Carbon nanotubes may be as hazardous to health as asbestos
Scientists have warned that carbon nanotubes could pose a cancer risk similar to that of asbestos.
They say the government should restrict the use of the materials, which are included in a variety of consumer products, to protect human health. In most products containing nanotubes, such as car body panels, tennis rackets, yacht masts and bike frames, the fibres are embedded in composite materials, which provide strength and lightness. In this form they are likely to be relatively harmless. But the researchers said further studies were necessary to confirm that — it was not good enough to simply assume that people could not be exposed to carbon nanotubes embedded in materials.
Scientists would have to demonstrate that exposure from products was safe, said Andrew Maynard at the Woodrow Wilson International Centre for Scholars in Washington.
Dr Maynard said the risks were greater during manufacture and at the time products reach the end of their life. “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 I think it is something that needs to be addressed.”
Wonder materialsCarbon nanotubes were developed in 1991 and have proved to be extremely useful materials, conferring great strength while also being very light. They are also superb conductors of heat and electricity and have been touted as wonder materials that could form the basis of a new generation of electronics.
“This is a reason for concern,” said Anthony Seaton, a professor and expert in asbestos-related diseases, working at the Institute of Occupational Medicine in Edinburgh. “Asbestos started in the same way — it had thousands of applications and people used it experimentally. It became very widespread, almost ubiquitous.”
The similarity between the size and structure of carbon nanotubes and asbestos fibres has always placed a question mark over how the former could affect lungs. The new research shows that, in mice, the tubes, like abestos, cause inflammation of the mesothelium, the slippery membrane that surrounds lungs and other bodily organs. With asbestos fibres, the inflammation is a stage leading towards the deadly cancer known as mesothelioma. It typically takes 20 to 50 years for the cancer to develop following exposure to asbestos fibres.
The researchers, who report the development in the journal Nature Nanotechnology, compared the effects of short and long nanotubes. With asbestos, stiff fibres about 10 micrometres in length (100 times smaller than a milimetre) are harmless because immune cells can engulf them and safely remove them. Stiff fibres longer than 15-20 micrometres are too big for the cells to handle and their presence provokes an inflammatory response. The researchers confirmed that carbon nanotubes seemed to have the same effect.
Theoretical risk“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 leader of the research. He stressed that the team had not demonstrated that carbon nanotubes actually caused cancer. First, the long nanotubes would need to be airborne in large enough quantities and they would need to be able to cross the lung lining.
The researchers said the government needed to 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.
Maynard said that companies using the substance ought to be more transparent about nanotubes, including about how they were being used. “It’s very very hard to work out where they are being used simply because there is no requirement for a manufacturer to actually say how they are using them and where they are using them,” he said.
The Department for the Environment, Food and Rural Affairs runs a voluntary reporting system for companies, but very few have signed up to it.
