Carbon nanotubes have been implicated in the onset of mesothelioma in mice, researchers say.
In a study published in the journal Current Biology, a team of scientists led by Marion MacFarlane of the UK’s Medical Research Council Toxicology Unit report that up to 25% of mice injected with carbon nanofibres developed mesothelioma, a cancer associated with asbestos.
The findings applied only to long, thin carbon nanofibres. Other shapes, such as short fat ones, were expelled successfully by the rodents’ immune systems. The study involved 32 mice, who were injected with the carbon nanotubes directly into the pleura – the membranes that line the thorax and envelope the lungs.
The study’s findings have not been replicated in humans.
Long carbon nanotubes are widely used in a range of applications. They are lightweight and very strong, so are useful in the manufacture of computer motherboards, cars, aircraft and sporting goods.
“Importantly, not all nanofibres pose a hazard,” says MacFarlane.
“We want our research to inform manufacturers and regulators about safer options when a nanofibre is being selected for the production of nanomaterials for emerging technologies.”
As well as sounding a note of caution for manufacturers who use this type of nanotube, the research is also throwing a much-needed light on the way asbestos fibres – which are also long and thin – catalyse mesothelioma.
“Because mesothelioma is diagnosed when it’s quite advanced, we don’t know much about the early mechanisms by which it forms,” says co-author Tatyana Chernova.
“This research could help us find biomarkers for early detection, as well as provide information for developing targeted therapies for this devastating disease.”
Ivan Kempson, foundation fellow in the Future Industries Institute at the University of South Australia, who was not involved in the study, calls it “an excellent piece of investigative research” and adds that there was very little danger to consumers.
“The greatest risk occurs for workers involved in the manufacture and handling of these materials,” he says.
“For the general public, a greatly reduced risk exists since these materials are typically embedded within other materials such as resins within products. There is very little chance of the nanotubes, firstly, maintaining their original properties and causing the health risk, and, secondly, becoming isolated from the product and able to be inhaled by an individual.”
Scott Fisher from the National Centre for Asbestos Related Diseases at the University of Western Australia also commends the experiment but notes it was not an “inhalation study”. The mice were injected with nanofibres, whereas the most likely route for human contamination – as it is with asbestos – is through breathing them in.
He said there was little likelihood of consumers becoming contaminated through everyday use of products containing long thin carbon nanofibres because they are “locked up”.
However, he adds that “it would be reasonable to presume a risk to people involved in manufacturing processes where raw carbon nanotubes are produced, particularly those that fall into the ‘long’ category.
“Not only does this work have implications for further understanding the early stages of diseases like mesothelioma, but it may also inform how best to protect people from exposure during manufacturing.”