A new study, conducted by the Medical Research Council Toxicology Unit, has been published in the Current Biology journal. Research has found that carbon nanotubes may cause mesothelioma.[i] As such, the study is suggestive of the fact that carbon nanotubes could pose the same risks as asbestos. Since the effects of asbestos exposure can take up to 40 years before manifesting into mesothelioma, this study sought to examine the effects of nanotubes from the first exposure.
Carbon nanotubes are a type of nanomaterial, meaning that one or more of their dimensions is the size of a few nanometers, where 1,000,000,000 nm is equivalent to 1 m. They are very long, thin tubes made up of carbon atoms and are used in the manufacture of very strong, lightweight materials. Further, they have applications in products such as bicycles, helmets, aircraft, cars, and computer motherboards.[ii]
Moreover, some variants share similar properties with asbestos, such as a high aspect ratio (length/diameter ratio) and biopersistent properties, meaning that they are not easily cleared from the lungs after inhalation.
In this study, in mice, long carbon nanotubes were placed in the pleural lining of the lung, which is the most common place for mesothelioma to develop in humans. Mice have an average lifespan of two to three years and develop mesothelioma within two years of initial exposure. They were therefore monitored for up to 20 months, and the different stages of disease development were studied.
In different groups of mice, between 10% and 25% developed mesothelioma. Long-term inflammation was observed in the pleural space, leading to inactivation and loss of the specific genes that suppress the formation of mesothelioma tumours. Nevertheless, Professor Anne Willis stated that:
‘The immune system does a good job of recognising shorter, thicker or tangled up nanotubes. Special cells break down these types of fibre and clear them out of the body, so not all nanofibres pose a hazard’.[iii]
The research concludes that, even though the findings were not replicated in humans, given the increase in manufacturing of long carbon nanotubes and the potential for human exposure, their observations reinforce the need to ‘inform manufacturers and regulators about safer options and contribute to a ‘Safe by Design’ approach when a nanofibre is being selected for the production of nanomaterials for emerging technologies’.
Reflecting on the results, senior author, Professor Marion MacFarlane said:
‘Unlike previously reported short-term studies, this is the first time the mesothelioma-causing effects of long and thin carbon nanotubes have been monitored in mice over many months … This research could help us define key indicators for early detection as well as provide information for developing targeted therapies for this devastating disease.’
[i] Chernova, T. et al. Long-Fiber Carbon Nanotubes Replicate Asbestos-Induced Mesothelioma with Disruption of the Tumor Suppressor Gene Cdkn2a (Ink4a/Arf). Current Biology 27, 3302–3314.e6 (2017). <http://www.cell.com/current-biology/fulltext/S0960-9822(17)31171-5> accessed 14 November 2017.
[ii] Subset of carbon nanotubes poses cancer risk similar to asbestos in mice. Science Daily, 6 November 2017. https://www.sciencedaily.com/releases/2017/11/171106132018.htm
[iii] Dr Zara Kassam, Carbon nanotubes may pose cancer risk similar to asbestos (7 November 2017 European Pharmaceutical Review) <https://www.europeanpharmaceuticalreview.com/news/69034/carbon-nanotubes-cancer-asbestos/> accessed 14 November 2017.