Carbon nanotubes, the wonder material that is used in some solar cells, batteries, and circuits, has the California Department of Toxic Substances beginning to wonder. The agency yesterday put manufacturers and importers of the material on notice that it wants more information on the health effects of exposure to CNT byproducts.The agency says its concern was prompted by two studies, one at Massachusetts Institute of Technology (MIT) and one at Georgia Institute of Technology, that detected the release of toxins during the manufacturing process of CNTs. "One study by … MIT detected 15 different aromatic hydrocarbons including 4 different polyaromatic hydrocarbons (PAHs) when they manufactured CNTs from a carbon vapor source using chemical vapor deposition. Another study by researchers at the Georgia Institute of Technology found that the fate of CNTs spilled into groundwater and the ability of municipal filtration systems to remove CNTs from drinking water is dependent on the characteristics of the water such as pH, natural organic content, etc."

Carbon nanotubes, which can have a length-to-diameter ratio as large as 28,000,000:1, are being considered for a litany of nanotechnology applications, from spacecraft to medical devices. They've also been used in integrated memory circuits. Indeed, ScienceDaily notes a recent finding involving the electrical conductivity of CNTs "could lead to nanoscale circuits that enable more compact and more powerful computers made of carbon nanotube materials that outperform silicon."

In August 2007, the journal noted that a "new analysis of by-products discharged to the environment during production of carbon nanotubes (CNTs) -- expected to become the basis of multibillion-dollar industries in the 21st century -- has identified cancer-causing compounds, air pollutants, and other substances of concern, researchers reported here today at the 234th national meeting of the American Chemical Society."

Among the questions the California agency is asking manufacturers: