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INTRODUCTION

1.1 WHY A BOOK ON NANOTECHNOLOGY HEALTH AND SAFETY?

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.

1.2 SOME SCENARIOS

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.

• A small company specializes in the manufacture of relatively small quantities of high-quality powders in the micrometer size range for specialized niche markets. The company is too small to employ a person with health and safety training. The company president wishes to modify their production equipment to produce powders in the nanometer size range but has read of general concerns about the safety of nanoparticles. He asks his production manager to find out whether manufacturing nanopowders will present any new hazards to their workers.
• A university laboratory is conducting research on the use of carbon nanotubes (CNTs) as a new form of digital storage device. As part of this research, the laboratory technician must transfer small quantities of dry bulk CNTs from a 2 L jar to a beaker, weigh them on a balance, and disperse them in a solvent. These steps are now done on a laboratory bench, and the technician is concerned that she may be breathing in some CNTs that are being released from the powder.
• A plastics manufacturing company has recently begun pilot-scale testing of a new composite material, consisting of polyester reinforced with 2% by mass of alumina nanoparticles. The composite is produced in a twin-screw extruder. The polymer pellets are dumped into one hopper and the nanoalumina in another; they are fed by gravity into the throat of the extruder, where the pellets are melted by high temperature and pressure and mixed with the nanoalumina to form the nanocomposite. The extruder operator has noticed some of the alumina powder on various work surfaces around the hopper and is concerned that this may not be completely safe.
• A company uses the nanocomposite material produced above to make tennis racket frames. The pellets are fed into an injection molding machine which produces the tennis racket shape. However, extraneous material has to be cut off the frame with a saw and the frame must be sanded smooth. The plant occupational hygienist is concerned that these operations may release nanoparticles. In addition, the tennis racket manufacturer labels the product "contains nanomaterials for added strength" and is receiving anxious questions from consumers on their web site.
• An occupational hygienist working in the health and safety office at a large research university conducted a university-wide survey which found that more than 50 laboratories across the university claimed to be doing research with some type of nanoparticle. Many of the respondents stated that they did not know what practices should be followed when working with nanoparticles; the occupational hygienist decided that the university needed a policy on good work practices but he did not know how he would gather the information to develop such a policy.
• A research laboratory recently purchased a chemical vapor deposition furnace for making CNTs. While the furnace is a closed system during CNT production, at the end of a run, it must be opened and the CNT material must be scraped from the furnace walls into a drum. This process creates visible dust, which has caused the operator some anxiety.
• A research laboratory was...