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Abstract
An estimated 150,000 brake mechanics and garage workers in the U.S. are potentially exposed to asbestos, a known health hazard. Earlier studies of airborne asbestos exposures to mechanics during brake maintenance operations showed overexposure to asbestos fibers during brake servicing, especially brake assembly cleaning. Most brake service operations are performed by small businesses that lack resources to evaluate control devices.
The results from the evaluation of five control methods for containing asbestos brake dust during brake maintenance are presented. These controls included two commercial enclosure devices with ventilation provided by high-efficiency particulate air (HEPA) filter-equipped vacuums, a HEPA filter-equipped vacuum cleaner without an enclosure, a wet brush/recycle system which recirculated the cleaning solution, and an aerosol spray for wetting the brake assembly. Detailed surveys of the controls were conducted at five separate facilities during actual brake servicing operations to automobiles, pickup trucks, vans, and vehicles with a four-wheel rear axle. Personal and area air samples collected during brake repair to each vehicle were analyzed by phase contrast microscopy (PCM) and transmission electron microscopy (TEM).
Personal sampling results for the brake mechanics show that concentrations determined by PCM analysis ranged from less than 0.004 f/cc to 0.016 f/cc. All exposures were below the National Institute for Occupational Safety and Health (NIOSH) recommended limit of 0.1 f/cc. Analysis by TEM indicated not only the presence of asbestos fibers not detected by PCM but also at levels well below 0.1 f/cc. The highest exposures measured were found for workers servicing heavy duty trucks.
The results from this study indicate that all the devices tested, in combination with the work practices used, controlled the mechanics' asbestos exposure during brake servicing to less than the NIOSH recommended exposure limit and the Occupational Safety and Health Administration permissible exposure limit.
