Tuesday, May 10, 2005

Brake Shoe Asbestos Exposures

BrooklynDodger assumes this study was funded to provide data for defense of asbestos liability suits. The Dodger reminds the gentle reader that OSHA estimates a near doubling of lung cancer risk at exposure at the 0.1 fiber/cc limit over a working lifetime. BrooklynDodger opines that these exposure levels are physiologically signficant although the effects may not be epidemiologically signficant.

Evaluation of fibers and total particulate generated during the servicing of drum brakes on motor vehicles as well as during the resurfacing (arcing) of brake shoes was conducted. Phase 1 estimated the release of asbestos fibers and total particulate during brake inspection and replacement of light-duty vehicle rear drum brakes at an auto/truck repair facility. One rear wheel from each vehicle was serviced using compressed air to remove dust while the second rear wheel was serviced without compressed air. Fiber levels without compressed air ranged from 0.05 to 0.2 f/cc. Fiber counts when using compressed air averaged from 0.05 to 0.9 f/cc. Results from real-time aerosol monitoring indicated elevated dust levels for about 15 minutes after blow out. With shop doors open, dust levels increased to 5.0 mg/m3 at blow out and returned to 0.08 mg/m3 within two minutes. When the shop doors were closed, the dust levels reached 13.5 mg/m3 at blow out and decreased to 1.68 mg/m3 within one minute and to background within 14 minutes.

For grinding operations conducted under conditions simulating a workplace, a mean of 0.19 f/cc was determined. Dust levels averaged 0.25 mg/m3 +/- 0.05. Considered on a time weighted average basis, should not exceed currently acceptable workplace standards whether or not the worker uses compressed air, nor during the arc grinding process when arcing is conducted in accord with the design of the equipment.

Appl Occup Environ Hyg. 2001 Dec;16(12):1139-46.

Characterization of vehicular brake service personnel exposure to airborne asbestos and particulate.

Weir FW, Tolar G, Meraz LB.Francis W. Weir, Ph.D, Inc, Houston, Texas, USA.

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