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Characterizing and discriminating airborne amphibole cleavage fragments and amosite fibers: implications for the NIOSH method.

Wylie AG; Virta RL; Russek E
Am Ind Hyg Assoc J 1985 Apr; 46(4):197-201
A study was designed to provide criteria for discriminating between airborne amphibole cleavage fragments and amphibole asbestos (1332214) fibers. Sixteen air monitoring filters were taken from two industrial sites where amosite (12172735) alone was used, and 11 air monitoring filters were collected from three mine sites where amphiboles were major constituents of the country rock. Scanning electron microscopy and energy dispersive X-ray analysis were done on about 1000 particles from each area sampled. Discriminant function analysis was performed to distinguish between amosite and cleavage fragments. Some general observations were drawn from the data. There were dimensions that were common to both airborne amphibole cleavage fragments and amosite asbestos fibers. Amosite fragments which were wide and had low aspect ratios resembled cleavage fragments, and cleavage fragments with narrow widths and high aspect ratios resembled amosite fibers. A fairly small percentage of total airborne particles could not be differentiated based on dimensions. Amosite fibers were generally wider with lower aspect ratios than other forms of commercial asbestos (crocidolite and chrysotile). However, only 19 percent of the airborne amosite fibers were indistinguishable from cleavage fragments. The findings suggest that an appropriate definition of a regulatory fiber would be a particle longer than 5 microns with a width less than 3 microns and an aspect ratio of 20:1 or greater. With these criteria, the currently used method would be greatly improved in its precision. An aspect ratio of 20:1 suggests reducing the current exposure limits from 2 to 1 fiber per milliliter, resulting in an overall reduction in amosite exposure.
Mineral-dusts; Particulate-dust; Airborne-particles; Dust-exposure; Dust-particles; Asbestos-mining; Asbestos-fibers; Fibrous-dusts; Airborne-fibers; Mining-industry; Air-sampling; Airborne-dusts; Analytical-methods; Microscopic-analysis
Publication Date
Document Type
Journal Article
Fiscal Year
Identifying No.
OP 55-85
Issue of Publication
NIOSH Division
Source Name
American Industrial Hygiene Association Journal
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division