Life Cycle Aspects of Nanoproducts, Nanostructured Materials, and Nanomanufacturing: Problem Definitions, Data Gaps, and Research Needs
Chicago, Illinois: November 5-6, 2009
Considerations for Life Cycle Assessment of Nanotechnologies
J. A. Isaacs
Department of Mechanical and Industrial Engineering
Northeastern University
Increasing attention to environmental health and safety (EHS) issues related to emerging nanotechnology has been recommended over the past several years, and the U.S. Environmental Protection Agency has been developing a roadmap for EHS research needs. An earlier study undertaken by the Royal Society and the Royal Academy of Engineering (2004) developed a list of recommendations ranging from actions to achieve more sufficient EHS data to suggestions on where regulation should be considered. The National Institute for Occupational Safety and Health (NIOSH) has published an overview of research in this area undertaken at that agency summaries of accomplishments, and suggestions for additional research needs. Although NIOSH also suggested preliminary guidelines for working safely with nanomaterials (NMs), research clearly is needed to define risks, provide guidance for safe handling of nanomaterials, and minimize workplace exposure. Various other U.S. government agencies are involved in contributions to the EHS research effort. An overview of the primary EHS research and information needs was developed by the National Science and Technology Council (NSTC 2008) of the U.S. National Nanotechnology Initiative to guide the vast effort needed to ensure responsible development of nanotechnology and to inform policy makers. Related nanomanufacturing EHS research findings are available through a searchable database of information through the International Council on Nanotechnology (ICON 2005).
Completion of this research, however, is expected to take some time, especially because new engineered NMs are being synthesized and modified at rapid rates. Until then, policy makers and businesses working with NMs are faced with significant uncertainty in how to proceed with commercialization of their products and regulatory safeguards. It may take several years to develop more complete EHS information, let alone consensus on policy to support responsible commercialization of manufactured goods. The first potential exposures will occur in the workplace, which raises issues of occupational safety and health in manufacturing facilities or laboratories. The evaluation of work practices, administrative actions, engineering controls, and personal protective equipment in manufacturing environments is likely to lead to improved best practices for reducing exposure to nanomaterials (NSTC 2006). Leading companies are working to develop guidelines, but, again, these results are not yet available or the benefits are unknown.
To investigate the potential risks posed by NMs, fast and inexpensive predictive assays are needed to screen for potential toxicity. It is widely acknowledged that toxicity of particulate matter is dependent on several physico-chemical parameters, including specific surface area, bioavailable transition metals, adsorbed organic matter, surface impurities and defects, biosolubility, crystallinity, surface charge, morphology, agglomeration status, etc. For reasons of cost, complexity, lack of all necessary instruments, and others, rarely are all of these parameters measured and/or reported. Even when all these properties are measured, their net toxicological potential cannot be elucidated based on individual measures. Identification of simple, easily interpretable, biologically-relevant, global metrics that capture the most important aggregate properties of NMs is highly desirable. Such assays can be very useful in prioritizing NMs based on their inherent toxicity for timely responses to exposure control, better risk assessment, and redesign efforts for developing greener materials. Evaluation of relative toxicity of a broad class of NMs is rare, and comparisons based on existing cellular testing are difficult due to differences in cell lines, exposure protocols, incomplete characterization of tested NMs, and variable measured endpoints. In addition, manufacturing-related variability in synthesized NMs properties is poorly understood and undocumented, presenting another serious challenge for safe development of nanotechnology.
In the particular case of carbon nanotubes (CNTs), there are few to no data regarding the EHS effects of CNTs. The large-scale production of CNTs is likely to be energy intensive. Given that often only small quantities of CNTs are required to achieve significant changes in properties in various applications (e.g., structural composites, electronics), the energy footprint on a functional unit basis will differ significantly from the simple comparison with other materials on a mass basis. New methods for production of CNTs are also under development through room-temperature chemical reactions, which could lead to reductions in this energy footprint. Regardless of the potential health and safety impacts of CNTs, determination of life cycle environmental loads for specific products would be necessary to identify the benefit or detriment of their manufacture, use, and disposal. In microelectronics, for example, a single-walled nanotube (SWNT) switch—made from one single CNT—requires no power to maintain its on or off positions and would result in significant energy reductions during the use phase of powered devices. Though the mass of CNT might be small, disposal of central processing unit (CPU) boards with CNT chips could be problematic if CNTs are found to cause significant health or environmental effects.
Use of LCA methodologies to assess alternate SWNT processes resulted in limited conclusions due to the lack of EHS data. Few LCA studies have been undertaken in nanotechnology, and although LCA can have major benefits and produce useful information, its application and use are restricted due to limited toxicity data. Given that it will be some time until toxicological data become available, risk assessment methods can be used to provide insight to policy makers and other decision makers. The use of Monte Carlo (MC) risk models has been used to study the impact of these uncertainties on long-term manufacturing costs, exposure risks, and inherent trade-offs as a means for more informed decision making.
There are possible environmental ramifications for end-of-life (EOL) products that contain nanomaterials. For example, personal computers with CNT non-volatile memory or with structured nanomaterials used for electromagnetic interference shielding may eventually proliferate, mature, and reach their end-of-life. Their short life cycle and the fact that they contain many hazardous materials (separate from CNTs) means that their retirement and disposal represent a potentially significant environmental concern.
Local governments have limited capacity to address potential environmental and public health effects of new technologies, yet such effects are often felt first at the local level. The Cambridge, MA, Nanomaterials Advisory Committee (NAC) in 2007-08 considered rules governing nanomaterial research and production within city limits. The NAC’s path of action was influenced by the experience of Berkeley, CA, which had implemented a nanomaterials reporting ordinance a year earlier, and, perhaps more important, by lessons obtained by the Cambridge Environmental Review Board (CERB), which for three decades has overseen what were the first regulations governing biotechnology enacted in the US.
In Cambridge, more than was apparent in Berkeley, deliberations involved open discourse among policymakers, industry representatives, academic researchers, legal experts, and local residents. Participants shared their respective expertise to build a common frame of knowledge from which to assess what was known about nanotechnology in general and activities in Cambridge in particular. The outcome – to not enact new regulations– reflected a sober yet watchful understanding that too little was known to promulgate specific rules just yet. Uncertainties surrounding the health and environmental effects of nanotechnology pose a unique dilemma to local and state governments invested in fueling economic growth through innovation. Understanding the processes by which Cambridge addressed this dilemma may guide other local governments in dealing with uncertainty. Some believe that the existing regulatory structure is capable of handling these new materials, while others believe that it is inadequate and that new frameworks should be developed to control these materials.