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RESEARCHERS WORRIED ABOUT potentially-harmful effects of carbon nanotubes might sleep a little easier, thanks to the effect of enzymes normally found in horseradish.

A team of researchers at the University of Pittsburgh found that horseradish peroxidise (HRP) can degrade carbon nanotubes in rubbish tips or at spillages in the laboratory or the environment. Materials scientists have taken a great deal of interest in using carbon nanotubes in a broad range of applications that would benefit from the tubes’ structural strength and electric conductivity.

"The many applications of nanotubes have resulted in greater production of them, but their toxicity remains controversial," says Alexander Star, assistant professor of chemistry at the university. "Accidental spills of nanotubes are inevitable during their production, and the massive use of nanotube-based materials could lead to increased environmental pollution. We have demonstrated a nontoxic approach to successfully degrade carbon nanotubes in environmentally-relevant conditions."

While the nanotubes are made of graphite, which is known to be harmless, the extremely small size and hair-like structure of nanotubes has still given rise to concern. In their pure form, carbon nanotubes resemble fine, graphite-like powder, which can cause severe lung inflammation. A recent study in Scotland raised the fear that some forms of the nanotubes could possibly be carcinogenic.

The team at Pittsburgh exposed the nanotubes to a solution of HRP and a low concentration of hydrogen peroxide at 4°C (39°F) for 12 weeks. Once fully developed, this method could be administered as easily as chemical clean-ups in today's labs, Star says.