They’re used to make plastics stronger and aircraft bodies lightning resistant. Tiny carbon nanoparticles help make light bulbs produce more natural light and better wires to carry electricity. But despite their widespread use in industry, there haven’t been any US guidelines on protecting workers who might inhale nanoparticles.
Federal health experts released new guidelines on Wednesday for carbon nanotubes and nanofibers, giving clear advice on how much it’s safe to breathe in and how workers can help protect themselves.
The effects of these microscopic particles can be similar to silica dust and asbestos when inhaled, says Charles Geraci of the National Institute for Occupational Safety and Health (NIOSH). They can nesGtle deep into tender lung tissue, causing inflammation and a scarring known as pulmonary fibrosis – at least in animals. There isn’t much good data on what they do to people.
But NIOSH says that doesn’t mean industry shouldn’t protect workers now.
“We need to protect workers by eliminating or reducing exposure,” Geraci said in a telephone interview. So his team reviewed tests on animals and determined that people should not breathe in any more than one microgram of carbon nanotubes or nanofibers per cubic liter of air per eight-hour working day.
It also suggests that employers send workers for lung tests if they've been exposed to high concentrations of nano-dust.
"I think it's significant that NIOSH recommends that employers implement medical screening and surveillance," says Chris Trahan, deputy director of CPWR—The Center for Construction Research and Training. She says the recommendation look similar to some of those made for workers exposed to asbestos.
Trahan, who has been watching for the guidelines, says the particles can also be released in construction and when workers take apart airplanes, for instance. "Sanding, sawing orgrinding -- they don't just disappear once they are used," she said.
It’s a broad guideline but the first for an industry that’s been growing with very little regulation and little research to show whether the powerful little particles pose any particular danger.
They’re so small that people can be exposed by breathing them in, swallowing them, or getting them on the skin. “These materials are very different in their physical state. They are extremely small. They almost float in the air at times,” Geraci says.
A carbon nanotube is a sheet of carbon atoms rolled into a six-sided tube. These little structures are 10,000 times smaller than a human hair in diameter, but their size and shape gives them unique physical, electrical, optical and thermal properties.
“There is no single type of carbon nanotube or nanofiber; one type can differ from another in shape, size, chemical composition,” the report reads.
The guidance warns workers against trying to sweep up dry nanoparticles – that can puff them up into the air to be breathed in or carried on the clothes. Food shouldn’t be put down on a surface that might also have nanoparticles on it. Air should be filtered.
NIOSH, part of the Centers for Disease Control and Prevention, has no estimate of how many workers are exposed to nanoparticles. But they are used now in countless industries, often to strengthen plastic, Geraci says.
“Carbon nanotubes are being used to increase the efficiency of solar cells,” he said. “An aircraft cabin that uses carbon nanotubes in the fuselage will survive a lightning strike much better than most do now.”
Carbon nanotubes are used to make tougher, lighter data transmission cables, are used in making semiconductors and in new ways of delivering drugs to the body.
Because they are almost always incorporated into something else by the time they reach the market, they are not a threat to most of the general public. It’s the workers in factories that NIOSH is worried about.