Therefore, a group of researchers conducted four separate tests in order to evaluate an auto mechanic, exposure to airborne
asbestos fibers while performing routine brake maintenance. Four nearly identical automobiles from 1960s having four wheel drum
brakes were used. Each automobile was fitted with new replacement asbestos-containing brake shoes and then driven over a predetermined public road course for about 2253 km. Then, each car was separately brought into a repair facility; the brakes removed and replaced with new asbestos-containing shoes. The test conditions, methods, and to;  were as commonly used during the 1960s. The mechanic was experienced in brake maintenance, having worked in the automobile repair profession beginning in the 1960s. Effects of three independent variables, e.g., filing, sanding, and arc grinding of the replace shoe elements, were tested. Personal and area air samples were collected and analyzed for the presence offibers, asbestos fibers, total dust, and respirable dust.

The results indicated a presence in the air of only chrysotile asbestos and an absence of other types of asbestos. Airborne chrysotilefiber exposures for each test remained below currently applicable limit of 0.1 fiber/rrl (eight-hour time-weighted average).