For the most part, all we have is speculation on toxicity, said Mark Wiesner, an expert on the environmental implications of nanotechnology. Some (nano)materials are likely to be toxic and some are likely to be completely benign, but we don't know.

Nanotechnology, which manipulates materials and manufactures machines on the scale of single atoms, is an emerging field promising new treatments for cancer, new techniques to clean pollution and new materials for a wide range of uses.

Already, new nanomaterials are being created with unique properties and unusual levels of strength. At the nanoscale level familiar materials take on strange characteristics. Gold for example, normally an extremely stable material, becomes a catalyst able to trigger chemical reactions at a particular size in the nanoscale range.

In fact, suggested Nancy Monteiro-Riviere, a toxicologist specializing in nanomaterials at North Carolina State University, the size of a nanomaterial may have to be considered separately from the raw material itself and the planned application when regulations are drafted for nano-derived products.

The use of cosmetics and sunscreens has been heavily tested in the past, Monteiro-Riviere said. Most of the nanomaterials that are in these cosmetics are zinc- or titanium-based. They have been tested using classic toxicity screens. They have been regulated based on their chemical composition, not on their size. I have been talking with some of the FDA people who are reevaluating this at the current time.

Monteiro-Riviere and Wiesner, a researcher at Rice University in Houston, corresponded Wednesday with readers during an Internet chat on nanotechnology and the environment sponsored by the American Association for the Advancement of Science.

The problem, they said, is scientists simply do not have enough information yet to know what the risks are in the body or in the environment. Some nanomaterials exist naturally in the environment and should pose no harm. Some materials could be rendered harmless in the environment while other could react with Mother Nature in a detrimental way.

What is unknown, Wiesner said, is how these materials will interact with the soup of materials naturally present in water, such as degradation products of leaves, products from bacteria and others. We believe that these materials can drastically change or perhaps dominate the properties of nanomaterials in nature.

In other words, it might be that nanomaterials, once released in nature, take on a natural coat.

My concern, said Monteiro-Riviere, is that the fish eat (the soup described above), and the people eat the fish.

Earnest efforts are underway to research the health and environmental risks, said Clayton Teague, director of the National Nanotechnology Coordination Office. The NNCO is part of an interagency effort to integrate federal nanotechnology activities.

The National Toxicology Program, within the Centers for Disease Control and Prevention in Atlanta, already has begun a five-year effort to research the toxicology of nanomaterials Teaque said. Some $12 million to $15 million will be devoted to studies focused on nanotubes and buckyballs - both of which are made of carbon - and quantum dots. Quantum dots are tiny devices made of semi-conductor materials that contain a controlled number of free electrons.

Many quantum dots are made from heavy metals, said Wiesner, and those heavy metals are a known environmental concern. Any medical waste would need to be managed.

The government already is looking at such manufacturing and work-related risks, Teague said.

The National Institute for Occupational Safety and Health over the last year has instituted a significant program of research to understand the various paths by which workers might be exposed to nanoscale materials and they have issued ... a statement about their thinking on nanoscale materials in the workplace, Teague told United Press International. They also will be issuing ... over the next six months or so, recommended practices about how to work with nanoscale materials, to do so in a safe manner.

Other research programs are underway at the National Cancer Institute, which is looking at the safe medical use of nanotechnology, and at the Environmental Protection Agency, Teague said. EPA is studying what happens to nanomaterial when it enters the environment.

Teague estimated it would take a minimum of five years to begin to get a handle on the toxicology of nanomaterials.

In the mean time, he said, it is important to realize any risk is limited, because the amount of nanomaterials in existence right now is very limited and mostly in laboratories.

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