools such as risk assessment, costbenefit analysis, and risk-benefit analysis have a number of limitations and have often proven inadequate to deal with complex and uncertain environment and health problems such as the ones posed by nanotechnologies [16, 34]. For instance, entities such as economists, governments, and public health agencies tend to think in utilitarian terms, assuming that, when faced with risks, all available information is used to calculate the expected value of costs and benefits. The best choice is then assumed to be the one with the greatest expected net benefits. However, in realistic political discourse, people tend to include values such as distribution of risks and benefits, dread of the unknown, fear of the

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uncontrollable, and anger at unfairness as well as the expected value of harm [26, 27, 34]. Conventional decision-support tools might be used in decision-making processes to help inform the often challenging decisions about competing risks. However, this requires due consideration of their limitations, and it is important to remember that the decisions need to be informed by public values (that is to say, value conflicts cannot be solved by science alone) [32, 34]. Past efforts have focused on identifying the exact quantitative risk or cost-/risk-benefit ratio of particular risks rather than providing guidance to decision-makers on how to interpret risk numbers and decision alternatives. Furthermore, they have provided little guidance on what to do with available information or on what actions might be warranted given the information, thus falling short of its ultimate aim [34]. Instead of going to great lengths trying to use and adapt conventional decisionsupport tools for nanomaterials, a trade-off analysis for manufactured nanomaterials could be focused on mapping and understanding known and suspected risks and benefits, and the availability of risk-superior alternatives (through alternatives assessment) without necessarily translating them into a common metric cost [2]. All effects should be described in their natural units and the time period in which each effect is experienced should be fully revealed, as should the uncertainties, e.g., in risk and probability distributions [2]. Group Producers Workers Consumers Others

Economic effects C$ C$ C$ C$

Health/safety effects

Environmental effects

BH/S BH/S BH/S

EH/S

In order to make the trade-off analysis successful, a broad stakeholder representation should be sought to enable a holistic analysis of the known and suspected risks and benefits. The lack of information for “red flags” such as persistence or bioaccumulation of nanomaterials should be considered as indicators of a strong potential for negative surprises. A wide range of preventive regulatory options must then be explored and implemented. Tradeoffs should not seem as inevitable, but rather spark additional research and investment into risk-superior alternatives, exploiting the fact that proactive regulatory measures to improve public health can spark innovation within industry [3, 4, 25]. 4. 4.1.

Policy Challenges CHALLENGES

The WG agreed that the challenges for manufactured nanomaterial-related policies include consideration of the risks and benefits of these materials and their uses. However, instead of focusing on estimating the exact risks and benefits, the WG noted that the efforts should be directed toward understanding tradeoffs and finding superior risk alternatives given information currently available.

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Another challenge is how to include a thorough understanding of risk perceptions, which can depend on the applications in which the technologies are being used, and then developing appropriate risk communication efforts. Public perception of the risks stemming from nanotechnology is important, not only with regard to a person’s own personal risk, but also with regard to perception of risk toward others (e.g., family) and the environment. In recent years, several studies have examined public perception of nanotechnology. Generally speaking, there seems to be little knowledge about nanotechnology in parallel with a low level of risk perception. Results from more detailed experiments show a much more complex picture (see Palma-Oliveira et al., this volume). The results demonstrate that the main factors which could explain most of the variance in the judgment data are related to notions of harm and benefits, the number of people exposed, the level of scientific knowledge, the fact that nanomaterials applied to biotechnology represent a new risk, the potential damage to the environment, and the degree to which the consequences were voluntary or observable. Furthermore, experts significantly and systematically perceived less risk for all of the seven biotech applications. Additionally, the risk from food-related applications was considered higher by both groups than the risk from medical applications. The WG also noted the challenges of considering the risk perceptions of policy makers and risk assessors, and that any differences with public perceptions should be highlighted and used to inform communication efforts. Such a pattern of results seems to indicate that despite the current positive view of nanotechnology, this picture could be easily be reversed if something negative and globally significant should happen. The need for improved public knowledge and good risk management and communication is therefore stressed. Several additional challenges were noted by the WG. For example, as with other substances in the environment, nanotechnology regulators need to consider the differences between natural and both engineered and non-engineered anthropogenic nanomaterials, and the associated scientific and legal challenges associated with separating these materials for risk assessment, risk management, and policy purposes. Another challenge discussed by the WG was the need to understand the complex relationships between sources and the related exposure pathways to many potential receptors. Further, the WG noted a need for a common, standardized taxonomy and terminology for nanomaterials, including capturing key aspects of their physical and chemical characteristics, together with the establishment of standardized “use categories.” 4.2.

STRATEGIES FOR ADDRESSING POLICY CHALLENGES

The WG generally agreed with the strategies noted in the Linkov and Satterstrom [24] book chapter. These include that, to best manage nanotechnology risk, regulatory agencies need an adaptive, tiered framework. The framework should employ multiple tools at different levels of the regulatory pyramid, with specific tools chosen on a case-by-case basis. The adaptive framework should be utilized to react to new developments and to gain additional information through policy. Further, a “regulatory pyramid” (with self-regulation at the pyramid’s base and

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prescriptive legislation at the apex) is needed. However, some members of the WG noted that the huge diversity of possible materials in nanotechnology makes the pyramid approach very challenging, and that it would be impossible to develop a “one-way-to-go” methodology to support the development of policies. This is especially true in countries where more than one regulatory agency is involved in the regulatory process for manufactured nanomaterials. In addition, the WG noted that information-based tools or economics-based tools would help the nanotechnology industry from the bottom up (i.e., selfregulation), in addition to the top-down approach (i.e., prescriptive regulation) offered by traditional risk assessment. Further, it was noted that multi-criteria decision analysis, including stakeholder engagement, can be used to prioritize regulatory knowledge gaps, select specific regulatory tools, and also to allocate limited resources and focus follow-up activities. The WG also felt that an adaptive, tiered integration of risk management with decision support would thus be ideal. Further, the WG agreed that a common, standardized taxonomy and terminology for nanomaterials, including the capturing of key aspects of their physical and chemical characteristics, together with the establishment of standardized “use categories,” should be the global goal. This would facilitate the development of information resources (e.g., publications and other documents, and databases) that provide easy access and sharing across countries as regulators attempt to understand and assess the properties of new materials compared to similar materials. Attempts could be made to have a leading global organization(s) for key aspects of this effort. Other challenges and needs noted by the WG included: ƒ The differences between sources and intended uses of nanoscaled particles (naturally occurring vs. manufactured) need to be acknowledged and considered when developing policies and frameworks. ƒ Interactions and collaborations among regulators, scientists, and other stakeholders need to continue to be encouraged to develop coherent, adequate policies to address such a dynamic field. ƒ The ideal policy should take a holistic viewpoint, considering the entire lifecycle of a nanomaterial, including not only use but also the production, transport, and disposal/recycling. ƒ The main exposure considerations for policy development include occupational, consumer, and general population exposures of humans, as well as environmental exposures of ecological receptors. ƒ Ecological and human health effects should be considered for all reasonably foreseeable multimedia exposures. ƒ Attempts should continue to be made by both companies and regulatory agencies to communicate information about manufactured nanomaterials to the public. The WG noted the efforts of the not-for-profit GreenFacts (http://www. greenfacts.org) to provide information.5 5

See http://copublications.greenfacts.org/en/nanotechnologies/index.htm.

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ƒ Development of a crisis-/catastrophe plan for manufactured nanomaterials should be considered by both companies and regulatory agencies. The recent case of the Magic Nano consumer products in Germany being associated with respiratory problems was discussed by the WG as both a good and bad example of how such crisis could/should not be addressed by the material 6 supplier, consumer product company, and a regulatory agency. 5.

Progress in Bridging Gaps and Overcoming Challenges

5.1.

PROGRESS IN DEVELOPING THE NOMENCLATURE AND TAXONOMY

The rapid development of nanotechnology has meant an accompanying and equally rapid increase in the number of terms used in both nanoscience and nanotechnology. These terms need to be organized and accurately described to avoid the development of different terms to describe the same material or property so that consistency can be ensured between all stakeholders. Examples of such terms include nanotube, nanoshell, nano-onion, etc. Along with these ambiguous terms, there needs to be an unambiguous system to describe specific nanomaterials to avoid duplication of work between researchers, allow industry to protect patents, and regulators/governments to accurately assess the risk of a specific material. These specific names take the form of a nomenclature system, similar to the ones currently in place for other materials, such as Chemical Abstract Service (CAS) and International Union of Pure and Applied Chemistry (IUPAC) for chemicals and polymers, and International Union of Biochemistry and Molecular Biology (IUBMB) for biological systems. The development of such terms and nomenclature has come under the auspices of the International Standards Organization (ISO) Technical Committee on nanotechnologies 229 (TC/229). TC/229 was mandated by the Organisation for Economic Co-operation and Development (OECD) Working Party on Manufactured Nanomaterials (WPMN) to develop standards for three themes: (1) terminology and nomenclature (TC/229 working group 1); (2) measurement and metrology (TC/229 working group 2); and (3) environmental health and safety (TC/229 working group 3). The scope of working group 1 (WG1) is defined as “(to) define and develop unambiguous and uniform terminology and nomenclature in the field of nanotechnologies to facilitate communication and to promote common understanding.” (ISO/TC229 N230 Business Plan). 5.1.1.

Taxonomy

Under Working Group 1(WG1), work is currently underway to develop a systematic procedure (i.e., taxonomy) to address terminologies dealing with nanomaterials. 6 See http://www.smalltimes.com/Articles/Article_Display.cfm?ARTICLE_ID=270664&p=109 and http://www.bfr.bund.de/cm/279/frequently_asked_questions_on_nanotechnology.pdf.

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There exist specific projects, such as (1) developing a hierarchy of terms (i.e., core and secondary terms) used to describe nanomaterials; and (2) defining these core and secondary terms. Once completed, the combination of these documents will provide a knowledge databank of all terms, consisting of appropriate definitions that describe nanomaterials and nanotechnologies, thereby enabling stakeholders to accurately describe their nanomaterials. 5.1.2.

Nomenclature

There is currently a Task Group set up under WG1 (Canadian lead) that is examining the development of a nomenclature system for nanomaterials. This nomenclature system would allow interested parties to unambiguously organize and identify nanomaterials based on a specific naming system. The Task Group involved in this project includes representatives from different nomenclature bodies (e.g., IUPAC and CAS), along with other stakeholders (academia, research, and government) as well as various ISO member states. This work is crucial for all stakeholders dealing with nanomaterials. For example, researchers in the field of nanotechnology require an accurate and systematic way to name materials so that, for example, extrapolation of effects (prediction) and their implicit assumptions can be both made and communicated in a meaningful way. In the case of industry, it must be possible to differentiate between the various nanomaterials for the purpose of patent protection as well as avoiding generalizations with regard to nanomaterial hazard and effects characterizations. Regulatory bodies will also require a consistent nomenclature system in order to make amendments to current legislation or write new legislation enabling nano-specific legal instruments. 5.2.

PROGRESS IN DEVELOPING ACCESS TO CONSUMER PRODUCT INFORMATION, INCLUDING EXPOSURE SCENARIOS

In addition to the progress described above in developing the nomenclature and taxonomy, progress has occurred in providing information about how materials, including manufactured nanomaterials, are used in various products. The Project on Emerging Nanotechnologies (http://www.nanotechproject.org/inventories/ consumer/) from the Woodrow Wilson International Center for Scholars and the Pew Charitable Trusts is an example of the development of Web-based access to global information about the uses of nanomaterials in consumer products and, as of mid-2008, its Consumer Products Inventory contained information on over 600 products, produced by over 320 companies located in 20 countries. For development of exposure assessments, the European Information System on “Risks from chemicals released from consumer products/articles” (EISChemRisks, http://web.jrc.ec.europa.eu/eis%2Dchemrisks/index.cfm) provides infrastructure, methods, and tools to help understand and assess the exposures to substances and materials associated with the reasonably foreseeable uses and misuses of consumer products and articles (e.g., clothing and toys). Developed since 2003 by the European Commission’s Joint Research Centre (JRC), Institute of Health and Consumer Protection (IHCP), Physical and Chemical Exposure Unit

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(PCE), EIS-ChemRisks, as of mid-2008, is being expanded for use in occupational, professional product, environmental, and life-cycle exposure assessments. These types of assessments are useful for addressing the European Union’s General Product Safety Directive (GPSD, 2001/95/EC), the EU’s REACH legislation, and for other purposes such as industry-led proactive risk assessments of new substances, materials, and consumer products. The EIS-ChemRisks “EU Exposure Assessment Toolbox” provides: (a) Web-based access and a central user interface, (b) standard formats for information entry and retrieval, and for developing scenario-based exposure assessment dossiers, (c) detailed product-, substance-, material-, and data-specific taxonomies, (d) “knowledge-based” data queries, and (e) the ability to generate detailed reports. The EIS-ChemRisks Toolbox includes examples of how information from nanomaterial-related publications can be placed into the Toolbox databases/modules, and used to develop exposure scenarios. 5.3.

PROGRESS IN DEVELOPING THE LIFECYCLE ASSESSMENTS

There is a growing list of efforts involving assessment of environmental impact through the life-cycle analysis (LCA) of manufactured nanomaterials. For example, the goals of a U.S. EPA-sponsored LCA project included (a) evaluating the life-cycle environmental profile of candidate nanomaterials for photovoltaic (PV) applications, (b) comparing these profiles with those of the micro-sized counterparts that they may replace, and (c) establishing a process-based approach that will be valuable for comparing nano- to micro-materials within groups of thin-film materials (e.g., semiconductors and superconductors). One source of ongoing information about LCA-related projects is http://nanotechproject.us/ inventories/ehs/browse/projects/. Another example investigated how carbon nanotubes (CNTs) might be released during their life-cycle in lithium-ion secondary batteries and synthetic textiles. The findings suggest that releases of CNTs might occur in the production, usage, and disposal phases, with the likelihood and form of release is determined by the way CNT are incorporated into the CNT-containing material [23]. Despite this progress, the life cycle is currently employed only as way to organize or identify potential source terms, rather than a formal life cycle assessment that encompasses a broader range of impact criteria. In the context of extraordinarily high uncertainty that is currently characteristic of nanotechnology, traditional LCA approaches may not be applicable. Seager and Linkov (2008 and chapter in this volume) stress the importance of carrying LCA forward through the impact assessment stage and developing new tools for life cycle impact assessment that draws upon a wide range of formal MCDA techniques. 5.4.

PROGRESS IN CREATING WEB-BASED ACCESS TO INFORMATION IN LOCAL LANGUAGES, AND IN PUBLICLY UNDERSTOOD WORDING

The current and future uses of and exposures to nanomaterials are global in scope, yet key publications and other forms of knowledge (e.g., web sites) may not be

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available in the native language of a country, and the nanomaterial-containing products may be manufactured in one country and imported into other countries. For general public knowledge, and for the benefit and use by experts and policy makers, it will be important to establish nanomaterial-related web sites that attempt to provide information in key languages, and ideally in the native languages of most of the world’s population. The European Union has made great strides in doing this in recent years for the citizens in its 27 Member States; for example, the web site for the European Chemicals Agency presents information in all 23 official EU languages. Similar efforts are also being made in Europe (and useful globally) by the not-for-profit GreenFacts organization, which provides web-based access in multiple languages to complex scientific reports on health and the environment for reading by non-specialists. 6.

Conclusions and Additional Policy-Related Needs

This chapter noted that many policy frameworks for manufactured nanomaterials have been developed globally, and that these frameworks range from voluntary methods and self-regulation to prescriptive regulation. It also noted that: (a) the methods can be from different levels of the regulatory pyramid, (b) the policies ideally need to include consideration of the risks and benefits of nanotechnology, (c) that risk perception and risk communication need to be considered, (d) the policies should consider the entire lifecycle of a manufactured nanomaterial, including use, and (e) that the ecological and human health effects for all reasonably foreseeable exposures should be considered. Finally, an ongoing need is for the establishment and sharing of skills for both developed and developing countries. Some important sets of skills (e.g., toxicologists) may not be available at all in some countries, both in industry and in government agencies. Ideally, this expertise would be developed in upcoming years, but it is realistic to assume that countries will continue to need to try to work together as much as possible to share information and expertise. This would allow for the development of risk assessments and policies within developed and developing countries that are based on the prevailing knowledge around the world. Global professional societies and other types of global organizations (e.g., World Health Organization and Organisation for Economic Co-operation and Development) can play roles in facilitating the information sharing and the development of expertise. References 1. Arcuri ASA, Grossi MGL, Martins PR, Pinto VRS, Maia PA, Rinaldi A. 2005. Developing Strategies in Brazil to Manage the Emerging Nanotechnology and Its Associated Risks. Springer, Netherland. 2. Ashford NA. 2002. Implementing a precautionary approach in decisions affecting health, safety, and the environment: Risk, technology alternatives, and tradeoff analysis. In: The Role of Precaution in Chemicals Policy (Freytag E, Jakl T, Loibl G, Wittmann M, eds.). Favorita Papers. Diplomatic Academy, Vienna, 128–140.

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3. Ashford NA, Ayers C, Stone RF. 1985. Using regulation to change the market for innovation. Harvard Environmental Law Review 9:419–466. 4. Ashford NA. 1993. Understanding technological responses of industrial firms to environmental problems: Implications for government policy. In: Environmental Strategies for Industry: International Perspectives on Research Needs and Policy Implications (Fisher K, Schot J, eds.). Island Press, Washington, DC. 277–307. 5. Bowman D, van Calster G. 2007. Reflecting on REACH: Global implications of the European Union’s chemicals regulation. Nanotechnology Law & Business 4:375–383. 6. (CAN) Environment Canada and Health Canada. Proposed Regulatory Framework for Nanomaterials Under the Canadian Environmental Protection Act, 1999. 10-9-2007. http://www.ec.gc.ca/substances/nsb/eng/nano_e.shtml 7. (CAN) Canadian Environmental Protection Act, 1999 (CEPA, 1999) http://www.ec.gc. ca/CEPARegistry/the_act/ 8. Chaudhry Q, Blackburn J, Floyod P, George C, Nwaogu T, Boall A, Aitken RJ. 2006. A Scoping Study to Identify Gaps in Environmental Regulation for the Products and Applications of Nanotechnologies. Department for Environment, Food and Rural Affairs. 24-3-2008. Ref Type: Report London. 9. Commission of the European Communities. Proposal for a Regulation of the European Parliament and of the Council on Novel Foods and Amending Regulation (EC) No XXX/XXXX [common procedure] (presented by the Commission) [SEC(2008) 12] [SEC(2008) 13]. COM(2007) 872 final 2008/0002 (COD). Commission of the European Communities, Brussels. 14-1-2008. 10. Council of the European Communities. 1989. Council Directive 89/391/EEC of 12 June 1989 on the introduction of measures to encourage improvements in the safety and health of workers at work. Official Journal L 183:0008. 11. Council of the European Communities. 1998. Council Directive 98/24/EC of 7 April 1998 on the protection of the health and safety of workers from the risks related to chemical agents at work (fourteenth individual Directive within the meaning of Article 16(1) of Directive 89/391/EEC). Official Journal L 131:23. 12. Council of the European Communities. 1991. Council Directive 91/689/EEC of 12 December 1991 on hazardous waste (91/689/EEC). Official Journal L 377:P.0020– 0027. 13. EDF 2008. EPA Nanotechnology Voluntary Program Risks Becoming a ‘Black Hole’. http://www.nanowerk.com/news/newsid=6547.php 14. European Commission. 2008a. Communication from the Commission to the European Parliament. The Council and the European Economic and Social Committee: Regulatory Aspects of Nanomaterials [SEC(2008) 2036]. http://ec.europa.eu/nanotechnology/pdf/ comm_2008_0366_en.pdf . 15. European Commission. 2008b. Commission Staff Working Document. Accompanying Document to the Communication from the Commission to the European Parliament, the Council and the European Economic and Social Committee: Regulatory Aspects of Nanomaterials. Summary of legislation in relation to health, safety and environment aspects of nanomaterials, regulatory research needs and related measures {COM(2008) 366 final}. http://ec.europa.eu/nanotechnology/pdf/com_regulatory_aspect_nanomaterials_ 2008_en.pdf . 16. European Environmental Agency (EEA). Late Lessons from Early Warnings: The Precautionary Principle 1896–2000. Harremoës, P., Gee, D., MacGarvin, M., Stirling, A., Keys, J., Wynne, B., and Guedes Vaz, S. 22. 2001. European Environmental Agency, Copenhagen, Denmark. Environmental Issue Report.

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17. European Parliament, Council of the European Union. 2006. Regulation (EC) No. 1907/2006 of the European Parliament and of the Council of 18 December 2006 concerning the Registration, Evaluation, Authorisation and Restriction of CHemicals (REACH), establishing a European Chemicals Agency, amending Directive 1999/45/EC and repealing Council Regulation (EEC) No. 793/93 and Commission Regulation (EC) No. 1488/94 as well as Council Directive 76/769/EEC and Commission Directives 91/155/EEC, 93/67/EEC, 93/105/EC and 2000/21/EC. 30.12.2006 EN. Official Journal of the European Union L:396-1. Key REACH information is accessible via http://echa.europa.eu/ 18. European Parliament and the Council of the European Union. 2002. Regulation (EC) No. 178/2002 of the European Parliament and of the Council of 28 January 2002 laying down the general principles and requirements of food law, establishing the European Food Safety Authority and laying down procedures in matters of food safety. Official Journal of the European Communities L:31-1, L:31/24. 19. Franco A, Hansen SF, Olsen SI, Butti L. 2007. Limits and prospects of the “incremental approach” and the European legislation on the management of risks related to nanomaterials. Regulatory Toxicology and Pharmacology 48:171–183. 20. Friends of the Earth (FOE). Out of the Laboratory and on to Our Plates Nanotechnology in Food & Agriculture. Friends of the Earth Australia, Europe & U.S.A. 3008. ort 21. Halliday J. EU Parliament Votes for Tougher Additives Regulation. Food Navigator.com Europe. 12-7-2007. 22. Hansen SF, Tickner J. 2007. The Challenges of Adopting Voluntary Health, Safety and Environment Measures for Manufactured Nanomaterials: Lessons from the Past for More Effective Adoption in the Future. Nanotechnology Law & Business. 23. Kohler AR, Som C, Helland A, Gottschalk F. 2008. Studying the potential release of carbon nanotubes throughout the application life cycle. Journal of Cleaner Production 16:927–937 24. Linkov I, Satterstrom K. Review of regulatory frameworks. In: Nanomaterial Risk Assessment and Risk Management. (Linkov I, Ferguson E, Magar VS, eds.). Real-Time and Deliberative Decision Making, 1–1. © 2008 Springer, The Netherlands. 25. Porter ME. 1991. America’s Green Strategy. Scientific American 264(4):168. 26. Responsible NanoCode (RNC). 2006. Workshop Report: How Can Business Respond to the Technical, Social and Commercial Uncertainties of Nanotechnology? http://www.responsiblenanocode.org/documents/Workshop-Report_07112006.pdf. 27. Slovic P. 1982. Facts versus fears: Understanding perceived risk. In: Judgment Under Uncertainty: Heuritics and Biases (Kahneman D, Slovic P, Tversky A, eds.). Cambridge University Press, Cambridge, 463–489. 28. (U.K.) Department for Environment, Food and Rural Affairs (DEFRA). 2006. UK Voluntary Reporting Scheme for Engineered Nanoscale Materials. Department of Environment, Food and Rural Affairs, London, UK. 22-3-2007. Available at: http://www.defra.gov.uk/environment/nanotech/policy/pdf/vrs-nanoscale.pdf. 29. (U.K.) Department for Environment, Food and Rural Affairs (DEFRA). 2006. Voluntary Reporting Scheme for Engineered Nanoscale Materials First Quarterly Report Covering the Period 22/09/06–22/12/06. Department for Environment, Food and Rural Affairs, London, UK. 30. (U.K.) Department for Environment, Food and Rural Affairs (DEFRA). The UK Voluntary Reporting Scheme for Engineered Nanoscale Materials: Fifth Quarterly Report. . Department for Environment, Food and Rural Affairs, London, UK, 22-122007. http://www.defra.gov.uk/environment/nanotech/pdf/vrs-5.pdf. 2007.

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31. (U.S.) Environmental Protection Agency (US EPA). 2007. Nanotechnology White Paper. Prepared for the US EPA by members of the Nanotechnology Workgroup, a group of EPA’s Science Policy Council, Washington, DC 20460. http://www.epa.gov/ OSA/pdfs/nanotech/epa-nanotechnology-whitepaper-0207.pdf. 32. (U.S.) National Research Council. 1996. Understanding Risk: Informing Decisions in a Democratic Society. National Academy of Sciences, Washington, DC. 33. Weiss R. 2005. Nanotechnology Regulation Needed, Critics Say. Washington Post 14-7-2008. http://www.washingtonpost.com/wp-dyn/content/article/2005/12/04/ AR2005120400729.html. 34. World Health Organization (WHO) Regional Office for Europe. 2006. Dealing with Uncertainty: Setting the Agenda for the 5th Ministerial Conference on Environment and Health. Report of a WHO Meeting, Copenhagen, Denmark, 15–16 December 2005. EUR/06/5067987. WHO Regional Office for Europe, Copenhagen.

THE SAFETY OF NANOTECHNOLOGIES AT THE OECD

P. KEARNS, M. GONZALEZ, N. OKI, K. LEE, F. RODRIGUEZ OECD, Environment, Health and Safety Division 2 rue André-Pascal 75775 Paris Cedex 16, France [email protected]

Abstract. This paper introduces the work of OECD’s Working Party on Manufactured Nanomaterials. In particular, it describes its “sponsorship programme” through which OECD member countries and other stakeholders are collaborating to fund and manage the safety testing of 14 manufactured nanomaterials. The paper describes the endpoints which will be addressed during the safety testing which cover both human health and environmental safety. There is also reference to supporting work including a preliminary review of existing test guidelines as well as work on alterative test methods which ultimately aims to avoid the use of animal testing. (This paper does not necessarily represent the views of OECD or its member countries.) 1.

A Brief Introduction to OECD

The Organisation for Economic Co-operation and Development (OECD) was founded in 1961. Today the OECD has 30 member countries.1 Its principal aim is to promote policies for sustainable economic growth and employment, a rising standard of living and trade liberalisation. By “sustainable economic growth”, the OECD means growth that balances economic, social and environmental considerations. The OECD brings together its member countries to discuss and develop both domestic and international policies. It analyses issues, recommends actions, and provides a forum in which countries can compare their experiences, seek answers to common problems, and work to co-ordinate policies.

1

OECD member countries are: Australia, Austria, Belgium, Canada, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Korea, Luxembourg, Mexico, the Netherlands, New Zealand, Norway, Poland, Portugal, the Slovak Republic, Spain, Sweden, Switzerland, Turkey, the United Kingdom and the United States. The European Commission also takes part in the work of the OECD.

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The OECD’s work is overseen by several governing bodies. At the highest level is the OECD Council, made up of Ambassadors from all member countries. The Council’s main role is to review and approve the OECD budget and programme of work. It can also adopt Council Decisions (which legally bind all member countries to a particular course of action) and Council Recommendations (which strongly encourage action within governments). The Council and all other OECD bodies work on many issues by consensus. Under the Council, work in the OECD is directed by specialised committees, and under these, there are subsidiary bodies (working parties and working groups), which are composed of experts representing member countries. The Chemicals Programme, for example, is managed by the Chemicals Committee. 2.

OECD’s Working Party on Manufactured Nanomaterials (WPMN)

The Working Party on Manufactured Nanomaterials (WPMN) was established in 2006 by OECD’s Chemicals Committee. The WPMN brings together more than 100 experts from governments and other stakeholders. The participants are from the OECD member countries and certain non-member economies such as Brazil, China, the Russian Federation, Singapore and Thailand. In addition, there a number of observers and invited experts from other intergovernmental organizations (for example, UNEP and WHO) as well as the International Standardization Organization (ISO). Other stakeholders include industry whose participation is organized by BIAC,2 trade 3 unions whose participation is organized by TUAC and environmental NGOs. The objective of the WPMN is to promote international co-operation in human health and environmental safety related aspects of manufactured nanomaterials (MN), in order to assist in the development of rigorous safety evaluation of nanomaterials. The main focus of the work is on the industrial chemicals sector. The Working Party is currently implementing its work through the eight projects listed below: ƒ ƒ ƒ ƒ ƒ ƒ ƒ

Safety testing of a representative set of manufactured nanomaterials Manufactured nanomaterials and test guidelines The role of alternative methods in nanotoxicology Co-operation on voluntary schemes and regulatory programmes Co-operation on risk assessment Exposure measurement and exposure mitigation Development of a database on human health and environmental safety research and ƒ Research strategies on manufactured nanomaterials

2

The Business and Industry Advisory Committee to the OECD.

3

Trade Union Advisory Committee to OECD.

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These eight projects are being managed by eight steering groups of the WPMN which are implementing their “operational plans”, each with their specific objectives and timelines. For the most part, these steering groups (which average around 20 participants) are being led/chaired by members of the WPMN, with support from the OECD secretariat. Much of the work has been (and is being) undertaken through teleconferences and electronic means. At the same time, there are close linkages amongst the projects, and for this reason, “face-to-face” meetings of steering groups are organized as the need arises. The results of each project are evaluated and endorsed by the entire WPMN. 3.

Safety Testing of a Representative Set of Manufactured Nanomaterials – A Sponsorship Programme

The focus of this paper is on the project of the WPMN entitled, Safety Testing of a Representative Set of Manufactured Nanomaterials. This project was one of the first developed by the WPMN and is built around the concept that much valuable information on the safety of manufactured nanomaterials, as well as the methods used to assess safety, can be derived by testing specific nanomaterials for human health and environmental safety effects. The objective of this project, therefore, has been to develop a programme to create an understanding of the kind of information on intrinsic properties that may be relevant for exposure and effects assessment of nanomaterials through testing. As a first step in this project, the WPMN selected a priority list of manufactured nanomaterials for testing (see Table 1). This list has also been referred to as a “representative set” of manufactured nanomaterials. The word “representative” refers to those manufactured nanomaterials now, or soon to enter into commerce, for inclusion in a set of reference materials to support measurement, toxicology and risk assessment of nanomaterials. Although the list was mainly selected taking into account those materials which are in commerce (or close to commercial use), other criteria were also considered: for example, production volume, the likely availability of such materials for testing and the existing information that is likely to be available on such materials. In developing this list, the WPMN recognized that it should remain flexible. It emphasized, for example, that certain nanomaterials not included may become important in the future and certain nanomaterials currently on the list may have (over time) reduced production and/or use. Accordingly, the list should be TABLE 1. Representative set of manufactured nanomaterials. Fullerenes (C60) Single-walled carbon nanotubes (SWCNTs) Multi-walled carbon nanotubes (MWCNTs) Silver nanoparticles Iron nanoparticles Carbon black Titanium dioxide

Aluminium oxide Cerium oxide Zinc oxide Silicon dioxide Polystyrene Dendrimers Nanoclays

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considered as a “snapshot in time”, of those nanomaterials in commerce or likely to enter into commerce in the near term. At the same time, some nanomaterials on the list may have variants that the WPMN may wish to consider in detail in the future. For example, C60 could be broadened to other fullerenes as well as chemically modified varieties of C60; it may also be important to analyze chemically modified single- and multi-walled carbon nanotubes; and the influence of surface coatings of elemental and metal oxide nanomaterials, and/ or their different shapes. As a second step in this project, the WPMN developed and agreed a list of endpoints for which these nanomaterials should be tested (see Table 2). They include a range of endpoints relevant to human health and environmental safety. Addressing this set should ensure consistency between the various tests to be carried out on specific nanomaterials. It should also lead to the development of “dossiers” for each nanomaterial including information on, for example, basic characterization, environmental fate, ecotoxicity and mammalian toxicity. In order to undertake this testing work, the WPMN launched a “sponsorship programme” at the end of 2007. This sponsorship programme is an international effort by which delegations to the WPMN will share the testing of those manufactured nanomaterials selected by the WPMN. There are three levels of participation available. For each nanomaterial, a lead sponsor(s) is designated who will conduct or co-ordinate all of the testing deemed to be appropriate and feasible to address the endpoints (Table 2) for a specific nanomaterial (Table 1). In addition, a co-sponsor may conduct some of the testing for a specific nanomaterial. Finally, a contributor may provide test data, reference or testing materials or other relevant information to the lead and co-sponsors. The current list of lead sponsors, co-sponsors and contributors is shown in Table 3. It is expected that other participants will join the programme as the work evolves. It is envisaged that this sponsorship programme will proceed in two phases. The first phase will test each nanomaterial (Table 1) for the set of endpoints (Table 2). This work is being supported by the development of a guidance manual for sponsors of the testing programme. It is also expected that the list of endpoints will be refined based on the practical results obtained through the testing programme. As such, phase one testing is expected to be of an exploratory nature, science-based and without any consequences for existing regulatory datasets. In addition, it is expected that this will identify those cross-cutting issues or tests, that will need further consideration, which will be undertaken during phase 2.

