Health Threat of Nanotubes May Be Similar to Asbestos, Study Warns

Scientists have warned that carbon nanotubes could pose a cancer risk similar to that of asbestos, saying the government should restrict the use of the materials to protect human health.

Carbon nanotubes were developed in 1991 and have proved extremely useful, conferring great strength while being very light. They are superb conductors of heat and electricity and have been touted as wonder materials that could form the basis of a new generation of electronics.

In most products containing nanotubes, such as car body panels, tennis rackets, yacht masts and bike frames, the fibers are embedded in composite materials, which provide strength and lightness. In this form the cylindrical molecules of carbon are likely to be relatively harmless.

But the researchers say further studies are necessary to confirm it; it cannot be assumed that people could not be exposed to carbon nanotubes held in materials.

Scientists will have to show that exposure from products is safe, said Andrew Maynard, of the Woodrow Wilson International Center for Scholars, in Washington. "What happens as you demolish products or throw them away in landfill sites? Is there a chance of carbon nanotubes coming out then and exposure occurring? We simply don't know the answer to that and that needs to be addressed."

"This is a reason for concern," Anthony Seaton, an expert in asbestos-related diseases, at the Institute of Occupational Medicine, in Edinburgh, said. "Asbestos started in the same way - people used it experimentally."

The similarity between the size and structure of carbon nanotubes and asbestos fibres has always posed a question on how the former could affect lungs. The new research shows that, in mice, the tubes, like asbestos, cause inflammation of the mesothelium, the slippery membrane around some bodily organs. With asbestos fibres, the inflammation is a stage leading towards cancer.

The researchers, whose report is in the journal Nature Nanotechnology, compared the effects of short and long nanotubes. "Nanotubes behave like asbestos in the sense that long ones are harmful, short ones aren't, and that exposure to some sorts of carbon nanotubes could carry a risk," said Ken Donaldson, professor at the University of Edinburgh, and the study's leader.

He stressed that the team had not demonstrated that carbon nanotubes actually caused cancer but they thought the government should take the threat seriously and prevent people from being exposed.

"The health and safety executive in the UK has to take appropriate measures to ensure that people are not being exposed to these things in the air or being exposed to the absolute minimum," said Seaton.

The highest potential risk was to workers involved in the manufacture of carbon nanotubes, he said.