Non-asbestiform Mineral Particles Included In Asbestos Exposure Limit, NIOSH Says

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Some non-asbestiform mineral particles will be included in the recommended exposure limit (REL) for asbestos, the National Institute for Occupational Safety and Health said March 23 in the final version of its road map on asbestos research.

The inclusion of these particles within the limit, set at 0.1 countable elongate mineral particles from one or more covered minerals per cubic centimeter, averaged over 100 minutes, comes despite past opposition from industry associations, such as the National Association of Manufacturers, the National Stone, Sand & Gravel Association, and others.

These groups have commented that eliminating exposures to those particles is not feasible, and that scientific research has not shown them to be harmful (40 OSHR 364, 4/29/10).

NIOSH, however, wrote in the final version of Current Intelligence Bulletin: Asbestos Fibers and Other Elongate Mineral Particles: State of the Science and Roadmap for Research that while it recognizes elongate mineral particles are not asbestos, current analytical methods cannot differentiate between asbestos fibers and other particles in mixed-dust environments.

“Clarification of the REL in this way does not change the existing NIOSH occupational health policy for asbestos, and no regulatory response by [the Occupational Safety and Health Administration] or [the Mine Safety and Health Administration] is requested or expected,” the road map said. “The REL remains subject to revision based on findings of ongoing and future research.”

Future Research.

In addition to the exposure limit, the road map also includes recommendations for developing a better understanding of the determinants of toxicity for asbestos and other elongate mineral particles; for learning more about exposures to both particle groups and their health outcomes; and for improving sampling and analytical methods.

“The NIOSH road map outlines a strategic framework for designing, conducting, and applying the research that will best serve the need to address persistent scientific uncertainties about occupational health and elongate mineral particles,” NIOSH Director John Howard wrote in a March 23 statement. “We look forward to working with our partners to advance this research, building on today's state-of-the-art scientific tools and methodologies.”

Researchers should conduct in vitro and animal studies to learn what particle characteristics, such as surface properties, influence their toxicity, the road map said.

Furthermore, they should conduct selective epidemiologic studies of workers exposed to different types of asbestos and elongate mineral particles, it added.

To support that research, scientists should develop a national reference repository of asbestos and related mineral samples, it said.

Path Forward.

Future asbestos research at NIOSH should lead to occupational safety and health recommendations “based on unambiguous science,” the roadmap said.

To do so, NIOSH plans to partner with other federal agencies, such as OSHA, MSHA, and the Environmental Protection Agency.

One initial project would involve developing a standardized set of terms to clearly describe minerals and establishing a reference repository, it said.

“Achieving the proposed goals will be well worth the investment because it will improve the quality of life of U.S. workers by preventing workplace exposure to potentially hazardous [elongate mineral particles], and it will reduce future healthcare costs,” the road map said.

Another early research effort could focus on collecting information on industries, occupations, and job tasks that involve asbestos exposures; on the number of workers exposed; levels of exposure; and associated particulate exposures, it added.

Finally, new analytical methods should be developed to distinguish between asbestos and elongate mineral particles, as well as to assess the biopersistence of those particles in the lungs.

By Greg Hellman


The NIOSH research roadmap is available at




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