Known catalytic activity

Sediment simulation testing Sewage treatment simulation testing Identification of degradation product(s)

Representative TEM picture(s) Particle size distribution

Soil simulation testing

Crystallite size

Representative TEM picture(s)

Simulation testing on ultimate degradation in surface water

Dustiness

Description of surface chemistry (e.g., coating or modification) Major commercial uses

Ready biodegradability

Crystalline phase

Structural formula/molecular structure Composition of nanomaterial being tested (including degree of purity, known impurities or additives) Basic morphology

Biotic degradability Ready

Dispersion stability in water

Environmental fate

Water solubility

Physical–chemical properties and material characterization Agglomeration/aggregation

CAS number

Nanomaterial name (from list)

Nanomaterial information/identification

Effects on microorganisms Other relevant information (when available)

Effects on terrestrial species

Effects on pelagic species (short term/long term) Effects on sediment species (short term/long term) Effects on soil species (short term/long term)

Environmental toxicology

TABLE 2. List of endpoints for testing.

Experience with human exposure*

Genetic toxicity*

Developmental toxicity*

Reproductive toxicity*

Chronic toxicity*

Repeated dose toxicity

Acute toxicity

Pharmacokinetics (ADME)

Mammalian toxicology

Incompatibility*

Explosivity*

Flammability*

Material safety

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*where available

Method of production (e.g., precipitation, gas phase)

Nanomaterial information/identification

Octanol-water partition coefficient, where relevant Redox potential Radical formation potential Other relevant information (where available)

Porosity

Photocatalytic activity Pour density

Zeta potential (surface charge) Surface chemistry (where appropriate)

Physical–chemical properties and material characterization Specific surface area

Adsorption- desorption Adsorption to soil or sediment Bioaccumulation potential Other relevant information (when available)

Further testing of degradation product(s) as required Abiotic degradability and fate Hydrolysis, for surface modified nanomaterials

Environmental fate

Environmental toxicology Other relevant test data*

Mammalian toxicology

Material safety

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TABLE 3. Sponsorship arrangements (as of 13 June 2008). Lead sponsor(s)

Co-sponsor(s)

Contributor

Fullerenes(C60)

Japan, United States (US)

SWCNTs

Japan, US

MWCNTs

Japan, US

Korea, BIAC (Business and Industry)

Germany, Canada, European Commission (EC), France Germany, Canada, EC, France

Silver nanoparticles

US, Korea

Germany, Canada

Australia, EC, France

Iron nanoparticles

Canada, US

Carbon black

Germany, US

Titanium dioxide

Germany

Canada, Spain, BIAC, Korea, US

Aluminium oxide Cerium oxide Zinc oxide Silicon dioxide

Germany, US United Kingdom (UK), Business and Industry (BIAC), United States UK, BIAC

Netherlands,

Australia, Germany, EC

BIAC

Australia, Canada,

BIAC, Korea

EC, France

Polystyrene Dendrimers Nanoclays

4.

France

Korea Spain

US US

Other Projects Related to the Testing and Assessment of Nanomaterials

It is important to know whether existing test guidelines (used for “traditional chemicals”) can be successfully applied to manufactured nanomaterials. Some information on this question will be derived from the sponsorship programme. In parallel, however, the WPMN has undertaken a preliminary review of existing test guidelines (especially the 115 OECD Test Guidelines [TGs]) with view to establishing whether they are suitable for nanomaterials. This preliminary review, which is expected to be published in early 2009, covers test guidelines for: physical

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chemical properties; effects on biotic systems; degradation and accumulation; as well as health effects. At the same time, the WPMN has initiated work on the role of alternative methods in nanotoxicology, which will avoid animal testing. As a first step, a report is being prepared including: (i) a list of in vitro endpoints on human health and ecotoxicity; (ii) the kind of information that the in vitro tests will provide; (iii) a list of validated in vitro tests that might be used for testing nanomaterials; and (iv) a background document on the feasibility for validating further in vitro methods and to consider the development of further in vitro tests. 5.

Additional Information

OECD’s WPMN has agreed that its work should be as open and transparent as possible. With this in mind, information derived from its projects will be made available in a timely way on its web site: www.oecd.org/env/nanosafety/.

NANOMATERIALS IN CONSUMER PRODUCTS Categorization and Exposure Assessment

S. FOSS HANSEN, A. BAUN Department of Environmental Engineering, NanoDTU Technical University of Denmark, Building 113 Kgs. Lyngby DK-2800, Denmark [email protected] E.S. MICHELSON Project on Emerging Nanotechnologies Woodrow Wilson International Center for Scholars Washington, DC, USA A. KAMPER, P. BORLING, F. STUER-LAURIDSEN DHI Hørsholm, Denmark

Abstract. Exposure assessment is crucial for risk assessment for nanomaterials. We propose a framework to aid exposure assessment in consumer products. We determined the location of the nanomaterials and the chemical identify of the 580 products listed in the inventory maintained by the Woodrow Wilson International Center for Scholars. It was found that in 19% of the products the nanomaterial were nanoparticles bound to the surfaces. Nanoparticles suspended in liquids were used in 37% of the products, whereas 13% used nanoparticles suspended in solids. One percent were powders containing free potentially airborne nanoparticles. Based on the location of the nanostructure we were able to further group the products into categories of: (1) Expected to cause exposure; (2) May cause exposure; and (3) No expected exposure to the consumer. Most products fall into the category of expected exposure, but we were not able to complete the quantitative exposure assessment mainly due to the lack of information on the concentration of the nanomaterial in the products – a problem that regulators and industry will have to address if we are to have realistic exposure assessment in the future. To illustrate the workability of our procedure, we applied it to a product scenario – the application of sun lotion – using best estimates available and/or worst case assumptions. The quantity of the active substance on the skin per application for a 2 year old child is found be Ader = 260 mg for a particle concentration of 10% if the amounts applied correspond to the European Commission’s recommendations on use of sunscreen. This value is about three times less than that for an adult. The potential

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worst case dermal uptake assuming full skin penetration is found to be 63 mg kg−1 bw day−1 for a particle concentration of 10% for a 2 years old child, which is twice the dermal uptake for an adult.1 1.

Introduction

Despite the fact that nanotechnology is often described as a future technology, few realize that nanomaterials are actually already being used in a wide variety of consumer products, and that the number of commercially available products seem to be increasing rapidly. In 2006, the Project for Emerging Nanotechnologies at the Woodrow Wilson International Center for Scholars (i.e. Project on Emerging Nanotechnologies) launched an inventory of the consumer products available to consumers (i.e. Woodrow Wilson inventory). Originally the inventory contained 212 different products in 2006, which has increased to 580 products in 2007. Projections are that this number will continue to increase as the unique properties of nanomaterials are explored further and translated into commercial products. At first glance, it might seem straight forward to conclude that since the number of consumer products is increasing, the levels of consumer exposure are too and as a consequence the risks related to nanomaterials would also be increasing should nanomaterials turn out to have hazardous properties. We argue that the situation may be more complex as the potential risks related to consumer products depend on other factors than the use and the properties of the nanomaterials. More specifically, determining the location of the nanomaterial in the product will be a key parameter for identifying likely exposure pathways and make realistic exposure assessments. For instance, the risk scenarios will be different for a free airborne nanoparticle that can be directly inhaled and for a nanoparticle suspended in liquids where dermal exposure maybe is the most relevant pathway. In this paper we propose a framework to aid exposure characterization and assessment of nanomaterials in consumer products. As an illustrative case study we apply it to the products currently listed in the inventory created by the Project on Emerging Nanotechnologies at the Woodrow Wilson Center for International Scholars. 2.

Location of Nanomaterials in Consumer Products

While knowledge on the chemical identity and the product categories are required for any risk assessment of consumer products, we propose that exposure assessment of products containing manufactured nanomaterials has to take into account the location of the nanomaterial in the products. Elsewhere we have 1

For a full version of the work and results presented in this paper see Hansen, S.F. et al [12].

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shown that nanomaterials can be categorized depending on the location of the nanostructure [3]. This divides all nanomaterials into three overall categories: (1) in the bulk; (2) on the surface; and (3) as particles. Each of these categories has a number of subcategories. Materials structured on the nanoscale in the bulk included one phase material (such as for instance nanocrystalline copper) and multiphase material (such as ceramic zeolites [porous] and diblock copolymers [non-porous]). Materials with nanoscale structures on the surface include: (a) one phase material structured on the nanoscale; (b) nanoscale thick, un-patterned film; (c) patterned film as films of nanoscale thickness or as surface pattern having nanoscale dimensions. Finally, the category of particles includes: (a) surface bound nanoparticles; (b) nanoparticles suspended in liquids; (c) nanoparticles suspended in solids; and (d) as free airborne particles (for a full explanation of this categorization framework see Hansen et al. [3]). Using the categorization framework to each of the 580 products in the consumer products inventory we were able to categorize about 75% of all the products in the inventory. Figure 1 shows the distribution of all the products categorized according to the location of the nanostructure in the products. It was found that in 19% of the products the nanomaterial were nanoparticles bound to the surfaces. Nanoparticles suspended in liquids were used in 37% of the products, whereas 13% used nanoparticles suspended in solids. One percent were powders containing free potentially airborne nanoparticles whereas we were not able to determine the location of the nanomaterial for 140 products given the available information from producers or through the data in the inventory. Distribution of products into various categories of nanomaterials Bulk

Surface

Particles

150

100

Unclassifiable

Airborne

Suspended in solids

Suspended in liquids

Surface bound

Structure film

Film

One phase

0

Structure surface

50

Multi phase

Number of products

200

Figure 1. Products in the Woodrow Wilson inventory categorized depending on the location of the nanostructure. Thirteen percent, 19%, 37% of the products used nanoparticles suspended in solids, bound to the surfaces, suspended in liquids, respectively. About 1% were powders containing free potentially airborne nanoparticles [12].

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Potential of Consumer Exposure to Nanomaterials

The categorization of the consumer products according to location of the nanomaterial enables the surveyed products to be grouped into three different exposure categories: 1. Expected to cause exposure – these products either requires or makes direct human exposure possible. For products belonging to this category the human exposure can be quantified based on the expected applied quantity of the product combined with the application frequency. The categories “Nanoparticles suspended in liquids” (IIIb) and “Airborne Nanoparticles” (IIId) fall into this exposure category. 2. May cause exposure – although the particles in the products are not meant to be released, a certain wear and tear must be anticipated leading to release of nanomaterials. For these products it is not possible to estimate a daily or a yearly consumption of products and there are currently no data available on the release of particles from this type of products. The category ‘Surface-bound nanoparticles’ (IIId) falls into this exposure category.

Figure 2. Distribution of the products with no, possible and expected exposure within each of the various products categories depending on the location of the nanomaterial in the product.

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3. No expected exposure to the consumer – expected negligible exposure because the nanoparticles are encapsulated in the product. The category of ‘Nanoparticles suspended in solids’ (IIIc) falls into this category (see Figure 2). Using the data behind Figure 1 in combination with the exposure grouping illustrated in Figure 2, it is found that expected consumer exposure is highest for products in the products categories “Appliances” and “Health and Fitness”. This is shown in Figure 3. Expected exposure 36% for products that fall into the category of home and garden whereas it is 58% for cross-cutting products. For the other categories of products the expected exposure ranges between these two percentages except for appliances for which exposure is only expected for 17% of the products. Possible exposure percentages are equally high ranging between 20–30% except for food and beverages and electronics and computers for which about 10% fall into the category of possible exposure.

Figure 3. Distribution of the products with no-, possible- and likely exposure within each of the various products categories [12].

The exposure grouping is based on the physical state in the application phase when the consumer exposure is expected to highest. It should be noted that some consumer products will change their exposure potential during the product lifecycle e.g. for paints where nanoparticles will be in liquid form when the paint is applied but in solid form once the paint has dried. In this case the major consumer exposure is expected to be from the liquid paint, but weathering and physical abrasion of the dried surface could potentially lead to an exposure. 4.

Quantitative Exposure Assessment

The approach described above can form the basis for exposure characterization of consumer products based on nanomaterials. However, to complete an exposure

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assessment it is necessary to include a quantification of the level of exposure. This kind of assessment is hampered by the fact that the content of nano-sized materials is only publicly available for a very limited number of consumer products. To illustrate the applicability of the framework outlined above, we have chosen to quantify the potential human exposure to the nanomaterials for a realistic product scenario, namely the application of a sunscreen lotion containing nano-sized TiO2 particles. The potential exposure and dermal uptake is calculated for an adult man and woman as well as a 2 year old child and are based on default values and equations taken from Part 1, Appendix II – “Consumer Exposure”, in the Technical Guidance Document (TGD) on risk assessment for existing substances [1]. Very few producers/distributors provide information about the content of the nanomaterials in the products. However, from a survey on the industrial production and application of nanotechnology in the Danish industry we know that producers of sun lotions use 10–20 nm TiO2 particles with a specific surface area of 50–200 m2/g as UV absorber and that the nanoparticles are present in concentrations up to 10% [11]. The route of exposure for a sun lotion will mainly be dermal contact. Intake of smaller quantities by contact with the area around the mouth is not taken into consideration. As the product is a “leave on” product, which should neither be TABLE 1. Equations, explanations, and default values for dermal exposure assessment of TiO2 applied in sunscreen lotion. Symbol Fprod Bw N Ader Uder pot Qprod child Qprod Qprod adult Qprod adult kchild kadult

Explanation

Equation

Scenario

Concentration of active substance in the product Body weight (adult ♀/♂/2 year old)

60/70 [1]/12.34 [4] kg

Number of applications

3 per day [1]

The quantity of active substance on the skin per application (mg) Potential daily uptake of quantity of active substance (mg/kg bw/day) The quantity of product per application for a child The quantity of product per application for an adult The quantity of product per application for an adult The quantity of recommended product per application for an adult Body area of a 2 year old child, weighting 12.34 kg and measuring 86.8 cm (m2) Body area of an adult woman (m2)

10% [11]

Qprod * Fprod

(1)

(Ader * n)/bw

(2)

(kchild * Qprod, adult)/kadult

(3)

8,000 mg [1] 36,000 mg [2] 0.55 [4] 1.69 [1]

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diluted when used nor washed off, the quantity of active substance on the skin (Ader) for an adult can be estimated by Eq. 1 in Table 1 to be Ader = 800 mg for a sun lotion containing 10% of nanomaterial. Assuming that all nanoparticles penetrate the skin Eq. 2 in Table 1 can be used to estimate the potential uptake per kilogram body weight per day. Uder, pot is equal to 40 mg kg−1 bw day−1 nano-TiO2 for women if the sun lotion contains 10% nanoparticles. For men Uder, pot is equal to 34 mg kg−1 bw day−1. The conversion of the value of applied sun lotion in an adult compared to a child can be calculated using Eq. 3 in Table 1. The quantity of the active substance on the skin per application for a 2 year old child is found be Ader = 260 mg for a particle concentration of 10%. This value is about three times less than for an adult. Uder, pot would on the other hand be two times higher i.e. 63 mg kg−1 bw day−1. The above calculated estimates for Ader and Uder, pot are based on the default values indicated in the TGD for the quantity of the actually applied sun lotion. However according to the recommendation of the European Commission of 22 September, 2006 on the effectiveness of sun protection preparations, sun lotion must be applied in quantities corresponding to 4.5 times what TGD stipulates in order to reach the protection level indicated by the sun protection factor. The quantity per application mentioned is therefore approximately 36 g for an averagesized adult [2]. Thus, for adult consumers that apply the recommended quantity, the quantity of active substance on the skin per application would 3,600 mg per application of sun lotion of sun lotion containing 10% of nanomaterials, whereas Uder, pot would be 102 mg kg−1 bw day−1. For a 2 year old child Ader would be 1,171 mg per application of sun lotion whereas the daily uptake of active substance is Uder, pot = 285 mg kg−1 bw day−1.

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5.

Discussion

Consumer exposure assessment for products containing nanomaterials has been acknowledged as an important knowledge gap [7, 9] and we have presented a categorization framework to aid such exposure assessment. Depending on the location of the nanostructure in the product (e.g. in the bulk; on the surface; or as particles) the categorization framework divides products into three different exposure categories: (1) Expected to cause exposure; (2) May cause exposure; and (3) No expected exposure to the consumer. Even despite the sometimes very limited information available in the Woodrow Wilson inventory on consumer products, we were still able to categorize 75% of the 580 products. Forty-five percent of the products fall into category of expected exposure and that almost 25% of the products could not be categorized regarding exposure. This is an element of concern given that the level of knowledge about the hazardous properties of nanomaterials is currently very limited [3, 5, 7]. Our use of scenarios based on best estimates and worst-case assumptions show how the methodology outlined in the Technical Guidance Document can be used to obtain overall estimates of the potential human exposure of nanomaterials through consumer products. Using this methodology we estimated the quantity of the active substance on the skin per application for a 2 year old child to be Ader = 260 mg for a particle concentration of 10% if the amounts applied correspond to the European Commissions recommendations on use of sunscreen. This value is about three times less than for an adult. The potential dermal uptake is found to be 285 mg kg−1 bw day−1 for a particle concentration of 10% for a 2 years old child, which is twice the amount compared an adult. It should be noted that these uptake values are worst-case scenarios assuming full skin penetration of nanoparticles. In its latest opinion on the safety of nanomaterials in cosmetic products the European Scientific Committee on Consumer Products stated that there is inadequate information on among other uptake of nanoparticles via physiologically normal and compromised human skin [9]. The extent to which nanoparticles actually do penetrate the skin is currently a matter of considerable debate internationally and will probably depend on specific particle properties and the local environment in which it is used [8]. The general lack of information about the kinds of nanomaterials used, how they are used, and in which concentrations hampers full scale, quantitative exposure assessments. One thing is that this information is not publicly available, another is that this information is often not available to regulators and that they have limited authority to obtain such information unless the health risk of these products has been assessed [6, 10]. This means that not even regulators have access to the information needed to do realistic exposure assessment in support of their overall decision-making process. The lack of information about chemical identifies of the nanomaterials used and the concentration of the material in the product is something that regulators and industry will have to address if realistic exposure assessments are to be possible in the future.

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Acknowledgements We thank Torben Dolin for the technical assistance with the graphic design. References 1. European Commission JRC (2003) Technical Guidance Document in Support of Commission Directive 93/67/EEC on Risk Assessment for New Notified Substances and Commission Regulation (EC) 1488/94 on Risk Assessment for Existing Substances. European Commission, Brussels 2. European Commission (2006) Commission Recommendation of 22 September 2006 on the Efficacy of Sunscreen Products and the Claims Made Relating Thereto (Notified Under Document Number C(2006) 4089) (Text with EEA Relevance) (2006/647/EC). Official Journal of the European Union L 265/39 3. Hansen S.F., Larsen B.H., Olsen S.I., Baun A. (2007) Categorization Framework to Aid Hazard Identification of Nanomaterials. Nanotox 1: 243–250 4. Lentner C. (1981) Geigy Scientific Tables: - 1: Units of Measurement, Body Fluids, Composition of the Body, Nutrition, 8th edn. CIBA-GEIGY, Basle 5. Maynard A. (2006) Nanotechnology: A Research Strategy for Addressing Risk. PEN 3. Project on Emerging Nanotechnologies. Woodrow Wilson International Center for Scholars, Washington, DC 6. National Materials Advisory Board (2006) A Matter of Size Triennial Review of the National Nanotechnology Initiative. National Materials Advisory Board, National Research Council of the National Academies. National Academy of Sciences, Washington, DC 7. SCENIHR (2006) Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR modified Opinion (After Public Consultation) on the Appropriateness of Existing Methodologies to Assess the Potential Risks Associated with Engineered and Adventitious Products of Nanotechnologies. 002/05. European Commission Health & Consumer Protection Directorate-General 8. SCENIHR (2007) The Appropriateness of the Risk Assessment Methodology in Accordance with the Technical Guidance Documents for new and existing substances for assessing the risks of nanomaterials. Scientific Committee on Emerging and NewlyIdentified Health Risks. European Commission, Brussels 9. Scientific Committee on Consumer Products (2007) Opinion on the Safety of Nanomaterials in Cosmetic Products Adopted by the SCCP after the public consultation on the 14th plenary of 18 December 2007 SCCP/1147/07. European Commission, Brussels 10. Taylor M.R. (2006) Regulating the Products of Nanotechnology: Does FDA Have the Tools It Needs? Project on Emerging Nanotechnologies. Woodrow Wilson International Center of Scholars, Washington, DC 11. Tønning K., Poulsen M. (2007) Nanotechnology in the Danish Industry - Survey on production and application. Environmental Project No. 1206 2007. 2007. Copenhagen, Danish Ministry of the Environment Danish Environmental Protection Agency 12. Hansen, S.F., Michelson, E., Kamper, A., Borling, P., Stuer-Lauridsen, F., Baun, A. (2008) Categorization Framework to Aid Exposure Assessment of Nanomaterials in Consumer Products. Ecotox 17: 438–447

STRATEGIC APPROACHES FOR THE MANAGEMENT OF ENVIRONMENTAL RISK UNCERTAINTIES POSED BY NANOMATERIALS

R. OWEN School of Biosciences University of Westminster 115 New Cavendish Street London W1W 6UW, UK UK Environment Agency Block 1 Government Buildings Burghill Road, Bristol BS10 6BF, UK [email protected] M. CRANE WCA Environment Limited 23 London Street Faringdon, Oxfordshire, UK K. GRIEGER Institute of Environment & Resources Technical University of Denmark Lyngby, Denmark R. HANDY School of Biological Sciences, University of Plymouth Drake Circus Plymouth, UK I. LINKOV U.S. Army Engineer Research and Development Center 83 Winchester Street Brookline, Massachusetts, USA M. DEPLEDGE Peninsula Medical School John Bull Building, Research Way Plymouth, UK

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Abstract. Central to the responsible development of nanotechnologies is an understanding of the risks they pose to the environment. As with any novel material or emerging technology, a scarcity of data introduces potentially high uncertainty in to the characterisation of risk. Early priorities are the identification of key areas of risk uncertainty and the strategic approach for managing and reducing these. This is important as the information subsequently gathered supports decision making and policy development. We identify one important source of uncertainty for the quantification of both hazard and exposure for nanomaterials, the complexity of their behaviour in natural systems. We then outline two approaches for managing this uncertainty, based on experiences with chemicals: one that primarily focuses on hazard and one that initially focuses on exposure. While each approach places emphasis on different information requirements a common feature is the considerable time lag between information gathering and subsequent decision making based on the evidence gathered. Complementary environmental surveillance approaches can act as a safety net, although it is not as yet clear how fit for purpose current monitoring programmes are in this regard.1 1.

Introduction

In recent years there has been considerable debate concerning the potential environmental risks posed by nanomaterials, and in particular manufactured nanoparticles (see for example [13, 16, 17, 22, and references therein]. There are at least two factors contributing to this: firstly the unprecedented growth in the development, manufacture and use of diverse nanomaterials in many sectors and secondly the altered and in some cases emergent properties that nanomaterials may possess in comparison with the bulk form of the same material. The concern is that such altered properties may result in enhanced or novel adverse impacts to environment and to human health arising from increased toxicity, bioavailability or environmental persistence of the nanomaterial, or that they may interact with other chemicals in the environment, influencing the toxicity of those chemicals (e.g. [1]). With the advent of any novel material or new technology an early priority is the identification of significant areas of risk uncertainty, and nanomaterials are no exception to this. The Royal Society and Royal Academy of Engineers 2004 report was, for example, one important document that identified key uncertainties and others have followed, often describing these in terms of research needs (e.g. [11]). Since that report, one important source of risk uncertainty is emerging from laboratory studies of the fate, behaviour and ecotoxicity of manufactured nanoparticles [2, 9, 14]. Once they enter the natural environment (as with many so-called ‘non-conservative’ chemicals), complex changes can occur to their structure and physico-chemical behaviour. This complexity is influenced by a 1

The views and opinions expressed in this paper are those of the individual authors and not those of the US Army, NATO, or other sponsor agencies.

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number of abiotic and biotic factors which themselves may vary, depending on the environment in which a nanoparticle occurs [9]. Complex behaviour in natural systems raises significant issues for ecotoxicological hazard assessment and the modelling of environmental exposure for nanomaterials [3, 6], some of which we describe in more detail below. An important consequence of complexity is the introduction of potentially high uncertainty to assessments of their environmental risks [3]. 2.

Complexity of Behaviour: A Major Source of Uncertainty in Nanomaterials Hazard and Exposure Assessment in Natural Systems

Two key areas in environmental risk assessment where the complexity of nanomaterials behaviour in natural systems poses significant issues are in the quantification of hazard and exposure. Central to this are firstly establishing the relationship between exposure and toxicity (dose-response) and calculation of predicted no effects concentrations (PNECs) and secondly, the calculation of predicted environmental concentrations (PECs) to which PNECs may be compared in a risk assessment scenario. These calculations form the cornerstones of environmental risk characterisation. By way of an example, we might consider the development of an Environmental Quality Standard (EQS) for a manufactured nanoparticle. A chemical EQS is a value (generally defined by regulation) which specifies the permissible concentration of a chemical over a period of time in environmental samples, and is a primary tool for chemical regulation. By comparing a measurement of the chemical with the EQS it is possible to determine whether the chemical poses an environmental risk and, if so (i.e. if the EQS is exceeded), to advocate risk management. The development of the EQS itself is based almost entirely around hazard assessment. A PNEC is usually calculated from Lowest Observed Effect Concentration (LOEC) or No Observed Effect Concentration (NOEC) data using standard ecotoxicity tests (for example those recommended by the Organisation for Economic Co-operation and Development, OECD), to which ‘assessment’ (or ‘uncertainty’) factors have been applied. The key issue is that the LOEC and NOEC for a manufactured nanoparticle derived from laboratory studies is likely to be strongly influenced by the abiotic (and biotic) composition of the environmental matrix in which exposure occurs, variations in which may influence nanoparticle structure, form and behaviour [9]. In aquatic systems some relevant abiotic factors are pH, ionic strength and the concentration of humic substances in the aquatic matrix [9], Figure 1. These are known to influence and modify physico-chemical characteristics of the particle. Of these, one of the more important is the surface charge of the nanoparticle, as this will influence how particles will agglomerate. Such abiotic factors are likely to play critically important roles in mediating the bioavailability, bioaccumulation and toxicity of nanomaterials when exposure occurs in natural settings.2 2

In fact this may be a more general phenomenon: for example dermal penetration by a nanoparticle is influenced by the surface charge of the particle concerned.

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Figure 1. Aggregation of iron oxide nanoparticles in water as a function of pH. (Images courtesy of Jamie Lead and Mohammed Baalousha, University of Birmingham, U.K.)

Perhaps the best example of how abiotic and biotic factors are known to influence bioavailability, bioaccumulation and toxicity of nanomaterials is that of asbestos fibres. Here, it is a combination of the aspect ratio of the fibre (or shape) i.e. length and width, and the durability or biopersistence of the nanofibre, in the context of the physiological response in the airways and the macrophages in the lung (i.e. clearance), that are critical determinants of subsequent toxicity and pathology [19]. This demonstrates the need to understand complexity and biological interaction when predicting toxicity and pathogenicity for nanomaterials, when exposure occurs in natural settings. A consequence of complexity is that laboratory exposures of organisms to nanomaterials following standard test protocols, for example using (standard) de-ionised water, may have only limited environmental relevance when compared with the natural environment in which exposure occurs.3 Issues of complexity and 3

Such issues of relevance are not restricted to nanomaterials: it might be argued that similar issues exist for chemicals in general.

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the associated environmental relevance of standard tests will also apply to terrestrial systems although, based on the experience with ‘conventional’ chemicals, aquatic toxicity data are likely to be the primary information required for assessing risks to both aquatic and terrestrial environments in many regulatory contexts [6]. The implications of complexity and environmental relevance are that these may introduce a considerable measure of uncertainty to any LOEC or NOEC when calculated using current standard tests employed for chemicals. Further uncertainty in hazard assessment will result from, for example, the paucity of data on adsorption, distribution, metabolism and excretion (ADME) in organisms and the lack of information on chronic effects. In a similar way, the complexity of environmental nanomaterial behaviour will introduce uncertainty into determinations of predicted environmental concentrations (PECs) in complex environmental settings. Of note here is that receiving environments for nanomaterials (e.g. estuaries where pH and ionic strength can vary considerably) and indeed some sources of exposure such as complex industrial effluents can be highly complex in nature. As a consequence, uncertainties in predictions of exposure (PEC) and hazard (PNEC) will be propagated during characterisation of environmental risk, amplifying overall uncertainty when these are compared. An important point to note is that uncertainty in both hazard and exposure assessment is likely to vary with the nanomaterial concerned and its degree of functionalisation. This implies that uncertainty is not likely to be uniform across nanomaterials and that the contributing sources of uncertainty may vary with the nanomaterial concerned and the context of exposure. However, given the scarcity of data on fate, behaviour and effects it seems likely that for many nanomaterials, at least in the short to medium term, current uncertainties in hazard and exposure will continue to be large [21, 22]. This combination of scarcity of risk data and associated high risk uncertainty will be a recurring feature of many novel materials and technologies in the early phases of their innovation.4 A key issue for nanomaterials (and indeed any emerging technology or novel material) is how risk uncertainty should be managed i.e. what is the strategic approach to reducing risk uncertainty. 3.

Approaches for Managing Environmental Risk Uncertainties for Nanomaterials

Experience with ‘conventional’ chemicals allows us to identify a number of options for managing uncertainties in the environmental risk assessment of nanomaterials, two of which we highlight below. Each of these approaches has a different emphasis in terms of the type of information that would be collected, the first focussing on hazard and the second initially on exposure.

4

Note emerging debates concerning converging technologies e.g. synthetic biology.

