Asbestos in brakes: exposure and risk of disease

Our plain-English summary of Asbestos in brakes: exposure and risk of disease, by R.A. Lemen (American Journal of Industrial Medicine, 2004).

The study

• Author: R.A. Lemen
• Journal: American Journal of Industrial Medicine
• Published: 2004;45(3):229-37
• Type of article: Review
• Cited by: 54 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos has been incorporated into friction products since the early 1900s. Epidemiological studies have been equivocal in their analysis of the incidence of disease among mechanics servicing brakes. Decomposition of asbestos occurs during the normal usage of the brake due to thermal decomposition into forsterite, although not all asbestos is so converted. Short fibers, below 5 microm in length, are also found in brake products. Several facts are discussed including the toxicity of the remaining asbestos fibers, short asbestos fibers, and the health implications of exposure to forsterite. Control methodologies, when used appropriately, have reduced exposure to asbestos during brake servicing, but have not been able to entirely eliminate exposure to asbestos, thus bring into question the controlled use of asbestos for friction product such as brakes. Even the so called "controlled" use of asbestos containing brakes poses a health risk to workers, users, and their families.

Copyright 2004 Wiley-Liss, Inc.

In plain English

This was a narrative review by a single author, who stated having testified as a plaintiff's expert in brake exposure cases. It reported no new data but gathered published studies on asbestos in brakes, which the author said used chrysotile almost exclusively. The author described how braking heat turns asbestos into non-fibrous forsterite, though not all fibers are changed. The author also argued that fibers under 5 micrometers cannot be assumed harmless. Cited studies found fibers released during brake servicing, in one study up to 125 fibers/cm3 when grinding truck and bus brake linings. Control methods reduced exposure but did not entirely eliminate it. The author called the epidemiological studies of mechanics equivocal. Even so, the author counted at least 165 mesothelioma cases in end-product users of friction products. It also cited an Australian estimate of 32.5 mesotheliomas per million person-years, over 30 times the commonly accepted background rate. That estimate was based on 43 cases in vehicle mechanics with no other exposures and the number of mechanics in the country. The author concluded that even "controlled" use of asbestos brakes poses a health risk to workers, users and their families.

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: Narrative literature review by a single author; no new data and no stated search method
• Who was studied: Published studies, case reports and registry data on people exposed to asbestos from brakes, mainly mechanics who service brakes, plus some family members and manufacturing workers
• Exposure: Asbestos in brakes and other friction products, which the author says was almost exclusively chrysotile; also forsterite, the heat-decomposition product, and short fibers below 5 micrometers in length
• Main results:
  • Braking heat converts asbestos into forsterite, but not all fibers are changed and some remain as true asbestos fibers
  • The author's position is that the available science does not justify assuming short fibers (less than 5 micrometers) are harmless
  • In a cited study (Kauppinen and Korhonen 1987) of brake maintenance on trucks and buses, grinding of brake linings released the most fibers, some as high as 125 fibers/cm3
  • The author described the epidemiological studies of brake workers as equivocal
  • The article cites Australian data from Dr. James Leigh. Using 43 cases from 1986 to 2001 in vehicle mechanics with no other exposures, and statistics on the number of mechanics in the country, the rate was 32.5 per million person-years. This was reported as over 30 times the commonly accepted background rate of 1 per million person-years.
  • The author's review of the published peer-reviewed literature found at least 165 cases of mesothelioma in end-product users of friction products
  • Control methods reduced asbestos exposure during brake servicing but did not entirely eliminate it
• The authors' conclusion: The author concluded that even so-called controlled use of asbestos-containing brakes poses a health risk to workers, users and their families

Topics

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

Medical terms in this study, explained in our Lexicon: Friction Products, Forsterite, Controlled Use.

Related studies

• RE: Asbestos in brakes: exposure and risk of disease — M.J. Teta (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 — D.J. Paustenbach, B.L. Finley, et al. (2004)
• Personal exposures to asbestos fibers during brake maintenance of passenger vehicles — M.F. Cely-García, M. Sánchez, et al. (2012)
• Brake mechanics, asbestos, and disease risk — M. Huncharek (1990)
• 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)

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