Several convergent themes can be found in past research-gap analyses of the environmental and health impacts of nanotechnology (see Chapter 1). Most notable for this analysis are
• The vital need for standardized ENMs, harmonized characterization methods, and standard biologic tests.
• Research gaps concerning the in vivo evaluation of ENMs, particularly for chronic exposures and their impact on physiologic or biochemical endpoints.1
• Gaps in understanding low-level environmental exposure to ENMs and their impact on organisms through changes in development, reproduction, and growth.
While this is not a complete list, those topics represent conclusions reached in multiple synthesis reports over the last few years.
The need for standardization has emerged repeatedly in research-needs discussions and reflects the communitywide sentiment that ensuring reproducible and meaningful findings requires a common platform of materials, methods, and, most recently, models. In 2002, EPA held a workshop on nanotechnology and the environment that included a discussion of impacts; that event and a workshop at the University of Florida began the analysis of the grand challenges in this field (EPA 2002). Those early efforts emphasized the need for uniform and standard materials to facilitate comparison of results between different exposure and toxicity studies. Later workshops echoed earlier findings and emphasized the need to harmonize protocols for toxicologic evaluations. Testimony given to the U.S. Congress on strategies for nanotechnology-EHS research also highlighted the need to standardize materials, methods, and models (for example, Denison 2005). Chapter 4 addresses these needs.
Some workshops have offered priorities for research. In 2006, a meeting at the Woodrow Wilson Center considered the toxicology of ENMs by route of exposure and noted the importance of dermal and gastrointestinal exposure of humans (Balbus et al. 2007). That emphasis reflected the perception that the substantial literature on the toxicology of inhaled particles in humans could inform understanding of that exposure route and that comparatively little was known about the potential for exposure to ENMs by the dermal and gastrointestinal routes. Also noted in many reports is the importance of chronic-toxicity and developmental-toxicity studies and the overemphasis on acute studies (for example, Hirose et al. 2009). This emphasis reflects the relative ease of performing acute studies in vitro, providing faster, lower-cost studies that dominate publications in the peer-reviewed literature.
1Physiologic or biochemical changes resulting from exposures.