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HAZARD-DRIVEN APPROACH

One approach for managing risk uncertainty is to take the view that the complexity of nanomaterials behaviour in the environment is so poorly understood, and detection methods so poorly advanced, that it would be unwise to rule out any potential exposure route for a nanomaterial i.e. make no a priori assumptions regarding environmental exposure at all. This would place the focus of data provision onto hazard, with potentially extensive toxicity assessments, with many types of organisms using endpoints that cover all potential exposure routes. This approach is somewhat counter to the tiered approach to risk assessment taken for conventional chemicals, where the exposure scenario guides hazard assessment and, within this, endpoint selection (see Section 3.2. below), and in this regard the case for making nanomaterials an exception would have to be made. One benefit of such an approach would be that it might be possible to assemble a comprehensive dataset of combined hazard and intrinsic properties of nanomaterials, and thereby ascertain which of these properties are important for governing toxicity. On the other hand, the burden of hazard testing, for both the nanomaterial and its functionalised variants, might be extensive, time consuming and costly. There also remain two outstanding issues with such an approach: the environmental relevance of a number of the tests that would be employed and the large residual uncertainty this introduces (discussed above), and the fact that some of the potential novel, indirect or chronic impacts might not necessarily be identified under current testing requirements, no matter how extensive these may be. Risk assessors have a useful tool that can be employed to address the issue of complexity and relevance and the associated uncertainty this introduces to hazard assessment: the use of uncertainty factors. This is a conventional and quantitative approach for managing high uncertainty associated with hazard (e.g. LOEC and NOEC calculations), where uncertainty factors of up to x1,000 can be applied to the LOEC or NOEC (e.g. [3] when calculating PNECs. This approach is recommended for managing uncertainty when hazard data are scarce or poor in quality, or where extrapolations are necessary (for example extrapolating from effects observed in laboratory rodent models to humans, or extrapolating from simple test systems to exposure in complex environments). The application of uncertainty factors to derive nanomaterial PNECs may appear to offer the risk assessor and risk manager an immediately applicable and pragmatic approach for defining a regulatory threshold, even where data are very scarce. However this approach is not without its limitations, not least of which is that the PNEC derived may be over precautionary. Additionally, where calculated PNECs are very low, characterising risk in the environment may require the development and optimisation of highly challenging or expensive analytical measurement methods (with very low limits of detection) to enable monitoring against the PNEC value. Such methods are either not available or require considerable optimisation for complex environmental matrices [10], all of which will take time. These are of course also similar issues for a number of ‘conventional chemicals’, such as endocrine disrupting oestrogens (e.g. ethinyl oestradiol), where experience indicates that such analytical challenges can pose significant

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feasibility questions when the implementation of very low EQS’s and associated costs are considered. 3.2.

EXPOSURE-DRIVEN APPROACH

In this approach the initial strategy is to gain a better understanding of environmental fate, behaviour, interaction and (importantly) bioavailability, with the premise that without exposure in a bioavailable form there can be no risk to organisms. A primary focus is in the initial development and subsequent validation of a conceptual model of exposure for the nanomaterial concerned, underpinned by a life cycle assessment approach that considers sources and pathways of exposure during production, use and end-of-life (e.g. waste disposal) [12]. Such models can be used to develop emission scenarios and mass flows in the environment [3] and suggest areas where better understanding of behaviour, form and fate in natural systems can reduce associated uncertainties5; these can be subsequently investigated to allow model refinement. To give one example of this, Blaser et al. [3] attempted to assess the risk of silver released from nano-functionalised plastics (i.e. silver from nanoparticles in a fixed form released via leaching). In developing a model of exposure they were able to observe that silver ions occur in solution at only low concentrations in the aquatic environment, with most silver occurring as silver-sulphide clusters; they noted however that most toxicological studies use silver nitrate (which forms silver ions in aqueous solution) and that the effects of the more environmentally – relevant forms of silver i.e. the clusters, have been only little studied. Their recommendation was that uncertainty in the environmental chemistry of silver per se and scarcity of toxicological studies that considered silver in its most environmentallyrelevant form posed the greatest uncertainties for risk assessment. This exemplifies one of the biggest challenges for environmental risk assessment of nanomaterials; a priority need to understand behaviour and bioavailability in natural systems. In developing a conceptual exposure model for a given nanomaterial, an understanding of sources to the environment, pathways and environmental fate are important, underpinned by an understanding of material physico-chemical properties. Measurements of such properties are recommended by OECD for risk assessments of conventional chemicals. It is likely that some currently required measurements (e.g. KOW, or octanol – water partition coefficient used to assess potential bioaccumulation and trigger sediment toxicity tests) may not be suitable for nanoparticles [6]). However, in general, measuring properties such as surface charge, chemical composition, particle size range and so on are a useful and established starting point for building the exposure scenario for any given nanomaterial, based on fundamental properties of the material itself.

5

It should be noted however that increasing knowledge within a complex system may initially reduce some uncertainties, but may also serve to increase other uncertainties simultaneously due to exposed knowledge-gaps that were previously unrecognized.

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In this approach a premium is placed on tools and data that allow better prediction of bioavailability through an understanding of the complexity of behaviour and speciation of nanomaterials in complex natural environments. To give an example from the world of ‘conventional chemicals’, the development of biotic ligand models for assessing hazards due to metals and the need to understand factors such as pH and DOC in receiving waters resulted from an understanding that bioavailability and toxicity must account for metal speciation and the factors that influence this [18]. In this regard the issues posed by nanomaterials have been faced before for chemicals such as metals in non particulate form. What is discussed above, including the development of a conceptual model of exposure, is in fact an important aspect of what is called risk ‘problem formulation’: this is the initial phase of a tiered environmental risk assessment approach that is accepted on a global basis. Problem formulation helps define the source-pathwayreceptor connectivity and, through an understanding of exposure routes and bioavailability, which endpoints should be assessed in subsequent quantitative risk assessment. Of course, hazard assessment remains an integral aspect of this approach, but rather than immediately measuring all endpoints, the selection of these is guided by an initial evaluation of exposure and bioavailability, with the emphasis initially being on collecting data that help reduce uncertainty in this area. To date, while there have been important considerations of the appropriateness of test methods for nanomaterials (e.g. Crane et al. [6]) less attention has been given to the problem formulation phase of environmental risk assessment and how this could be strengthened [17]. This initial phase is fundamentally important in setting the context and boundaries of the subsequent qualitative and quantitative risk assessments, and (importantly) justifies the intent to undertake such assessments [7]. While it is acknowledged that poor problem formulation results in inappropriate risk analysis [20], this aspect of risk assessment is an area which has to date received only limited consideration in the context of nanomaterials. The need for effective problem formulation is further emphasised by a defining feature of nanomaterials: the cosmopolitan nature of these group of substances. Not only is there an ever growing number of materials, from carbon nanotubes to metal oxides, but individual nanomaterials can be functionalised (e.g. by surface modification and ligand chemistry), which may in turn influence their environmental behaviour and effects. There are also potential impurities within nanoparticles, the quantity and nature of which may vary depending on the manufacturing process. It seems unfeasible to undertake full quantitative risk assessments for every nanoparticle, and its functionalised variants. Nor may this be necessarily desirable, if effective problem formulation suggests it is not justified. Tools that can support problem formulation for nanomaterials go beyond those that can help with understanding exposure and bioavailability. Grouping and readacross approaches could also help, and may indeed allow defensible testing of only a representative substances within a category (e.g., see OECD QSAR

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Application Toolbox6 [15]). Structure–activity relationships may also play an important role. The value of structure–activity relationships in chemicals risk assessment is in fact best exemplified by a nanomaterial: asbestos fibres. The fibre–pathogenicity model is probably one of the most studied and robust structure–activity models in chemicals risk assessment. In this model, an understanding of asbestos pathogenicity has led to development of a structure– activity model for high aspect ratio nanofibres that have specific dimensions (i.e. >20 µm in length and <3 µm in diameter) and that are biopersistent. Nanofibres that exhibit these properties are known to be potentially harmful to human health if exposure is via the airways. There is a reasonable basis within problem formulation to prioritise high aspect ratio nanotubes and fibres for quantitative hazard and exposure assessment, based on both the structure –activity relationship and the source–pathway–receptor connectivity i.e. justifying the intent. Indeed recent work by Poland et al. [19] based on this structure–activity model suggests its applicability for some carbon nanotubes which exhibit a high aspect ratio. However, when moving beyond this specific scenario, the lack of data linking nanomaterials properties to effects suggests that the application of traditional QSAR models may be as yet limited for emerging chemicals. The results of important initiatives such as the OECD safety testing of a representative set of nanomaterials may perform a useful role to this end. The above approach, in which problem formulation and development of a conceptual model of exposure drive the risk assessment process, defining the endpoints for hazard assessment, is in line with established thinking for environmental risk assessment of chemicals in general. However, the ever changing innovation landscape and diversity of nanomaterials and the convergence of technologies (e.g. bio and nano) suggests that such problem formulation needs to be iterative, and interfaced with horizon scanning activities and technology roadmaps (Figure 2).

Figure 2. Interfacing horizon scanning and iterative problem formulation to justify the intent to undertake quantitative environmental risk assessment.

6 However, for this approach to be acceptable the key physical and chemical parameters that influence toxicity within a nanoparticle category will need to be known.

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Incremental Research to Reduce Risk Uncertainties – The Right Strategy?

In outlining the options for managing large risk uncertainties in an initially data scarce environment, we are challenged with the question, what sort of information should be assembled to enable confident decision making about risks? Each of the two approaches outlined above places different emphasis on the information gathered, for example through the commissioning of research from public or private budgets. This is an important question, because the nature and quality of the information gathered, and the way this information is framed socially, will form the evidence base on which decisions concerning the development or amendment of regulation will be made. Many research programmes on nanomaterial Safety, Environment and Health have been established over recent years with the intention of providing the evidence base to inform development of policy and appropriate controls. These programmes provide an important mechanism to reduce risk uncertainties, and although the information gathered cuts across both the strategic options outlined above, it is becoming clear that understanding exposure and bioavailability is a growing priority. However, irrespective of the strategic approach taken, pragmatism and experience suggest that the development of models of exposure and bioavailability, the establishment of mechanisms of toxicity, pathogenicity and ecological effects, and the development of structure–activity models and their subsequent validation through empirical research all suffer from one common and critical issue, the time required to obtain the information on which subsequent decisions are made, relative to the pace of innovation of the technology [13, 23], Figure 3. This issue is becoming increasingly recognised: for example, a recent review of the US EPA Nanomaterial Research Strategy [24] highlighted the fact that decisions on the safe use of engineered nanomaterials in the near-term need to be made within a data-poor environment; it further recognised the potential value of approaches such as Expert Judgment and Multi-Criteria Decision Analysis to address this issue [13], the latter being an approach that allows the structuring of fragmented information for application in environmental management. In some cases, for example when a large environmental impact is observed or a laboratory study suggests a material is very harmful (e.g. [19]) management decisions are made over shorter timescales, often through the invoking of the precautionary principle. In general however, incremental research to advocate amendment or development of new regulation is an inherently slow process, and (as seen with nanomaterials), follows the introduction of the technology into society. Given this, it might be argued that a strategy of reducing risk uncertainties through incremental, often reductionist research may provide important information to support confident decision making, but this may only extend to a small number of nanomaterials and even then, take many years to realise.

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Figure 3. Time lags in emergence of nanoproducts, generation and analysis of environment, health and safety data and regulatory decision making [13].

It might also be argued, based on our experience with chemicals in the past, that even with the most comprehensive programme of research to reduce risk uncertainties, some nanomaterials may ‘fall between the cracks’, due to unforeseen, novel or indirect impacts. Could it have been predicted, for example, that the automobile internal combustion engine would have such wide impacts on society and the environment through greenhouse gas mediated climate change? Experience has taught us that the nature of the potential chronic and indirect environment, health, safety and social impacts of novel chemicals and technologies are sometimes difficult to identify early on in the development of a technology [5]. In this regard the concern may be less about making a priori assumptions concerning exposure and more about making a priori assumptions of the nature of impacts that might ensue. In part, this further emphasises the need to ensure problem formulation is iterative and not static, developing a weight of evidence that in turn guides the risk assessment process through an adaptive learning architecture, allowing management and control at an early stage, before irreversible entrenchment of the technology within society [5]. However, it also cautions us to develop a safety net around a strategy that seeks to manage risk uncertainties through incremental research. The question then becomes, what would that safety net be? 5.

The Case for Environmental Reconnaissance and Surveillance

One potential safety net is through reconnaissance and surveillance, enacted for example through environmental monitoring programmes. One approach might be

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to amend ongoing programmes to monitor levels of one or more nanomaterials, particularly where inputs to the environment are significant. However, as discussed above, while sophisticated measurement techniques do exist, they are currently very expensive to use, or not optimised for use in complex matrices, or not widely available for use by regulators. Even assuming that the problems of appropriate field instruments can be overcome, monitoring would have to address both the nanomaterial itself and any breakdown products. The latter is key as some of the secondary products could turn out to be more harmful than the parent nanomaterial itself. A particular technical challenge to be overcome is that current concentrations of manufactured nanoparticles in ecosystems are likely to be small, compared with concentrations of naturally occurring nanoparticles. Consequently, monitoring programmes would need to be capable of detecting quite low concentrations of manufactured nanoparticles against a relatively high background concentration of naturally occurring nanomaterials. However, the very high level of investment in nanotechnologies suggests that in the future nanomaterials will continue to be released, intentionally or unintentionally into our ecosystems. This highlights the importance of determining where manufactured nanomaterials accumulate and for how long they will persist. One approach might be to actively look for sites at which nanomaterials might be expected to accumulate, thereby enhancing the exposure assessment process. This active, intelligence-led reconnaissance deserves much more attention than it has received in the past. Here, a challenge is to develop tools that permit a rudimentary, conceptual life cycle model of environmental exposure to be undertaken by manufacturers and users of nanomaterials that allow identification of where important environmental sinks for those nanomaterials may be. This might then allow the targeted deployment of reconnaissance tools (e.g. the deployment of passive sampling devices in aquatic environments, especially in sediments, which might allow nanomaterials to be concentrated and detected more readily). In reality however, without a regulatory driver, the justification to develop analytical techniques and to amend routine monitoring programmes would follow the results of incremental research, whereby curiosity driven studies would drive the development or optimisation of those techniques to detect nanomaterials in the form in which they occur in the environment, and subsequently apply them to quantify environmental burdens. Where these were found to be significant and above levels thought to be harmful (see Section 3.1 above) regulatory monitoring would be enacted and programmes amended accordingly. This seems unlikely to address the issue of the time lag between innovation, information gathering and decision making described above. An alternative approach would be to monitor primarily for biological impacts in the environment, and subsequently apportion observed impacts to nanomaterials through confirmatory analyses (so called Toxicity Identification and Evaluation). Indeed, ecotoxicologists have thought long and hard about this, in their search for an approach that can help to pragmatically manage high risk uncertainties associated with known and unknown chemicals in complex natural environments, where toxicity or bioavailability are poorly understood. To give one example, the development and implementation of Direct Toxicity Assessment (DTA) within the

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Pollution Prevention and Control legislation in the UK reflected the need to quantify hazards and risks of discharges of complex chemical mixtures into the aquatic environment that are of unknown or uncertain bioavailability and toxicity (this might include many current nanomaterials in production). It is worth expanding slightly on DTA (also known as Whole Effluent Assessment), as it potentially offers a promising approach in this regard. It begins with ‘whole discharge’ toxicity testing to assess the integrated effects of chemicals as complex mixtures. DTA is applied where a discharge contains one or more unknown chemicals and their breakdown products, or where the toxicity of these substances is unknown or has been insufficiently evaluated. This would at first glance apply to many nanomaterials for which environmental bioavailability and toxicity data are scarce. It takes the form of acute, and where necessary chronic, standard ecotoxicity tests on the discharge itself (perhaps addressing the issue of environmental relevance of tests discussed before). Where toxicity is found, an assessment of risk accounting for effluent dilution in the receiving waters is undertaken. Of course, it goes without saying that the subsequent toxicity identification and evaluation (TIE) process necessary to define the source of the toxicity in the effluent and apportion this to the constituent nanomaterials in the waste stream would be associated with the same sort of analytical challenges discussed above. However, end of pipe DTA approaches may at the very least allow a toxicological screening of direct sources of nanomaterials into the environment without an immediate need for these highly sophisticated analytical techniques. Such an approach, which could be quite rapidly extended to cover nanomaterials in waste streams, might afford a level of protection for the environment, through the identification of the most significant point sources of nanomaterials in terms of toxicity, and screening out of those effluents where toxicity is not observed. The argument against such an approach is that there is still, at least in the U.K., a reliance on largely acute toxicity tests (e.g. using Daphnia immobilisation or algal growth), which may not address any indirect or novel impacts, but this is a more general issue for chemicals and is not specific to nanomaterials. In addressing this, it might be possible for example to amend standard tests used in DTA to assess genotoxicity [4], which along with oxidative stress are two toxic impacts that have been associated with exposure to at least some nanomaterials. Whether the endpoints chosen are entirely appropriate or not, the principle behind DTA is to place an emphasis on measuring biological effects first and then understanding the causes of toxicity where this is observed. When considering novel materials or technologies and their potential to cause environmental impacts, it seems sensible to consider such biological effects surveillance approaches as a safety net for the management of risk uncertainties through incremental research. Such surveillance is best enacted if it is undertaken within the context of an integrated risk assessment approach, for example combining ecological monitoring in a water body with measures of toxic impact at an organismal level (using for example appropriate biomarkers), both undertaken within the context of an understanding of sources of chemicals to that water body and modelling of the potential for exposure [8]. In Europe, there is a vehicle for

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this through the most important piece of legislation for managing and conserving water resources, the Water Framework Directive. It would be worth considering which of the surveillance systems currently in place could offer an effective safety net to ensure environmental impacts are first monitored and then apportioned to nanomaterials, whether they need amending and, if so, what amendments might be made. There have been numerous examples of chemicals that have slipped through the risk assessment process in the past (e.g. DDT, methyl mercury, endocrine disruptors, etc.) and it is probably unrealistic to imagine that at least some forms of nanomaterials will not pose new kinds of problems in the environment. If applied appropriately, such biological surveillance approaches could provide some added security that these unexpected effects are detected early and are dealt with rapidly. 6.

Conclusions

As with any emerging technology or novel material the risk scenario for nanomaterials is one of data scarcity and associated high risk uncertainty. Several strategies for managing risk uncertainties are available to risk assessors and risk managers, each of which places emphasis on different information requirements. The key issue becomes, with the advent of any new technology or novel material, what sort of information should be assembled to enable confident decision making about risks and the associated development of proportionate controls. Irrespective of the strategy employed for managing and reducing the uncertainties identified, each suffers from a common issue: the potentially large time lag between innovation, uncertainties identification and the acquisition of data to reduce uncertainties. This suggests the need to develop or optimise environmental surveillance approaches that can act as a safety net, although how fit for purpose current monitoring and surveillance programmes are to meet this objective has yet to be evaluated. Acknowledgements We thank Peter Van der Zandt (European Commission) Rick Canady (US Food and Drug Adminstration), Sophie Rocks and Simon Pollard (Cranfield University), Paul Whitehouse and Steve Robertson (Environment Agency, UK) for their insightful discussions. Disclaimer The views here do not necessarily represent those of the Environment Agency.

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References 1. Baun, A., Sørensen, S.N., Rasmussen, R.F., Hartmann, N.B., and Koch, C.B. (2007) Toxicity and bioaccumulation of xenobiotic organic compounds in the presence of aqueous suspensions of aggregates of nano-C60, Aquatic Toxicology 86, 379–387. 2. Baun, A., Hartmann, N.B., Grieger, K., and Kusk, K.O. (2008) Ecotoxicity of engineered nanoparticles to aquatic invertebrates: a brief review and recommendations for future toxicity testing, Ecotoxicology 17, 387–395. 3. Blaser, S.A., Scheringer, M., Macloed, M., and Hungerbuhler, K. (2008) Estimation of cumulative aquatic exposure and risk due to silver: contribution of nano-functionalized plastics and textiles, Science of the Total Environment 390, 396–409. 4. Cheung, V.V., Owen, R., Depledge, M.H., and Galloway, T.S. (2006) Development of the in vivo chromosome aberration assay in oyster (Crassostrea gigas) embryo-larvae for genotoxicity assessment, Marine Environmental Research 62, S278. 5. Collingridge, D. (1980) The Social Control of Technology. Francis Pinter Ltd, London, pp 200. 6. Crane, M., Handy, R.D., Garrod, J., and Owen, R. (2008) Ecotoxicity test methods and environmental hazard assessment for engineered nanoparticles, Ecotoxicology 17, 421– 437. 7. DETR (2000) U.K. Guidelines for Environmental Risk Assessment and Management. Available online at www.defra.gov.uk/environment/risk/eramguide/index.htm, last accessed 23 July 2008. 8. Hagger, J.A., Jones, M.B., Lowe, D., Leonard, D.R.P., Owen, R., and Galloway, T.S. (2008) Application of biomarkers for improving risk assessments of chemicals under the Water Framework Directive: a case study, Marine Pollution Bulletin 56, 1111– 1118. 9. Handy R.D., van der Kammer, F., Lead, J.R., Hassellöv, M., Owen, R., and Crane, M. (2008) The ecotoxicology and chemistry of manufactured nanoparticles, Ecotoxicology 17(4), 287–314. 10. Hassellöv, M., Readman, J.R., Ranville, J.F., and Tiede, K. (2008) Nanoparticle analysis and characterisation methodologies in environmental risk assessment of engineered nanoparticles, Ecotoxicology 17, 344–361. 11. HM Government (2005) Characterising the Potential Risks Posed by Engineered Nanoparticles: A First UK Government Research Report. Department of Environment, Food and Rural Affairs, HM Government, pp 57. PB 11485. Available online at http://www.defra.gov.uk/environment/nanotech/nrcg/, last accessed 23 July 2008. 12. Kohler, A.R., Som, C., Helland, A., and Gottschalk, F. (2008) Studying the potential release of carbon nanotubes throughout the application lifecycle, Journal of Cleaner Production 16, 927–937. 13. Linkov, I., and Satterstrom, K. (2008). Nanomaterial risk assessment and risk management: Review of regulatory frameworks. In: Linkov, I., Ferguson, E., Magar, V. (eds), Real Time and Deliberative Decision Making: Application to Risk Assessment for Non-chemical Stressors. Springer, Amsterdam 129–158. 14. Neal, A., (2008) What can be inferred from bacterium – nanoparticle interactions about the potential consequences of environmental exposure to nanoparticles. Ecotoxicology 17, 362–371. 15. OECD Environment Directorate (2008) OECD Quantitative Structure-Activity Relationships [(Q)SARs] Project. Available online at http://www.oecd.org/document/23/ 0,3343,en_2649_34379_33957015_1_1_1_1,00.html, last accessed 23 July 2008.

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16. Owen, R., and Depledge, M.H. (2005) Nanotechnology and the environment: risks and rewards, Marine Pollution Bulletin 50, 609. 17. Owen, R., and Handy, R. (2007) Formulating the problems for environmental risk assessment of nanomaterials, Environmental Science and Technology 41(16), 5582– 5588. 18. Paquin, P.R., Gorsuch, J.W., Apte, S., Batley, G.E., Bowles, K.C., Campbell, P.G.C., Delos, C.G., Di Toro, D.M., Dwyer, R.L., Galvez, F., Gensemer, R.W., Goss, G.G., Hogstrand, C., Janssen, C.R., McGeer, J.C., Naddy, R.B., Playle, R.C., Santore, R.C., Schneider, U., Stubblefield, W.A., Wood, C.M., and Wu, K. (2002) The biotic ligand model for metals – current research, future directions, regulatory implications, Comparative Biochemistry and Physiology, Part C, 133, 3–35. 19. Poland, C.A., Duffin, R., Kinloch, I., Maynard, A., Wallace, W.A.H., Seaton, A., Stone, V., Brown, S., MacNee, W., and Donaldson, K. (2008) Carbon nanotubes introduced into the abdominal cavity of mice show asbestos – like pathogenicity in a pilot study, Nature Nanotechnology 3, 423–428. 20. Pollard, S.J.T. (2006) Risk Management for the Environmental Practitioner, IEMA Practitioner No. 7, Best practice series, Institute of Environmental Management & Assessment, Lincoln, UK. 21. Royal Commission on Environmental Pollution (2008) Novel Materials Study, expected publication date November 2008 (http://www.rcep.org.uk/novelmaterials. htm), last accessed August 4, 2008 (in press). 22. Royal Society and Royal Academy of Engineering (2004) Nanoscience and Nanotechnologies: Opportunities and Uncertainties. Available online at http://www.nanotec. org.uk/finalReport.htm, last accessed 23 July 2008. 23. Linkov, I., Satterstrom, K., Steevens, J., Ferguson, E., and Pleus, R. 2007. Multi-criteria decision analysis and environmental risk assessment for nanomaterials, Journal of Nanoparticle Research 9, 543–554. 24. http://es.epa.gov/ncer/nano/publications/nano_strategy_012408.pdf

METHODS OF ECONOMIC VALUATION OF THE HEALTH RISKS ASSOCIATED WITH NANOMATERIALS

S. SHALHEVET SustainEcon – Environmental Economics Consulting 126 Thorndike Street Brookline, MA 02446, USA [email protected] N. HARUVY Netanya Academic College 1 University Street Netanaya, Israel 42365

Abstract. The worldwide market for nanomaterials is growing rapidly, but relatively little is still known about the potential risks associated with these materials. The potential health hazards associated with exposure to nanomaterials may lead in the future to increased health costs as well as increased economic costs to the companies involved, as has happened in the past in the case of asbestos. Therefore, it is important to make an initial estimate of the potential costs associated with these health hazards, and to prepare ahead with appropriate health insurance for individuals and financial insurance for companies. While several studies have examined the environmental and health hazards of different nanomaterials by performing life cycle impact assessments, so far these studies have concentrated on the cost of production, and did not estimate the economic impact of the health hazards. This paper discusses methods of evaluating the economic impact of potential health hazards on the public. The proposed method is based on using life cycle impact assessment studies of nanomaterials to estimate the DALYs (Disability Adjusted Life Years) associated with the increased probability of these health hazards. The economic valuation of DALY’s can be carried out based on the income lost and the costs of medical treatment. The total expected increase in cost depends on the increase in the statistical probability of each disease. 1.

Introduction

The worldwide market for nanomaterials is growing rapidly, and is expected to reach nearly $2.6 trillion by 2014, up from $50 billion in 2006 [1]. But despite the growing usage, relatively little is still known about the potential risks associated with these materials. So far, information on the health risks associated with I. Linkov and J. Steevens (eds.), Nanomaterials: Risks and Benefits, © Springer Science + Business Media B.V. 2009

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nanomaterials is available mostly from studies of pollution-derived incidental nanoparticles exposure. Many studies show that exposure to particulate air pollutants increases the risk of pulmonary, cardiovascular, and central nervous system (CNS) disease. Some studies show that exposure to the nanoparticle component of the particulate pollution increases the health risks at much lower exposure concentrations than the exposure to micron-sized particles [26]. Moore [20] quotes a large body of research showing that ultrafine particles can be dangerous to human health. The US Environmental Protection Agency has attributed 60,000 deaths per year to the inhalation of atmospheric nanoparticles, and there is evidence for direct transfer into the brain. For example, several studies have found potentially significant pulmonary toxicity of carbon nanotubes [26], and other studies have found that carbon fullerenes (buckyballs), currently being used in some face creams and moisturizers, can cause damage to fish, and may be toxic to humans [6]. Weisner et al. [29] point out that most of the human exposure to nanomaterials is likely to be caused during the manufacturing process, putting the workers at the greatest risk. However, some exposure is possible from the use of nanomaterials and their release into the atmosphere and accumulation in soil and water resources. The exposure to nanomaterials may be through inhalation of particles in the air, ingestion of food or water containing nanomaterials or even of the materials themselves. Some damage may also occur through dermal exposure to sunscreen or cosmetics [29], although significant dermal absorption seems to be unlikely [27]. The potential health hazards associated with exposure to nanomaterials may lead in the future to increased health costs as well as increased economic costs to the companies involved, as has happened in the past in the case of asbestos. Furthermore, fear of the unknown health hazards may cause consumers to reject the use of nanotechnology, similarly to the widespread consumer rejection of agricultural biotechnology products. The rejection of GMO foods based on the perception of risk had cost some biotechnology companies billions of dollars [19], and there are signs of a similar phenomena developing in nanotechnology. For example, the Soil Association, a British organic agriculture association, announced in January 2008 that it has banned human-made nanomaterials from the organic cosmetics, food and textiles that it certifies [4]. A widespread public rejection of nanomaterials could result in even greater losses, because the technology is being incorporated into a greater variety of industries. Therefore, it is important to make an initial estimate of the potential costs associated with these health hazards, and to prepare ahead with appropriate health insurance for individuals and financial insurance for companies. Currently, the data on the health impacts of nanomaterials needed to make these estimates is rather limited. A survey of nanotechnology firms in the Massachusetts region found that the greatest barrier to understanding and managing the EHS risks is the lack of quantitative information available. This barrier is compounded by the shortage of material and staff resources in the smaller firms [17]. The survey found that firms rely mostly on data from suppliers, expert judgement, best practices, or current regulations as guidelines for risk assessment and management.

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One of the common methods of evaluating the environmental impacts of new products is life cycle assessment (LCA), which takes into accounts all the inputs used in production and the outputs generated throughout the product’s life cycle. The input and output analysis starts with the inputs used to extract the raw materials and build the machinery used for production, transportation of materials, and continues up until the point that the final product is disposed of as waste at the end of its life cycle. This method is generally considered most useful as a tool to compare the impacts of different products that serve similar functions and can substitute for each other. A general general framework for incorporating life cycle assessments in nanotechnology risk management was suggested by Sweet and Strohm [27], based on their review of the existing findings on health and environmental impacts. But one of the most comprehensive attempts to date to build a system for data assessment and life cycle assessment was carried out jointly by Environmental Defense Fund and DuPont, who published a joint proposal for a Nano Risk Framework that includes a detailed process of evaluating and addressing the potential risks of nanoscale materials [18]. DuPont applied this framework to three nanomaterials it produces: DuPontTM Light Stabilizer 210, a s titanium dioxide that acts as a UV stabilizer and UV screener for polymers; carbon nanotubes (CNTs), cylindrical carbon molecules that have a variety of applications; and a nano-sized zero-valent iron (nano-Fe0), which may potentially be used to destroy contaminants in groundwater. The results of their life cycle assessments are posted on their website (www.NanoRiskFramework.com). Other studies have made life cycle assessments of nanomaterials, combined with economic assessments of their profitability. For example, Roes et al. [25] conducted a life cycle impact assessment of the use of a polypropylene (PP)/layered silicate nanocomposite as packaging film, agricultural film, and automotive panels. They found that the incorporation of nanoclays in nanocomposites can have an impact on the environment, but that impact can be compensated for if the environmental benefits are large enough (in this case, the benefits from a lower weight of the produced film). The life cycle costs depend on the specific application, and were found to be higher than those of conventional products in the case of packaging film and lower in the case of agricultural film and automative panels. However, these studies concentrated on the cost of production, and did not estimate the economic impact of the health hazards on the general population. Economic evaluation of the health impacts is important in order to make decisions comparing products based on nanomaterials with conventional products. 2.

