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NIOSH Proposes Exposure Limits for Carbon Nanotubes

BY Gwyneth K. Shaw | DEC 7, 2010 11:20 AM

(NHI Nanoblog) The National Institute for Occupational Safety and Health has put out draft recommendations for protecting workers from carbon nanotubes and nanofibers, including the first exposure limit level for the tiny materials.

NIOSH, a division of the federal Centers for Disease Control, has been a leader in conducting and analyzing research about a variety of nanomaterials, with an eye on creating a framework for workplace safety. Carbon nanotubes—super-small cylinders of carbon that are prized for their strength and ability to both insulate and conduct electricity—have been on the agency’s radar screen for some time.

CNTs are a hot item in the nanotechnology field, and are becoming increasingly common, in things like electronics, lithium-ion batteries, and solar cells.

They’ve also raised a number of safety concerns, mostly because they’re small enough to be inhaled—but often, not big enough to be seen.

Research has shown that once in the lungs, nanotubes can lodge there. In mice, the tubes are known to cause fibrosis. And the substance can reach the same space in the lungs where mesothelioma, a serious lung disease that’s mostly associated with asbestos exposure, turns up.

But only two studies offered useful information about what carbon nanotubes do to people, said said Paul Schulte, director of the Education and Information Division at NIOSH.

NIOSH is proposing a limit of seven micrograms of nanotubes or nanofibers per cubic meter of air over the course of an eight-hour shift, and encourages employers to work to keep exposure below even that level. Seven micrograms is basically the smallest amount that’s detectable using the agency’s sampling mechanism, Schulte said.

In addition, the agency wants manufacturers to take a number of precautions, ranging from educating workers who might be exposed to the materials to using a host of controls to prevent the substances from reaching employees in the first place. These include using proper ventilation in rooms where the tubes are produced as well as adding personal protection, such as respirators, protective suits and gloves, for workers when the environmental controls are not enough to get the exposure level below the proposed limit.

Workers also should change their clothes and wash any exposed areas before heading home, according to the recommendations.

Every company that makes these substances might not have the equipment needed to protect their workers to this extent, Schulte said, but the recommendation is definitely “doable” for the industry.