Asbestos exposure during servicing of motor vehicle brake and clutch assemblies (Current Intelligence Bulletin 5)

Our plain-English summary of Asbestos exposure during servicing of motor vehicle brake and clutch assemblies (Current Intelligence Bulletin 5) (1975).

The study

• Published: National Institute for Occupational Safety and Health (NIOSH), Center for Disease Control, U.S. Department of Health, Education, and Welfare, Rockville, Maryland; Current Intelligence Bulletin 5, August 8, 1975
• Type of article: Government report
• Our copy: from Johns-Manville's own medical library.

In plain English

This document was not a research study. It was a NIOSH (National Institute for Occupational Safety and Health) bulletin dated August 8, 1975, warning of a potential asbestos hazard during servicing of motor vehicle brake and clutch assemblies. It reported data that Mount Sinai School of Medicine investigators presented at a NIOSH meeting on July 21, 1975. In personal air samples taken within ten feet of the worker, average peak asbestos concentrations were 10.5 fibers per ml for blow-out of automobile drum brakes, 3.75 for grinding used truck brake linings, and 37.3 for bevelling new truck brake linings. The bulletin, as scanned, describes the fibers counted as '5 microns in length'. In brake drum dust, almost all asbestos fibers found were shorter than 0.4 microns. The bulletin said brake servicing workers had not been studied systematically. It noted that a literature review found at least four cases of mesothelial tumors of the pleura and peritoneum in people employed in automobile brake servicing. It set out interim NIOSH procedures, including high-efficiency vacuum cleaning and a ban on compressed air or dry brushing.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Government alert bulletin (NIOSH Current Intelligence Bulletin). It reports measurement data presented at a meeting, refers to case reports in the earlier literature, and gives interim recommended procedures. It is not an original study.
• Who was studied: Workers who maintained and repaired automobile and truck brake linings, as studied by investigators from the Mount Sinai School of Medicine in New York City. The number of workers or samples is not given.
• Exposure: Airborne asbestos dust (fiber type not specified) during three jobs: blow-out of automobile drum brake assemblies, grinding of used truck brake linings, and bevelling of new truck brake linings. Clutch servicing is also covered in the recommendations.
• Main results:
  • Average peak asbestos air concentrations, from personal samples taken within ten feet of the operator, were 10.5 fibers per ml for drum brake blow-out, 3.75 for grinding used truck linings, and 37.3 for bevelling new truck linings. The scanned text describes these as fibers '(5 microns in length)'.
  • In samples of brake drum dust, almost all asbestos fibers found were shorter than 0.4 microns in length.
  • A review of the scientific literature found at least four cases of mesothelial tumors of the pleura and peritoneum in persons who had been employed in jobs involving automobile brake servicing. These cases come from earlier published studies.
  • NIOSH's interim procedures called for cleaning dust with an industrial vacuum cleaner fitted with a high-efficiency filter, then a damp rag. They prohibited compressed air and dry brushing, and called for respirators, warning signs, and labeled sealed disposal of asbestos waste.
• The authors' conclusion: The bulletin concluded that enough asbestos survives in brake dust to produce significant exposures during certain brake servicing procedures. Earlier studies had found only a very small fraction of the original asbestos in brake drum dust.
• Limitations the authors state:
  • The full extent of asbestos-related disease in brake servicing workers was not known, because this group had not been studied systematically.
  • The procedures were interim and subject to revision pending ongoing NIOSH research.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, NIOSH, Brake Lining, Pleura, Peritoneum.

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