NIOSH officials, working at the direction of an interagency nanotechnology group, are developing the guidelines and hope to release them within a year, according to Andrew Maynard, a senior service fellow at NIOSH, a research agency.

While the guidelines are still being developed, he said, the primary message would be to treat nanomaterials with caution and take appropriate steps, such as wearing a protective mask when working with materials that could pose a risk.

There is a "big gap in knowledge" between the understanding of the toxicology of some nanomaterials and the potential effects that exposure to them may have on human health, Maynard said in an interview following the briefing.

NIOSH and other government agencies have launched several studies on the potential health and environmental effects of nanomaterials.

Maynard said that up to two million U.S. workers are currently exposed to ultra-fine materials, and an estimated one million more Americans could be exposed through work in nanotechnology-based industries in the next decade.

Among the issues that researchers need to tackle: Predicting the types of exposure and the exposure routes of nanomaterials being released in the workplace and what is being exposed to them. Once that is determined, the next challenge will be to find out how to control hazardous nanomaterials and to limit exposure to them.

OSHA has yet to issue any specific guidelines related to nanotechnology for employers.