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Library of Congress Cataloging-in-Publication Data:
Ellenbecker, Michael J.
Exposure assessment and safety considerations for working with engineered nanoparticles / Michael J. Ellenbecker, Sc.D., CIH, Professor Emeritus of Occupational and Environmental Hygiene, Director, Massachusetts Toxics use Reduction Institute, Department of Work Environment, College of Health Sciences, University of Massachusetts Lowell, Su-Jung (Candace) Tsai, Sc.D., Assistant Professor of Occupational/Environmental Health and Hygiene, School of Health Sciences, College of Health and Human Sciences, Purdue University.
pages cm
Includes bibliographical references and index.
ISBN 978-0-470-46706-0 (cloth)
1. Nanotechnology–Safety measures. 2. Nanostructured materials industry–Employees–Health and hygiene. 3. Nanotechnology–Health aspects.
4. Nanoparticles–Toxicology. 5. Industrial hygiene. I. Tsai, Su-Jung. II. Title.
T174.7.E454 2015
363.17′9–dc23
2014029773
Cover image credit:
Image courtesy of Argonne National Laboratories
Image title: Fireworks over Night Sky
Image was taken by Vilas Pol and Natalie Fitzgerald
Description of image:
A dramatic fireworks display over a night sky is demonstrated. Golden yellow lights pournward along with colorful and radiant clusters of pink, purple and orange. The viewer’s perspective is that of looking up at the fireworks coming down to the earth in a shower of light. Originally, it’s a scanning electron micrograph of photo-luminescentlanthanum hydroxycarbonate superstructure, prepared in critical autogenic reactions.
The U.S. Department of Energy’s Argonne National Laboratory, 2011
I (ME) dedicate this book to my wife, Marlene Goldman, for her understanding throughout the long process of research and writing leading to its publication. I greatly appreciate her support. I also dedicate it to our daughters, Anne and Heidi, and our five grandchildren, in the hope that the safe application of nanotechnology will bring them a better world.
I (CT) dedicate this book to my husband, Chunyuan Chen, and children, Xenia and Steven, for their understanding and encouragement while I spent the time doing the research followed by the writing. I appreciate my parents’ support of my career. Being in the forefront conducting research on this important topic, I hope that nanotechnology will bring a bright future to the next generation with a safe environment for everyone.
The field of nanotechnology is expanding rapidly, with new discoveries being announced almost daily in fields ranging from the fairly mundane (e.g., advanced composite materials) to the exotic (e.g., targeted anticancer drug delivery). As with any new technology, however, excitement over the likely benefits to society must be balanced with attention to any potential adverse effects that may arise. For nanotechnology, there is growing evidence that at least some of the new engineered nanomaterials may have adverse health and safety aspects that must be addressed in order to ensure that they are used in a safe and effective manner.
Hence this book. We the authors, occupational hygienists, have been performing research into the occupational and environmental health and safety aspects of nanotechnology since 2003. Here we have attempted to present our view of the current state of this rapidly advancing field. The primary audience for the book is health and safety professionals who find that they have to develop a working knowledge of this new field. Given our backgrounds, the book’s primary focus is on occupational exposures, and we have attempted to give attention to environmental exposures. It is our hope that the reader will be able to use the information from this book to apply the occupational hygiene model of anticipation, recognition, evaluation, and control to nanotechnology development.
We would like to acknowledge the contributions of Rick Reibstein of the Massachusetts Office of Technical Assistance and Technology, who provided valuable information and insight to Chapter 11. We also acknowledge the support received from the National Institute for Occupational Safety and Health (NIOSH) and the National Science Foundation (NSF) funded Center for High-rate Nanomanufacturing, which supported much of our research as reported in the book’s case studies.
Michael J. Ellenbecker
Candace Su-Jung Tsai
Asbestos, once hailed as a “miracle” material for its insulating properties, has been an occupational and environmental health disaster. Many thousands of people, mostly workers but also members of the general population, have developed serious illnesses, including asbestosis, lung and colon cancer, and mesothelioma, and many have died as a result of their exposure. The reader may ask, “why start a book on nanoparticle health and safety with a discussion of asbestos, which most definitely is not a nanoparticle?” The answer leads us to our purpose in writing this book, at this time.
The authors have been to many nanoparticle health and safety meetings over the past several years. A constant theme at those meetings, both in the formal presentations and also in the informal discussions among the scientists in attendance, is “we have to prevent the next asbestos.” Starting in the 1920s, exposure to asbestos from its mining, milling, and incorporation into products such as textiles was associated with severe lung disease that came to be called asbestosis; other hazards from asbestos exposure, such as lung cancer and mesothelioma, were not discovered until years later. In addition, the risks to workers using products containing asbestos and to individuals in the general population took some time to be appreciated.
