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Carbon nanotubes behave like asbestos, study shows
A new study published by Nature Nanotechnology shows that inhaling long, thin carbon nanotubes may result in asbestos-related disease.
By Ann Steffora Mutschler, Senior Editor -- Electronic News, 5/21/2008
In a wakeup call for nanotechnology in general and carbon nanotubes in particular, a major study published in Nature Nanotechnology suggests some forms of carbon nanotubes -- a poster child for the “nanotechnology revolution” -- could be as harmful as asbestos if inhaled in sufficient quantities, according to the Project on Emerging Nanotechnologies, an initiative launched by the Woodrow Wilson International Center for Scholars and The Pew Charitable Trusts in 2005.
The Project on Emerging Nanotechnologies is tasked with helping business, government and the public anticipate and manage possible health and environmental implications of nanotechnology.
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Led by Professor Kenneth Donaldson at the University of Edinburgh in the UK, a team of researchers examined the potential for long and short carbon nanotubes, long and short asbestos fibers, and carbon black to cause pathological responses known to be precursors of mesothelioma. Material was injected into the abdominal cavity of mice -- a sensitive predictor of long fiber response in the lung lining.
“The results were clear. Long, thin carbon nanotubes showed the same effects as long, thin asbestos fibers,” Donaldson asserted in a statement.
Asbestos fibers are harmful because they are thin enough to penetrate deep into the lungs, but sufficiently long to confound the lungs' built-in clearance mechanisms for getting rid of particles.
Carbon nanotubes, discovered nearly 20 years ago, have been described as the wonder material of the 21st century, and that they are as light as plastic and stronger that steel, they are being developed for use in new drugs, energy-efficient batteries and futuristic electronics.
Carbon nanotubes are atom-thick sheets of graphite formed into cylinders that can be formed from a single layer of graphite or consist of multiple concentric layers of graphite, resulting in multi-walled carbon nanotubes. The diameter of a nanotube can vary from a few nanometers up to tens of nanometers, and can be hundreds or even thousands of nanometers long. Carbon nanotubes come in many forms, with different shapes, different atomic arrangements, and varying amounts and types of added chemicals -- all of which affect their properties and might influence their impact on human health and the environment.
Since their discovery, questions have been raised about whether some of these nanoscale materials may cause harm and undermine a nascent market for all types of carbon nanotubes, including multi- and single-walled carbon nanotubes.
Market researchers have forecast that sales of nanotubes could reach $2 billion annually within the next 4 to 7 years, according to an article in Chemical & Engineering News.
Andrew Maynard, chief science advisor to the project on emerging nanotechnologies and a co-author on the paper commented in a statement, “This study is exactly the kind of strategic, highly focused research needed to ensure the safe and responsible development of nanotechnology. It looks at a specific nanoscale material expected to have widespread commercial applications and asks specific questions about a specific health hazard. Even though scientists have been raising concerns about the safety of long, thin carbon nanotubes for over a decade, none of the research needs in the current US federal nanotechnology environment, health and safety risk research strategy address this question.”
Indeed, widespread exposure to asbestos has been described as the worst occupational health disaster in US history and the cost of asbestos-related disease is expected to exceed $200 billion, according to US think tank RAND Corp.
Dr. Anthony Seaton, a co-author on the paper and a professor emeritus at the University of Aberdeen in the UK asserted, “The toll of asbestos-related cancer, first noticed in the 1950s and 1960s, is likely to continue for several more decades even though usage reduced rapidly some 25 years ago. While there are reasons to suppose that nanotubes can be used safely, this will depend on appropriate steps being taken to prevent them from being inhaled in the places they are manufactured, used and ultimately disposed of. Such steps should be based on research into exposure and risk prevention, leading to regulation of their use. Following this study, the results of which were foreseen by the Royal Society in the UK in 2004, we can no longer delay investing in such research.”
Donaldson stressed that there are still pieces of the puzzle to fill in. “We still don't know whether carbon nanotubes will become airborne and be inhaled, or whether, if they do reach the lungs, they can work their way to the sensitive outer lining. But if they do get there in sufficient quantity, there is a chance that some people will develop cancer -- perhaps decades after breathing the stuff,” he said.
At the same time, Donaldson said there is a silver lining to the research. “Short or curly carbon nanotubes did not behave like asbestos, and by knowing the possible dangers of long, thin carbon nanotubes, we can work to control them. It's a good news story, not a bad one. It shows that carbon nanotubes and their products could be made to be safe.”
However, the present study only tested for fiber-like behavior and did not exonerate carbon nanotubes from damaging the lungs in other ways and more research is needed to understand how to use these materials as safely as possible, he notes.
The paper can be found here.
