Asbestos exposure during brake lining maintenance and repair

Our plain-English summary of Asbestos exposure during brake lining maintenance and repair, by A.N. Rohl, A.M. Langer, M.S. Wolff, et al (Environmental Research, 1976).

The study

• Authors: A.N. Rohl, A.M. Langer, M.S. Wolff, I. Weisman
• Journal: Environmental Research
• Published: 1976;12(1):110-28
• Cited by: 65 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001137).

In plain English

This study measured asbestos in brake dust and in workplace air during brake repair. The authors analyzed ten samples of automobile brake drum dust and took air samples at franchised auto dealer garages, taxi fleet repair shops and a municipal truck repair shop in New York City. X-ray diffraction found chrysotile in all ten dust samples, at about 2 to 15% by weight, averaging about 3 to 6%. Electron microscopy found free chrysotile fibers in all ten, about four-fifths of them shorter than 0.4 micrometers, too small for optical microscopy. In short samples taken while mechanics blew dust out of brake drums with compressed air, fiber levels averaged 16 fibers/ml, and fibers were still measurable 75 feet away and 14 minutes later. Beveling truck brake linings averaged about 37 fibers/ml. Mechanics used no respiratory protection. In eight air samples, optical and electron microscope results were positively correlated, though the data were limited. The authors concluded that standard optical counting may considerably underestimate total asbestos exposure. The study did not examine workers' health.

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: Workplace exposure measurement study: laboratory analysis of brake drum dust plus personal and area air sampling during brake repair work. No health outcomes were studied.
• Who was studied: Ten automobile brake drum dust samples from auto maintenance shops in the New York area. Air samples were taken at franchised auto dealer garages, taxi fleet repair shops and a New York Department of Sanitation truck repair shop in New York City. Air samples came from the breathing zone of brake mechanics and from other areas of the shops.
• Exposure: Chrysotile asbestos from brake linings and brake drum dust, released during: blowing dust out of brake drums with compressed air; cleaning drums with a dry brush; grinding and beveling truck brake linings; punching rivets; chipping rust; and sweeping floors.
• Main results:
  • Chrysotile was detected by X-ray diffraction in all ten brake drum dust samples.
  • Chrysotile made up about 2 to 15% of the brake drum dust by weight, averaging about 3 to 6%.
  • Free chrysotile fiber bundles and fibrils were seen by electron microscopy in all ten dust samples.
  • In the ten dust samples, about four-fifths of chrysotile fibers were shorter than 0.4 micrometers in length.
  • Near mechanics blowing dust from automobile brake drums with compressed air, the average was 16 fibers/ml (optical count). These were peak samples taken over 3 to 8 minutes.
  • After compressed-air blowing, measurable fiber concentrations were found at least 75 feet from the work site and for at least 14 minutes afterward.
  • When brake drums were cleaned with a dry hand brush instead, the operator-level concentration was 2.5 fibers/ml.
  • At the municipal truck shop, grinding truck brake shoes produced an average of about 4 fibers/ml in the operator's breathing zone.
  • Beveling truck brake linings produced an average of 37 fibers/ml.
  • During the beveling sampling, eight to 15 other garage mechanics were working within the area where airborne fibers were found.
  • Workers did not use respiratory protection.
  • In eight air samples, optical fiber counts and electron microscope asbestos mass results showed a positive correlation, judged by visual inspection.
• The authors' conclusion: The authors concluded that potentially hazardous asbestos exposure exists during automotive brake servicing. They also concluded that the standard optical method of counting asbestos fibers may considerably underestimate total asbestos exposure. They recommended stringent industrial hygiene measures to control exposure.
• Limitations the authors state:
  • The optical and electron microscopy comparison rested on limited data, and the scatter was too great for a regression analysis.
  • Particles of pulverized brake lining that contained asbestos were not included in the electron microscopy mass calculation.
  • Optical microscopy was generally not useful for detecting asbestos in brake drum dust.
  • Forsterite, the heat-transformation product of chrysotile, could not be positively identified by X-ray diffraction.
  • The authors stated that further studies are needed to confirm and extend the findings.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Auto mechanics and brake work.

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

Related studies

• Asbestos dust exposure during brake repair — K. Rödelsperger, H. Jahn, et al. (1986)
• Asbestos content of dust encountered in brake maintenance and repair — A.N. Rohl, A.M. Langer, et al. (1977)
• Environmental and occupational health hazards associated with the presence of asbestos in brake linings and pads (1900 to present): a "state-of-the-art" review — D.J. Paustenbach, B.L. Finley, et al. (2004)
• Environmental and occupational health hazards associated with the presence of asbestos in brake linings and pads (1900 to present): A "state-of-the-art" review — S.S. Paskal (2004)
• Personal exposures to asbestos fibers during brake maintenance of passenger vehicles — M.F. Cely-García, M. Sánchez, et al. (2012)
• Asbestos content of dust encountered in brake maintenance and repair — W.J. Smither (1977)

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