Assessment of Asbestos Exposure Associated with a Brake Grinder

The wear patterns for drum-style automotive brakes tend to enlarge internal drum diameters. Such enlargement is most profound when used brake drums are machined restore the metal friction surfaces. Specialized arc grinding machinery has been match replacement shoe-style materials enlarged drums. process of removes material, thereby producing dust. When organic-style contained asbestos, use posed an asbestos fiber exposure risk operators and proximate personnel. manufacturers have incorporated local exhaust ventilation systems designed capture remove this dust at point contact propel into collection bags or other systems. This research was evaluate retention characteristics a specific grinder product, custom grind asbestos-containing materials. A Bear Model 1420 shoe subject study. During two separate but consecutive test sessions, newly relined sets automobile were precision ground. Both area personal air samples collected throughout each testing session. work took place within closed unventilated building, with total interior volume 2500 m3. Collected analyzed using phase contrast microscopy (PCM) transmission electron (TEM). results analysis PCM (n = 6) ranged from <0.044 0.055 fibers per cc (f/cc) (mean 0.05). Follow-up these TEM indicated asbestos-adjusted exposures ranging <0.0074 f/cc ≤ 0.041). Area samples, taken distances 1.5 9 meters 12), showed concentrations <0.0075 0.041 0.017). shoe-style, can cause airborne fibers. However, done properly equipped machines, such not expected exceed current occupational limits 0.1 8-hour time-weighted average (TWA) 1.0 30-minute average.