Asbestos content of dust encountered in brake maintenance and repair

Our plain-English summary of Asbestos content of dust encountered in brake maintenance and repair, by A.N. Rohl, A.M. Langer, R. Klimentidis, et al (Proceedings of the Royal Society of Medicine, 1977).

The study

• Authors: A.N. Rohl, A.M. Langer, R. Klimentidis, M.S. Wolff, I.J. Seilikoff
• Journal: Proceedings of the Royal Society of Medicine
• Published: 1977;70(1):32-7
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002698).

Summary of the article

The authors examined whether chrysotile asbestos, which makes up about 50% of automotive brake lining friction material, survives braking, and how much is released into the air during brake maintenance and repair. Ten brake drum dust samples from New York City repair shops were examined by optical microscopy, X-ray diffraction, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy. A further 29 samples came from four European countries and Australia. By X-ray diffraction, chrysotile was found in 29 of the 39 samples. Mean content ranged from 1.4% in Australian samples to 4.5% in New York City samples, where the range was 2 to 15%. The breakdown product forsterite was not unambiguously detected. TEM showed chrysotile fibres in all 39 samples, mostly with unaltered form and crystal structure. In New York samples about 80% of chrysotile was in free fibril form shorter than 0.4 µm, too small for optical microscopy. Personal air sampling was carried out in New York City automobile, taxi fleet and municipal truck repair shops. Blowing dust from brake drums with compressed air gave a mean peak of 15.0 fibres/ml (range 6.6-29.4) at 1-1.5 m, with measurable levels up to 22 m away. Grinding used truck linings gave 1.7-7.0 fibres/ml, and bevelling new linings gave a mean of 37.3 fibres/ml (up to 72). The authors concluded that exposure was significant. They called for exposure controls, clinical studies of garage mechanics and mortality studies of exposed workers.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

The authors examined whether chrysotile asbestos in brake linings survives braking and how much reaches the air during brake work. They analysed 39 brake drum dust samples, 10 from New York City repair shops and 29 from Great Britain, West Germany, France, Finland and Australia. X-ray diffraction found chrysotile in 29 of the 39. In the New York samples it made up 2 to 15 percent by weight (average 4.5). Electron microscopy found chrysotile fibres in all 39 samples, mostly structurally intact, and forsterite, a heat breakdown product, was not clearly detected. About 80 percent of the chrysotile in the New York dusts was free fibrils shorter than 0.4 micrometres. In New York City personal air samples, average peak fibre concentrations were 15.0 fibres per millilitre (range 6.6 to 29.4) within 1 to 1.5 metres of compressed-air blowing of car brake drums. They were 4.8 (1.7 to 7.0) for grinding used truck linings and 37.3 (23.7 to 72.0) for bevelling new truck linings. The authors concluded that brake servicing involved significant exposure, and they called for exposure controls and studies of disease in mechanics.

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: Laboratory analysis of brake drum dust samples (X-ray diffraction, optical and transmission electron microscopy) combined with personal air sampling during brake repair work
• Who was studied: 39 brake drum dust samples: 10 from brake repair shops in New York City and 29 collected in Great Britain, West Germany, France, Finland and Australia. Personal air samples were taken at automobile repair shops, taxi fleet repair shops and a municipal truck repair shop in New York City.
• Exposure: Chrysotile asbestos from automotive and truck brake linings, which the authors describe as about 50% of the friction material. Exposures were measured during compressed-air blowing of brake drums, grinding of used truck linings and bevelling of new truck linings.
• Main results:
  • In the 10 New York City dust samples, X-ray diffraction detected chrysotile in all samples, at an estimated 2 to 15 weight percent (average 4.5)
  • Across all 39 dust samples, X-ray diffraction found chrysotile in 29 (about three-fourths)
  • Forsterite, the thermal breakdown product of chrysotile, was not unambiguously detected in any sample
  • Transmission electron microscopy found free chrysotile fibre bundles and fibrils in all 39 dust samples
  • Most of the chrysotile in the dust samples retained its characteristic form without significant alteration
  • In the 10 New York City dusts, about 80% of the chrysotile was in free fibril form and shorter than 0.4 micrometres
  • Chrysotile was identified by electron microscopy in all 8 personal air samples selected from brake repair work. The authors judged that standard OSHA optical fibre counts may be only indicative of total asbestos exposure.
  • Automobile brake repair, blowing dust from brake drums at 1 to 1.5 m: 4 samples, mean peak fibre concentration 15.0 fibres per ml (range 6.6 to 29.4)
  • Truck brake repair, grinding used linings: 10 samples, mean 4.8 fibres per ml, with breathing-zone concentrations of 1.7 to 7.0 fibres per ml
  • Truck brake repair, bevelling new linings: 4 samples, mean peak fibre concentration 37.3 fibres per ml (range 23.7 to 72.0)
• The authors' conclusion: The authors concluded that significant exposure exists during brake servicing. They called for industrial hygiene controls, clinical studies of garage mechanics, and mortality studies of exposed workers.

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Brake Lining, X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), Forsterite, Crystal Structure, Fibril.

Related studies

• Asbestos content of dust encountered in brake maintenance and repair — W.J. Smither (1977)
• Asbestos content of dust encountered in brake maintenance and repair — M.L. Newhouse (1977)
• Asbestos exposure during brake lining maintenance and repair — A.N. Rohl, A.M. Langer, et al. (1976)
• Asbestos dust exposure during brake repair — K. Rödelsperger, H. Jahn, et al. (1986)
• Exposure to brake dust and malignant mesothelioma: a study of 10 cases with mineral fiber analyses — K.J. Butnor, T.A. Sporn, et al. (2003)
• Evaluation of the fate and pathological response in the lung and pleura of brake dust alone and in combination with added chrysotile compared to crocidolite asbestos following short-term inhalation exposure — D.M. Bernstein, R.A. Rogers, et al. (2015)

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