Effects of Nanotubes May Lead to Cancer, Study Says
Wednesday, May 21, 2008
Microscopic, high-tech "nanotubes" that are being made for use in a wide variety of consumer products cause the same kind of damage in the body as asbestos does, according to a study in mice that is raising alarms among workplace safety experts and others.
Within days of being injected into mice, the nanotubes -- which are increasingly used in electronic components, sporting goods and dozens of other products -- triggered a kind of cellular reaction that over a period of years typically leads to mesothelioma, a fatal form of cancer, researchers said.
Only longer versions of the vanishingly small fibers have that toxic effect, the study found. And further experiments must be done to prove that the engineered motes can cause problems when inhaled, the way most people might be exposed to them.
But the preliminary evidence of cancer risk is strong enough to justify urgent follow-up tests and government guidance for nano factory workers, who are most likely to be exposed, experts said. Others called for labels to guide consumers or recyclers, who might encounter the material when incinerating or otherwise destroying discarded nano products.
"In a sense, we are forewarned and forearmed now with respect to nanotubes," said Anthony Seaton of the Institute of Occupational Medicine in Edinburgh, Scotland, who contributed to the research, published in yesterday's online edition of the journal Nature Nanotechnology. "We know that some of them probably have the potential to cause mesothelioma. So those sorts of materials need to be handled very carefully."
The research comes at a crucial time in the science, business and regulation of nanotechnology, a promising new field that involves the creation of particles a few billionths of a meter in diameter.
Such minuscule bits of material behave very differently than larger pieces of the very same substances. So while some kinds of carbon in chunks do not conduct electricity well, for example, nanotubes made of carbon atoms conduct it easily, making them useful in computer components and other materials that would be harmed by a buildup of static charges.
Companies around the world have begun to churn out thousands of tons of nanomaterials per year, including nanotubes, spherical nanoscale "Buckyballs" and other engineered specks called quantum dots, which show promise in medical diagnosis. Nanotubes alone are expected to be a $2 billion industry within the next few years.
But that production frenzy has raised concerns because the materials are being regulated on the basis of what they are made of -- such as "carbon" -- even though, by virtue of their size, some pose very different health and environmental risks.
The amount of government money going into environmental and health impacts of nanomaterials has been far outweighed by federal spending to support the fledgling industry. That is an issue Congress is currently wrestling with as it prepares to reauthorize the National Nanotechnology Initiative, which has been pumping about $1.5 billion a year into research, with only about 5 percent focused directly on health and safety.
"We've got to have the right research and really fast," said Andrew Maynard of the Project on Emerging Nanotechnologies in Washington, a co-author of the new research report. "We've got to have a strategy in place. But no matter what the government says, if you look at it, there is not a clear vision of where they need to be or a plan of how to get there."
The new study, led by Ken Donaldson of the MRC/University of Edinburgh Centre for Inflammation Research, tracked the short-term effects of various kinds of carbon nanotubes and asbestos fibers injected into the animals' abdomens, near the mesothelium, tissue surrounding the lungs and other organs. The mesothelium is where certain kinds of asbestos fibers tend to migrate after being inhaled. The longer nanotubes caused granulomas, early cellular changes that can eventually lead to cancer.
"We need information about exposure to these materials in the workplace," Donaldson said. Unfortunately, Maynard added, scientists have not even agreed on what the best method is for measuring airborne levels of nanotube dust.
Brooke Mossman, a professor who heads the University of Vermont's environmental pathology program, said she was not persuaded by the experiment, because no one knows whether the doses used reflect realistic conditions and because the nanotubes were injected instead of inhaled.
"The system is so artificial, it's hard to evaluate what to make of this," she said. She also said that granulomas are a common reaction to irritants and do not necessarily portend cancer.
Seaton, in a media briefing, countered that granulomas formed by fibers in the mesothelium always progress to cancer.
Vicki Colvin, who heads the Center for Biological and Environmental Nanotechnology at Rice University, said that although the research "indicates that we should be handling these materials with a great deal of caution," it was her impression that most manufacturers are already using gloves and masks and other protections that are probably adequate. "I think they are taking control measures very seriously," she said.
But she agreed with others that because industry has been less than forthcoming about what exactly it is making and by what processes, little is known about the risks that workers and the public may face.
"I think we are really coming to a critical juncture relating to transparency and stewardship," said John M. Balbus, health program chief at the Environmental Defense Fund, which has been collaborating with big nanotech companies such as DuPont to create safety principles for the industry. "We will see whether various companies are going to be proactive and up front with people, and communicate openly in a way that inspires confidence and not repeat mistakes that other industries made in the past where there was too much denial and it comes back to haunt them."