NIOSH Taking Comments on Asbestos Research Plans

The agency's revised "current intelligence bulletin" for asbestos fibers and other elongate mineral particles explains what NIOSH still wants to explore and also clarifies the 1990 NIOSH recommended exposure limit for airborne asbestos fibers.

How many U.S. workers are still exposed to asbestos fibers on the job is unknown, but OSHA estimated in 2008 that 1.3 million workers in construction and general industry may face significant exposures. NIOSH now has released a revised current intelligence bulletin for asbestos fibers and other elongate mineral particles in which the agency explains what it still wants to research and clarifies the 1990 NIOSH recommended exposure limit (REL) for airborne asbestos fibers.

That REL, 0.1 airborne asbestos fibers per cubic centimeter, has created confusion over which materials included in the NIOSH definition are "asbestos" and whether the definition is optimal for protecting workers' health. The revised document, for which NIOSH seeks comments by April 16, clarifies but does not change the exposure limit. The REL now is "0.1 countable elongate mineral particles from one or more covered minerals per cubic centimeter averaged over 100 minutes where:

  • A countable elongate mineral particle (EMP) is an fiber or fragment of a mineral longer than 5 um with a minimum aspect ratio of 3:1 when viewed microscopically using NIOSH Analytical Method #7400('A' rules) or its equivalent; and
  • A covered material is any mineral having the crystal structure and elemental composition of: one of the asbestos varieties (chrysotile, riebeckite asbestos [crocidolite], cummingtonite-grunerite asbestos [amosite], anthophyllite asbestos, tremolite asbestos, and actinolite asbestos) or one of their nonasbestiform analogs (the serpentine minerals antigorite and lizardite, and the amphibole minerals contained in the cummingtonite-grunerite mineral series, the tremolite-ferroactinolite mineral series, and the glaucophane-riebeckite mineral series.)"

The document contains a framework for NIOSH research indicating the agency wants to develop a broader understanding of the important determinants for toxicity of asbestos fibers and other EMPs, and wants to know more about occupational exposures to them. A chart included in the executive summary portion of the draft indicates U.S. imports of asbestos have dropped sharply from 35,000 metric tons in 1991 to under 3,000 metric tons in 2006 and 2007, with domestic production having ceased in 2003. But worldwide use stood at 2 million metric tons as recently as 2006, mainly for use in building materials, according to the draft.

About 1,500 people die from asbestosis annually in the United States. Because of the long latency period between exposure and related disease, "asbestosis deaths in the United States are anticipated to occur for several decades," according to the draft.

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