Methods of Economic Evaluation

A full comparison of different products with different types of impacts needs to consider the economic aspects as well. Environmental economics methodologies are commonly employed to take into account the environmental impacts of a product in the final comparison of the economic costs and benefits from comparative

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products. The analysis of the economic impacts of the health risks associated with production relies on a variety of methods, such as estimating people’s willingness to pay to reduce their health risks. Similarly, health economics methodologies are commonly employed to compare the outcomes of products or services that may improve population’s health, relying on methods of estimating the value of changes in quality of life for individuals. The discussion in this section focuses mostly on concepts from health economics, but the basic principles are very similar in both environmental and health economics [14]. A general framework for decision analysis based on economic valuation of health impacts is presented in Figure 1. The process is based on data collected from epidemiological studies on the health impacts of different materials. This data is translated into health risk assessments, taking into account exposure at varying amounts and the probabilities of different health outcomes. Economic analysis is based on combining these results with economic data in order to estimate the economic value of different health impacts. At the micro (company) level, the results of economic evaluation of their products may be used to assess the risk involved, as well as the scope of insurance which may be needed to cover these risks. At the macro (national) level, the results may be used to determine national policies on regulations and investments in different nanotechnologies. Economic data

Epidemiological data

Health risk assessment

Economic analysis

Results Micro level:

Company risk management; Insurance decisions.

Macro level:

Public investments; National policies & standards.

Figure 1. Risk management model.

Evers et al. [5], Kenkel [14], Kuper et al. [15], Rice and Hammitt [24], and others summarize the methodologies of economic evaluation of health impacts. An economic evaluation usually compares the product in question with the alternative, which may be an existing product or an alternative new development. There are four basic types of economic evaluation of health impacts: cost-

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minimization, cost-benefit, cost-effectiveness and cost utility [15, 16]. In cost minimization it is assumed that the products have similar impacts and differ only in their costs; this method would generally not be appropriate for evaluating products based on emerging technologies, such as nanotechnology based products. Cost effectiveness analysis (CEA) and cost-utility analysis are illustrated in Figure 2. Both methods are based on comparing the physical health impacts rather than their economic value of the benefits, and making a monetary evaluation only of the costs involved. Cost effectiveness analysis compares specific alternative products with different health impacts, and is therefore most suitable for microlevel comparisons of one company’s product against its alternative. The basic unit of measurement is time – health impacts are measured by the impact on a person’s time. This includes the impact (positive or negative) on longevity – extension of life years due to improved health, or reduced life expectancy due to the product examined. This measure also includes the time lost due to the disability – lost time due to illness or time spent on additional health care. The total time of life years lost is termed Disability Adjusted Life Years (DALY). Cost utility analysis provides a measure of the value people place on their life and on different states of health [3]; and assigns different weights to different periods of life, based on one’s health. A state of perfect health is assigned a weight of 1; death is assigned a value of 0; and disabilities of varying degrees are assigned weights between zero and one. It is also possible to assign a negative weight, to a state defined as worse than death. The total sum of life years multiplied by life quality weight for each period is termed Quality Adjusted Life Years (QALY) [24]. Cost effectiveness analysis is less suitable for comparing products with different types of impacts [22]. For decisions involving different categories of impacts, or comparisons with a multitude of different options for investments, cost-benefit analysis should be carried out. This method, as illustrated in Figure 3, requires an economic evaluation of the benefits as well as the costs involved in each alternative. In this case, the health impacts are expressed in monetary rather than in time units. The economic valuation of the health impacts is based on assigning an economic value to life years as measured in DALY or QALY, by applying one or more of the range of economic methods for monetary valuation of societal & environmental benefits. The monetary valuation can be based either on the Human Capital Approach (HCA) or the Value of Statistical Life (VSL) method. The Human Capital Approach (HCA), is based on calculating the value of disability time based on a total of the costs of treatment and the loss of potential earnings. Treatment costs may include direct costs of providing health care, such as emergency room visits, hospital stay and subsequent treatment; as well as the indirect costs, or patient time costs, of restricted activity days, and the cost of workday loss [3, 24]. The loss of potential earnings includes both the loss of annual earnings and the assigned value for the loss of household services performed, In cases where the health impacts of the exposure of pregnant women or children may result in impaired development, the cost of developmental delays is calculated by multiplying the probability of each type of developmental delay with its expected impacts on lifetime earnings. The example in Figure 4 shows the

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economic impact of developmental delays as a result of exposure to mercury. The IQ deficit resulting from fetal exposure or exposure as small child to mercury is estimated based on epidemiological data; and the economic evaluation is presented under both the Human Capital Approach (HCA) and the Value of Statistical Life (VSL) method. The Value of Statistical Life (VSL) is defined as the willingness to pay to avoid a small change in risk of dying – that is, the incremental value of a minor increase in risks and NOT the value of saving the individual’s life. There are many methods of estimating the value of statistical life. One of these methods is contingent valuation – disseminating surveys asking people what they are willing to pay to avoid a small increase in specific risk. Another method is averting behaviour measurement – examining people’s investments in preventive measures as an indicator of willingness to pay for risk avoidance. A third method is hedonic valuation, which looks at the relationship between some market price and risk, usually by performing a regression analysis between risk and independent

Level of Analysis

Comparing specific alternatives with different health impacts

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CEA Cost Effectiveness/Utility Analysis

Method

Unit of measurement

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DALY Methods of evaluation

Identifying the alternative with highest benefit/cost ratio

Measuring health benefits in time units (cost per life year saved)

Cost Effectiveness Analysis: Disability Adjusted Life Years

QALY Figure 2. Economic analysis methods: cost-effectiveness analysis.

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CBA Cost Benefit Analysis

Method

Unit of Measurement

Methods of Evaluation

Applies economic methods for monetary valuation of societal & environmental benefits

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Human Capital Approach: Cost of illness Value of Statistical Life: Willingness to pay

Figure 3. Economic analysis methods: cost-benefit analysis.

variables. An example of the latter method is hedonic valuation based on wages – that is, observing the risk premiums paid for riskier jobs as an indicator of people’s willingness to accept a monetary compensation for increased risk. Researchers estimate that the value of a lost productive day, using the human capital approach, is about $150/day [9]. Estimates of the Value of Statistical Life (independent of age), range between $3–9 million; The US Environmental Protection Agency (EPA) uses an estimate of $5.9 million for its calculations [24]. As a general rule, economic valuations of the Value of Statistical Life usually yield much higher values than the Human Capital Approach. An example of the discrepancy between the two values, for the health impacts of exposure to mercury by gender, is shown in Figure 4, which is based on the data published by Rice and Hammitt [24]. Gyrd-Hansen [10] notes that even within the VSL measure, different estimation can result in variations by a factor of 40, and that the results are affected by the respondents’ income level. Despite these limitations, he concludes that using contingent valuation methods for economic evaluation of health impacts is a useful, if imprecise, tool for decision-making.

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3500 VSL: Females

Billion US$ (2000)

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2500 2000 1500 1000 500

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0 Figure 4. Valuation of health risks from exposure to mercury in consumers of commercial fish (total for the US). (Prepared from data in [24], Tables 71 and 80.)

Economic analysis is an essential component in determining public health policy, but it is often unclear how it should be carried out, and with whom the responsibility lies. John Graham, administrator of the Office of Information & Regulatory Affairs at the Executive Office of the US President, states that “... costeffectiveness analysis and cost-benefit analysis ... can help us accomplish more public health and medical protection at less cost than will occur when decisions are made without good analysis ... it is fair to say that their influence on practical decision making in both the public sector and the private sector has been limited to date” [8]. Furthermore, Graham suggests that university-based scientists’ ability to offer solutions to emerging health issues is limited, because addressing these issues requires multidisciplinary teams of the type university students find difficult to put together. 3.

Application to Nanomaterials

The neglect of economic analysis in the formulation of public health policies is particularly notable in the field of nanotechnology, because of the special difficulties involved in analysing emerging technologies [8]. However, although there is little direct data available, it is possible to compare the known hazards of nanoparticles with other toxic agents, in order to evaluate the statistical probability of different health hazards, such as the impact of carbon nanotubes (CNTs) on pulmonary toxicity. Von Gleich et al. [7] suggest an approach to making life cycle assessments of nanomaterials that takes into consideration the limitations of available information. Mueller and Nowack [21] present exposure models of engineered nanoparticles of different types that may be used to model risk

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assessments. Quantifying the disability adjusted life years can be done based on the known health hazards of similar components, and its economic valuation can be done based on the income lost and the costs of medical treatment. The total expected increase in cost depends on the increase in statistical probability of each disease. Existing research on life cycle impact assessment has yielded enough information to enable a simplified initial evaluation of a variety of nanomaterials. For example, Pietrini et al. [23] published a life cycle assessment of poly (3hydroxybutyrane) (PHB) based composites, incorporated into cathode ray tube (CRT) monitor housing and the internal panels of an average car, as compared with the conventional, currently used products. Vince et al. [28] conducted a comparative life cycle assessment of different desalination methods, including nanofiltration-based desalination. Krishnan et al. [13] conducted a detailed life cycle inventory study for semiconductor fabrication based on nanofabrication technologies, and incorporated the results in a life cycle assessment of a complete set of semiconductor manufacturing processes. Bauer et al. [2] conducted life cycle assessments of PVD coatings (a type of vacuum coating techniques) and CNT-based FED screen (carbon nanotube field emission displays for screen displays). Several additional life cycle assessments of nanomaterials were published in a special issue on sustainable nanotechnology development in the Journal of Cleaner Production [12]. These life cycle assessments include, by definition of the LCA methodology, estimates of the Disability Adjusted Life Years associated with the increased probability of health hazards from the products examined. The DALY data can be used for economic evaluation of the health impacts of these materials. This method has been applied in other fields, for example, to carry out an economic evaluation of the health impacts found in a life cycle assessment of agricultural crops [11]. Further research should be done in multidisciplinary teams, composed of economists, LCA analysts and nanotechnology experts to assess the possible health impacts and their economic implications for the companies and for society in general, and to establish recommendations for public health policy based on both scientific and economic considerations. References 1. Begeson, L.L., 2007, Nanotechnology, boom or bust. Pollution Engineering, August, pp. 14–15. http://www.polIutionengineering.com . 2. Bauer, C., Buchgeister, J., Hischier, R. Poganietz, W.R. Schebek, L., and Warsen, J., 2008, Towards a framework for life cycle thinking in the assessment of nanotechnology. Journal of Cleaner Production 16 (8/9):910–926. 3. Brosnan, C.A., and Swint, J. M., 2001, Cost analysis: Concepts and application. Public Health Nursing 18(1):13–18. 4. ETC Group, 2008, Organic pioneer says no to nano. ETC Group News Release, January 14, 2008.

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5. Evers, S., Salvador-Carulla, L., Halsteinli, V., McDaid, D., and The Mheen Group, 2007, Implementing mental health economic evaluation evidence: Building a bridge between theory and practice. Journal of Mental Health 16(2):223–241. 6. The Futurist, 2007, Nanotech: Big risks, big opportunities. World Future Society publication. July–August 2007, p. 8 7. von Gleich, A., Steinfeldt, M., and Ulrich, P., 2008, A suggested three-tiered approach to assessing the implications of nanotechnology and influencing its development. Journal of Cleaner Production 16 (8/9):899–909. 8. Graham, J.D., 2003, Cost-effectiveness analysis in health policy. Value in Health 6(4):417–419. 9. Grosse, S.D., 2003, Productivity loss tables (Appendix 1). In: Prevention Effectiveness: A Guide to Decision Analysis and Economic Evaluation, 2nd ed., Haddix, A.C., Teutsch, S.M., and Corso, P.S., eds., Oxford University Press, New York, pp. 245–257. 10. Gyrd-Hansen, D., 2005, Willingness to pay for a QALY: Theoretical and methodological issues. Pharmaeconomics 23(5):423–432. 11. Haruvy, N., and Shalhevet, S., 2006, Economic Evaluation of the Local and Global Ecological Services of Agriculture. Nekudat Chen Report, Israel. http:www.nekudathen.org.il/English/publication_list.asp (In Hebrew with English summary). 12. Helland, A., and Kastenholz, H., eds., 2008, Sustainable nanotechnology development. Special issue of the Journal of Cleaner Production 16(8–9):885–1020. 13. Krishan, M., Boyd, S., Somani, A., Raoux, S., Clark, D., and Dornfeld, D., 2008, A hybrid life cycle inventory of nano-scale semiconductor manufacturing. Environmental Science & Technology 42(8):3069–3075. 14. Kenkel, D., 2006, WTP-and QALY-based approaches to valuing health for policy: Common ground and disputed territory. Environmental and Resource Economics 34(3):419–437. 15. Kuper, H., Jofre-Bonet, M., and Gilbert, C., 2006, Economic evaluation for ophthalmologists. Ophthalmic Epidemiology 13:393–401. 16. Li, S.C., 2003, An introduction to pharmaeconomic evaluation in rheumatology. APLAR Journal of Rheumatology 6:192–200. 17. Lindberg, J.E., and Quinn, M.M., 2007, A Survey of Environmental, Health and Safety Risk Management Information Needs and Practices among Nanotechnology Firms in the Massachusetts Region. Project on Emerging Nanotechnologies. PEN Brief No. 1. 18. Medley, T., and Walsh, S., 2007, Nano Risk Framework, Environmental Defense – DuPont Nano Partnership Report. June. 19. Mekel, M., 2006, Nanotechnologies: Small science, big potential and bigger issues. Development 49 (4):47. 20. Moore, M.N., 2006, Do nanoparticles represent ecotoxicological risks for the health of the aquatic environment? Environment International 32:967–976. 21. Mueller, N.C., and Nowack, B., 2008, Exposure modeling of engineered nanoparticles in the environment. Environmental Science & Technology 42(12):4447–4453. 22. Palmer, S., Byford, S., and Raftery, J., 1999, Types of economic evaluation. BMJ: British Medical Journal 388(7194):1349. http://bmj.com/cgi/content/full/318/7194/ 1349 23. Pietrini, M., Roes, L., Patel, M.K., and Chiellini, E., 2007, Comparative life cycle studies on poly (3-hydroxybutyrane)-based composites as potential replacement for conventional petrochemical plastics. Biomacromolecules 8(7):2210–2218. 24. Rice, G., and Hammitt, J.K., 2005, Economic Valuation of Human Health Benefits of Controlling Mercury Emissions from US Coal-Fired Power Plant. Northeast States for Coordinated Air Use Management (NESCAUM), Boston, MA. http:www.nescaum.org.

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25. Roes, A.L., Marsili, E., Nieuwlaar, E., and Patel, M.K., 2007, Environmental and cost assessment of a polypropylene nanocomposite. Journal of Polymers & the Environment 15(3):212–226. 26. Stern, S.T., and McNeil, S.C., 2008, Nanotechnology safety concerns revisited. Toxicological Sciences 101(1):4–21. 27. Sweet, L., and Strohm, B., 2006, Nanotechnology – life-cycle risk management. Human and Ecological Risk Assessment 12(3):528–551. 28. Vince, F., Aoustin, E., Breant, P., and Marechal, F., 2008, LCA tool for the environmental evaluation of potable water production. Desalination 220(1–3):37–56. 29. Wiesner, M.R., Lowry, G.V., Alvarez, P., Dionysiou, D., and Biswas, P., 2006, Assessing the Risks of Manufactured nanomaterials. Environmental Science & Technology 40(14):4336–4345.

NANOMATERIALS Applications, Risks, Ethics and Society

A. VASEASHTA Nanomaterials Laboratories & Characterization Labs Marshall University One John Marshall Drive Huntington, WV 25575, USA [email protected]

Abstract. This study is conducted to provide a balanced, concise yet comprehensive perspective of potentials and risks associated with the use of nanotechnology. Risk assessment modality is based on parameters that evolve as a result of interaction of reduced dimensional materials with its environment and observed toxicological effects, as compared to the one based on conjecture. An overview of the fate and transport of nanomaterials in air, water, and soil, resulting in environmental impacts, human health, and ecology is briefly discussed. A three pillared approach to assessing nanotechnology risk is discussed, viz.: to develop a framework for assessing nanotechnology risk; to develop a survey instrument for assessing risks from expert elicitation; and to conduct a Delphi based study to build upon initial survey results. A framework for developing a comprehensive survey instrument is discussed. 1.

Introduction

Materials approaching nanoscale dimensions exhibit characteristics with numerous unique and hitherto unexploited applications. Advances in synthesis and characterization methods have provided the means to study, understand, control, or even manipulate the transitional characteristics between isolated atoms and molecules and bulk materials. Fundamental understanding and technological advances arise from the potential of nanoscale materials to exhibit properties that are attributable to their small size, physical characteristics, and chemical composition. Furthermore, the nanoscale geometrical dimensions are comparable to the smallest engineered entity, the largest molecules of living systems, and several fundamental physical quantities. Unique characteristics and functionalities of nanomaterials have already been utilized in cosmetics, apparel, and sports industries; while proof-of concept electronic and optical devices have been demonstrated and further progress will lead to commercialization. Recently, functional and architectural innovations in nanoscale materials have initiated applications in chemical and biological sensing [1, 2] environmental

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pollution sensing [2, 3] monitoring [4], mitigation and remediation [5], advanced energy generation and storage devices [2, 6], nano-biotechnology [7], nanophotonics [8], in-vivo analysis of cellular processes [9], and futuristic health and clinical medicine platforms [10]. A nanotechnology based sensor platform enables direct electrical detection of biological and chemical agents in a label-free, highly multiplexed format over a broad dynamic range. Nucleic acid layers combined with nanomaterials-based electrochemical or optical transducers produce affinity biosensors such as the “DNA Biosensor” or “Genosensor” that are attractive devices for converting the hybridization event into an analytical signal for obtaining sequencespecific information in connection with clinical, environmental, or forensic investigations [11]. Further, applications of nanotechnology in material sciences, health care, and information technology will likely have a positive impact on our society. The transformational potential of nanotechnologies has also been a cause of concern since the dimensions are comparable to biological molecules, thus possibly leading to toxicological effects. The new paradigm of collaborative research environment and virtual shared resources produce innovations faster than the Federal agencies can either produce standards, safety instructions or informed policies that address risks associated with use of nanotechnology based products. Often, “voluntary codes of conducts” are adopted or employed to address societal concerns. These complex dynamics may lead to possible erosion of public confidence, thus tipping of the playing field from “potentials” to “risks. The objective of this investigation is to provide balanced, concise, yet comprehensive and objective perspective of potentials and risks associated with the use of nanotechnology. A comprehensive list of parameters that may determine toxic potential of nanomaterials is provided, which may provide better perspective of toxicological investigations as compared to isolated studies. Also, a discussion concerning fate and transport further provides guidance about the dispersal and transport of these materials in the environment, water streams, and soil. Scientists share additional responsibility to address societal concerns by keeping the publicat-large informed with a balanced perspective. Risk assessment employing expert elicitation is primarily aimed to provide a balanced perspective. 2.

Present and Future of Applications of Nanomaterials

Nanotechnology is a transformational technology that utilizes inherently unique properties of matter in reduced dimensions. Applications of nanotechnology range from material sciences, medicine, energy, environment, communications and electronics among others. A comprehensive list of applications is beyond the scope of this section but is provided as a working group recommendation in this proceeding [12]. Some of the applications in the context of health and environment vis-à-vis risk scenarios are provided below. Nanoengineered platforms possess unprecedented potential for early detection, diagnosis, and site-specific and time-controlled cure for diseases. Multifunctionality provides a key advantage to nanoengineered platforms, where targeting,

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imaging, site and time specific therapeutics and drug delivery, and numerous other functionalities can be integrated to allow for site-specific and targeted molecular imaging, therapy and diagnostics probes, demonstrating tremendous potential to enhance the sensitivity, specificity, and signaling capabilities of various biomarkers in human diseases. Furthermore, nano-biotechnology will help identify cell-source to be divided by specific cellular phenotypes, thus improving strategies for in-vivo detection and monitoring of the cellular implants, techniques to enhance integration of the transplant within the host tissue, and deliver genes to cells. Nanomaterials have also been used for bactericidal, antibiotics, and drug-resistant strains. Quite to the contrary, this investigation also deals with risk scenarios and assessment instruments associated with interaction of nanomaterials with human body. Nanomaterials have been studied in the context of environmental applications to solve problems such as pollution and issues that support sustainability. Nanomaterials have been used as active, anti-reflective, and spectrum-shifting layers to produce high efficiency solar cells inexpensively. Work has also been reported to use nanomaterials to reduce energy load by using lightweight materials for vehicles; materials and geometries that contribute to more effective temperature control; technologies that improve manufacturing process efficiency; materials that increase the efficiency of electrical components and transmission lines; materials that contribute to new and improved fuel cells (FC) – for hydrogen economy; and biodegradable materials for reduced and benign landfill volume. Nanoscale materials are used for cosmetics – viz. sunscreens, house paints, clothing, and computers. Despite of its abundant use and potential, there exists a societal concern that nanomaterials pose health hazards, thus necessitating risk assessment and guidelines for using engineered nanomaterials. The challenge of nanotechnology is to deploy the benefits with minimal risks. There is a significant gap in our knowledge of the environmental, health, and ecological impacts associated with nanostructured materials. Since innovations in the field of nanotechnology occur faster than policymakers can develop safe handling practices; a comprehensive and fundamental investigation is necessary based on dynamic transport of nanomaterials in the environment and its impact on human health and ecology. It is imperative, therefore, to put the entire subject in a balanced perspective to provide end-users of nanotechnology unbiased and fair choices. 3.

Risk Scenarios

Origin, physical dimensions, and characteristics of nanomaterials vary significantly. Nanomaterials are produced by nature, commercial and industrial processes (not intended for nanomanufacturing), and laboratory, industrial, and commercial process designed to produce nanomaterials (also known as engineered nanomaterials). At present, there is insufficient information to predict dispersal and distribution of nanomaterials in mediums such as air, water, and soil. Hence, toxicity scenarios leading to exposure to nanomaterials in the workplace environment are rendered rather complicated to define, especially as they relate to the point of origin. For

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lack of detailed scientific studies, some of the risks reported in literature range from legitimate concerns to pure fiction or rather exaggerated extrapolation from results tangentially related to nanomaterials. An understanding of the toxicity of nanomaterials related to human beings, environment, and perhaps for sustainable use in the future requires understanding the interface between nanomaterials and its environment. More specifically, an understanding of the agglomeration and dispersion, i.e. how nanomaterials transport themselves in the environment, the fate and transport and life-cycle analysis of nanomaterials is critical. 3.1.

NANOMATERIALS–ENVIRONMENT INTERFACE

Size and surface collectively control characteristics of nanoscale materials due to the existence of large boundaries adjoining their surrounding medium and interplay of physicochemical interactions. The surface free-energy is size-dependent and hence increases almost inversely with the decreasing feature sizes of the material. Collective response of a nanomaterial-medium system that is attributable to reduced dimensions, viz. size, and surface structure, physical, chemical, and biological interactions is vital to developing a scientific basis to predict its pathways for toxicity. It is an exceedingly complex task due to a large matrix of parameters consisting of nanomaterials, the surrounding environment, and influencing mechanisms of interactions. Further complexities arise due to production and diversity of nanoparticles. Hence, to develop guidelines for occupational exposure it will become increasingly important to understand how nanoparticles and biological systems interact in terms of bio-physico-chemical properties of nanoparticles produced by nature, engineered, and produced as a result of routine industrial and commercial processes. An extensive investigation is underway in the context of specific functions ranging from bio-nanomaterials interface to toxic potential of industrial pollution. Figure 1 shows environments of a NP and various biophysico-chemical interactions scenarios. The characteristics which provide beneficial aspects are also believed to be responsible for toxicity of nanomaterials. Consequently, NP toxicity is studied in context of its ability to induce tissue damage through the generation of oxygen radicals, electron-hole pairs, and oxidant stress by abiotic and cellular responses, mitochondrial injury and cellular effects in the lung, cardiovascular system and brain [13]. Some studies suggest that NPs absorb cellular proteins which could induce protein unfolding, fibrillation, and thiol cross-linking; leading to neurotoxicity and reduced enzymatic activity [14]. Nanoparticles which are cationic are also believed to induce toxicity via acidifying endosomes that lead to cellular toxicity and apoptosis in epithelial lung, mitochondrial targeting, and cytosolic deposition. Nanomaterials composed of redox-active elements are particularly reactive and can initiate potentially detrimental chemical transformations. Furthermore, even chemically benign NPs may become activated by light absorption. Hence, fundamental understanding of a nanomaterial-surrounding medium is vital to sustaining technological advances of nanoscale materials as a catalyst for new scientific and technological avenues.

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Figure 1. Nanoparticles/medium/cell interaction – physico-chemical characteristics.

3.2.

FATE AND TRANSPORT

Despite beneficial effects and major developments in the field of nanomaterials, there is a significant gap in our knowledge of the environmental, health, and ecological impacts associated with nanostructured materials. A comprehensive and fundamental investigation into the dynamic transport of nanomaterials in the environment and its impact on human health and ecology is needed to guard public welfare. The complex nature of naturally occurring and engineered nanomaterials and transport, either in the environment or via different exposure routes with human body necessitates further studies. A matrix of parameters which govern fate and transport modeling of nanomaterials such as exposure routes, chemical composition, surface structure, solubility, size and shape effects, toxicity, absorption, distribution, metabolism, agglomeration, and excretion rate and mechanisms is under investigation via three most common routes – inhalation, ingestion, and dermal exposure. The accumulation, dispersion, and functional surface groups play an important role in cytotoxicity and in evaluating pathways of cellular uptake, sub-cellular localization, and targeting of sub-cellular organelles. Studies relating to the thermodynamic properties, interfaces, and free energy of nanoparticles as a function of particle size, composition, phase and crystallinity influence particle dissolution in a biological environment. This investigation in conjunction with plume modeling and predictive modeling approaches will assist in prioritizing, testing, and correlating with in-vivo exposure models. A comprehensive investigation

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will prove beneficial to development of risk assessment tools and ensuring safe practice in nanotechnologies. 4.

Preliminary Framework for Risk Analysis

In business management, decisions are made even though there is an element of uncertainty about the outcome, often estimated as probability in mathematics. Nanotechnology poses a rather unique challenge due to rapid development in this relatively new field and rather insufficient studies of the effect of nanoparticles with human health. The environment consists of nanomaterials produced by the nature, industrial and transportation exhaust emission, and to some extent inadvertent release of engineered nanomaterials. To help understand the structure of this rather vast and complicated task, a preliminary framework is developed for this investigation. A more detailed overview of basis, influence diagrams, and corresponding survey instrument, is discussed elsewhere. Effective risk analysis involves identifying, assessing, and mitigating risk to a satisfactory level. Risk analysis is a process of evaluating critical assets and systems, threats, vulnerabilities, and controls for mitigating threats. Outcomes of risk assessment form a strategic plan for managing risks. Three pillars of risk analysis are to assess, manage, and communicate. Assessment is the process of identifying risk. Managing is the process of mitigating risks in an optimal manner. Communication ensures that policy and decision makers and the general public understand outcomes of risk assessment and risk management. Nanotechnology risk assessment occurs in a climate of uncertainty and change; therefore, effective decision making by participating experts is critical for a successful outcome. According to Howard [15], high quality decisions are characterized by the following elements: 1. 2. 3. 4. 5. 6.

Appropriate framing of decisions Analysis of creative alternatives Accurate information and sound models Clear preferences for future status Sound logic Commitment to process and outcomes

Policy and decision makers are increasingly relying on expert-opinion elicitation techniques for forecasting advances, reliability, and risks related to science and technology [16]. Structured expert-opinion elicitation techniques effectively support complex decision-making in the face of risk and uncertainty [17]. Since nanotechnology risk assessment is in its infancy, incorporating formal expert-opinion elicitation methods within the risk assessment process may help to prevent cognitive biases and faulty cognitive processes attributing to poor decision quality. This report introduces the concept of using a structured expert-opinion elicitation technique, a computerized Delphi technique to assess nanotechnology risks by expert panels. Tversky and Kahneman [18] investigated factors contributing to poor quality decisions arising from risk analysis processes. First, unreliable

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information including incomplete, inaccurate, unrepresentative historical data about threats, vulnerabilities, and occurrences leads to poor quality risk analysis decisions. Second, unreliable forecasting including bad estimates of probabilities and excluding outlier events impacts the quality of risk analysis decisions. Third, a host of cognitive biases including representativeness, availability, anchoring and adjusting, optimistic biases, risk biases, and a false sense of control may negatively affect risk analysis processes. Finally, dysfunctional group dynamics arising from strong personalities, organizational hierarchies, and miscommunications impede the risk analysis process and resulting decisions. The Delphi Technique is a structured interactive group communications technique effective for reaching consensus about judgments, forecasts, or decisions from expert panels [19]. The Delphi process occurs as follows: ƒ ƒ ƒ ƒ

Facilitator distributes survey to the expert panel. Survey is answered anonymously and independently by an expert panel. Facilitator summarizes and distributes results and rationale. Expert panel anonymously and independently reviews summarized results and rationale. Panelists may revise individual responses, optional.

The process of eliciting, summarizing, and distributing anonymous and independent responses continues until consensus, stable responses, or a given number of rounds is met. The Delphi Technique benefits decision making and forecasting processes involving expert panelists in many ways. First, the Delphi technique supports expert panels ranging from a few participants to a few thousand participants. Second, the Delphi technique effectively overcomes constraints in time, geographic location, cost, or anonymity needs. Third, the Delphi technique proves effective when actuarial, technical, or economic data is unavailable thus mandating expert judgment. Fourth, the Delphi technique has proven effective in the exploration and forecasting of novel, complex, or uncertain problems or events. Finally, the Delphi technique overcomes social barriers related to diversity, hierarchy, personality, or hardened conflicts. Because the Delphi technique has proven merit in forecasting trends and risks for many scientists, researchers, policy, and decision makers; the authors propose a future investigation involving a Delphi Study for assessing NT risks. Efforts are underway to prepare an initial comprehensive survey. Then, a pilot study will be conducted comprising a small group of experts at a forthcoming nanotechnology conference. Then, the survey will be reviewed and revised accordingly. A large number of nanotechnology scientists, researchers, industry, and government experts will be contacted to participate in a formal Delphi Study for Assessing Nanotechnology Risks. The Delphi Study for Assessing Nanotechnology Risks will be conducted and results will be published. Figure 2 conceptually shows various means to receive input from the survey instrument (shown in Figure 3).

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Figure 2. Conceptualization of expert elicitation using Delphi.

4.1.

RISK ASSESSMENT SURVEY INSTRUMENT

Every technology that mankind has adopted has risks associated with it. The understanding of environmental effects and health risks associated with nanotechnology is very limited and sometimes contradictory. At present, a well defined risk assessment modality is needed, as the “voluntary code of conduct” for using nanomaterials is somewhat trepidation based and not entirely on scientific methodology. Effective risk analysis involves identifying, assessing, and mitigating risk to a satisfactory level. Outcomes of risk assessment form a strategic plan for managing risks. Nanotechnology risk assessment occurs in a climate of uncertainty and change; therefore, effective decision making by participating experts is critical for successful outcomes. Strategic planning encompasses seven categories, viz.: taxonomy, significance, implementation, sustainability, precaution, inclusiveness, and accountability. Risk analysis is a process of evaluating critical assets and systems, threats, vulnerabilities, and controls for mitigating threats. High quality decisions are characterized by the following elements: appropriate framing of decisions; analysis of creative alternatives; accurate information and sound models; clear preferences for future status; sound logic; and commitment to process and outcomes. Policy and decision makers are increasingly relying on expert-opinion elicitation techniques for forecasting advances, reliability, and risks related to science and technology. Structured expert-opinion elicitation techniques effectively support complex decision-making in the face of risk and uncertainty. Since nanotechnology risk assessment is in its infancy, incorporating formal expert-opinion elicitation methods within the risk assessment process may help to prevent cognitive biases and faulty cognitive processes attributing to poor decision quality.

