sizes, and surface coatings further determine structure and function of these molecules. Each such material has been specifically designed for function, such as the fullerene C60, which is used for fuel cell applications. Very little is known about engineered nanoparticles and how they interact with cells or human organisms, noted Colvin.

BENEFITS AND POTENTIAL NEGATIVE IMPACT OF NANOTECHNOLOGY

Nanotechnology has direct beneficial applications for medicine and the environment, but like all technologies it may have unintended effects that can adversely impact the environment, both within the human body and within the natural ecosystem. While taking advantage of this new technology for health, environmental, and sustainability benefits, science needs to examine the environmental and health implications.

Recently, nanotechnology has received considerable attention from the media. Most of the initial reports have been positive; however, scientists should not forget that not all nanomaterials will be benign, said Kenneth Olden, National Institute of Environmental Health Sciences. Therefore, it is very important to identify the negative aspects of the technology before we introduce it to the marketplace. During the workshop, many speakers and participants spoke of the paucity of data for engineered nanoparticles and cautioned against solely relying on the research of natural and incidential nanoparticles.

Determining toxicity can be complicated because not all engineered nanoparticles are more toxic than fine-sized particles of the same chemical composition. The surface coatings of particles, exposure to UV radiation, and dispersion properties can change the behavior of the particles, noted Eva Oberdörster of Southern Methodist University. For example, in pulmonary studies, whether particles aggregate and then disaggregate once they reach the lung fluids as well as the process for generation of nanoparticles, for example, fumed versus precipitated silica seems to be relevant. David Warheit, of the DuPont Company, suggested that developing a working hypothesis for determination of particle toxicity will depend on the capacity of the particles to cause cell and lung injury, promote inflammation, inhibit macrophage function, and persist in the lung. Finally, Warheit observed that species differences complicate research; for example, rats appear to be particularly sensitive to particle-induced pulmonary toxicity.

Some current hypotheses suggest that some engineered nanoparticles may be more toxic (inflammatory) than other fine-sized particles of identical chemical composition, noted Warheit. This concept is based primarily on a system evaluation of three particle types: titanium dioxide, carbon black, and diesel particles. However, he noted that the current hypotheses are based on a paucity of data.

John Froines of UCLA raised the question whether the research that scientists are doing on airborne particulate matter related health effects has relevance



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