Microscopical Analyses of Asbestos-Containing Fibrous Adhesive

2020:176:Millette

Microscope, Vol 68:2 p.71-79

Millette, Compton, DePasquale

Abstract:

An asbestos-containing, sodium silicate-based fibrous adhesive was applied to insulating materials from the 1940s to the 1970s. Batch formulation sheets for Benjamin Foster 81-27 fibrous adhesive were used to determine that the concentration of chrysotile asbestos in the dried product ranged from 8% to 32%. The application of the thick viscous adhesive is not considered to be a source of airborne asbestos fibers, but the cleanup of the dried material that might fall near workers and on their clothing, bodies, and tools is of concern. Also of concern is the fiber release that occurs during breakup of the fibrous adhesive films during repair work on piping systems. Testing done with reconstituted Foster 81-27 adhesive showed that scraping and sanding of dried 81-27 produced levels in a glove box that ranged up to 0.19 asbestos fibers per cubic centimeter (f/cc) as determined by NIOSH 7400 values modified by NIOSH 7402 asbestos ratios. Brushing the dried 81-27 on denim produced levels up to 0.16 asbestos f/cc and removing the dried 81-27 material brushed onto a polyester cloth with a hammer and chisel, as had been described by workers, produced a level more than 10 f/cc. In another test, breathing-zone air samples were taken from an industrial hygienist, who had removed the 81-27 brushed onto cheesecloth with a hammer and chisel inside a room-size chamber. These samples were overloaded. It was conservatively estimated that the asbestos levels in this test were well over 2 f/cc.

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