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Figure 3. A sample of questions used for expert elicitations.

The Delphi Technique is a structured interactive group communications technique effective for reaching consensus about judgments, forecasts, or decisions from expert panels. The Delphi process occurs as follows: a facilitator distributes survey to the expert panel; the survey is answered anonymously and independently by the expert panel; a facilitator summarizes and distributes results and rationale, and the expert panel anonymously and independently reviews summarized results and rationale, and panelists are allowed to revise individual responses. The process of eliciting, summarizing, and distributing anonymous and independent responses continue until consensus, stable responses, or a given number of rounds are met.

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The Delphi technique has proven merit in forecasting trends and risks for many scientists, researchers, policy, and decision makers. 5.

Conclusion and Future Directions

Nanotechnology presents the promise of a diverse array of manufactured goods and products that incorporate improved and innovative properties. National and international governmental agencies, companies and research organizations have all recognized significance of proactive steps to identify potential undesirable health consequences of nanomaterials and to minimize impact in occupational environments. Due to advantages offered by such materials and associated uncertainty about untoward health effects from exposures should not impede tremendous momentum and significant advantage towards applications in medical, security, environment, and energy generation and storage. Development of proposed survey instrument, its analysis, and efforts by companies to develop worker safety programs based on the guidelines will minimize potential health effects. Such an approach can further minimize the likelihood of worker exposures to nanomaterials and subsequent financial liability claims and litigation. Hence, exposure assessment using the proposed tools and data collection by expert elicitation is important for the elucidation of potential health risks assessment. References 1. Vaseashta, A. and Mihailescu, I. N. (2008) Functionalized Nanoscale Materials, Devices, and Systems, Springer Science and Business Media, Dordrecht, The Netherlands. 2. Vaseashta, A., Dimova-Malinovska, D., and Marshall, J. (2005) Nanostructured and Advanced Materials, Springer Science and Business Media, Dordrecht, The Netherlands. 3. Pummakarnchana, O., Phonekeo, V., and Vaseashta, A. (2007) Sensors & Transducers Journal 77(3), 1065–1072. 4. Pumakaranchana, O., Phonekeo, V., and Vaseashta, A., “Semiconducting Gas Sensors, Remote Sensing Techniques, and Internet GIS for Air Pollution Monitoring in Residential and Industrial Areas”, pp: 339 (2008) in “Functionalized Nanoscale Materials, Devices, and Systems”, ed. Vaseashta, A. and Mihailescu, I. Springer, Dodretcht, The Netherlands. 5. Vaseashta, A., Vaclavikova, M., Vaseashta, S., Gallios, G., Roy, P., and Pummakarnchana, O. (2007) Science and Technology of Advanced Materials 8, 47–59. 6. Vaseashta, A., “Nanoscale Materials, Devices, and Systems for Chem.-Bio Sensors, Photonics, and Energy Generation and Storage”, pp: 3 (2008) “Functionalized Nanoscale Materials, Devices, and Systems”, ed. Vaseashta, A. and Mihailescu, I. Springer, Dodretcht, The Netherlands. 7. Vogel, V., and Baird, B. (Eds.) (2003) Nanobiotechnology: Report of the National Nanotechnology Initiative Workshop, October 9–11, Arlington, VA. 8. Vaseashta, A., and Stamatin, I. (2007) JOAM 9(6), 1506–1613. 9. Prasad, P. (2004) Nanophotonics. Wiley, Hoboken, NJ. 10. Denkbas, E., and Vaseashta, A. (2008) NANO: Brief Reports and Reviews (in press).

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11. Erdem, A., and Vaseashta, A. (2008) NANO: Brief Reports and Reviews (in press). 12. Adlakha-Hutcheon, G., Darov, R., Korenstein, R., Varma, R., Vaseashta, A., Stamm, H., and Abdel-Mottaleb, M. This proceeding. 13. Joshi, G., Sultana, R., Tangpong, J., Paulette Cole, M., St Clair, D., Vore, M., Estus, S., and Butterfield, D. (2005) Free Radical Research 39(11), 1147–1154. 14. Arnedo, A., Irache, J. M., Merodio, M., and Espuelas Millán, M. S. (2004) Journal of Controlled Release, 94(1), 217–227. 15. Howard, R. (2007) Decision analysis: A personal account of how it got started and evolved. In: Advances in Decision Analysis: From Foundations to Applications, edited by W. Edwards, R. Miles, Jr., and D. von Winterfeldt (Eds.) (Cambridge University Press, New York), pp. 32–56. 16. Ayyub, B. (2001) Elicitation of Expert Opinions for Uncertainty and Risks. CRC Press, Boca Raton, FL. 17. Rowe, G., and Wright, G. (2001) Expert opinions in forecasting: The role of the Delphi technique. In: Principles of Forecasting: A Handbook for Researchers and Practitioners, edited by J. S. Armstrong (Kluwer, Norwell, MA), pp. 125–144. 18. Tversky, A., and Kahneman, D. (1974) Science, 185(4157), 1124–1131. 19. Linstone, H. and Turoff, M. (Eds.) (2002) The Delphi Method Techniques and Applications. Retrieved (October 10, 2007), from New Jersey Institute of Technology Web site; http://is.njit.edu/pubs/delphibook/

GROUP DECISION-MAKING IN SELECTING NANOTECHNOLOGY SUPPLIER AHP Application in Presence of Complete and Incomplete Information

B. SRDJEVIC Faculty of Agriculture University of Novi Sad Trg Dositeja Obradovica 8 21000 Novi Sad, Serbia [email protected] Z. SRDJEVIC, T. ZORANOVIC, K. SUVOCAREV Faculty of Agriculture University of Novi Sad Trg Dositeja Obradovica 8 21000 Novi Sad, Serbia

Abstract. A group decision-making context is created to enable assessment of the Analytic hierarchy process (AHP) performance in presence of complete and incomplete information. To illustrate it, four recognized nanotechnology suppliers are evaluated across seven commonly used company/product attributes (net price, delivery, quality, production facilities, technical capability, management and organization, and geographical location) to identify the best one in multicriteria sense. Broad overview of applicable selection criteria and related MCDM methodologies is also presented. 1.

Introduction

Selecting the right supplier is difficult task, because each potential supplier has its advantages and disadvantages. One can have good price, but low availability of a skilled labor force necessary to produce the component. Other supplier can be more reliable. Third one can have the best technical support for maintaining the components. It is up to purchasing managers to define selection criteria and to evaluate potential supplier according to them. To make the right decision, managers must have reliable, trustworthy and comprehensive decision framework. Decision making nowadays assumes scientifically supported process, which in most cases includes several decision makers and interest groups. To successfully deal with different attitudes and opinions of different people, variety of methods is in use. Not many of them can involve quantitative, qualitative and semi-qualitative

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criteria as the Analytic Hierarchy Process (AHP) can do; and this is probably the main reason why it is popular worldwide. The major advantage of AHP is that it involves a variety of tangible and intangible goals. For instance, it reduces complex decisions to a series of pair-wise comparisons, implements a structured, repeatable and justifiable decision making approach and build consensus [26]. Method is used in business and industry, by the governmental bodies and even by politicians, in individual and group contexts. Problems addressed are prioritization and selection, planning and budgeting, project and portfolio selection, vendor and source selection, trade studies, performance and risk assessment, market research, resources allocation, etc. Here we use AHP as a group decision support tool in the supplier selection problem, with complete and incomplete information. First part of the paper gives brief overview of the supplier selection problem; analyses selection criteria and selection methods. AHP basics are given next, with emphasis on the a priori and a posteriori aggregation of individual judgments and on the meaning and influence of complete and incomplete information on the final decision. Illustrative example is given in the following section, while discussion and conclusions close the paper. 2.

2.1.

Supplier Selection SELECTION CRITERIA

The first step in the supplier selection process is to define selection criteria. Pioneering work on this subject is done by Dickson [9], when he asked 170 purchasing agents and managers to evaluate 23 supplier selection criteria using the five point scale: extreme (4), considerable (3), average (2), slight (1) and no importance (0). Average value for each criterion is then calculated from all 170 assessments, as given in Table 1. Five top ranked are: quality, delivery, performance history, warranties and claim policies and production facilities. Price is ranked as the 6th criterion. Similar results were obtained in 1991, when eight senior buyers in engineering company made assessments of the same criteria [32]. Weber et al. [30] analyzed 74 papers and found that the most discussed criteria for supplier selection are net price, delivery and quality (last column of Table 1). Also, production facilities, technical capability, management and organizations and geographical location are mentioned as selection criterion in more then ten papers, with recommendation that they should be considered as decision elements in the selection process.

GROUP DECISION-MAKING IN SELECTING NANOTECHNOLOGY SUPPLIER 411 TABLE 1. Supplier selection criteria [32].

2.2.

SELECTION TECHNIQUES

The vast majority of the methods suggested in the related literature can be classified into three categories: mathematical programming models, rating/linear weighting models and artificial intelligence (AI) techniques [2]. Table 2 shows the supplier selection techniques by methodological area. TABLE 2. Supplier selection techniques. (Selected from [2].)

Total cost of ownership Mathematical programming techniques AI methods AHP Linear weighting techniques and other MCDM methods Outranking techniques DEA

References Ellram [12], Bhutta and Huq [3], Dogan and Sahin [10] Wang et al. [29], Amid et al. [1], Kumar et al. [22] Choy et al. [6], Choy et al. [7] Kahraman et al. [21], Liu and Hai [23] Grando and Sianesi [17], Chen et al. [4] De Boer et al. [8], Dulmin and Mininno [11] Weber et al. [31], Talluri and Narasimhan [28]

The selection of the most appropriate method for a particular priority setting situation, with regard to criteria depends on (1) the time available for the study, (2)

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the availability of data in relation to the degree of analysis, (3) analytical capacity, (4) participation in the process, and (5) transparency within the process [14]. Time

Degree of intensity: 1: low 2: moderate 3: high

3

Mathematical programming / Simulation Economic surplus

2

Analytic Hierarchy Process Scoring

1 3

Partcipation

2

1

1

2

1

3

Transparency

2

3

Data and analysis Figure 1. Priority setting methods compared [14].

Figure 1 [14] illustrates a comparison of five different priority setting methods: mathematical programming, simulation, economic surplus, analytic hierarchy process (AHP) and scoring. Scoring and AHP are more transparent and participatory, while mathematical programming, simulation, and economic surplus require more time, resources, and data analysis. As we are looking for a tool allowing especially participation, the latter are not considered as candidates for selection methodology in our case. Although scoring can be conducted in a relatively short period of time, is transparent, allows participation, and does not require advanced quantitative skills, AHP is selected as a solution framework since it minimizes the shortcomings of scoring (for example poorly measured or overlapping criteria for determining the best alternative) through careful structuring the decision hierarchy. The major advantage of AHP is that it involves a variety of tangible and intangible goals. For instance, it reduces complex decisions to a series of pair-wise comparisons, it implements a structured, repeatable and justifiable decision-making approach, and it builds consensus. An introduction to the method and its theoretical foundations is given in Saaty [24]; for this reason only the basic properties of the method that are necessary for understanding the decision-making process will be described in the next section.

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3.

Analytic Hierarchy Process

The AHP is a multicriteria decision-making method which requires a wellstructured problem, represented as a hierarchy. Usually, at the top of the hierarchy is the goal; the next level contains the criteria and sub-criteria, while alternatives lie at the bottom of the hierarchy. AHP determines the preferences among the set of alternatives by employing pair-wise comparisons of the hierarchy elements at all levels, following the rule that, at given hierarchy levels, elements are compared with respect to the elements in the higher level by using the Saaty’s importance scale (Table 3). TABLE 3. The fundamental Saaty’s scale for the comparative judgments. Num. values

Verbal terms

1

Equally important

3

Moderately more important

5

Strongly more important

7

Very strongly more important

9

Extremely more important

2, 4, 6, 8

Intermediate values

By assumption, value 1 corresponds to the case in which two elements contribute in the same way to the element in the higher level. Value 9 corresponds to the case in which one of the two elements is significantly more important than the other. Also, if the judgment is that B is more important than A, the reciprocal of the relevant index value is assigned. For example, if B is felt to be notably more important as a criterion for the decision than A, then the value 1/7 would be assigned to A relative to B. The results of the comparison are placed in comparison matrices. After all judgments are made, the local priorities of the criteria, sub criteria and alternatives can be calculated using the principal eigenvector of a comparison matrix, as suggested by Saaty [24]. The synthesis is performed by multiplying the criteria specific priority vector of the alternatives with the corresponding criterion weight, and then appraising the results to obtain the final composite alternatives priorities with respect to the goal. The highest value of the priority vector indicates the best-ranked alternative.

3.1.

GROUP DECISION MAKING

In the case of the group decision making, the aggregation can be performed on individual priorities (1a) and individual judgments (1b) by the Geometric Mean Method (GMM) [16]. If priorities are aggregated, AHP methodology is followed for each decision maker separately till final alternatives’ priorities are obtain. Priorities are then aggregated by equation:

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ziG =

K

∏ z (k )α i

k

(1a)

k =1

where K stands for the number of decision makers, zi (k) for the priority of i-th alternative for k-th decision maker, αk for the ‘weight’ of k-th decision maker, and ziG for the aggregated group priority value. Notice that weights αk should be additively normalized prior to their use in Eq. 1a and that the final additive normalization of priorities ziG is required. To aggregate individual judgments and form combined (group) matrix AG = G

{ a ij }, judgments from K matrices on each (i,j) position are aggregated by: aijG =

K

∏ a (k )α ij

k

(1b)

k =1

where

aij (k ) is individual judgment of the decision maker k on the position i,j in

his/her decision matrix, αk for the ‘weight’ of k-th decision maker, and

aijG

combined (group) judgment on position i,j in combined matrix. Final alternatives’ priorities are calculated using combined matrices as there is only one decision maker. Both mentioned methods assume that all positions in decision matrices a ij (k ) exist, i.e. that input is complete. 4.

Complete and Incomplete Inputs

Decision matrix is, as described above, filled with decision-maker’s individual judgments. If all matrix elements in the upper triangle exist, input matrix is considered complete and standard AHP synthesis procedure for calculating priorities can be performed. If at least one element is missing, input is incomplete. Harker [18] discussed three reasons why one would want to make fewer than the full set of judgments for each of one or more sets of factors in an AHP model: ƒ To reduce the time to make the judgments ƒ Because of an unwillingness to make a direct comparison between two particular elements ƒ Because of being unsure about some comparisons

In such cases, it is not possible to calculate priorities and it is necessary to estimate missing element using the existing ones. There are different methods used for solving this problem: consistency optimization [15]; back-propagation multi layer perceptron – neural network based method [20]; connecting paths [19, 5]; characteristic polynomial-based method [25]; and revised geometric mean method [18]; to name but a few.

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Simulation employed in [20] comparing the efficiency of four methods (connecting paths, revised geometric mean method , characteristic polynomial-based method and back-propagation multi layer perceptron), showed that connecting paths can be considered as most efficient for small size matrices such are incomplete matrices in our example. 4.1.

CONNECTING PATHS

If aij (i ≠ j) is missed in a positive reciprocal matrix, aij can be determined by a connecting path of size k, CPk, as follows: CPk = ai,p1 ap1,p2 ... apk,j

(2)

Missing element aij is a geometric mean of all connecting paths related to aij: q

aij = q

∏ CP

(3)

k

k =1

where CPk is a connecting path, k defines the number of elements in the connecting path, and q is the number of all possible connecting paths. Major drawback of this method is that the number of connecting paths can be high for large matrices. For example, for matrix of size 10, number of connecting paths is 109,000. 4.2.

INCOMPLETE INPUT AND GROUP DECISION-MAKING

If incomplete matrix appears in the group decision framework, one solution is to use existing individual judgments to estimate the missing one by the connecting paths method and then to aggregate priorities or judgments using the Eq. 1a or b. Another solution is proposed in [27]. Missing judgment

aijG is estimated by using

the existing judgments a ij (l ) on the same positions in the decision matrices of the other decision makers in the group. It is assumed that at least one judgment exist on the analyzed position in M decision matrices for M members of the group. Aggregation is then performed by using the following equation:

a ijG = [∏ a ij (l )]1 / M

(4)

l∈L

where L denotes set of group members that have made pairwise comparison of the elements (Ei, Ej), and M is number of those group members. Since matrix A is reciprocical, aggregated values are also reciprocical and it is not necessary to aggregate values for the position (j,i); element (j,i) is reciprocical value of (i,j).

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Figure 3. Comparison matrices of criteria regarding goal for: (a) Evaluator 1, (b) Evaluator 2 and (c) Evaluator 3.

Next step in the evaluation process was to compare alternatives regarding criteria. As an illustration, comparison matrix of alternatives vs. criterion PRICE for Evaluator 2 is presented on Figure 4.

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Figure 4. Comparison matrix: alternatives vs. PRICE, Evaluator 2.

Applying the AHP methodology for each evaluator separately, priority vectors of alternatives are calculated and given in Table 4. TABLE 4. Alternatives’ weights and rankings. Alternatives Keithley Instruments Inc. Orthodyne Electronics

Evaluator 1 Weight Rank 0.381 1

Evaluator 2 Weight Rank 0.238 2 4

Evaluator 3 Weight Rank 0.331 1

0.232

3

0.175

0.236

2

AIXTRON AG

0.234

2

0.225

3

0.211

4

Centrotherm Thermal Solutions

0.152

4

0.363

1

0.222

3

As expected, evaluators have quite different perspective of the problem and that resulted in differences in alternatives’ rankings. For example, Evaluator 1 believes that Centrotherm Thermal Solutions is the least favorable supplier according to given criteria, while Evaluator 2 believes it is the best one. Since Evaluator 2 is more experienced, his weight is set to 0.5 (α2 = 0.5). Weights of the other two evaluators are set to 0.25 giving α1 = α3 = 0.25. After applying Eq. 1b, group decision is obtained as given in Table 5. TABLE 5. Group decision. Alternatives Keithley Instruments Inc. Orthodyne Electronics AIXTRON AG Centrotherm Thermal Solutions

Group

Weight

Rank

0.299 0.215 0.227 0.260

1 4 3 2

Highest overall weight has Keithley Instruments Inc. (0.299) and should be considered as the best supplier. It is followed by Centrotherm Thermal Solutions, having the overall weight of 0.260, and by AIXTRON AG (0.227). Lowest position is of the Orthodyne Electronics.

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5.2.

INCOMPLETE INPUT

Assuming that Evaluator 1 does not have all information needed to compare suppliers Keithley Instruments Inc. and Centrotherm Thermal Solutions vs. criteria Facility, incomplete matrix appeared as given in Figure 5.

Figure 5. Incomplete matrix: alternatives vs. Facility, Evaluator 1.

To calculate missing judgment a14, a total of four connecting paths is constructed (Eq. 2) CP1 = a12 a24 = 3 ⋅ 1/3 = 1 CP2 = a13 a34 = 1 ⋅ 4 = 4 CP3 = a12 a23 a34 = 3 ⋅ 1/3 ⋅ 4 = 4 CP4 = a13 a32 a24 = 1 ⋅ 3 ⋅ 1/3 = 1.

By using Eq. 3, 4

a14 = 4

∏ CP

k

= 4 CP1 ⋅ CP2 ⋅ CP3 ⋅ CP4

k =1

missing matrix element is then calculated as a14 = 2. Weights of alternatives regarding criterion Facility have changed if missing element is estimated, as given in Table 6. TABLE 6. Alternatives’ weights regarding criterion facility. Alternatives Keithley Instruments Inc. Orthodyne Electronics AIXTRON AG Centrotherm Thermal Solutions

Complete input

Incomplete input

Weight

Weight

0.357 0.094 0.394 0.156

0.280 0.144 0.264 0.311

The final alternatives’ weights and ranks remain unchanged. Change in local priorities does not influence the final decision in this case, because:

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(1) Evaluator 1 has the weight 0.25 in the group. During the aggregation, judgments of Evaluator 1 are brought to power 0.25 and the difference between 30.25 (3 was the Evaluator 1 judgment on position a14) and 20.25 (2 is estimated value on position a14) is not significant. (2) There were 24 pondered matrices (8 for each evaluator); combined (final) matrix elements aij are obtained as mean value of powered judgments and change in one position can not cause significant change in the final result. 6.

Discussion and Conclusion

To evaluate potential suppliers, one must have methodology that will involve quantitative, qualitative and semi-qualitative criteria in the process. Also, most frequently, decision have to be made as the group decision, by several decision makers. The Analytic Hierarchy Process meets both of these requirements, as presented in this paper. Three evaluators participated in the selection process. First, complete information situation is analyzed. Applying the AHP methodology for each evaluator separately, three different alternatives’ rankings were obtained. Only one rank was the same: Evaluator 1 and Evaluator 3 ranked nanotechnology supplier Keithley Instruments Inc. as the first ranked. All other ranks differ. To select the best supplier by the group, aggregation on individual judgments is performed and the group (final) decision is obtained. Example included also the case of the incomplete information. We have analyzed the situation when only one judgment is missing in the matrix of size 4. Estimation of the missing matrix element is made by the connecting paths method. For the larger size matrices, one should consider some other estimation method since computation time can considerably increase if connecting paths method is used. Another problem with the larger incomplete matrix is that the more comparisons one makes, the more likely is that the matrix will be estimated accurately. On the other hand, the more comparisons one makes, the longer it will take, and the possibility of errors in the judgments increases. If too many elements are missing, incomplete matrices should be discarded and decision process repeated. Acknowledgment

The authors wish to thank The Serbian Ministry of Science and Secretariat for Science and Technological Development (Province of Vojvodina) for supporting this research.

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References 1. Amid, A., Ghodsypour, S.H., and O’Brien, C.O. (2006) Fuzzy multiobjective linear model for supplier selection in a supply chain, International Journal of Production Economics 104(2), 394–407. 2. Araz, C., and Ozkarahan, I. (2007) Supplier evaluation and management system for strategic sourcing based on a NEW multicriteria sorting procedure, International Journal of Production Economics 106(2), 585–606. 3. Bhutta, K.S., and Huq, F. (2002) Supplier selection problem: A comparison of the total cost of ownership and analytic hierarchy process approaches, Supply Chain Management: An International Journal 7(3), 126–135. 4. Chen, C.T., Lin, C.T., and Huang, S.F. (2006) A fuzzy approach for supplier evaluation and selection in supply chain management, International Journal of Production Economics 102, 289–301. 5. Chen, Q., and Triantaphyllou, E. (2001) Estimating Data for Multi-criteria Decision Making Problems: Optimization Techniques. In: Pardalos, P.M., and Floudas, C. (eds.), Encyclopedia of Optimization, vol. 2, Kluwer, Boston, MA, pp. 27–36. 6. Choy, K.L., Lee, W.B, and Lo, V. (2003) Design of a case based intelligent supplier relationship management system—The integration of supplier rating system and product coding system, Expert Systems with Applications 25, 87–100. 7. Choy, K.L., Lee, W.B., Lau, H.C.W., and Choy, L.C. (2005) A knowledge-based supplier intelligence retrieval system for outsource manufacturing, Knowledge-Based Systems 18, 1–17. 8. De Boer, L., Van der Wegen, L., and Telgen, J. (1998) Outranking methods in support of supplier selection. A review of methods supporting supplier selection, European Journal of Purchasing and Supply Management 4(2/3), 109–118. 9. Dickson, G.W. (1966) An analysis of vendor selection systems and decisions, Journal of Purchasing 2, 5–17. 10. Dogan, I., and Sahin, U. (2003) Supplier selection using activity-based costing and fuzzy present-worth techniques, Logistics Information Management 16(6), 420–426. 11. Dulmin, R., and Mininno, V. (2003) Supplier selection using a multi-criteria decision aid method, Journal of Purchasing and Supply Management 9, 177–187. 12. Ellram, L.M. (1995) Total cost of ownership: An analysis approach for purchasing, International Journal of Physical Distribution and Logistics Management 25, 8. 13. Expert Choice 11.5, Expert Choice Inc., Arlington, USA, 2008. 14. Falconi, C. (1999) Methods for Priority Setting in Agricultural Biotechnology. In: Cohen, J.I. (ed.), Managing Agricultural Biotechnology: Addressing Research Program Needs and Policy Implications, ISNAR Biotechnology Service, The Hague, pp. 40–52. 15. Fedrizzi, M., and Giove, S. (2007) Incomplete pairwise comparison and consistency optimization, European Journal of Operational Research 183, 303–313. 16. Forman, E., and Peniwati, K. (1998) Aggregating individual judgments and priorities with the analytic hierarchy process, European Journal of Operational Research 108, 165–169. 17. Grando, A., and Sianesi, A. (1996) Supply management: A vendor rating assessment, CEMS Business Review 1, 199–212. 18. Harker, P.T. (1987) Alternative modes of questioning in the analytic hierarchy process, Mathematic Modeling 9(3–5), 353–360. 19. Harker, P.T. (1987) Incomplete pairwise comparisons in the analytic hierarchy process, Mathematical Modelling 9(11), 837–848.

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UNCERTAINTY IN LIFE CYCLE ASSESSMENT OF NANOMATERIALS Multi-criteria Decision Analysis Framework for Single Wall Carbon Nanotubes in Power Applications

T.P. SEAGER Golisano Institute for Sustainability Rochester Institute of Technology Rochester, NY 14623, USA [email protected] I. LINKOV US Army Engineer Research and Development Center Concord, Massachusetts, USA [email protected]

Abstract. Despite concerns regarding environmental fate and toxicology, engineered nanostructured material manufacturing is expanding at an increasingly rapid pace. In particular, the unique properties of single walled carbon nanotubes (SWCNT) have made them attractive in many areas, including high-tech power applications such as experimental batteries, fuel cells or electrical wiring. The intensity of research interest in SWCNT has raised questions regarding the life cycle environmental impact of nanotechnologies, including assessment of: worker and consumer safety, greenhouse gas emissions, toxicological risks associated with production or product emissions and the disposition of nanoproducts at end of life. However, development of appropriate nanotechnology assessment tools has lagged progress in the nanotechnologies themselves. In particular, current approaches to life cycle assessment (LCA) – originally developed for application in mature manufacturing industries such as automobiles and chemicals – suffer from several shortcomings that make applicability to nanotechnologies problematic. Among these are uncertainties related to the variability of material properties, toxicity and risk, technology performance in the use phase, nanomaterial degradation and change during the product life cycle and the impact assessment stage of LCA. This chapter expounds upon the unique challenges presented by nanomaterials in general, specifies sources of uncertainty and variability in LCA of SWCNT for use in electric and hybrid vehicle batteries and makes recommendations for modeling and decision-making using LCA in a multicriteria decision analysis framework under conditions of high uncertainty.1 1

The views and opinions expressed in this paper are those of the individual authors and not those of the US Army, NATO, or other sponsor agencies.

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1.

Introduction

The concept of the product life cycle in an environmental context refers to the total, aggregated impact of all the economic or industrial activities engendered by meeting product demands including: raw materials and energy extraction, benefaction, parts manufacture, assembly, distribution and sale, use and final disposition (such as disposal, remanufacturing, recycling or energy recovery of obsolete products). The advantage of the life cycle perspective is that it avoids problem shifting, in which solutions to environmental problems at one life cycle stage create new problems at other stages (e.g. [9]). Failure to conduct a thorough life cycle assessment (LCA) of a critical policy or design decision can sometimes result in catastrophic consequences, such as the addition of MTBE to oxygenated gasoline that was intended to improve tailpipe emissions (use phase), but also resulted in extensive groundwater contamination resulting from leaking underground storage tanks in the distribution phase [4]. The idea that the product life cycle is the proper perspective for assessing the environmental implications of materials, including engineered nanostructured materials, is now nearly universally accepted (e.g. [14, 40, 43]). However, there remains a paucity of research regarding LCA of nanomaterials, per se. The primary focus of scientific literature concerning environmental aspects of engineered nanomaterials consists of toxicological studies that screen or compare different materials in an effort assess dose-response relationships (e.g. [5, 27, 28]). In this context, the ‘life cycle’ is employed only as way to organize or identify potential source terms, rather than a formal life cycle assessment that encompasses a broader range of impact criteria such as ozone depletion, climate change, eutrophication, smog or acidification. Compared with conventional products, such as electronics, automobiles, chemicals, or even biofuels, where LCA has been applied extensively, there is practically no understanding of the broader environmental implications of nanomaterial substitution in products such as sports equipment, cosmetics, or clothing. In power applications the life cycle perspective is especially important. As another example related to energy applications, there is the problem of coal. From an energy independence perspective, the vast coal reserves of the United States present an opportunity to reduce petroleum imports, spur the domestic economy, narrow trade and current account deficits and reduce energy costs. But from an environmental standpoint, coal is problematic. It results in higher life cycle greenhouse gas emissions than other fossil-based alternatives such as petroleum or natural gas. It is typically contaminated with trace minerals and metals such as sulfur, mercury or arsenic that can be released to the environment through the production of fine particles, vapors or ash. And coal mining can be a dangerous and/or land intensive enterprise. Consequently, the use of coal in the United States is not expanding as rapidly as alternative or renewable energy sources such as wind, solar and biofuels. Nonetheless, if development of SWCNT-enhanced lithium ion batteries for electric or plug-in hybrid vehicles is successful, there may be widespread deployment of vehicles that depend upon coal-fired electric power plants as a primary or supplemental energy source – as well as increased demand

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from the manufacturing sector for large scale battery production. Both coal consumption and concomitant environmental impacts are likely to increase. The purpose of life cycle assessment in this case would be to compare the relative increase in adverse environmental effects in the power generation sector with the benefits realized in the use phase of the transportation sector. Similarly, the extraordinary controversy regarding alternative automotive fuels such as ethanol and biodiesel has, to a great extent, focused on whether the investment of energy required to produce crop-based fuels (e.g., natural gas for fertilizer production, diesel fuel for operation of farm equipment, and electricity and/or heat for fuel processing) is justified by the energy content in the fuels themselves (e.g. [11, 44]). More recently, as new policies encourage the rapid expansion of biofuel crops cultivation, the boundaries of scientific interest have expanded even further to include issues such as land clearing (e.g. [6]), eutrophication (e.g. [15]) and indirect greenhouse gas emissions (e.g. [3, 37]) that manifest at stages of the life cycle far upstream from fuel consumption itself. Use of SWCNT (or other nanomaterials) in power applications such as solar cells, batteries or wires presents a set of problems that are analogous to biofuels in several ways. For example, the energy required to manufacture SWCNT – and especially pure phase SWCNT materials – is considerable. In addition to the energy consumed in preparation of pure carbon feedstocks, metal catalysts, and inert gas, energy is consumed in the vaporization of solid carbon and purification of the resultant SWCNT. Material yields are typically low – e.g., less than 30% at the laboratory scale [32]. Ultimately, only power applications that result in a high return of energy during the use phase can justify the energy ‘invested’ during earlier stages on a thermodynamic or economic basis (e.g. [2]. In static energy production devices, such as photovoltaic solar cells, the adoption of nanotechnologies (beyond niche applications, such as spacecraft) is dependent upon whether an improvement in photon conversion efficiency results in increased total energy output over the life of the device. However in batteries, e.g. for hybrid or electric vehicles, because they only store energy and do not produce energy of their own, the critically important improvement that must be provided by nanotechnology is increased energy density (kW-h/kg). Given constraints such as the maximum vehicle range between recharge or refuel, increased energy density in a vehicle battery would result in improved energy economy (i.e., mileage) due to the lighter vehicle weight. Therefore, to the extent that hybrid or electric vehicles may be a direct technological substitute for gasoline, ethanol or biodiesel vehicles, a comparative life cycle investigation into the suitability of SWCNT technologies for hybrid vehicle batteries is essential – albeit problematic. 2.

