Ultrafine Particles Come Under the Microscope

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Nanotechnology is an umbrella term for the science and technology of controlling the structure and properties of materials and systems at the scale of 10-9 meters , 1/100,000 the width of a human hair, or less than 0.1 . Growth projections for nanotechnology applications are 33% a year, according to the National Science Foundation, which has estimated that by 2015 such applications may total $1 trillion in the global economy. The federal government's support of nanotechnology is illustrated by Congress's swift enactment of The 21st Century Nanotechnology Research and Development Act on Dec. 3, 2003. This authorizes $3.7 billion over four years in federal support for nanotechnology.

The strong growth prospects of nanotechnology are prompting an increase in government attention to the potential health effects of nano- and other ultrafine particles (UFPs), which can be even smaller: less than 0.01 . So, this column reviews this interest and the nascent stage of research into these health effects.

Are there health risks?

Questions about the health risks posed by nanotechnology have arisen in the last few years. Almost all of the current, modest body of research relates to naturally occurring UFPs rather than particles produced by nanotechnology. UFPs are ubiquitous in urban areas, in the form of combustion soot, diesel exhaust particles, and products of gasoline exhaust and industrial processes.

Research so far on health effects is limited. Some studies link UFPs with respiratory tract toxicity and indicate that UFPs pose a greater risk of producing an inflammatory response in the lungs than larger particles. These studies show the ability of UFPs to cross the blood-brain barrier, which has the potential to adversely affect the central nervous system. Most recently, on June 1, the American Heart Association issued a statement that exposure to airborne particulate matter poses an increased risk of death due to heart disease. According to the statement, several studies link a greater incidence of heart disease with exposure to particulate pollution. Some experts say that such UFPs ultimately may present a far more substantial health threat than particulate byproducts of nanotechnology applications.

Researchers recommend undertaking inhalation studies to try to discover the operative toxicity mechanisms causing these adverse effects. The federal government agrees, and several federal agencies, including the National Institute for Occupational Safety and Health (NIOSH), the National Toxicity Program (NTP), EPA, and the Food and Drug Administration (FDA), are engaged in such research.

Some work will focus specifically on nanomaterials. For instance, NTP intends to evaluate in research animals the toxic and carcinogenic potential of inhalation exposure to quantum dots (tiny devices that contain a droplet of free electrons) and nanotubes. EPA also is slated to initiate $4 million in research beginning in fiscal year 2004 to investigate the toxicology of certain manufactured nanomaterials.

Occupational hazards also are a primary focus of current government concern. NIOSH has staked out nanotechnology as a key research area and is now developing a National Nanotechnology Research Center to coordinate its research initiatives. NIOSH acknowledges that more research is necessary to understand the effects of exposure to nanoparticles.

Another area NIOSH has identified for further study is the potential toxicity of nanoparticles that contact skin. In vitro assays have yielded strong evidence of oxidative stress and the destruction of dermal cell structure. Further research is needed to understand the relationship between nanoparticles and dermal sensitization or irritation.

The research now underway will shed more light on the toxicity of UFPs and nanoparticles. Companies employing or planning to use nanotechnology should monitor these developments to ensure that their practices and hazard communication strategies remain current and fully reflect health effects research in these areas.

By Lynn Bergeson, regulatory editor. She is a founding shareholder of Bergeson & Campbell, P.C., a Washington, D.C.-based law firm concentrating on chemical industry issues. The views expressed herein are solely those of the author.

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