Research to Support Comprehensive Environmental Assessments of Nanomaterials
The U.S. Environmental Protection Agency's mission and mandates call for an understanding of the health and ecological implications of engineered nanomaterials. The Agency uses the comprehensive environmental assessment (CEA) approach as part of its engineered nanomaterial research portfolio. CEA identifies and prioritizes research to support future assessments and risk management decisions.
Nanomaterials pose special risk assessment challenges due to their diversity, unique properties, and seemingly limitless uses. For example, nanomaterials are so small they may have multiple or unique ways to come in contact with people or ecosystems. And because of their complex physical and chemical properties, it is also a challenge to determine the amount of exposure or dose that will cause an adverse effect. Ongoing research seeks to identify whether the relevant dose metric of a nanomaterial depends on the weight (mass), size, number of particles, shape, surface area, electrical charge, or some combination of these or other characteristics.
To evaluate the broad environmental implications of nanomaterials, it is important to consider how these materials are produced, shipped, stored, used, and disposed of or recycled across the entire life cycle of a product. A holistic view also includes how nanomaterials and waste by-products might move and change properties in air, water, and soil before coming into contact with humans and other organisms.
The CEA approach structures these and other types of information in a framework to support evaluations of near- (risk-related trade-offs) and long-term (research gaps) priorities for assessment and risk management decisions. Evaluations are carried out with a diverse expert stakeholder group to support consideration of potential impacts in the environment as well as ecological and human health related to exposure to nanomaterials and their by-products.
A series of case documents is being developed to systematically structure available information pertaining to the product life cycle, environmental transport and fate, exposure-dose in receptors (i.e., humans, ecological populations, and the environment), and impacts in these receptors for particular nanomaterials in specific applications. Two case studies on nanoscale titanium dioxide (nanoTiO2) are available. One examines the nanomaterial's use for water treatment in the removal of arsenic and the other looks at its use as an ingredient in topical sunscreens. A similar case study on nanoscale silver in disinfectant sprays is also available. Current efforts are focused on developing a case study on multiwalled carbon nanotubes (MWCNT) in flame-retardant coatings applied to upholstery textiles. This latest document builds on previous case studies by incorporating a comparative aspect with a non-nanoenabled flame-retardant material. The relatively more robust database of the non-nanoenabled material is intended to help identify relevant research gaps for MWCNT and lay a foundation for future efforts to compare nanomaterial and non-nanoenabled products.
These case studies provide a starting point for the next step of the CEA approach, which engages stakeholders representing diverse technical backgrounds (e.g., toxicology, chemistry, ecological risk assessment) and sector perspectives (i.e., industry, academia, government, non-government organizations). Through structured decision-support methods stakeholders reach a collective judgment about priority areas of research to inform future risk assessment and management efforts for the nanomaterial of focus in a case study document.
Application and Impact:
Many nanomaterials are currently in use and new ones keep coming on the market. EPA needs scientific tools and information to make informed risk assessments about this emerging technology, both in the near term and longer range. The CEA approach is an effort to identify priority research gaps that would inform such assessments. By focusing on prioritization, the CEA approach recognizes that there is a greater number of potential research questions than can be realistically pursued at any one time given logistical and budgetary constraints, and that there may be trade-offs associated with pursuing one research path over another. In turn, the CEA approach may help inform research managers as they determine how to best allocate the resources of their particular organization between different research areas. Importantly, these priorities are reached through structured decision-support methods with diverse stakeholders, such that the outcome reflects each perspective equally. Efforts are underway to build upon previous work to engage stakeholders in face-to-face meetings by utilizing novel, web-based tools that facilitate input from a larger number of stakeholders in remote locations prior to bringing a subset of them together for face-to-face input. The use of these virtual tools is intended to decrease the economic and environmental costs associated with brining stakeholders together face-to-face, while still benefiting from the input of diverse perspectives. By combining the holistic CEA framework with these innovative, structured decision-support methods this work will inform future research planning, assessment, and risk management efforts for nanomaterials.
These efforts will help in protecting public health and the environment as the field of nanotechnology continues to emerge.
Davis, J. M. How to assess the risks of nanotechnology: learning from past experience. J. Nanoscience and Nanotechnology, 7: 402-409, 2007
Christina Powers (firstname.lastname@example.org), National Center for Environmental Assessment, EPA's Office of Research and Development, 919-541-5504.