LCA for SWCNT: Challenges

Originally developed for application in mature industries such as plastics, automobiles petroleum and metals, LCA was originally envisioned as a tool for comparing or improving technologies that were fairly well understood. Later, LCA was successfully applied to newer technologies such as semiconductors (e.g.

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[45]). In contrast, nanotechnologies are barely in the nascent stages of research, development and commercialization. As is typical of rapidly growing industries, nanotechnology manufacturers are more focused on maximizing production and technological development than on environmental efficiency or sustainability. Moreover, the analytical techniques of LCA are not fully adapted to domains of such extraordinary uncertainty. Nevertheless, application of LCA in an emerging industry such as nanotechnology may present a unique opportunity to avoid the types of environmental crises that are the legacy of the industrial revolution (e.g. [35]) by applying appropriate life cycle risk measures early. Therefore, at least three significant challenges to existing LCA techniques must be overcome: material variability, uncertainty in toxicity and risk and uncertainty in functional performance [36]. Each of these is described in separate sections below. Material Variability. Even within a seemingly narrow class of nanomaterials such as SWCNT, there are an incredible variety of material possibilities and characteristics. It is inappropriate to make generalizations based upon studies that fail to carefully differentiate SWCNT purity, length, diameter, chirality or state of agglomeration [31, 42]. Almost any important performance property is dependent upon the characteristics of the SWCNT employed. From an environmental risk perspective, one of the most important characteristics of SWCNT may be their toxicity. Nevertheless, with few exceptions, toxicity studies using SWCNT have failed to robustly characterize the materials under investigation [10]. A typical toxicological protocol might involve comparison of SWCNT to positive (e.g., ultra fine quartz) and negative (e.g., carbon black) controls, or comparison of SWCNT from different sources (e.g. [12]). Some of these studies have shown positive (i.e., deleterious to health) responses that are sensitive to SWCNT dosages (e.g. [25]). However, where characterization is poor or non-existent, it is not possible to understand the mechanism or determining factors causing toxicity. For example, even SWCNT sold as “purified” may contain biologically significant concentrations of metals [20]. There are currently no industry standard specifications to aid in characterization of SWCNT – making cross-comparison of different toxicological (or other) findings problematic. Characterization procedures are still evolving [49]. However, in LCA the properties of the materials themselves are no more important than the processes employed to manufacture them. In this regard, there is significant variety in approaches to synthesis of SWCNT, including: laser ablation, arc discharge, flame, chemical vapor deposition and high pressure carbon monoxide, to name a few (e.g. [36, 38]). Each process is expected to have a unique life cycle environmental profile [47]. Uncertainty in Toxicity and Risk. Toxicological risk assessment typically emphasizes characterization of exposure, dose and health response relationships. (For a review relevant to nanomaterials, see Oberdörster et al. [28, 48]). By contrast, LCA places particular emphasis on quantification of source terms, which constitute the inventory of chemicals released into the environment. Only in the impact assessment stage of LCA is information regarding the environmental fate and transport, exposure, dose and response (for health impacts) considered in the analysis. In the first step of impact assessment, the chemical emissions inventory must be aggregated into several midpoint categories that are representative of the

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types of impacts that are relevant to the study (e.g. [13]). The mathematics employed is a simple weighted sum, in which all emissions related to a particular midpoint, such as global warming or ozone depletion, are compared to a single chemical standard representative of the impact category. For example, all emissions that impact climate are expressed in equivalent kilograms of carbon dioxide, whereas the ozone depletion category is expressed as equivalent kilograms of CFC-11 (a chlorofluorocarbon that was frequently used as a refrigerant, foamblowing agent or in other applications prior to the production ban promulgated in the Montreal Protocol). For health impacts, midpoints may be expressed in terms of kilogram benzene (or other chemical) equivalents, kilogram PM10 (particles less than 10 µm in diameter) or both. In some cases, there are extraordinary uncertainties related to characterization of inventory data, which may be viewed as justification for truncating life cycle impact assessment at the midpoint characterization stage, rather than continuing the analysis to complete damage assessment (e.g., in terms of disability adjusted life-years, or DALYs), normalization and weighting (e.g. [46]). However, selection of standard LCA midpoint equivalencies pre-dated the explosion of interest in nanomanufacturing. In the case of nanostructured materials, even the characterization framework itself may not be inappropriate. For example, without understanding the mode of action of toxicity, characterization of SWCNT emissions in relation to benzene equivalents may be wildly incorrect. Similarly, characterizing nanomaterials in terms of kilogram PM10 (or even PM2.5) may be wholly unjustified, as it is not yet clear that mass concentration drives toxicity at the nanoscale. Surface properties, functionalization, interaction with environmental media, and microbial activation may all play roles in nanomaterial toxicity that can not be captured in terms of mass, volume or even surface area concentrations. As a result, characterization factors for nanomaterials in the context of life cycle impact assessment do not exist; nor is their development trivial. The idea of benchmarking nanomaterial toxicity in terms of characterization factors relating to existing LCA midpoint equivalencies may be unrealistic. Uncertainty in Functional Performance. In determining the scope and boundaries of a life cycle assessment, it is necessary to select the functional unit that represents the economic demand motivating the life cycle activities. Misrepresentation of the functional unit can lead to misunderstanding of the production system. It is important (when selecting a functional unit) to view life cycle problems from the perspective of the consumer in the use phase, rather than from the perspective of the manufacturer at the point of sale. For example, automobile manufacturers often normalize operations data (such as man-hours, lost-time accidents or product defects) in terms of vehicles produced. It may seem natural to the manufacturer to consider life cycle data in the same terms such as carbon dioxide equivalents per vehicle produced. Similarly, SWCNT manufacturers may track environmentally relevant data relative to the total mass of SWCNT produced. But from the consumer’s perspective, the vehicles or the SWCNT themselves are not the object of demand (except in rare cases, such as collectors). Consumers only purchase cars so that they can be driven. Consequently, a vehicle LCA is best expressed in terms of vehicle-miles traveled, although nearly equivalent results can be obtained

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when a functional unit is expressed in terms that are essentially equivalent to vehicles-miles, such as total battery energy. On this basis, Matheys [23] estimated that lead-acid, nickel-cadmium and nickel-metal hydride batteries all have comparable environmental impacts, whereas lithium-ion batteries may have lower impacts. However, the performance of lithium-ion batteries employing SWCNT (e.g., as an anode) are still largely untested on all but laboratory scales. Moreover, nanomaterials are rarely used in the pure phase. More typically, they are additives or substitutes in composite materials. In many cases, the type and quantity of nanomaterials have not been optimized and the mechanisms of functionality may not be entirely understood. In other cases, laboratory-scale processes have not yet been sufficiently scaled up to understand the potential environmental implications of high-rate manufacturing. Depending on the end-use application, they may require different levels of purification effort to remove metals or surface coatings (e.g., of adsorbed carbon). Additionally, the relationship between SWCNT content and functionality in the final application may be dependent upon the synthesis methods and purification techniques employed. Because the synthesis, purification and separation processes employed in manufacture can result in important changes in the nanotube characteristics, these processes can not be assessed independently of the end-use application. 3.

Life Cycle Impact Assessment in High Uncertainty Applications

Although engineered nanomaterials represent a serious challenge to traditional approaches to both toxicological risk and life cycle assessment, to some extent these challenges can be met by employing a “decision-directed” approach to the analysis, as has been recommended in chemical toxicology for over a decade (e.g. [39]). This approach emphasizes a relative or comparative rather than absolute approach. Already, a comparative screening of nanotech to other more mature industries estimates that nanomanufacturing risks may be relatively low [33]. There may be several advantages to a decision-directed, comparative approach under conditions of high uncertainty [18]. First, it requires a finite set of alternatives and well-defined decision criteria, both of which serve to bound the analysis. Second, analysis can be focused on areas in which the decision may be sensitive to a narrowing of uncertainty bounds. Analytical effort may be conserved and the sensitivity of decision outcomes to both uncertainty and variability can be explored. Lastly, a decision directed approach implies coupling of the assessment with a structured decision aid, such as cost-benefit or multi-criteria decision analysis (MCDA). It is this latter aspect that may prove most challenging, as decision analysis demands incorporation of knowledge from social science fields (e.g. [8]) that are outside the domain of physical science and engineering, where much of the expertise regarding nanotechnology, toxicology and power technologies resides. Moreover, LCA is much less fully developed in impact assessment (the stage that applies MCDA techniques, such as normalization and weighting) than data gathering. Consequently, advances in both the theory and

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practice of LCA that expand the role of cutting-edge MCDA techniques are required [36]. 4.

Stochastic Decision Tools for MCDA

With its emphasis on broad systems boundaries, LCA necessarily requires the analyst to consider a set of incommensurate decision criteria and the viewpoints of multiple stakeholders or decision makers [1]. In power applications, criteria as diverse as climate change, economy, human and ecological health, water quality, energy independence, efficiency and renewability may be brought to bear. Under such conditions, utility-based, normative decision analytic techniques such as cost benefit analysis (which is a single criterion approach) are typically less likely to be informative than more practical decision strategies that elucidate trade-offs and contrast opposing points of view. In particular, MCDA approaches such as outranking are especially suitable for problems where there are a large number of alternatives, strong heterogeneity exists between criteria (making aggregation difficult) and compensation of loss in a given criteria by gain in another is unacceptable (e.g. [41]). An example applying outranking to nanomaterials has been reported [17, 19] and MCDA has been recommended as one of the most promising nanotechnology risk governance tools [34]. However, the sources and implications of high variability and uncertainty in MCDA are still not fully understood. A decision directed approach allows consideration of uncertainty and variability beyond those due to material variability, toxicity and risk, or functional performance: namely, the preferences of the decision-makers or stakeholder vested in the decision. In the United States, policy and decision-making has been dominated by a utilitarian approach that draws heavily on microeconomic theory, which posits that where preference functions are known, maximization of riskadjusted utility is a logical decision objective. However, in the case of environmental decision making, preference functions are rarely (if ever) known or describable. Environmental preferences are typically constructed by decision makers as they progress through the process of decision analysis, rather than preexisting in the minds of the decision makers and revealed at the end of the analytic process [30]. That is, people often change their minds. Or their thinking evolves. Whether there are stable preference functions for any good or service is a matter of debate among economists – but for environmental goods such as those represented in the decision criteria of LCA, decision makers have precious little experience exploring their own state of mind. Even the decision context can influence the preferences [24] and decision makers may express seemingly contradictory preferences for similar criteria in two different decision problems (e.g. [16]). Because LCA has been promulgated by the International Standards Organization as an objective, scientific tool, the methodology of techniques for incorporating stakeholder preferences has lagged other aspects of LCA. For example, the impact and decision analytic tools offered practitioners in automated software packages are generally simplistic, if extant at all. In some cases, current decision analytic tools in LCA may even be counter-productive by masking relevant aspects of a

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problem [50]. However, there has been some effort to investigate the sensitivity of LCA results to stakeholder preferences in green building applications, where it has been reported that a group of LCA experts may weight global warming as little as 7% or as much as almost 70% of an overall merit function, depending on the time horizon of interest [7]. The clear conclusion is that there is considerable variability between different decision makers and that even within a narrow group (or single decision maker) there may be variability or uncertainty with regard to preference for trade-offs in performance of technological alternatives. The ultimate conclusion of a comparative study may depend upon a subjective preference for one type of impact at the expense of another. To more accurately represent uncertain human values in risk and life cycle impact assessment, the decision criteria weights in MCDA should be modeled stochastically using Monte Carlo Analysis [50]. Explicit incorporation of uncertainty in the weighting and impact assessment stage of LCA would allow for a more accurate representation of how stakeholders actually perceive environmental trade-offs. Moreover, it allows a rapid exploration of multiple views for screening or comparison of alternatives without extensive value function elicitation [41]. The general approach, called stochastic multi-attribute acceptability analysis (SMAA) is appropriate for situations in which the weights may be only partially or even completely unknown due to the number of decision-makers (i.e., variability), high uncertainty, or characterized by mixed qualitative and quantitative preference information. In these cases, reducing uncertainty or describing variability may be prohibitively expensive. However, it is still possible to explore the sensitivity of alternative rank preferences to different weight spaces or constraints and whether a technological alternative is likely to be preferred relative to other alternatives. 5.

Incorporating Uncertainty and Variability into LCA

Figure 1 depicts a general approach to collecting and aggregating data for LCA of SWCNT anode vehicle batteries. The life cycle stages are listed horizontally in the middle of the figure, with the resource inputs at each stage depicted in columns below. Consequently, the figure reads best from bottom to top (depicting the flow of data) and from left to right (depicting the flow of materials). Elements of the analysis that are common to both conventional graphite anodes and SWCNT anodes have been grayed out, inside the bubbles. These aspects of the system need not be quantified in a comparative approach, as they are identical under each alternative. Different types of data uncertainty and variability manifest at different stages of LCA. Process yields, functional performance and material variability are all represented in the inventory data. Table 1 lists several of the sources of uncertainty and/or variability relevant to SWCNT in vehicle batteries at this stage. However, toxicological information is represented in data characterization and aggregation (Table 2). Lastly, uncertainty in criteria weightings is represented in the final stages of impact assessment (depicted in Figure 1 at the top as SMAA).

Impact Criteria

Inventory Data Acquistion

Soot Production

Acid Reflux

Metals Removal

Free Carbon Removal

SWCNT Anode Manufacturing

Energy Use Environment

Electrolytic

Half and Separators

Electrodes, Supplies, Casing

Cathode Production

Battery Production

Vehicle Manufacturing

Electricity Generation and Transmission

Vehicle Use

Data Characterization and Aggregation

Economy

End of Life

Vehicle Recovery

Battery Recovery

Society / Regulation

Figure 1. Aggregation of data variability and uncertainty in LCA of SWCNT for vehicle batteries.

Human/Ecology Health

Stochastic Multi Attribute Assessment

Life Cycle Impact Assessment

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Cooling

Disposition of waste materials (i.e., CO2)

Free carbon removal

Purity requirements

Solvent (e.g., acetone and/or water) requirements, disposition of metals

Heating requirements & heat source

Metals removal Filter membrane consumption

e.g., closed refrigerant, open water loop, evaporative

Technological learning curves, experimental vs. high-rate manufacturing rates

Extent of metals dissolution

Production yield (i.e., tube vs. free or amorphous carbon)

Process

Scale

Acid type (e.g., HCl, HNO3)

Inert gas (e.g., Ar, N2) & waste gas disposition

Acid reflux

Solvents & wastes

Technology

Energy

Consumables

Nanotube soot production Catalyst (e.g., Ni, Fe, Co) and consumption rate Energy sources (e.g., source of electricity, gas consumption) Vaporization technique (e.g., arc, flame, laser)

SWCNT paper anode thickness, content

Cathode selection

Battery production

TABLE 1. Sources of variability & uncertainty in inventory data acquisition for LCA of SWCNT Li-ion batteries.

Lifetime (i.e., vehicle range & charge cycling) Weight & energy consumption for cooling

Battery weight

Tailpipe & electricty generation emissions

Energy losses

Use phase

Recovery & recycling rates

End-of-life

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UNCERTAINTY IN LIFE CYCLE ASSESSMENT OF NANOMATERIALS 433 TABLE 2. Sources of variability & uncertainty in data characterization for LCA of SWCNT vehicle batteries. Process & performance Proximity of sources Quantity equivalencies (e.g., manufacturers, for dose determination users, recyclers) to (e.g., mass, surface area, receptors (e.g., volume) workers, consumers, ecosystems) Discount rates, Experience curves, Mitigation, worker depreciation schedules, salvage scale-up costs protection, remediation costs values Quality of energy aggregation measures (e.g., energy, exergy, cost), renewability, imported vs. domestic Source term interactions, (e.g., nitrogen & phosphorus for eutrophication, VOCs & NOx for smog) Public & regulatory responses, attitudes Material variability

Human & ecological health

Economy Energy Environment Socio-political

Toxicology & risk Environmental fate & transport (e.g. agglomeration), exposure routes, toxicological equivalency benchmarks (e.g., kg PM2.5 equivalents)

The SMAA approach has the advantage of applying stochastic methods to preference modeling in a mathematical approach that is consistent with uncertainty modeling in other aspects of LCA. Although most life cycle inventories use point estimates, where information is available, Monte Carlo analysis is sometimes used to propagate uncertainty and/or variability through several analytic phases [22] – albeit few studies incorporate uncertainty through a complete impact assessment [21]. Consequently, a combined inventory and impact assessment Monte Carlo model can be used to explore which uncertainties drive the final preference ordering of alternatives. However, where multiple types of uncertainty are extraordinarily high, traditional Monte Carlo analysis alone is inadequate [26]. Probability distributions under conditions of model and boundary uncertainty lack meaning (at best) or may lead to overconfidence (at worst). In the case of SWCNT, stochastic analysis should be combined with scenario analysis, in which certain parameters may be fixed (sometimes at extreme or improbable boundary conditions) by decision makers to explore a range of possibilities (e.g. [29]). The focus in scenario analysis can be on exploring possible outcomes, rather than identifying the most likely outcomes. The critically important aspect of the integrated SMAA-LCA approach is that it allows exploration of different types of uncertainty and variability in an integrated, systematic way. Without considering the entire system in a specific decision context, it is impossible to ascertain whether additional research effort into reducing uncertainty or characterizing uncertainty is relevant to the final outcome. Only by exploring the sensitivity of the decision outcome to all types of uncertainty in concert can those with the greatest influence be discovered, as uncertainties in one aspect of the analysis may overwhelm those in other areas that may have otherwise been considered important areas to investigate further. The

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overall result of a comparative life cycle exploration of uncertainty and variability that is tightly coupled with a SMAA decision-analytic approach can be a better understanding of the sensitivity of the system to important design variables or parameters, a reprioritization of research and development efforts, a better understanding of decision-maker preferences and ultimately, better decisions and environmentally advantageous technologies. Acknowledgements The authors thank Drs. Brian Landi and Ryne Raffaelle at the Nanopower Research Laboratory, Rochester Institute of Technology for helpful conversations regarding purification and characterization of SWCNT for anode materials. Matt Ganter and Kali West contributed to Table 1. Alexander Tkachuk prepared Figure 1. Permission was granted by the Chief of Engineers to publish this information. The studies described and the resulting data presented herein were obtained from research supported by the Environmental Quality Technology Program of the US Army Engineer Research and Development Center (Dr. John Cullinane, Technical Director). References 1. Basson, L., and Petrie, J.G. (2007) An integrated approach for the consideration of uncertainty in decision making supported by life cycle assessment, Environmental Modeling & Software 22(2), 167–176. 2. Cleveland, C.J., Hall, C.A.S., and Herendeen, R.A. (2006) Energy returns on ethanol production, Science 312(5781), 1746. 3. Crutzen, P.J., Mosier, A.R., Smith, K.A., and Winiwarter, W. (2008) N2O from agrobiofuel production negates global warming reduction by replacing fossil fuels, Atmospheric Chemistry and Physics 8, 389–395. 4. Davis, J.M. (2007) How to assess the risks of nanotechnology: Learning from past experience, Journal of Nanoscience and Nanotechnology 7, 1–8. 5. Donaldson, K., Aiken, R., Tran, L., Stone, V., Duffin, R., Forrst, G., and Alexander, A. (2006) Carbon nanotubes: A review of their properties in relation to pulmonary toxicology and workplace safety, Toxicological Sciences 92(1), 5–22. 6. Fargione, J., Hill, J., Tilman, D., Polasky, S., and Hawthorne, P. (2008) Land clearing and the biofuel carbon debt. Science 319, 1235–1238. 7. Gloria, T.P., Lippiatt, B.C., and Cooper, J. (2007) Life cycle impact assessment weights to support environmentally preferable purchasing in the United States, Environmental Science & Technology 41(21), 7551–7557. 8. Gregory, R., and McDaniels, T. (2005) Improving environmental decision processes. In: Decision Making for the Environment, Brewer, G.D., and Stern, P.C. (eds.), National Academy Press, Washington, DC. 9. Guinee, J.B. (ed.) (2002) Handbook on Life Cycle Assessment: Operational Guide to the ISO Standards, Kluwer, Boston, MA. 10. Hansen, S.F., Larsen, B.H., Olsen, S.I., and Baun, A. (2007) Categorization framework to aid hazard identification of nanomaterials, Nanotoxicology 1(3), 243–250.

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31. Powers, K.W., Palazuelos, M., Moudgil, B.M., and Roberts, S.M. (2007) Characterization of the size, shape and state of dispersion of nanoparticles for toxicological studies, Nanotoxicology 1(1), 42–51. 32. Rinzler, A.G., Liu, J., Dai, H., Nikolaev, P., Huffman, C.B., Rodriguez-Macias, F.J., Boul, P.J., Lu, A.H., Heyman, D., Colbert, D.T., Lee, R.S., Fischer, J.E., Rao, A.M., Eklund, P.C., and Smalley, R.E. (1998) Large-scale purification of single-wall carbon nanotubes: Process, product, and characterization, Applied Physics A. 67, 29–37. 33. Robichaud, C.O., Tanzil, D., Weilenmann, U., and Wiesner, M.R. (2005) Relative risk analysis of several manufactured nanomaterials: An insurance industry context, Environmental Science & Technology 39, 8985–8994. 34. Roco, M.C. (2008) Possibilities for global governance of converging technologies, Journal of Nanoparticle Research 10, 11–29. 35. Seager, T.P., Satterstrom, F.K, Tuler, S.P., Kay, R., and Linkov, I. (2007) Typological review of environmental performance metrics (with illustrative examples for oil spill response), Integrated Environmental Assessment & Management 3(3), 310–321. 36. Seager, T.P., and Linkov, I. (2008) Coupling multi-criteria decision analysis and life cycle assessment for nanomaterials, Journal of Industrial Ecology 12(3), 282–285. 37. Searchinger, T., Heimlich, R., Houghton, R.A., Dong, F., Elobeid, A., Fabiosa, J., Tokgoz, S., Hayes, D., and Yu, T.-H. (2008) Use of US croplands for biofuels increases greenhouse gases through emissions from land-use change, Science 319, 1238–1240. 38. Şengül, H., Theis, T., and Ghosh, S. (2008) Towards sustainable nanoproducts: An overview of nanomanufacturing methods, Journal of Industrial Ecology 12(3), 329–359. 39. Stern, P.C., and Fineberg, H., eds. (1996) Understanding Risk: Informing Decisions in a Democratic Society, National Academy Press, Washington, DC. 40. Sweet, L., and Strohm, B. (2006) Nanotechnology—life-cycle risk management, Human and Ecological Risk Assessment 12(3), 528–551. 41. Tervonen, T., and Lahdelma, R. (2007) Implementing stochastic multicriteria acceptability analysis, European Journal of Operational Research 178, 500–513. 42. Tsuji, J.S., Maynard, A.D., Howard, P.C., James, J.T., Lam, C.-W., Warheit, D.B., and Santamaria, A.B. (2006) Research strategies for safety evaluation of nanomaterials, Part IV: Risk assessement of nanoparticles, Toxicological Sciences 89(1), 42–50. 43. United States Environmental Protection Agency (2008) Draft Nanomaterial Research Strategy, United States Environmental Protection Agency, Office of Research and Development, Washington, DC, publication EPA/600/S–08/002. 44. Von Blottnitz, H., and Curran, M.A. (2007) A review of assessments conducted on bio-ethanol as a transportation fuel from a net energy, greenhouse gas, and environmental life cycle perspective, Journal of Cleaner Production 15, 607–619. 45. Williams, E.D., Ayres, R.Y, and Heller, M. (2002) The 1.7kg microchip: Energy and material use in the production of semiconductor devices, Environmental Science and Technology 36, 5504– 5510. 46. Bare, J.C., Norris, G.A., Pennington, D.W., and McKone, T. (2003) TRACI: The Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts, Journal of Industrial Ecology 6, 49–78. 47. Healy, M.L., Dahlben, L.J., and Isaacs, J.A. (2008) Environmental assessment of single wall carbon nanotube processes, Journal of Industrial Ecology 12(3), 376–393. 48. Oberdörster, G., Oberdörster, E., and Oberdörster, J. (2005) Nanotoxicology: An emerging discipline evolving from studies of ultrafine particles, Environmental Health Perspectives 113(7), 823–839. 49. Raffaelle, R.P., Landi, B.J., Harris, J.D., Bailey, S.G., and Hepp, A.F. (2005) Carbon nanotubes for power applications, Materials Science and Engineering B 116, 233–243. 50. Rogers, K. (2008) Environmental Decision-Making Using Life Cycle Impact Assessment and Stochastic Multi-Attribute Decision Analysis: A Case Study on Alternative Transportation Fuels. Master’s thesis, Civil Engineering, Purdue University, West Lafayette, IN.

KNOWING MUCH WHILE KNOWING NOTHING Perceptions and Misperceptions About Nanomaterials

J.M. PALMA-OLIVEIRA, R.G. DE CARVALHO, S. LUIS, M. VIEIRA Faculty of Psychology and Educational Sciences (FPCE) University of Lisbon Alameda da Universidade 1100 Lisboa, Portugal [email protected]

Abstract. Nanomaterials are not technological newcomers. However the use of an integrative concept to describe the diverse and complex array of these very small products is new. This chapter aims to describe some of the attitudes and risk perception studies about these materials. Furthermore it will be presented an empirical research where we will introduce some of the psychological factors that could help in understanding the psychometrics of the nanomaterials risk perception. One could conclude that despite the agreement that there is a widespread lack of knowledge, people can still apply attitudes and deduce a risk perception estimate that differs essentially according to the application domains. Furthermore risk perception about nanomaterials can be easily modified if some new negative phenomena arrive. In this context the design of a good risk communication strategy is particularly important especially because according to many studies and the one to be presented, the nano experts have difficulty in understanding what the factors that underlie lay people’s judgments are. 1.

Knowing Much

European citizens seem to be generally optimistic about the contribution of technology to our way of life. An index of optimism shows a high and stable level for computers and information technology and solar energy from 1991 to 2005. Over the same period the index for biotechnology declined steeply from 1991 to 1999. From 1999 to 2005 the trend reversed, and now biotechnology is back to the same level of optimism seen in 1991. Optimism about nanotechnology has increased since 2002 – the ratio of optimists to pessimists being eight to one.

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Will improve

No effect

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79

11

6

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3 6

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Percentage

Figure 1. Optimism and pessimism for eight technologies in 2005 [33].

According to an Eurobarometer study [33] (see Figure 1), the European public is not risk-averse about technological innovations that are seen to promise tangible benefits. In fact, in all of the areas studied (except for nanotechnology, in which the percentage of non-response was high in all countries), most respondents declared that they believed the new technologies development will have a positive effect in society in the next 20 years. While the majority is willing to delegate responsibility on new technologies to experts, making decisions on the basis on the scientific evidence, a substantial minority would like to see greater weight given to moral and ethical considerations in decision taking about science and technology and to the voices of the public. As an example, there is widespread support for medical (red) and industrial (white) biotechnologies, but general opposition to agricultural (green) biotechnologies in all but a few countries. Europeans support the development of nanotechnology, pharmacogenetics and gene therapy. All three technologies are perceived as useful to society and morally acceptable. Neither nanotechnology nor pharmacogenetics are perceived to be risky. While gene therapy is seen as a risk for society, Europeans are prepared to discount this risk as they perceive the technology to be both useful and morally acceptable. In a set of questions asking for opinions on these four technologies (gene therapy; pharmacogenetics; GM food; and nanotechnology), respondents were first asked if they had ever heard of them. Figure 2 shows the percentages of respondents in each EU Member State who said they had heard of each of the applications. Respondents were then asked whether they thought the different technologies were morally acceptable, useful for society, risky for society, and whether they should be encouraged. Figure 3 shows EU-wide mean scores for assessments of these applications, on a scale ranging from +1.5 to −1.5.

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GM foods EU25

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Pharmacogenetics

27

73

89 87 92

0

Nanotechnology

29 29 33 31 24 21

150 Percentage

200

250

300

Figure 2. Familiarity with four technologies [33].

The figure shows varying levels of support for these technologies. The European public is most positive about nanotechnology, followed by pharmacogenetics, and then gene therapy, though on balance it regards the latter as risky. By contrast, GM food is predominantly perceived as negative. Morally acceptable

Useful

Risky

Should be encounraged

1.0 0.8 0.5 0.3 0.0 −0.3 −0.5

Nanotechnology

Pharmacogenetics

Gene therapy

GM Foods

Figure 3. Evaluations of four technologies [33].

As the judged usefulness of technologies declines perceived risk increases, along with a decline in perceptions of moral acceptability and overall levels of support. For nanotechnology and pharmacogenetics, agreement that they should

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be encouraged goes along with the perception that they are not risky. This is mirrored in the case of GM food, for which overall opposition is accompanied by perceptions of relatively high risk. By contrast, gene therapy is supported despite the tendency for it to be perceived as risky; it seems that the risk attached to gene therapy is tolerable, whereas for GM food it is unacceptable. There is clear evidence of differences in evaluations between those who have heard of a technology and those who have not. Specifically, those who say they have heard of gene therapy, pharmacogenetics and nanotechnology tend to express notably more positive views than those who are unfamiliar with them. For these Nanotechnology

EU25

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58 50

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35 34

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Greece

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Netherlands

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61

Slovakia

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62

Denmark

GM foods

27

60

54

Sweden

Gene therapy

50

52

Czech Republic

France Luxembourg

Pharmacogenetics

29 33

20

100

150

Percentage

Figure 4. Support for four technologies [33].

200

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technologies people who are familiar with them are more likely than people who are not familiar with them to agree that they are morally acceptable, useful and should be encouraged, and more likely to disagree that they are risky. Looking a little more closely at overall levels of approval (whether the technologies should be encouraged) we see varying levels of support across countries. Figure 4 shows the stacked percentages of respondents who either ‘agree’ or ‘totally agree’ that each application should be encouraged. These different attitudes towards this category of new technologies according to the type of the specific applications is a very important feature that will come across the whole chapter. Specifically, despite the global positive evaluation of these new technologies, the attitudes and, for that matter, the risk perception is strongly qualified by the specific attitudes towards the particular application. This psychological framing will be discussed in the next sections. 2.

