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Investigation of asbestos exposures associated with vermiculite expansion and vermiculite use in production of industrial and horticultural products.

Hewett D
American Industrial Hygiene Conference and Exposition, June 1-6, 2002, San Diego, California. Fairfax, VA: American Industrial Hygiene Association, 2002 Jun; :51
The former W.R. Grace mine in Libby, Montana was so contaminated by asbestos that the company eventually closed the mine. More recently, the Environmental Protection Agency (EPA) began exposure assessments to determine health risks associated with asbestos from vermiculite remaining in the area. In light of the concern over the Libby Montana deposit, the Occupational Safety and Health Administration (OSHA) requested NIOSH investigate worker exposures to asbestos at plants where vermiculite is expanded and mixed and at horticultural operations where expanded vermiculite is mixed. Major sources of vermiculite were determined and users were identified. Exposure assessments were performed at numerous sites and samples were split between OSHA, NIOSH, and EPA to apply different analytical methods to the quantification of asbestos. Air samples were analyzed by EPA with NIOSH Manual of Analytical Methods (NMAM) 7400 Asbestos and Other Fibers by PCM, ASTM D 5755-95 Microvacuum Sampling and Indirect Analysis of Dust by TEM for Asbestos Structure Number Concentrations and International Standard ISO 10312 Ambient air-Determination of asbestos fibres-Direct-transfer transmission electron microscopy method. Air samples were analyzed by OSHA with ID 160 Asbestos in Air, and analyzed by NIOSH by NMAM 7400, 7402 Asbestos by TEM and 7402 (modified) where fibers less than 0.25 microns are counted. Bulk samples were analyzed by EPA with EPA/600/R_93/116 Method for the Determination of Asbestos Building Materials, by OSHA with ID 191 Polarized Light Microscopy of Asbestos, and by NIOSH by NMAM 9002 Asbestos (bulk) by PLM. This presentation describes the approach that was taken to identify facilities for investigation, and sampling and analytical issues that arose from the investigation.
Asbestos-fibers; Asbestos-mining; Asbestos-workers; Exposure-levels; Health-hazards; Workers; Analytical-methods; Air-samples
Publication Date
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Fiscal Year
NIOSH Division
Priority Area
Research Tools and Approaches: Exposure Assessment Methods
Source Name
American Industrial Hygiene Conference and Exposition, June 1-6, 2002, San Diego, California
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division