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Further evidence linking nanoparticles to mesothelioma

New research has confirmed that carbon nanotubes — straw-like cylinders of pure carbon used to manufacturer a growing number of consumer products — can be just as dangerous as asbestos fibers when inhaled.


In the latest in a series of studies on the health effects of nanotubes, researchers at Queen's Medical Research Institute at the University of Edinburgh’s MRC Centre for Inflammation Research found that short carbon nanotubes, when injected into the pleural cavities of mice, are relatively harmless.


Longer nanotubes, however, were more likely to become lodged in the lung lining and ultimately lead to mesothelioma, an incurable disease caused by the inhalation of asbestos fibers.


The study, published in the American Journal of Pathology, underscores the need for the design of safe nanofibres that are long enough to be useful but short enough to avoid causing disease, said Ken Donaldson, professor of respiratory toxicology at the University of Edinburgh.


“The industrial-scale manufacture of carbon nanotubes is increasing,” Donaldson said. “This research shows that there is a potential hazard in the manufacture of certain types of carbon nanotubes.”


In an earlier study, in 2008, Donaldson and his colleagues injected long and short carbon nanotubes, long and short asbestos fibers, and carbon black into the abdominal cavity of mice to measure the pathological responses. "The results were clear," he concluded. "Long, thin carbon nanotubes showed the same effects as long, thin asbestos fibers."


First discovered in 1991, nanotubes are about 1/50,000th the width of a human hair and resemble asbestos fibers in size and shape. Ounce for ounce, they are among the strongest materials known — 117 times stronger than steel and 30 times stronger than Kevlar, the material used in bulletproof vests – and have a high conductivity for heat and electric current. They are being used to make everything from electronics to building materials to sports equipment to medical devices.


While there is no evidence to date of adverse effects in workers making or using carbon nanotubes, nanotubes were found in four of seven first responders to the 2001 World Trade Center attacks who developed severe respiratory impairment.


In 2010, the National Institutes for Occupational Safety and Health reviewed the scientific evidence on nanotube exposure, including in vivo studies linking it to pulmonary inflammation and fibrosis in rodents. The agency set a preliminary recommended exposure limit of 7 micrograms per cubic meter of air in late 2010, and urged investigators and the industry to gather more data on workplace exposures and the measures currently being used to reduce potential health risks.