NIOSH issues bulletin to limit exposure to certain nanoscale particles
The National Institute for Occupational Safety and Health has issued a Current Intelligence Bulletin to guide employers on protecting employees from overexposure. It marks the first time NIOSH has released two separate guidelines for the same chemical based on size.
Titanium dioxide is a noncombustible, white, crystalline, solid, odorless powder used in many commercial products, such as paint, cosmetics, plastics, paper, and food. The bulletin makes recommendations for occupational exposure limits and suggests techniques for monitoring and controlling worker exposure.
NIOSH recommends exposure limits of 2.4 milligrams per cubic meter for "fine" titanium dioxide and 0.3 milligrams per cubic meter for "ultrafine" titanium dioxide, as time-weighted average concentrations for up to 10 hours per day during a 40-hour workweek. The recommendations represent levels that over a working lifetime are estimated to reduce risks of lung cancer to below 1 in 1,000, according to the bulletin.
NIOSH has determined that ultrafine titanium dioxide is a potential occupational carcinogen but that there are insufficient data at this time to classify fine titanium dioxide as a potential occupational carcinogen.
Bulletins are issued by NIOSH to highlight new scientific information about specific occupational hazards. They are shared with people from academia, industry, organized labor, public health agencies, public interest groups, and other federal agencies.
The titanium dioxide bulletin includes reviews of animal and human data relevant to assessing the carcinogenicity of titanium dioxide. In addition to the recommended exposure limits, it also includes chapters on:
- A quantitative risk assessment using dose-response data in rats for both cancer and noncancer responses and extrapolation to humans with lung dosimetry modeling.
- A description of exposure monitoring techniques and exposure control strategies.
- A discussion of avenues of future research.
The report only addresses occupational exposures by inhalation.
"NIOSH realizes that knowledge about the health effects of nanomaterials is an evolving area of science," the bulletin says. "Therefore, NIOSH intends to continue dialogue with the scientific community and will consider any comments about nano-size titanium dioxide for future updates of this document."
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May 16, 2011
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