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Carbon Nanotubes: California Has Big Questions For The Small Packages

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:

-- What is the value chain for your company? For example, in what products are your carbon nanotubes used by others? In what quantities? Who are your major customers?

-- What sampling, detection, and measurement methods are you using to monitor (detect and measure) the presence of your chemical in the workplace and the environment? Provide a full description of all required sampling, detection, measurement, and verification methodologies. Provide full QA/QC protocol.

-- What is your knowledge about the current and projected presence of your chemical in the environment that results from manufacturing, distribution, use, and end-of-life disposal?

-- What is your knowledge about the safety of your chemical in terms of occupational safety, public health, and the environment?

-- What methods are you using to protect workers in the research, development, and manufacturing environment?

-- When released, does your material constitute a hazardous waste under California Health & Safety Code provisions? Are discarded off-spec materials a hazardous waste? Once discarded, are the carbon nanotubes you produce a hazardous waste? What are your waste handling practices for carbon nanotubes?

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