Today, engineered nanoparticles represent a miracle new material (actually, a range of materials, as discussed later), just as asbestos was a miracle new material early in the last century. And, as with asbestos, there are early indications that there may be adverse health effects associated with at least some of these new materials; in fact, carbon nanotubes may have similar health effects as asbestos (see Section 5.4). The extent of the risk to workers and the general public is not known at this time. The answer to the question posed above leads to another question, that is, have we learned our lessons from asbestos and other similar occupational and environmental health disasters, so that we can develop the exciting new field of nanotechnology while protecting the health of workers and the general population, and prevent any adverse effects to the environment?
We believe that the answer to this question is “yes.” The nanotechnology industry is still in its infancy, meaning that proactive steps can be taken to further its development in a safe, sustainable manner. Andrew Maynard and colleagues summarized the risks and opportunities in their 2006 Nature article as follows (Maynard et al., 2006):
The spectre of possible harm—whether real or imagined—is threatening to slow the development of nanotechnology unless sound, independent and authoritative information is developed on what the risks are, and how to avoid them. In what may be unprecedented pre-emptive action in the face of a new technology, governments, industries and research organizations around the world are beginning to address how the benefits of emerging nanotechnologies can be realized while minimizing potential risks.
This book has been written in an attempt to contribute to the minimizing of the potential risks of nanotechnology. In occupational and environmental health, we have a very simple model that guides our work, that is, exposure to a material or physical agent may lead to an adverse health effect in the exposed population. Although we have included a brief review of the current state of nanoparticle toxicology in Chapter 5, in order to put the need for exposure assessment and control in their proper context, this is a book about the exposure side of our model. In considering exposure, the two most important aspects are to evaluate the magnitude of the exposure and, in those cases where the exposure is judged to be excessive, take steps to control the exposure. These are the two major topics covered in this book.
It is important to emphasize that this book pays relatively little attention to the judgment step just mentioned. In most cases, environmental health professionals make the decision as to whether a measured exposure is excessive by comparison to standards, such as published occupational exposure limits. These standards, in turn, are established based on results of toxicology and epidemiology studies that quantify the risk of exposure for a certain material. The difficulty with engineered nanomaterials, as discussed in Chapter 5, is that at this time there is insufficient information to set such standards. The consensus among occupational and environmental health scientists studying engineered nanoparticles is that until sufficient toxicology and epidemiology information is available for any given material, the precautionary approach must be followed in order to minimize the risk to workers, the general public, and the environment. This concept is further discussed in Section 1.4.
In the occupational environment, exposure assessment and control are the purview of industrial hygiene or, more widely used today, occupational hygiene; regarding the general environment, the equivalent field might be called “environmental hygiene,” although this term is not widely used. In any case, the subject of this book is the current state of knowledge concerning the occupational and environmental hygiene aspects of nanotechnology. It is fair to say, however, that most of the focus in on occupational hygiene, and there are two reasons for this. First is the fact that the authors are occupational hygienists, so most of our experience and expertise, such as it is, falls within this field. The second reason is perhaps more important, which is that in a new and growing industry such as nanotechnology, most of the significant exposures will be to those workers who are doing research with and manufacturing nanomaterials. Consequently, most of the concerns and attention of the research community to date has been focused on nanotechnology workers, rather than the general public. As nanotechnology-enabled products become more widely used, we can expect more of the focus to shift to their environmental impact.
Some scenarios may help to put the need for nanoparticle health and safety in its proper context. These scenarios are all fictional but based more or less on real situations now being encountered in the nanotechnology field.
These scenarios share certain characteristics, that is,
This text does not address the first point above but is meant to address the other two. We hope to provide the reader with the latest information concerning techniques to evaluate and control occupational and environmental exposures to nanoparticles.
The remainder of the book generally follows the basic occupational hygiene model for addressing a possible worker exposure, which is the four-step process of anticipation, recognition, evaluation, and control. We start in Chapter 2 with a presentation on the terms used in this field—the definition of a nanoparticle, the different types of nanoparticles, and so on. In the anticipation phase, we attempt to identify possible problems of concern. Chapter 3 discusses the unique properties of nanoparticles that may make them more toxic than larger particles of the same material, and Chapter 4 describes the various pathways by which a nanoparticle might enter the body. We then move to the recognition phase in Chapter 5 with an overview of the current knowledge on engineered nanoparticle toxicity, followed by a discussion of possible sources of exposure in Chapter 6.
