The twin toxics: nanotubes and asbestos
A new study shows that, just like their look-alike asbestos, carbon nanotubes can cause mesothelioma.
Like other nanomaterials, tiny but strong-as-steel nanotubes are touted as this century's wonder materials. Researchers and manufacturers expect these nanomaterials to usher in a new era of drugs, high-efficiency batteries, and exciting electronics. But scientists fear that the nanotubes' striking resemblance to asbestos also implies a likelihood of asbestos-like impacts on humans. A new study published in Nature Nanotechnology on May 20 proves these fears to be well founded. It shows that the materials can induce lung cancer in mice.
In the study, Ken Donaldson of the University of Edinburgh (U.K.) and his colleagues exposed the lungs of mice to 50 micrograms of multiwalled carbon nanotubes by injecting the nanotubes into the mice's abdominal cavities. The effects—inflamed mesothelium (a membrane that lines lung tissue) and development of lesions—were similar to those of mesothelioma, a known health hazard caused by inhaling asbestos over an extended period of time.
The study "really confirms that the fiber hypothesis applies to carbon nanotubes," says coauthor Andrew Maynard of the Woodrow Wilson International Center for Scholars Project on Emerging Nanotechology. According to this hypothesis, fibers that are long, thin, straight, and durable have similar effects on the body, regardless of whether they are made of asbestos or carbon atoms, Maynard adds.
The results provide evidence of potential harm if people are exposed to carbon nanotubes in sufficient quantities. But the study cannot say whether people will be exposed and, if so, under what conditions. "That's one of the big unknowns here that's really got to be addressed as fast as possible," says Maynard. Still, the results show the need for more research on exposure scenarios, the health effects of nanomaterials, and guidelines from