While Knowing Nothing

Previously, we showed that people’s knowledge of nanotechnologies is low and people have a positive opinion about its usefulness and moral acceptance, showing slight concerns about its risks. However, how can people have these evaluations about nanotechnologies not knowing what they actually are? This section’s aim is to answer this question and discuss possible socialtechnical implications that are relevant to risk management. To begin with, a review of some research about the nature of human judgment and decision under uncertainty will be presented, focusing on three features: (1) the evaluations formation process, (2) how affect strongly influences evaluations, (3) and judgmental heuristics involved in these. First of all, if people never heard of “nanotechnology” before how can they evaluate its risk? People can form judgments in two different ways [1]. If they already have some information about the evaluation target, let’s say “nanotechnology”, they can form an evaluation based on the data stored in memory. Otherwise, the evaluation can be formed on-line after the acquisition of an initial piece of information and then revised and updated as each subsequent piece of information is acquired [12]. For example, in our own research participants were first told “Nanotechnology deals with the development of procedures in which materials are created or manipulated in the atomic and molecular scale” and latter on, by filling the questionnaire they could infer that nanotechnologies deal with general applications (“food, military…”) and different products (“sunscreen, toys, cancer treatments”). Even if one might think that this information was kind of poor, with the respondents themselves stating their perceived knowledge regarding general nanotechnologies applications as low (M = 2.06; SD = 0.91), results illustrate that even with this minimal amount of information they still formed opinions that were consistent throughout the sample. In fact, when not privy to specific and direct evidence necessary for an inductive inference about an attribute, people tend to draw from whatever sources of information they have available [11]. In some instances, attributes are inferred

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from more global judgments or expectancies, such as a superordinate categorization of the target (e.g., [2]) or an overall attitude towards the target [4, 18]. Besides that, stronger inferences or evaluations are drawn with the passage of time, as memory of the absence of initial information fades [19]. This means people can simply judge nanotechnologies as technologies in general for example, and as time goes by, this judgment becomes less doubtful. We highlight that the first pieces of information that people receive tends to have more impact on evaluations than latter information [7, 13]. Even if the original information may be forgotten or inaccessible, its evaluation remains in memory and available for recall when it is needed. First impressions do matter! It’s also important to note that negative information has more impact than positive information [13]. Risk managers should pay special attention to this issue: one single and unfortunate accident involving nanotechnologies might be more remembered than years of good practice and improvements on nanotechnologies different applications. Continuing our discussion, how can people make a consistent risk estimate based on poor information? To make an evaluation we don’t necessarily gather all relevant information and deliberate about it. Many times our evaluations follow much easier and faster paths. If we analyze most our evaluations and decisions we can notice they reflect an apparent lack of “rationality”. Human decision “fail” to be explained by economic models: people do not decide in order to maximize profit or minimize costs all of the time [22]. For example, think about your house or car. Did you search all your options and settle for the better price/quality option or did you just knew that there was “something” about it that made it worthy? This “something”, sometimes has to do with affect. Many times people intuitively use it instead of reason because usually rational choices consume more cognitive resources and time, while affect-based decisions and judgments allow the opposite. This means that instead of comparing nanotechnologies advantages and disadvantages, people might rely on their spontaneous feelings towards it. The point is that these feeling can be the result of very simple and basic psychological process, such as the degree of exposure or familiarity with the subject [10, 31], which influence people are usually not aware of. Because they derive not from conscious evaluations but from unconscious and automatic affective evaluations towards the object, they can produce an “I don’t like it, but I don’t know why” phenomena. This justifies that “liking” may support attitudes or choices that cannot be justified by people’s “rational” beliefs. This doesn’t mean that people are irrational! It means that in certain cases their judgments are based on affect. Functionally, these judgments are easier and faster and, in “known” situations, they prove to be “correct”. So, to the question: “Do you think nanotechnologies are risky?” we can unknowingly be answering “Oh yes, I don’t like it!” Other times, this “something” might have to do with the “boundaries” of intuitive rationality. The research program on judgmental heuristics, by the Nobel Prize Daniel Kahneman and his colleague Amos Tversky, illustrates that people’s intuitive judgments (the judgments that spontaneously and effortlessly come to mind) are biased by factors that “reasonably” should be irrelevant. Specifically, the researchers found (a) persistent errors in estimates of known quantities and

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statistical facts and (b) systematic discrepancies between the regularities of intuitive judgments and the principles of probability theory, Bayesian inference, or regression analysis. This means that when an individual has to judge a risk, his intuitive judgment probably will not have correspondence to its statistical meaning. We emphasize that this happens both to lay people and to people with statistical knowledge! Surprisingly, even the intuitive judgments of statistically sophisticated researchers don’t conform to statistical principles with which they are thoroughly familiar [26]. So, how do people judge things intuitively? In making predictions and judgments people rely on a set of heuristics or rules of thumb. Sometimes these yield reasonable judgments, other times they lead to severe and systematic errors. One can distinguish between “individuals” heuristics, such as the availability or ease with which particular mental contents come to mind [27], seriously influenced by the mass medias coverage’s and “contextual” heuristics, like anchoring, the presence of contextual information that temporary raise its availability in individuals memory [27], and framing, with alternative formulations of the exactly same situation making different aspects of it accessible in memory, thus leading to different judgments [29]. On top of that, people don’t’ seem to be aware of these biases and tend to have a great confidence on the accuracy of their judgments [27]! So, when asked “Do you think nanotechnologies are risky?” we can unknowingly be answering “Oh yes, I’m absolutely sure they are risky! Just yesterday I saw on TV what a nanotechnology produced sunscreen did to a little child’s skin.” 3.

Going Beyond Knowledge: Predicting Nanotechnologies Acceptance and Risk Perception

To answer this question we must comprehend the intuitive rules of risk perception. Fischhoff et al. [5], followed the work on judgmental heuristics and combined a compendium of hazards situational characteristics known to cause, at least, “strange” risk perceptions, i.e., perceptions that diverge from risk technical assessments. Introducing the so called Psychometric Paradigm, the researchers describe nine characteristics which allow us to predict risk perception across specific hazards: (1) voluntariness of risk (do people get into risky situations voluntarily?), (2) immediacy of effect (to what extent is the risk of death immediate – or is death likely to occur at some later time?), (3) knowledge about risk to those exposed (to what extent are the risks known precisely by the persons who are exposed to them?), (4) science knowledge about risk (to what extent are the risks known to science?), (5) control over risk (if people are exposed to each risky activity or technology, to what extent can they, by personal skill or diligence, avoid death while engaging in the activity?), (6) newness (are risks new and novel or old and familiar?), (7) chronic-catastrophic (is this a risk that kills people one at a time – chronic risk – or a risk that kills large numbers of people at once – catastrophic risk?), (8) common-dread (is this a risk that people have learned to live with and can think about reasonably calm, or is it one that people have great dread for – on

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the level of a gut reaction?), (9) severity of consequences (when the risk from the activity is realized in the form of a mishap or illness, how likely is it that the consequence will be fatal). Testing across a wide range of hazards, research has shown that considering these dimensions in addition to perceived benefits, it is possible to predict lay people’s risk perceptions and acceptance judgments, despite people’s individual differences. Furthermore, these characteristics tend to be highly intercorrelated (for example, hazards judged to be voluntary tend also to be judged as controllable) and can be effectively reduced to two factors by means of factor analysis [23]. One first factor, that explains most of the data and is usually labeled “dread risk”, apparently discriminates between high- and low- risk technology activities, with the high end being characterized by perceived lack of control, dread, catastrophic potential, fatal consequences, and the inequitable distribution of risks and benefits (e.g., nuclear weapons technology). The second factor, “unknown risk”, is defined at its high end by hazards judged to be unobservable, unknown, new, and delayed in their manifestation of harm (e.g., chemical technologies). Many studies have also found a third factor, related to the number of people exposed to risk. Lay people’s risk perceptions and attitudes are closely related to the position of a hazard within this type of factor space. The higher a hazard’s score first on “dread risk” and second on “unknown risk”, the higher its perceived risk and the more people wish to reduce it. Siegrist et al. [21] have adapted this paradigm for the examination of nanotechnology hazards (adding characteristics such as “trust in governmental agencies” and “ethical justification”). Their results shown that perceived dreadfulness of applications and trust in governmental agencies are also important factors in determining perceived risk, with the author’s suggestion that public concerns about nanotechnology would diminish if measures were taken to enhance laypeople’s trust in governmental agencies. We followed this psychometric paradigm and developed a study in order to understand different nanotechnologies risk perceptions, partially replicating the study by Siegrist et al. [21] and adding other variables and general nanotechnology applications not considered by them. Two hundred and sixty-nine participants filled a two-part web based questionnaire on “nanotechnologies and society” voluntarily. From these, 24.8% were males and 75.2% were females, 74.5% had a high-school degree, 21.8% a university degree, 3.3% a master’s degree and 0.4% a Ph.D. The mean age was 24.9 and participants were mostly from the Lisbon area. Initially, they received the first part of the questionnaire, in which they were given a definition of nanotechnologies (“Nanotechnology deals with the development of procedures in which materials are created or manipulated in the atomic and molecular scale, in order to create new products whose properties have different characteristics compared to materials created or manipulated on the basis of other types of technologies”) and nanoparticles (“Particles with a dimension less than 100 nm that can be formed by natural processes or manufactured trough nanotechnology processes, having applications in various fields such as medicine, pharmacy, clothing, food and telecommunications”). The aim was to give baseline information

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that was equal to all participants, independent of their prior knowledge. Following this information, they rated six general nanotechnology applications in a five point scale based on eight risk perception attributes: Probability of health damage (1 = very improbable; 5 = very probable); Worries about risks (1 = not worried; 5 = very much worried); Voluntariness of risk (1 = voluntary; 5 = involuntary); Knowledge of risk to those exposed (1 = known precisely; 5 = not known); Adverse health effects strength (1 = not at all; 5 = very strong); Control over risk (1 = controllable; 5 = uncontrollable); Trust in institutions responsible for protecting people’s health regarding the technology (1 = no trust; 5 = much trust); Ethically justifiable to develop the application (1 = absolutely justifiable; 5 = not at all justifiable). In the second part, participants had to rate 20 specific nanotechnology applications, in the same 8 risk perception attributes. However, given the length of the questionnaire with the 20 specific nanotechnology applications, we divided it in two parts with 10 specific applications each, with the participants being randomly ascribed to one of them. From these, seven scales were created by averaging results on each item, creating composite measures with good psychometric properties overall and reliability indexes (Cronbach’s Alpha). The scales are as follows: General Nanotechnology Risk (α = 0.73); Clothes Nanotechnology Risk (α = 0.73); (α = 0.72); Food Nanotechnology Risk (α = 0.78); Communications Nanotechnology Risk (α = 0.74); Medical Nanotechnology Risk (α = 0.68); Military Nanotechnology Risk (α = 0.81); Overall Nanotechnology Risk Perception, developed through the aggregation of all these general and specific nanotechnology risk ratings (α = 0.81). The results show that the Overall Nanotechnology Risk Perception (considering both general and specific applications) is neutral (neither positive nor negative) with this view being highly consistent across the sample (M = 3.00; SD = 0.44), the same happening for the General Nanotechnology Risk (M = 2.89; SD = 0.55). Of these general applications, food (M = 3.38; SD = 0.63) and military applications (M = 3.39; SD = 0.74) are perceived as significantly more threatening than any of the others (p < .000). The lowest perceived level of threat is obtained for the clothes application (M = 2.79; SD = 0.58), followed by the communications application (M = 2.95; SD = 0.63) and the medical application (M = 3.08; SD = 0.56). These results seem to highlight more the general evaluations toward the applications than the specific evaluations regarding their risks. The results concerning the eight psychometric risk attributes for the Overall Nanotechnology Risk Perception are presented in Table 1. As we were expecting, results show that the “Knowledge of Risk to those Exposed” is the attribute with the highest mean and, in the absence of knowledge, the attribute “Ethically Justifiable to Develop the Application” is the one with the lowest. Analyzing these eight psychometric attributes for the general nanotechnology risk applications, some major differences arise. For the clothes application, the results show that the participants consider that there is a high lack of “Knowledge of Risk to those Exposed” (M = 3.63; SD = 1.05), with the lowest results being for the “Worries about risks” (M = 2.41; SD = 1.01),

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“Probability of health damage” (M = 2.44; SD = 1.04), “Adverse health effects strength” (M = 2.56; SD = 0.78) and “Control over risk” (M = 2.52; SD = 0.91), and the other attributes being around a medium point. TABLE 1. Means and standard deviations for the eight psychometric risk attributes. M

SD

Lack knowledge

3.4907

0.72977

Involuntary

3.1838

0.60379

Lack trust

3.0148

0.64362

Health damage

3.0023

0.65461

Effects strength

2.9870

0.54246

Worries

2.9164

0.66749

Uncontrollable

2.8519

0.63891

Ethic unjustifiable

2.7047

0.62721

For the food application, results in Figure 5 show a high lack of “Knowledge of Risk to those Exposed”, as well as medium-high “Worries about risks”, “Probability of health damage”, lack of “Voluntariness of risk”, “Adverse health effects strength”, with the other attributes being around a medium point. Food risk 5,00

4,50

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$

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$

$

$

$

$

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1,50

1,00 Health dama ge La ck of knowledge La ck of trust Worries E ffec ts s trengh E thic ally unjustifiable Involunta ry Uncontrollable

Figure 5. Nanotechnologies food risk.

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For the communications application, the results show a medium-low lack of “Knowledge of Risk to those Exposed” (M = 3.41; SD = 1.10), with the lowest results being for the “Ethically justifiable to develop the application” which a low value in this scale meaning that people consider it to be justifiable (M = 2.41; SD = 1.10), for “Control over risk” (M = 2.75; SD = 0.99) and “Worries about risks” (M = 2.76; SD = 1.07), with the other attributes being around a medium point. For the medical application, the results show a medium-low lack of “Knowledge of Risk to those Exposed” (M = 3.53; SD = 1.02), with the lowest result being for the “Ethically justifiable to develop the application”, being this the most ethically justifiable application of all the general applications (M = 2.29; SD = 0.92), with the other attributes being around a medium point. For the military application, results in Figure 6 show the highest consistency comparing to the other applications, with all the attributes scoring medium-high or medium-low (all results are above point 3 in the scale). Military risk 5,00

4,50

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$

$

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1,00 La ck of trust La ck of knowledge Health dama ge E thic ally unjustifiable E ffec ts s trengh Worries Uncontrollable Involunta ry

Figure 6. Nano military risk.

Regarding the specific applications, mean values for the perceived risks can be seen in Table 2. The one perceived as more threatening is Ammunition with a medium-high perceived level of threat, followed by Water Sterilization, Sunscreen and Toys Coating. The one’s perceived as less threatening were Cancer Treatment with Nanocapsules, Medical Nanorobots, Data memory and Storage of Hydrogen as a Gasoline Substitute. Once again, these results seem to reflect more the general evaluations regarding the applications than the specific evaluations regarding their risks.

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TABLE 2. Perceived risks for the 20 specific applications. M

SD

Ammunition

3.5329

0.67142

Water sterilization

3.2412

0.56518

Sunscreen

3.2103

0.63596

Toys coating

3.1159

0.53760

Food packaging

3.0365

0.55487

Textiles coating

3.0251

0.60469

Building materials protection

2.9990

0.53873

Car paint

2.9461

0.56479

Photographic paper

2.9091

0.58095

Release of medication Implants coating

2.8844

0.55434

2.8805

0.61551

Monitors

2.8565

0.59994

Food biosensors

2.8510

0.61244

Tires

2.8471

0.62260

Lightweight building materials

2.8318

0.55332

Skis

2.7996

0.56768

Hydrogen storage

2.7975

0.57061

Data memory

2.7653

0.59224

Medical nanorobots

2.7418

0.56440

Cancer treatment

2.6684

0.54212

A Principal Components Analysis (PCA) was performed to assess the underlying psychological factors in the risk assessment of the general and specific applications of nanotechnology. For this we averaged the ratings for each of the eight attributes over participants and aggregated the data across applications (following the procedure suggested by Willis et al. [31], and performed a PCA on this data with a varimax rotation. Given the results on the screen-test and the percentage of variance explained considering the factors extraction, as seen in Table 3 we decided for three factors with 84.78% of variance explained: Factor 1 – Dread (including “Probability of health damage”, “Worries about risks” and “Adverse health effects strength”); Factor 2 – Unknown (including “Knowledge of risk to those exposed” and “Control over risk”); Factor 3 – Trust & Ethics (including “Trust in institutions responsible for protecting people’s health regarding the technology” and “Ethically justifiable to develop the application”).

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TABLE 3. PCA loadings with a varimax rotation. Dread

Unknown

Trust & ethics

Health damage

0.656

0.486

−0.120

Worries

0.932

0.120

−0.032

Involuntary

0.085

0.876

0.298

Lack of knowledge

−0.173

0.896

0.301

Effects strength

0.878

−0.142

0.324

Uncontrollable

0.879

−0.130

0.284

Lack of trust

0.253

0.486

0.691

Ethically unjustifiable

0.106

0.272

0.895

Loadings above 0.50 are signaled

Following the PCA analysis, a spatial representation of the general and specific nanotechnology applications was performed. For the sake of parsimony and clarity and of the interpretation, we performed another PCA analysis with only two factors, explaining 74.22% of the variance, with the attributes reorganized in this way: Factor 1 – Dread (including “Probability of health damage”, “Worries about risks”, “Adverse health effects strength” and “Control over risk”); Factor 2 – Unknown, trust and ethics (including “Knowledge of risk to those exposed”, “Trust in institutions responsible for protecting people’s health regarding the technology”, “Ethically justifiable to develop the application” and “Voluntariness”). Figure 7 represents all the applications in this two-dimensional plot, developed from the two factors scores, labelled by application. From this representation, we can see that the most trustworthy institutions responsible for protecting people’s health regarding the technology are associated with general and specific medical applications, with these being the applications also with a higher knowledge of risk to those exposed, more control over exposure and where is more ethically justifiable to develop the application. However, at the same time, they also have a medium level of dread. The applications with higher perceived risk are the ones where there is the lowest knowledge, control over exposure, trust and ethical justification, combined with a high perceived dread risk, namely the one’s associated with general and specific military applications and general food applications. The applications perceived as safer or with the lowest perceived risk, are the ones where there is a higher knowledge, control over exposure, trust and where is more ethically justifiable to develop the technology, combined with low levels of perceived dread risk, namely data memory, food biosensors and hydrogen storage.

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Factor 2 - Unknown + lack of trust and unethical

3,000

2,000 Ammunition

1,000

Water Sterilization Food

Building materials protection Car paint Lightweight building Photographic paper Skis Tires Clothes

0,000

Data memory

Toys coating Textiles coating Food packaging Monitors

Communication

Military

Sunscreen

Medical

Food biosensors Hydrogen storage Release of medication

-1,000

General Implants coating

-2,000 Medical nanorobots

Cancer treatment

-3,000 -3,000

-2,000

-1,000

0,000

1,000

2,000

3,000

Factor 1 - Dread

Figure 7. Spatial factorial representation of the general and specific nanotechnology applications – laypeople.

Thus, even in the absence of information, people did judge nanotechnologies in a consistent way, in accordance with intuitive judgments rules, and currently they perceived them as moderately risky. Some applications stand out (military, food), we believe not because people had more knowledge about them but because of their evaluations towards technologies operating in those fields, along with a low sense of control over exposure, distrust in institutions and perceived poor ethical justifications. 4.

Coping with Nanotechnologies Perceived Risk

In a negative scenario, if risk management isn’t successful it’s possible that when people hear more about nanotechnologies in the future they will start evaluating it as risky, because it is not only a matter of information but also attitudes. The point is that even if public concerns about risks don’t turn out to be true, as might be the case for nanotechnologies, the perception of being in risky circumstances is a stressful situation [15] that might actually induce psychological, physical and behavioral consequences (e.g. [32]). How might people act in this situation? One way to cope with it is by means of social comparison [6]. There are evidences that in certain groups under threat,

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people who cope better are the ones who perform explicit self-evaluation against a less fortunate target (downward evaluations), expressing peoples clear efforts to regulate emotions by making the person feel better in comparison with worse-off others [25]. For example, cancer patients that engage in this kind of comparisons cope better with the disease than those who don’t. As Taylor and Brown [25] argue, the healthy human mind seems to cordon off negative information, creating positive illusions that help coping and are particularly adaptive when one is threatened by adversity. In our case people might compare nanotechnologies with other events, reevaluate them and psychologically accept being in a risky situation. A way to cope is reflected in the so-called “NIMBY” effect. This acronym stands for “Not In My Backyard”. It’s a phenomenon that strikes whenever a community has been chosen to host a hazardous facility or a facility that will carry some cost for the local residents. Describes the fact that people usually agree with the need to build some hazards facility but are against building that construction near their home (e.g. [9, 17]). In this case, people cope with the situation not by reevaluating it but by changing it. We argue that nanotechnologies, due to its “nano” operative nature, can put people into a somehow similar phenomenon: “Not In My Body” (NIMB) [1]. NIMB would describe people agreeing with the general need to use nanotechnologies but refusing to use nanotechnologies that would “enter” their body, (consider, for example, the differences in the clothes and food applications). We recall the psychometric analysis of our data illustrated that most of its variance was explained by a factor that combined attributes concerning people’s health (“Dread” factor). So, we analyzed if it might be important to isolate the risk perception of nanotechnologies to the body level, comparing it with the risk for the self, other people and family. Participants in our study evaluated the risk of nanotechnologies in general to self, to their own body, to their family and to other people, perceived general control regarding the general applications, the adverse health effects due to nanoparticules entering the body to evaluate the NIMB effect, and the knowledge perception, in Likert type 5 point scales (1 = Totally disagree; 5 = Totally agree). Once again we created scales by averaging results on each item, creating composite measures with good psychometric properties overall and reliability indexes (Cronbach’s Alpha). The scales are as follows: Perceived Nanotechnology Risk to the Body, for the general applications (α = 0.81); Perceived Nanotechnology Risk to Self, for the general applications (α = 0.81); Perceived Nanotechnology Risk to the Family, for the general applications (α = 0.80); Perceived Nanotechnology Risk to Other People, for the general applications (α = 0.86); Perceived Control over Nanotechnology Risk for the general applications (α = 0.73); NIMB effect (α = 0.88); Perceived Knowledge of Nanotechnology Risk for the general applications (α = 90.). To what concerns an assessment of the general applications the results for other variables show no significant differences in the level of perceived exposure to the risk, namely between the perceived risk to self, to their own body, to their family and to other people, with all having a medium value and the highest value

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being the perceived risk to self (M = 3.09; SD = 0.76). Also the perceived level of general control over the nanotechnologies risk is medium (M = 2.95; SD = 0.77), the same happening with the perceived adverse health effects due to nanoparticules entering the body (NIMB, M = 3.03; SD = 0.83).The level of knowledge, however, is perceived as low (M = 2.06; SD = 0.91). Besides that, this scale has the highest internal consistency index (α = 90.): people’s knowledge toward general applications is only slightly differentiated. These results confirm our suspicions: with the current state of lack of knowledge people do not evaluate nanotechnologies in general as threatening and have a moderate perceived level of general control. Currently there are also no differences between the perceived risk to them (or their body) and their family (usually comparatively higher when people are in stress) and the risk to other people (usually comparatively higher when people are successfully coping with stress). We also performed a Multiple Regression Analysis to find out how the perceived risk for the five applications could be better explained by these variables. As previously theorized, the model that explained most data variability (52.7%; p < .001) predicts the mean risk for the five applications raises when there is an increase both in Perceived Nanotechnology Risk to Self (β = 0.379; p < .001) and Perceived Nanotechnology Risk to the Family (β = 0.247; p < .05) and viceversa; at the same time decreases when there is an decrease in Perceived Control over Nanotechnology Risk (β = −0.220; p < .001) and vice-versa. Thus, by analyzing risk to self, family and control, we can predict people’s risk perception for these five applications. Perceived control might play a leading role in nanotechnologies risk management. 5.

What the Experts Think Laypeople Think: Perceptions and Misperceptions About Nanomaterials

Nanotechnologies possible “dread” and actual “lack of knowledge” makes it highly vulnerable to the impact of an unfortunate event (such as an accident, sabotage, contamination or a product tampering). Even if its specific or direct impact is small, the indirect effect might be extremely powerful and even tamper with the field’s development. This might happen because of the social informativeness or “signal potential” of that event that might be perceived as a harbinger of further and possibly catastrophic mishaps [23]. An example refers to the consequences of GMO contamination of natural non-modified plants in the surrounding fields and the negative publicity it brought to GMO production. As for any activity or technology with a certain probability of risk associated to it, experts in the field acknowledge the need to develop risk management and communication strategies for the general public. Given the newness of this technology and its present neutral perceived level of threat, we are at the right moment to develop them and prevent the negative impact of an unfortunate event. The problem is that, in spite of being new it shares one characteristic with other older technologies, which makes the process of risk management and communication more difficult, if not paid attention to. This characteristic is that there seems to be

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a huge gap between how technicians and lay people evaluate risks, with this gap existing whether the risk is known or not, i.e. it is not only a matter of knowledge level but also of perceptual and cognitive processes that technicians and lay people privilege in order to “calculate” risk [23, 28]. The work on risk perception has systematically highlighted the differences between the expert’s and laypeople’s assessments, emphasizing the formers technical and objective character and the latter’s biases, inconsistencies and risk perception illusions [14]. There is no doubt that the concept “risk” means different things to different people. For example, when experts judge risk their responses correlate highly with technical estimates of annual fatalities, with their assessment being based on the factual data they have. Lay people usually go beyond this information with their judgment of “risk” being based on other criteria, such as the perceived threat to future generations or the equity in the distribution of risks [23], as identified by the psychometric risk paradigm. Moreover, this perception is systematically influenced by socio-demographic and cultural variables (e.g. [8]). This is not surprising, since people and technicians are “trained” to evaluate risks in different ways. In fact, experts are trained during their education and work to evaluate risks in a set of established, shared and standardized criteria (i.e. all professionals in the field are supposed to evaluate in the same manner). This level of agreement is not so high when we talk about laypeople since that different cultural experiences, frequency of exposure to the risks, socio-demographic characteristics, personality type and other individual and social group differences makes them use different criteria in different contexts for different risks. This means that the difference between laypeople and experts is not only a matter of knowledge but also about the framing with which they assess risks. Therefore, both groups were “trained” either through experience, knowledge or both, to evaluate with different criteria and eventually reached a point in which they could do this spontaneously, without much rational thought associated with it. Particularly, the experts were trained to frame and judge the risks and the situation in a less intuitive way but, again, this is only a question of training since that given the right conditions, laypeople can also evaluate under the same criteria as the experts and experts can also fall prey to their intuitive assessments and judge under the same criteria as laypeople. We will get back to this point later on. For now, we will give next some examples of these different risk judgments between experts and laypeople. One example comes from Savadori et al. [20] who used the psychometric paradigm to examine the difference between expert and layperson risk perception on different biotechnology applications, specifically food and medical applications. Results regarding food applications showed that lay people judged the risk as higher than the experts did. The main factors which could explain most of the judgment’s variance both for laypeople and experts were related to perceived harm, dread and usefulness. Additionally to these, people also made their evaluation in terms of newness and level of scientific knowledge of the risk associated with biotech food applications, having a broader perception than the experts for this application. Results regarding medical applications also showed that lay people judged it as higher than the experts, however here the factors considered by lay

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people were less, when compared to the experts. The factors that explained laypeople’s evaluation of the risk associated with medical biotech applications were perceived harm and usefulness, while the experts considered these but also the level in which would expose themselves and many people to the risk, its newness and level of scientific knowledge. These results show that although the risk’s newness and level of scientific and social knowledge about it are important factors, people can still judge a risk as high, even though these factors are not considered in the judgment, as it was the case for people’s evaluation of medical biotech applications risk. Therefore, although people appear to be irrational, since they systematically evaluated the risks for the medical and food biotech applications as long as five other applications as higher than the experts did, their evaluation depends on the nature of the hazards, with different judgment criteria being used for different hazards. Equally interesting, the experts have gone beyond their specialized knowledge and expertise to make their judgements, using the same criteria as people did, but for different types of applications. In a different study also comparing expert and laypeople, Siegrist et al. [21] used the same psychometric paradigm to analyze the risk perception for various nanotechnology applications. Results showed that people’s nanotechnology risk judgements were higher and their trust in authorities responsible for protecting people’s health regarding the technology was lower, than for the experts. However, results regarding perceived benefits were not significantly different between laypeople and experts. To what concerns the factors influencing individual differences, the best predictors of people’s perceived risk regarding nanotechnologies in general were: perceived nanotechnology benefits, social trust and attitudes regarding technology in general (perceived benefits and fears). For the experts risk perception, the best predictor was only social trust, basing their judgements only on this but not on their attitudes or perceived benefits. We consider this to be an expected result given the fact that they work in the area and apparently consider that the control over these risks should be handed in to the people in the same area as them, since that they are the ones with the highest knowledge level. Considering all this, we can infer that if some unfortunate negative event happens regarding some kind of nanotechnology application, as long as it doesn’t undermine the perceived trust in authorities responsible for protecting people’s health regarding the technology, experts risk perception regarding nanotechnologies should remain “untouched”, independently of the type of application. The same is not expected to happen with laypeople’s perception, given that their judgements are also based on their attitudes and perceived nanotechnology benefits and that even in the absence of specific knowledge about the nanotechnology application for which the unfortunate negative event might happen, they can still make their judgments. Moreover, the magnitude of the risk perception increase should be higher for those applications identified as more dreadful, unknown and distrusted, as identified in Siegrist et al. [21] and in our own study presented before, based on the psychometric paradigm (although this should happen only until a certain level, due

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to a ceiling effect resulting from the presence of normal adaptation processes [15, 16]). Finally, given the similarities of some nanotechnology applications in terms of their perceived dreadfulness, lack of knowledge, trust and ethical assurance that we identified (e.g. food and military general applications), it is expected that if an unfortunate negative event happens for one of them, a spreading activation effect should be expected [3] translating into a heightened risk perception for the other applications perceived as similar in terms of these psychometric attributes (as it might happen for example with any activity associated with the term “nuclear”). For the reason presented before, regarding the maintenance of a high level of trust as perceived by the experts, these changes aren’t expected to occur so suddenly and with such a high magnitude, for the experts. In spite all of this, there are still many misconceptions in the literature regarding the differences between experts and lay people. It is a fact that, as we seen, they both evaluate risks in a different way but that doesn’t mean, as sometimes is implicit in the literature and most of the times explicit in the real world, that experts are better than people at judging risks. In fact, this is somewhat of an illusory conclusion, since for example laypeople can also evaluate annual fatalities if they are asked to [23] and perform accurate frequency estimates of causes of death, making difficult estimations based only on their judgments, in the absence of any other information [14]. The opposite is also true, in the sense that experts are “only humans” and there is no assurance that their judgments are immune to biases, when they are forced to make evaluations that go beyond the data they have [24]. As the psychometric approach shows, these divergences occur systematically but can be successfully framed in a participated risk management process, as long as we consider both expert and lay people different “languages” and “valuations”, that go beyond the level of existing knowledge about a technology. However, most of the times what hampers with risk communication and management strategies it is not the existence of these different ways in which experts and people evaluate risks. What often does the harm is that these strategies are designed on a misperception of these differences and are based on the expert’s expectations and implicit knowledge about how people think and perceive risks. This implies the design of strategies in order to match how the experts think people think or how people will react to a certain level of risk, and not to match how people actually think or might react. It is obvious from what we have shown before that the experts evaluate risks in a different way from the lay people and that both, given the right conditions, can have similar risk evaluations. However, how good are they to evaluate how people perceive risks i.e., how much of a good intuitive psychologist are they? To answer this question we performed a study with an expert sample asked to fill the questionnaire while attending our nanotechnology meeting, with all participants giving their informed consent after a brief explanation of the research aims. This sample was comprised of 24 experts with interests and/or experience in the nanotechnology area, which answered a questionnaire on “nanotechnologies and society” voluntarily. From these, 60.9% were males and 39.1% were females and

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the mean age was 47.59, with 34.8% coming from Europe, 26.1% from the USA, 17.4% from Canada, 13.0% from Brazil and 8.7% from other countries. These experts worked in areas such as Nanotoxicology and nanomaterials (N = 6), Ecotoxicology (N = 5), Risk assessment (N = 5) and other nanotechnology and risk assessment related areas. In this study, the participants had to fill the same questionnaire as in our study presented before but without the 20 specific applications. However, differently from study 1, they were presented a set of statements, for which they were asked to choose the response (from the possible 5) that most matched the opinion of the general public, i.e., what nanotechnology experts believe to be the laypeople’s perceptions on this field. This is an original framing, since most of the literature on risk assessment analyses how the experts perceive the risks but not how the experts perceived how people in general perceive the risks, i.e. what the experts think laypeople think. The introduction was stated as follows: “As you’re probably aware one of the most recent fields of technological research is the field of nanotechnology. Like several other technological breakthroughs nanotechnology is likely to prompt specific perceptions and attitudes by the general public. In this study we are interested in studying what nanotechnology experts believe to be the perceptions of the general public on this field, i.e., the layperson’s beliefs about several features of nanotechnology.” Therefore, the items were similar to study 1 but with a different framing, as seen in the following example: “The general public views the probability of health damage derived from nanotechnology as (1 = Very unlikely 5 = Very likely)”. The results showed that the experts consider the layperson’s General Nanotechnology Perceived Risk to be moderate (M = 3.21; SD = 0.47) but significantly higher than the risk perception level that laypeople reported in study 1 (M = 2.89; SD = 0.55; p = .005), which shows that they think people consider nanotechnologies more threatening than laypeople actually consider. However, to what concerns the general applications, experts have an accurate view by considering that food (M = 3.40; SD = 0.46) and military applications (M = 3.36; SD = 0.68) are seen as the most threatening, while the applications to clothing (M = 2.87; SD = 0.43), medicine (M = 2.89; SD = 0.44) and communications (M = 2.92; SD = 0.45) considered to be the least threatening, with no significant differences compared to what laypeople reported in study 1. The results concerning the eight psychometric risk attributes for the General Nanotechnology Risk Perception show that in the same way as in people’s perception in study 1, they also consider the “Knowledge of Risk to those Exposed” as the attribute with the highest mean, meaning that the experts consider that there is a high level of lack of knowledge in laypeople. However, they consider this lack of knowledge to be higher (M = 3.75; SD = 58) than what people report (M = 3.49; SD = 73), although this being only marginally non-significant (p = .079). The same happens for “Trust in institutions responsible for protecting people’s health regarding the technology”, with the experts considering that this lack of trust is perceived as higher (M = 3.27; SD = 1.02) than it actually is (M = 3.02; 0.64; p = .075).

