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 W.J. Smither (Proceedings of the Royal Society of Medicine, 1977).

The study

• Author: W.J. Smither
• Journal: Proceedings of the Royal Society of Medicine
• Published: 1977;70(5):369-70
• Type of article: Letter
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002255).

In plain English

This letter to the editor is not a research study and reported no new data. The author, chairman of the Asbestosis Research Council's Research Committee, responded to a Rohl et al. article on asbestos in brake maintenance and repair dust. That article suggested submicroscopic fibres can produce disease. The author was disturbed by this, arguing that such short fibres can be engulfed by a single alveolar macrophage and so have a finite chance of clearance via the airways. The letter described earlier animal experiments by others using chrysotile, crocidolite, amosite and glass fibre. The author said most of these found long fibres produced more fibrosis than short ones. In one rat study, tumour incidence appeared similar with standard and more finely ground chrysotile, but the ground sample's fibre lengths were not reported. The author acknowledged clear-cut results had not been possible because of the difficulty of preparing samples of different fibre lengths, noting a suggestion that grinding may alter the dust. On brake lining dust, the author described low temperature ashing as a way to restore chrysotile residues' optical activity.

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: Letter to the editor (commentary responding to another article, with a narrative discussion of earlier animal studies by others); no original data
• Who was studied: No study population. The letter discusses animal experiments published by other researchers (rabbits, rats, guinea pigs, hamsters, monkeys).
• Exposure: Asbestos fibre length (short versus long fibres) in relation to fibrosis and tumours, and the chrysotile residues found in brake lining dust
• Main results:
  • The author argued that the short fibres Rohl et al. suggested could cause disease can be engulfed by a single alveolar macrophage and so have a finite chance of clearance via the airways.
  • The author stated that the vast majority of published papers on fibre length suggest that long asbestos fibres are much more dangerous than short ones.
  • The author noted one rat study in which standard UICC chrysotile A and a more finely ground sample of the same material appeared to produce similar tumour incidence. The fibre length distribution of the finely ground sample was not given.
  • For brake lining dust, the author described low temperature ashing as a method that removes organic material from the fibres, restores their optical activity, and removes resin particles that may obscure the fibres.
• The authors' conclusion: The author concluded that, judging from the animal studies reviewed, the length of asbestos fibres appears to be the main factor in determining fibrosis.
• Limitations the authors state:
  • The author acknowledged that clear-cut results had not been possible because of the difficulty of preparing dust samples of different fibre lengths.
  • The author noted a suggestion that the prolonged grinding used to make short-fibre samples may alter the dust, so that the biological results may not represent what happens when short fibres are inhaled in a factory.
  • The author stated that whether the surface chemistry of asbestos and other mineral fibres adds a further fibrogenic effect had not yet been determined.

Related studies

• Asbestos content of dust encountered in brake maintenance and repair — A.N. Rohl, A.M. Langer, et al. (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)
• Asbestos fiber concentrations in the lungs of brake repair workers: commercial amphiboles levels are predictive of chrysotile levels — G.M. Marsh, A.O. Youk, et al. (2011)
• Exposure to asbestos during brake maintenance of automotive vehicles by different methods — T. Kauppinen, K. Korhonen (1987)

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