Microscopy in the Investigation of Asbestos-Containing Friction Products

2020:175:Millette, Compton, DePasquale

The Microscope, 2020, Volume 68:3/4, pp. 111-131, 2020

Abstract

Bulk analyses of approximately 100 asbestos-containing friction products showed levels of chrysotile ranging generally from 15% to 60% by volume. Small amounts of amphibole asbestos (primarily tremolite) were found in over 95% of the brake and clutch products tested. The amphibole asbestos was present in the range of 0.0001 to 0.4% by weight. Although the levels of amphibole asbestos were less than 1% by weight, the concentration of amphibole fibers was in the millions fibers per gram of friction material in many cases. The results of 11 studies of asbestos fiber release from brake materials, conducted by MVA Scientific Consultants (MVA), involved various activities such as sanding, filing, grinding, rivet removal, drilling, sweeping, compressed-air blowing, brake removal, and handling of contaminated clothing are presented. Following acid/base digestion, amphibole asbestos fibers were found in air samples in two of the studies. An analysis of brake wear dust found chrysotile asbestos fibers but no forsterite.

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