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The only significant misperception in these, refers to the “Voluntariness of risk”, i.e. experts consider that people’s exposure to nanotechnologies risk is more involuntary (M = 3.44; SD = 57) than actually people consider it to be (M = 3.18; SD = 0.60; p = .035). This can be seen as the work of a defense mechanism, in which people deny and try not to think about the fact that they might be exposed to a risk unknown to them and to which they didn’t chose voluntarily to be exposed to, showing a natural adaptation process that lowers the stress in this sense [16, 25]. This was demonstrated in our study with the laypeople’s sample, in which perceived control was one of the best negative predictors of perceived risk, meaning that an increase in one implies a decrease in the other. Differently, the expert’s defense mechanism regarding nanotechnologies is to trust the authorities in controlling the risks, as seen in the Siegrist et al. [21] study. When we consider the eight psychometric attributes for the five general nanotechnology risk applications, the differences arise. We found a very good level of expert’s accuracy in judging people’s perception for the communications and military nanotechnology applications, with no significant differences between laypeople and experts. Moreover, we found a good level of accuracy for the clothes application, with the only difference being in terms of trust, with the experts considering it to be significantly higher (M = 3.33; SD = 1.20) than actually people perceive it (M = 2.92; SD = 0.83; p = .027) and also a rather good accuracy regarding the food application, with the differences being in terms of trust and voluntariness, with the experts considering trust to be significantly higher (M = 3.46; SD = 1.10) than actually people perceive it (M = 3.10; SD = 0.88; p = .056), and the involuntariness in the exposure to the risk to be significantly higher (M = 3.92; SD = 0.88) than actually people perceive it (M = 3.44; SD = 1.02; p = 0.026). The lowest level of accuracy was for the medical nanotechnology application, with the experts considering the worries about the risk to be significantly lower (M = 2.58; SD = 0.97) than actually people perceive it (M = 3.27; SD = 1.10; p = .003), the effects strength to be significantly lower (M = 2.71; SD = 0.81) than actually our sample perceive it (M = 3.23; SD = 0.88; p = .006), the health damage to be significantly lower (M = 2.71; SD = 1.04) than actually people perceive it (M = 3.22; SD = 1.08; p = .027), the lack of control over exposure to the risk to be significantly higher (M = 3.38; SD = 1.17) than actually people perceive it (M = 2.84; SD = 0.95; p = .009), the involuntariness in the exposure to the risk to be lower (M = 2.88; SD = 1.19) than actually people perceive it (M = 3.29; SD = 1.00; p = .059). Concerning the general applications, the results for other variables showed only one misperception. As we expected, the experts consider the perceived adverse health effects due to nanoparticules entering the body (NIMB effect) to be higher (M = 3.60; SD = 0.81) than actually people perceive it (M = 3.03; SD = 0.83; p = .001). A PCA Analysis was performed to assess the underlying psychological factors in the risk assessment the experts consider that the people have, regarding the five general applications of nanotechnology. For this, we averaged the ratings for each of the eight attributes over the expert sample and aggregated the data across

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applications. A PCA was performed on this data with only one factor being extracted, explaining 74.93% of the variance. All attributes saturated above 0.60 on this factor, except for the attribute “control over exposure” (saturation of −0.926) which lost its explanatory power among the others. This shows that the expert’s judgments of people’s perception have an overall narrower explanatory level, compared to the underlying factors for people’s actual perception (given that there were three factors identified in study 1, for the laypeople’s perception). This misperceptions and lack of knowledge about what and how people think, significantly affects the experts intuitive and non-factual predictions of how people will judge a certain risk for a certain nanotechnology application, and consequently how they will react to that risk. This is a very dangerous endeavor since that if experts do this without knowing anything about human cognitive functioning and behavior, instead of managing and communicating risk with the aim of reducing it, they will actually increase it and also the possible negative reactions and manifestations associated to it. These misperceptions are evident in Figure 8 which represents the general applications in a two-dimensional plot, developed from the two factor scores resulting from another PCA we performed, labeled by application. We should

Factor 2 - Exposure, trust and ethics

1,500

General

1,000

Food Clothes

0,500

Military

0,000

-0,500

Communication

-1,000

Medical

-1,500 -1,500

-1,000

-0,500

0,000

0,500

1,000

1,500

Factor 1 - Dread

Figure 8. Spatial factorial representation of the general and specific nanotechnology applications – experts.

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warn however that the confidence in this analysis is lower than the one performed in study 1, since that the two factors obtained in this one are not completely independent, even after performing a varimax rotation, which can insert a certain error level in the analysis. In spite of this, we’ll present the results since the differences from the laypeople’s two-dimensional plot are very clear, even discounting the measurement error. In this figure, we can see that only the military and food applications are in the same quadrant as in study 1. All the other applications are influenced by misperceptions regarding the risks, especially to what concerns the medical applications, which are considered to have a high level of knowledge, trust and ethical justification and a low level of dreadness. However, according to laypeople’s perception they would be in a different quadrant, characterized by a moderate knowledge of risk to those exposed, control over exposure and ethical justification but, at the same time, with a medium level of dread. In a nutshell, we can see that while experts are accurate in analyzing lay people perceived nanotechnologies risk in general considering the eight psychometric attributes, this accuracy disappears when they have to consider the five applications based on these same eight attributes. This demonstrates that their implicit knowledge about laypeople’s cognitive functioning cannot compensate for the differences between applications, i.e. they think people evaluate the risks always in the same manner. Also, intuitively the experts judge the high level of lack of specific knowledge to be the main cause of differences between applications and since that they consider people to have similar lack of knowledge in every application, then there shouldn’t be differences. Since that in the Siegrist’s et al. [21] study the experts risk perception regarding nanotechnology was best predicted by social trust, we can infer that experts expect that people in the absence of knowledge regarding the applications, also use trust as a criteria for their judgments. However, as we saw in our results, there is a misperception about the trust level in the food and clothes nanotechnology applications. Moreover, as we know from the same study, people use criteria as perceived nanotechnology benefits, social trust and attitudes regarding technology in general (perceived benefits and fears) to make their risk assessments. This might explain why the highest misperception was for medical nanotechnology applications, which seems to be more influenced by attitudes and perceived benefits than any of the others. This is exactly where the experts implicit knowledge about laypeople’s functioning fails, by not considering that differences in risk assessments might occur given the presence of attitudes and other perceptions, i.e. they seem to be only accurate in assessing laypeople’s perception when these influences are not so strong.

6. Conclusions From the above results and discussion one can extract several important conclusions that qualify the usual reflections about the nanomaterials’ risk perception and attitudes.

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The first point that is important to stress is that the widespread positive attitudes about nanomaterials might actually be based on the global attitudes about technology. When people are asked to evaluate specific nano applications this global positive picture starts to fade. The details of this process were analyzed and our revision and research was able to shed some light on the psychological process that underlies the formation of specific attitudes and risk perception based on small amounts of information. Worth mentioning is the somewhat sharp differences within the evaluation of global applications where food and military ones shown a different profile. When we detailed even further the specificity of nano applications, a factorial picture also illustrated that some applications like ammunition and food have higher risks, while others have comparatively much lower risks (e.g., medical). Thus, and as mentioned above, even in the absence of information, people did judge nanotechnologies in a consistent way, in accordance with intuitive judgments rules, and currently they perceive them as moderately risky (i.e. people “know much” in spite of their overall moderate to high lack of knowledge). Some applications stand out (military, food), we believe not because people had more knowledge about them but because of their evaluations towards technologies operating in those fields, along with a low sense of control over exposure, distrust in institutions and perceived poor ethical justifications. Additionally to this, the individual perceived control was also one of the most important factors. Comparing experts and lay people perceptions of nanotechnologies one can easily conclude that experts have somewhat a misguided perception of people’s evaluations. One of the reasons for this mismatch is the fact that the complexities of the factors that guide lay risk perception are much more subtle and diverse than expected by the experts. The complexity of values and perceived benefits that are behind the attitudes and risk perceptions regarding specific applications are not fully understand by the experts. The data and literature revised above also points out a potential negative scenario of hypothetical events related with nanomaterials. Given the lack of knowledge shown by people across studies and the specific values and ethical factors implied in the specific domain applications, a negative attitude and higher risk perception can be facilitated in that context, if no risk management and communication strategy is developed to address these specific factors. All of this stresses the importance of a participated strategy that could take in to account the specificities of lay people world views connected with the nanotechnology application domain and also the factors that are important for risk evaluation such as e.g., perceived control. The understanding of these processes probably has to start within the nanotechnology expert’s community who, most probably, will be in the front line of a potential crisis.

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PARTICIPANTS

AbdelMottaleb, Sabry

Department of Chemistry Faculty of Science Ain Shams University 11566 Abbassia, Cairo, Egypt

Tel.: + 2010 168 6244 Fax: + 202/ 2634 7683 Emails: sabry.abdel-mottaleb@ daad-alumni.de; [email protected]

Abdel-Shafy, Hussein

Water Research & Pollution Control Dept., National Research Centre Cairo, Egypt

Email: husseinshafy@ yahoo.com

AdlakhaHutcheon, Gitanjali

Defense Research and Development Canada 305 Rideau Street, Ottawa K1A 0K2, Canada

Tel.: 613-996-3183 Fax: 613-996-5177 Email: Gitanjali. Adlakha-Hutcheon@ drdc-rddc.gc.ca

Arcuri, Arline Sydneia Abel

Foundation on Occupational Safety and Health Researches and Studies – FUNDACENTRO – Ministry of Labour and Employment Rua Capote Valente 710 San Paolo 05409-002, Brazil

Tel.: 5511 3066 6140 Fax: 55 11 3066 6341 Email: arline@fundacentro. gov.br

Bayramov, Azad

Institute of Physics National Academy of Sciences G.Javide 33 Baku AZ 1143, Azerbaijan

Tel.: +994124394057 Fax: +994124470456 Email: bayramov_azad@ mail.ru

Bayramova, Svetlana

Institute of Geology National Academy of Sciences of Azerbaijan G.Javide av. 29 Baku AZ 1143, Azerbaijan

Bennett, Erin

Environmental Biologist 18, Commercial Street Salem, MA 01970

Tel.: 978-740-0096 x529 Fax: 978-740-0097 Email: ebennettt@ bioengineering.com

Blank, Nelly

International Nanotechnology Research Center Polymate Kibbutz Ind. Zone Migdal Ha’Emeq Haifa 23100, Israel

Tel.: 972-50-653392 Fax: 972-4-8248050 Email: [email protected]

ChanRemillard, Sylvia

Golder Associates Ltd/HydroQual Laboratories Ltd #4 6125-12th Street S.E. Calgary T2H 2K1, Canada

Tel.: 1.403.253.7121 Fax: 1.403.252.9363 Email: sylvia_chanremillard@ golder.com

463

464

PARTICIPANTS

Chappell, Mark Environmental Laboratory U.S. Army Corps of Engineers 3909 Halls Ferry Road Vicksburg, MS 39056, USA

Tel.: 601-634-2802 Fax: 601-634-3410 Email: Mark.a.chappell@ usace.army.mil

Colvin, Vicki

Tel.: 713-348-5741 Fax: 713-348-2578 Email: [email protected]

ICON Rice University 141 Dell Butcher Hall Houston, TX 77005, USA

Cullinane, John Environmental Laboratory U.S. Army Corps of Engineers 3909 Halls Ferry Road Vicksburg, MS 39180, USA

Tel.: 601.634.3723 Fax: 601.634.2854 Email: John.M.Cullinane@ usace.army.mil

Davis, J. Michael

Tel.: (919) 541-4162 Fax: (919) 685-3331 Email: Davis.Jmichael@ epa.gov

National Center for Environmental Assessment Office of Research and Development U.S. Environmental Protection Agency Research Triangle Park, NC 27711, USA

Davis, Thomas Environment Canada and Department of Chemistry University of Montreal C.P. 6128, succursale Centre-Ville Montreal (QC) H3C 3J7, Canada

Tel.: (514) 343 6111 poste 4929 (514) 804 5957 Fax: (514) 343 7586 Email: [email protected]

Depledge, Michael

Peninsula Medical School Plymouth, PL6 8BU, UK

Tel.: 44 (0) 1752 437402 Fax: 44 (0) 1752 517842 Email: [email protected]

Elder, Alison

University of Rochester Department of Environmental Medicine 575 Elmwood Avenue, Box 850, Rochester, NY 14610, USA

Tel.: 585-275-2324 Fax: 585-256-2631 Email: Alison_Elder@ urmc.rochester.edu

Figovsky, Oleg International Research Center Polymate 3a Shimkin Street Haifa 34750, Israel

Tel.: 972-4-8248072 Fax: 972-4-8248050 Email: [email protected]

Figueira, José Rui

Instituto Superior Técnico Technical University of Lisbon DEG, Tagus Park, Avenue Cavaco Silva Porto Salvo 2780-990, Portugal

Tel.: +351-21-423-35-07 Fax: +351-21-423-35-68 Email: [email protected]

Figueira, Marianne

480 Boul. Armand-Frappier, Laval (Québec), Canada H7V 4B4

Tel.: (450) 680-3471 Fax: (450) 687-5860 Email: figueiramm@ hotmail.com

465

PARTICIPANTS

Fonseca, Carlos Department of Electronic Engineering and Informatics Faculty of Science and Technology University of Algarve Campus de Gambelas Faro 8005-139, Portugal

Email: [email protected]

Foss Hansen, Steffen

Department of Environmental Engineering, NanoDTU Technical University of Denmark Building 113, Kgs. Lyngby DK-2800, Denmark

Tel.: +45 45 25 15 93 Fax: + 45 45 93 28 50 Email: [email protected]

Gatti, Antonietta

Laboratory of Biomaterials University of Modena & Reggio Emilia Via Campi 213 A, Modena 41100, Italy

Tel.: +39059798778 Fax: +390597579182 Email: antonietta.gatti@ unimore.it

Gnewuch, Harald

Naneum Ltd Canterbury Enterprise Hub Canterbury CT2 7NJ, UK

Tel.: +44 1227824631 +44 1227827778 Email: harald.gnewuch@ naneum.com

Goss, Greg

Biological Sciences Building University of Alberta Edmonton, Alberta T6G 2E9, Canada

Tel.: 1-780-492-2381 [email protected]

Goudey, J. Stephen

HydroQual Laboratories Golder Associates Ltd #4, 6125 12th Street SE Calgary, Alberta T2H 2K1, Canada

Tel.: (403) 253-7121 (403) 560-6028 Fax: (403) 252-9363 Email: [email protected]

Grieger, Khara Department of Environmental Engineering, NanoDTU Technical University of Denmark Building 115, Kgs. Lyngby DK-2800

Tel.: +454525 2164 Fax: +4545932850 Email: [email protected]

Grossi, Maria Gricia

University of Stuttgart Port-Talbot-Str. 17 Heilbronn 74081, Germany

Tel.: 0049 7131 6427616 Fax: 00 49 711 685 65495 Email: [email protected]

Gulledge, William

American Chemistry Council 1300 Wilson Blvd. Arlington, VA 22209, USA

Tel.: (703) 741-5613 Email: William_Gulledge@ americanchemistry.com

Hakkinen, Pertti Bert

Senior Toxicologist National Library of Medicine National Institutes of Health 6707 Democracy Boulevard Suite 510, Bethesda, MD 20892 USA

Tel.: 301-827-4222 Fax: 301-480-3537 Email: pertti.hakkinen@ nih.gov

PARTICIPANTS

466

Haraza, Mahmoud Ahmed Shafy

Quality Assurance Quality Control Email: shafymahmoud@ Department yahoo.com National Center of Nuclea Safety and Radiation Control Atomic Energy Authority Ahmed El Zomor Street, Nasr City 11672, Box 7551 Cairo, Egypt

Haruvy, Nava

Netanya Academic College One University Street Netanya 42100, Israel

Tel.: +972-8-946-3189 Fax: +972-8-936-5345 Email: navaharu@ netvision.net.il

Kaczmar, Swiatoslav

O’Brien and Gere Engineers Inc. 5000 Brittonfield Pkwy Syracuse 13221, USA

Tel.: 315-345-4545 Fax: 315-437-3555 Email: [email protected]

Kadeli, Lek

US Environmental Protection Agency, 1200 Pennsylvania Avenue, NW 8101R, Washington, DC 20460, USA

Tel.: (202) 564-6989 or 6620 Fax: (202) 564-2244 Email: [email protected]

Kapustka, Larry

LK Consultancy 8 Coach Gate Place SW Calgary, AB T3H 1G2, Canada

Email: [email protected]

Karkan, Delara Health Canada Canada

Email: Delara_karkan@ hc-sc.gc.ca

Kearns, Peter

ENV/EHS OECD 2 rue Andre-Pascal 75775 Paris Cedex 16, France

Tel.: +33 1 4524 1677 Fax: +33 1 4524 1675 Email: [email protected]

Kenawy, ElRefaie

Polymer Research Group, Department of Chemistry Faculty of Science University of Tanta, Egypt

Tel.: +040-3344352 +012 2372276 Fax: +040-3350804 Email: [email protected]

Khaydarov, Renat

Institute of Nuclear Physics Uzbekistan Academy of Sciences Tashkent, Uzbekistan

Email: [email protected]

Kondratyev, Mikhail

St. Petersburg Technical University Russia, St. Petersburg, 198152

Email: [email protected] Tel.: +79213400875 Fax: +78122971639

Korenstein, Rafi

Marian Gertner Institute for Medical Nanosystems Department of Physiology and Pharmacology Faculty of Medicine Tel Aviv University 69978 Tel-Aviv, Israel

Tel.: 972-3-6406042 Fax: 972-3-6408982 Email: [email protected]

467

PARTICIPANTS

Kuhlbusch, Thomas

Institute for Energy and Environmental Tel.: +49 2065 418 267 Technology, Air Quality & Sustainable Fax: +49 2065 418 211 Nanotechnology Unit, Bliersheimer Street Email: [email protected] 60, Duisburg 47229, Germany

Linker, Fenneke

Manager Industrial Hygiene & Toxicology Occupational Health Care Services DSM ARBOdienst DSM Alert & Care Centre Kerenshofweg 200 NL-6167AE Geleen The Netherlands

Tel.: +31 (0)46 47 610 98 +31 (0)6 512 99 125 Fax: +31 (0)46 47 647 62 Email: Fenneke.Linker@ DSM.com

Linkov, Igor

Environmental Laboratory U.S. Army Corps of Engineers 83 Winchester Street Suite 1 Brookline, MA 02446, USA

Tel.: +1 617-233-9869 Email: Igor.linkov@ usace.army.mil

Lynch, Iseult

Irish Centre for Colloid Science & Tel.: 00 353 1 7162418 Biomaterials Fax: 00 353 1 7162127 School of Chemistry & Chemical Biology Email: [email protected] University College Dublin Ireland

Matias, Sara

Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais 1049-001 Lisboa, Portugal

Tel.: +351 210 733 756 Email: Sara.matias@ yahoo.com

McQuaid, James

NATO Environmental Security Panel 61 Pingle Road Sheffield S7 2LL, UK

Tel.: 0044 114 2365 349 Email: jim@mcquaid. demon.co.uk

Melkonyan, Marine

Institute of Crystallography of RAS Leninsky pr., 59 Moscow 119333, Russia

Tel.: +7(499)135-05-81 Fax: +7(499)135-10-11 Email: [email protected]

Metcalfe, Chris Trent University 1600 West Bank Drive Peterborough, Ontario K9J 7B8, Canada

Tel.: 705-748-1011, x7272 Fax: 705-748-1569 Email: [email protected]

Monica, John

Tel.: (202) 778-3000 (202) 778-3050 Fax: (202) 778-3063 Email: jmonica@ porterwright.com

Porter Wright Morris & Arthur LLP 1919 Pennsylvania Avenue, NW Suite 500 Washington, DC 20006-3434, USA

MonteiroCenter for Chemical Toxicology Riviere, Nancy Research and Pharmacokinetics Department of Clinical Sciences College of Veterinary Medicine North Carolina State University 4700 Hillsborough Street Raleigh, NC 27606, USA

Tel.: 919-5136426 Fax: 919-513-6358 Email: Nancy_Monteiro@ ncsu.edu

468

O’Brien, Niall

PARTICIPANTS

Biosystems Engineering School of Tel.: 0035317165546 Agriculture, Food Science and Veterinary Fax: 0035314752119 Medicine, College of Life Sciences Email: [email protected] University College Dublin Earlsfort Terrace Dublin 2, Ireland

Owen, Richard DEFRA, Environment and Human Health Programme UK Environment Agency Block 1 Government Buildings Burghill Road Bristol BS10 6BF, UK

Tel.: +44 (0) 7990 800051 Fax: + 44 (0) 117 914 2673 Email: richard.owen@ environment-agency.gov.uk

Palma-Oliveira, FPCE, University of Lisbon José Manuel Alameda da Universidade 1100 Lisboa, Portugal

Tel.: +351 21 781 62 80 +351 96 150 44 44 Fax: +351 21 781 62 89 Email: [email protected]

Picado, Ana

Instituto Nacional de Engenharia, Tecnologia e Inovação, I.P. Estrada do Paço do Lumiar, Edif. E - 1º Andar Lisboa 1649-038, Portugal

Tel.: 351 210 924 706 Fax: 351 217 166 966 Email: [email protected]

Pinto, Valéria

Foundation on Occupational Safety and Health Researches and Studics-FUNDACENTRO Av. Quintino Bocaiúva, 187 apto 302 São Francisco Niterói 24360022, Brazil

Tel.: +552125088548 Fax: +552125079041 Emails: valeria.pinto@ fundacentro.gov.br; [email protected]

Ramadan, Abou Bakr

National Egyptian Environmental and Radiation Monitoring Network 3 Ahmed El Zomor Street Nasr City 11672 Box 7551 Cairo, Egypt

Tel.: +202 27 48 787 +2012 346 8077 Fax: +202 22876 031 Emails: [email protected]; [email protected]

Rudnitsky, Robert

Physical Science Officer Office of Space & Advanced Technology U.S. Department of State OES/SAT, SA-23, 1990 K Street, NW Suite #410 Washington, DC 20006, USA

Tel.: 202-663-2399 Fax: 202-663-2402 Email: RudnitskyRG@ state.gov

Satterstrom, F. Kyle

Harvard School of Engineering and Applied Sciences Engineering Sciences Laboratory 224 40 Oxford Street Cambridge, MA 02138, USA

Tel.: (206) 919-9337 Email: satterst@ fas.harvard.edu

469

PARTICIPANTS

Savolainen, Kai Finnish Institute for Occupational Health New Technologies and Risks Topeliuksenkatu 41 a A Helsinki FI-00250, Finland

Tel.: +358 30 474 2851 Fax: +358 30 474 2114 Email: [email protected]

Shalhevet, Sarit Sustain Econ – Environmental Economics Consulting 126 Thorndike Street Brookline, MA 02246, USA

Tel.: 617 879-0577 Fax: 617 879-0577 Email: sarit.shalhevet@ gmail.com

Shvedova, Anna

Tel.: 304 285 6177 Fax: 304 285 5938 Email: [email protected]

CDC/NIOSH 1096 Willowdale Road Morgantown, WV 26505, USA

Srdjevic, Bojan Faculty of Agriculture, University of Novi Sad Trg D. Obradovica 8 Novi Sad 21000, Serbia

Tel.: +381-21-4853-337 Fax: +381-21-455-713 Email: [email protected]

Stamm, Hermann

Institute for Health & Consumer Protection, EC Via Fermi, Ispra 21020, Italy

Tel.: +39 0332 789030 Fax: +39 0332 785388 Email: hermann.stamm@ ec.europa.eu

Steevens, Jeffery

U.S. Army ERDC 3909 Halls Ferry Road Vicksburg, MS 39056, USA

Tel.: 601-634-4199 Fax: 601-634-2263 Email: Jeffery.A.Steevens@ us.army.mil

Tervonnen, Tommi

CEG-IST, Centre for Management Studies, IST Technical University of Lisbon Instituto Superior Técnico, Taguspark Porto Salvo 2780-990, Portugal

Tel.: +351 96 529 1326 +421 910 119 209 Fax: +351 214 233 568 Email: tommi.tervonen@ ist.utl.pt

Varma, Rajender

Sustainable Technology Division National Risk Management Research Laboratory, US EPA Cincinnati, Ohio, USA

Tel.: (513) 487-2701 Fax: (513) 569-7677 Email: Varma.Rajender@ epa.gov

Vaseashta, Ashok

On Detail from Nanomaterials Laboratories & Characterization Labs Marshall University One John Marshall Drive Huntington, WV 25575, USA

Tel.: 2026478548 Fax: 2026474920 Email: VaseashtaAK@ state.gov

Vieira, Teresa

Departamento de Mecânica University of Coimbra Rua Luis Reis Santos Coimbra 3030-788, Portugal

Tel.: +351239790711 Fax: +351239790701 Email: [email protected]

Vieira, Mariana

FPCE, University of Lisbon Alameda da Universidade 1100 Lisboa, Portugal

Tel.: +351 21 781 62 80 +351 96 150 44 44 Fax: +351 21 781 62 89

470

Wonkovich, Betty

PARTICIPANTS

US Environmental Protection Agency 1200 Pennsylvania Avenue, NW 8101R Washington, DC 20460, USA

Tel.: (202) 564-6989 or 6620 Fax: (202) 564-2244 Email: Wonkovich.Betty@ epamail.epa.gov

AUTHOR INDEX

A

F

Abdel-Hay, F.I..........................247 Abdel-Mottaleb, M...................195 Adlakha-Hutcheon, G. .............195 Arcuri, A.S.A. .................. 299, 329 Asbach, C. ................................233

Figovsky, O. .............................275 Figueira, J.R..............................179 Fissan, H. ..................................233 Foss Hansen, S.................. 329, 359

B Baun, A. ...................................359 Bayramov, A.A. .......................317 Beilin, D. ..................................275 Bennett, E. ..................................95 Blank, N. ..................................275 Bonina, S.M.C. .........................139 Borling, P. ................................359 C Casman, E.A.............................125 Chan-Remillard, S. ......... 3, 53, 149 Chappell, M. ............... 95, 111, 179 Cho, S.Y. ..................................287 Crane, M. . ................................369 Cummins, E. .............................161 D Darnault, C.J.G. ........................139 Davis, T.A. ...............................329 de Carvalho, R.G. .....................437 Depledge, M. ...................... 95, 369 E Elder, A. ................................. 3, 31 El-Newehy, M.H. .....................247 Endres, C. .................................287 Estrin, Y. ..................................287 Evgrafova, S. ............................287

G Gapurova, O..............................219 Gatti, A.M............................... 3, 83 Glavin, A. ...................................67 Gnewuch, H. ......................... 3, 225 Gonzalez, M..............................351 Gorbunov, B. ............................225 Goss, G. ......................................95 Goudey, S. .................... 53, 95, 149 Grieger, K. ............................3, 369 Grossi, M.G.L...........................299 Gulledge, W..............................329 H Handy, R. .................................369 Haruvy, N. ................................385 I Ieleiko, L. ...................................67 J Jackson, P.R. ............................225 K Kaczmar, S..................................95 Kamper, A. ...............................359 Kapustka, L. .............. 53, 149, 329 Karkan, D..................................330 Kearns, P. .................................351 Kenawy, E. .......................... 3, 247

471

472

AUTHOR INDEX

Khaydarov, R.A................ 219, 287 Khaydarov, R.R. ....... 195, 219, 287 Korenstein, R. ...................... 4, 195 Kozyrev, S. ...............................309 Kuhlbusch, T.A.J.................. 4, 233 L Lee, K. ......................................351 Linker, F. ......................................4 Linkov, I. .......... 179, 330, 369, 423 Lowry, G.V. .............................125 Luis, S. .....................................437 Lynch, I. ................................. 3, 31 M Maia, P.A. ................................299 Martins, P.R..............................299 Matias, S. ......................................4 Melkonyan, M. ................. 309, 330 Merad, M. .................................179 Metcalfe, C. ................................95 Michelson, E.S. . ......................361 Mikhailenko, V...........................67 Monica, J. .................................330 Montanari, S. ..............................83 Monteiro-Riviere, N.A. .......... 4, 43 Muir, R. ....................................225

R Ramadan, A.B.A. ............... 96, 265 Rinaldi, A..................................299 Rodriguez, F. ............................351 Rudnitsky, R. ................................4 S Satterstrom, F.K. ......................329 Savolainen, K................................4 Scheper, T.................................287 Seager, T.P. ..............................423 Shafy Haraza, M.A. ..................329 Shalhevet, S. .............................385 Shvedova, A..................................5 Snee, P.T. .................................139 Sorochinska, J. ...........................67 Srdjevic, B. ....................... 330, 409 Srdjevic, Z. ...............................409 Stamm, H. .................................195 Steevens, J. ......................... 95, 179 Stuer-Lauridsen, F. ...................359 Suvocarev, K. ...........................409 T Tervonen, T. .............................179 U

N

Uyusur, B..................................139

Nadagouda, M.N. .....................209

V

O

Varma, R.S. ...................... 195, 209 Vaseashta, A. .................... 195, 397

O’Brien, N. .................................95 Oki, N. ......................................351 Owen, R............................ 330, 369 P Palma-Oliveira, J.M. ........ 330, 437 Picado, A. ...................................95 Pinto, A.C. ................................299 Pinto, V.R.S..........................4, 299 Priest, N.D. ...............................225

W Wnek, G.E. ...............................247 Z Zhang, L.W. ...............................43 Zoranovic, T. ............................409