Certain types of carbon nanotubes -- microscopic graphite cylinders used in a small but growing number of Space Age applications -- could pose a cancer risk similar to that of asbestos if inhaled, scientists reported Tuesday.
Researchers found that mice injected with nanotubes quickly developed the same biological damage associated with early exposure to asbestos fibers, a known carcinogen.
The study showed "the potential to cause harm if these things get into the air and into the lungs," said coauthor Andrew Maynard, a physicist at the Woodrow Wilson International Center for Scholars in Washington.
Maynard said the nanotubes posed the greatest danger to workers who could inhale the dust-like particles during manufacturing. In finished products, the nanotubes are embedded in other material and thus pose less risk to consumers.
Sean Murdock, head of the NanoBusiness Alliance, an industry trade group based in Skokie, Ill., said precautions were now in place in many factories, usually requiring workers to wear respirators. Nanotubes are largely made in closed chemical reactors, he added.
"The good news is that we're understanding the potential hazards before we have large-scale use of these products and not four decades later," he said.
From the time nanotubes were discovered in the early 1990s, they have been billed as wonder particles for their incredible strength, low weight and ability to conduct heat and electricity.
Nanotubes are starting to be used in some products, including bicycle components, computer displays and car bumpers. Researchers envision them becoming common in medical devices, solar panels and hydrogen fuel cells.
But early on, scientists suspected that certain types of nanotubes could pose the same danger as asbestos fibers, which get stuck in the outer lining of the lung known as the mesothelium.
The damage results when the body's defenses repeatedly try and fail to expel the fibers, eventually leading to mutations that can cause cancer decades later.
In the current study, published in the journal Nature Nanotechnology, nanotubes were injected into the abdominal cavities of mice. The tissue of these cavities is similar to the lining of human lungs.
One group of mice received tubes at least 20 microns long with walls several atoms thick. Other mice got shorter, thinner tubes that were bundled together. A third group was injected with asbestos fibers.
Among the mice killed by researchers after 24 hours, only those that had received asbestos or the longer tubes showed cellular inflammation, the first step in a long process leading to cancer.
Mice in those same groups that were killed after a week showed a buildup of scar-like tissue known as granuloma, another step in the process.
Mice that received the shorter and thinner tubes were unaffected. The researchers speculate that the fibers were small enough to be engulfed and expelled by immune cells.
Most of the nanotubes currently being used are the longer, stiffer variety, researchers said.