Fears that legions of molecule-sized robots will turn our planet into a polluted wasteland of gray goo have now prompted even the Prince of Wales to speak out about the potential dangers of nanotechnology. But while public debate rages on nanotech's potential threat to the environment (see "Measuring the Risks of Nanotechnology" TR April 2003), research groups at U.S. universities and start-up companies have made progress in building nanotechnologies that not only don't pollute the planet-but that will actually clean it up.

Nanotechnology is the science of creating nanoscale structures (usually defined as under 100 nanometers) atom by atom, with properties that are made-to-order for a given task. In the case of pollution clean-up, these molecules are made to identify, attract, and react with toxic waste far more efficiently than conventional treatments-and to leave behind only harmless byproducts.

The U.S. Environmental Protection Agency is providing $7 million in R&D funding for nanoscale solutions to big pollution problems, from groundwater toxins to air pollution to soil contamination. That's a small amount of money when compared with, say, the $2 billion in federal funds earmarked for the Clean Coal initiative, which is aimed at using less exotic methods to reduce pollution caused by the mining and burning of coal. But even with relatively modest level of federal support, the progress in green nanotechnology at the 16 universities and 11 companies conducting the research has been rapid.

One of the first of these technologies to prove itself in field trials was developed by Wei-xian Zhang, a professor of civil and environmental engineering at Lehigh University. Zhang has developed a nanoscale material that, when applied to water contaminated with carcinogenic solvents used in industrial processes, converts the contaminants into harmless byproducts. Treatment of these toxic materials now typically involves pumping contaminated water into deep trenches, then seeding the water with millimeter-sized iron filings; as the iron corrodes, it react with the waste and converts it to safe hydrocarbons and chlorides. But that process is expensive and inefficient-and can take years.