Control of Asbestos Exposure During Brake Drum Service (1989)

A 1989 NIOSH field study of mechanics' airborne asbestos exposure during brake drum service at five facilities, testing five ways of controlling the dust: two commercial enclosures ventilated by HEPA-filtered vacuums, a HEPA vacuum alone, a wet brush with recirculating cleaning solution, and aerosol spray cleaners. With the work practices used, every method kept exposures below the OSHA permissible exposure limit and the NIOSH recommended limit as measured by phase contrast microscopy; electron microscopy found fibers the optical method missed, and higher levels during brake work on heavy-duty trucks. The report compares these results with earlier studies of brake cleaning with compressed air and brushes, and estimates that 150,000 U.S. brake mechanics and garage workers were potentially exposed.