We then move to the main topics of this book, evaluation, and control. Chapter 7 reviews the current state of instruments and methods available to evaluate exposures to engineered nanoparticles, and Chapter 8 reviews in detail how those tools are used to perform an engineered nanoparticle exposure characterization. Included in Chapter 8 are three detailed case studies arising from work in our laboratory that illustrate the practical application of the exposure assessment methodology. Chapters 9 and 10 are concerned with solutions—methods to control occupational and environmental exposures that an exposure assessment found to be problematic. Again, the basic techniques are supplemented by case studies from our research.
We end the book by considering important policy issues facing the nanotechnology health and safety community. Chapter 11 discusses the current state of health and safety regulations, both in the United States and internationally, and Chapter 12 concludes with our thoughts and recommendations for needed next steps if we are to continue to make progress toward our goal of preventing occupational injuries and disease related to nanotechnology.
We will return to this topic at the end of Chapter 12, but we believe that it is important for the reader to understand the basic philosophy behind our approach to nanoparticle health and safety, since it informs all of the topics covered throughout the text. At the time of this writing in 2014, much is not known about the toxicology of engineered nanoparticles, but enough is known to certainly raise concerns. Likewise, we know that workers and the general public have the potential to be exposed to engineered nanoparticles. Therefore, we believe that a precautionary approach must be followed—specifically, we believe that until toxicology and/or epidemiology tell us differently, all reasonable steps should be taken to minimize exposures to engineered nanoparticles. In order to accomplish this, exposures must first be measured and, where exposures are found to be measurably above background levels, steps must be taken to reduce those exposures.
This approach is not unique to us—indeed, many researchers and government agencies responsible for nanotechnology health and safety have taken similar positions. The precautionary approach relies on the concept of the “precautionary principle,” first developed in Europe and adopted into the 1987 Ministerial Declaration on the protection of the North Sea (Anonymous, 1987), which stated, regarding contamination of the North Sea by chemicals, that “…a precautionary approach is necessary which will require action to control inputs of such substances even before a causal link has been established by absolutely clear scientific evidence.” The precautionary principle was affirmed at the United Nations Conference on Environment and Development, held in Rio de Janeiro in June 1992; Principle 15 of the Rio Declaration on Environment and Development (UNEP, 1992) states:
In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.
The precautionary principle has been applied by others when addressing engineered nanoparticle health and safety. For example, the US National Institute for Occupational Safety and Health (NIOSH) has written (NIOSH, 2009):
Until further information on the possible health risks and extent of occupational exposure to nanomaterials becomes available, interim protective measures should be developed and implemented. These measures should focus on the development of engineering controls and safe working practices tailored to the specific processes and materials where workers might be exposed [emphasis in original].
Such recommendations of caution are not limited to US sources. For example, the British Standards Institute issued the following recommendation (BSI, 2007):
This Published Document recognizes that there is considerable uncertainty about many aspects of effective risk assessment of nanomaterials, including the hazardous potential of many types of nanoparticles and the levels below which individuals might be exposed with minimal likelihood of adverse health effects. The guide therefore recommends a cautious strategy for handling and disposing of nanomaterials.
ASTM International, a widely recognized consensus standard-setting organization, recommends the following (ASTM, 2007):
Exposure control guidance in this Guide is premised on the principle (established in this guide) that, as a cautionary measure, occupational exposures to UNP [unbound, engineered nanoscale particles] should be minimized to levels that are as low as is reasonably practicable. This principle does not refer to a specific numerical guideline, but to a management objective, adopted on a cautionary basis, to guide the user when (a) assessing the site-specific potential for such exposures; (b) establishing and implementing procedures to minimize such exposures; (c) designing facilities and manufacturing processes; and (d) providing resources to achieve the objective.
Circling back to where we began, with asbestos, Schulte and colleagues recently published an article (Schulte et al., 2012) that reviewed what is known of the hazards of CNTs and recommended a program of action. They conclude:
In the evolution of human civilizations, learning from the history and not repeating it has been a key guiding principle. Society can learn from how asbestos was inappropriately considered and not make the same mistake with CNTs. It is possible to safely realize the benefits of CNTs, but it will require rigorous and timely actions. The time to act is now.
We firmly believe that, not just for CNTs but for engineered nanoparticles in general, we must act now to ensure that this exciting new industry moves forward in a way that is protective of human health. It is with this conviction that this book is written.