No matter which way you look at it, nanotechnology is poised to influence our lives to some degree over the coming years. Rapid advances in our ability to engineer materials, structures, and devices at atomic and near-atomic scales are broadening our horizons at an ever-increasing rate.
Nanotechnology is fundamentally based on exploiting the unique properties of nanoscale structures. However, these same properties present tough new challenges to understanding, predicting, and managing how the technology will impact health and the environment. In recent months, the need to address the potential risks associated with nanotechnology has received widespread media coverage. In April 2003, the Canadian-based nongovernmental organization Action Group on Erosion, Technology, and Concentration (ETC) made the case for a global moratorium on nanotech research until the risks are more fully understood. More recently, the UK's Royal Society and Royal Academy of Engineering stressed the need to address gaps in our understanding of the impact on health and the environment. Although the health and environmental risks of nanotechnology must be evaluated over the lifetime of products, the first point of impact in many cases will be in the workplace. So what risks are there at work? As nanotechnology is essentially a process rather than a product, this cannot easily be answered. However, the production and use of insoluble nanostructured materials has driven much of the current concern over potential health risks.
Studies over the past decade have established that the toxicity of inhaled insoluble materials is more closely associated with particle surface area than mass. The implications for how we evaluate and control the risk from inhalation exposures are profound. With the exception of fibers, exposure to airborne particles is evaluated using mass concentration and bulk chemistry. Evaluating and controlling risk in terms of surface area and surface chemistry will require new characterization and monitoring methods, and a re-evaluation of established control methodologies and working practices. Where specific surface area is low, or good empirical data are available on a particular substance, it is conceivable that the mass-based paradigm will suffice. But nanotechnology is likely to lead to many new low-solubility materials with high specific surface areas and diverse chemistries. The extent to which current mass-based methodologies can be applied to these materials is debatable.
Surface area is only part of the issue. Particle size is another physical factor that potentially effects risk. As well influencing the unique material properties associated with nanostructured materials, particle size is associated with deposition probability following inhalation, deposition location within the respiratory system, and translocation to other parts of the body.
Of course, nanostructured materials may enter the body through routes other than inhalation. Ingestion and skin penetration may be significant in some situations – particularly where nanomaterials are produced and handled in solution or suspension. Risk evaluation in each case will be a balance between toxicity and exposure. Thus, if toxicity is relatively high but the chance of exposure minimal, risk may be low. For instance, studies indicate that single-walled carbon nanotubes may be relatively toxic in the lungs. But there are also indications that large quantities of respirable particles are not released into the air when the bulk material is handled. In this case, the health risk will clearly be strongly influenced by both toxicity and exposure probability.
It appears that we currently know enough to treat engineered nanomaterials with caution, but not enough to predict their potential health impact. Also, we have only limited information on how to manage possible risks through the development of exposure limits and the use of engineering controls, personal protective equipment, and appropriate working practices. The speed with which the knowledge gaps are filled to enable effective risk management will depend partly on how necessary the research is perceived to be. Past experience demonstrates fairly conclusively that responding reactively to technological advances can severely impact the health of workers and the industry as a whole. In a post-GMO (genetically modified organism) world, this approach is becoming less feasible. The success of a new technology now depends much more on public acceptance: part of the acceptance process must surely involve the quantification and management of risk in relation to benefits.
Despite the tremendous societal benefits offered by nanotechnology, there are indications that it may negatively impact the health of workers, consumers, and the environment if not developed in a responsible manner. Fortunately, and perhaps uniquely, these indications have already prompted action within governments, non-governmental organizations, industry, and the research community. There is currently a growing body of targeted research underway worldwide to identify and address critical issues. By developing collaborations and partnerships among stakeholders and proactively developing an understanding of risk as nanotechnology becomes commercially viable, we have the chance to develop a truly responsible technology.
[1] Andrew D. Maynard is a Senior Service Fellow at the US National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention.