Asbestos exposures during reprocessing of automobile brakes and clutches

Our plain-English summary of Asbestos exposures during reprocessing of automobile brakes and clutches, by K. Sakai, N. Hisanaga, E. Shibata, et al (International Journal of Occupational and Environmental Health, 2006).

The study

• Authors: K. Sakai, N. Hisanaga, E. Shibata, Y. Ono, Y. Takeuchi
• Journal: International Journal of Occupational and Environmental Health
• Published: 2006;12(2):95-105
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos exposures of workers in three small factories reprocessing automobile brakes and clutches in Japan were investigated. Airborne asbestos was collected on a membrane filter using an air sampler. From 1982 to 1989, asbestos counting was performed on 295 samples (198 personal and 97 stationary), using phase contrast microscopy. Only chrysotile asbestos was detected. Workers who reprocessed automobile brakes and clutches were exposed to asbestos concentrations of 0.025-76.4 fibers/cm3. Geometric mean asbestos concentrations during attaching linings to brake shoes and attaching facings to clutch disks were 0.859 fibers/cm3 and 0.780 fibers/cm3, respectively. Concentrations during stripping worn brake linings and clutch facings were 0.484 fibers/cm3 and 0.382 fibers/cm3, respectively. Machine grinding and leveling of new brake-lining surfaces represent potential sources of heavy asbestos exposures, unless enclosures and local ventilation are efficient.

In plain English

This study measured airborne asbestos in three small factories in Nagoya, Japan, that reprocessed used automobile brakes and clutches. From 1982 to 1989 the authors took 295 air samples (198 worn by workers, 97 at fixed points) and counted fibers by phase contrast microscopy. Chrysotile was the only fiber type detected. Workers' exposures ranged from 0.025 to 76.4 fibers/cm3. The highest geometric mean, 44.2 fibers/cm3, came from grinding brake linings with a band grinder, despite local exhaust ventilation. Geometric means were 0.859 fibers/cm3 for attaching linings to brake shoes and 0.780 fibers/cm3 for attaching facings to clutch disks. These were measured per operation rather than over full shifts. The factory with more local exhaust ventilators generally had the lowest levels. In 14 of 15 fixed-point work-area assessments, levels were classed as above 0.15 fibers/cm3, the administrative control level Japan set in 2004. The authors concluded that machine grinding and beveling of new brake linings can be sources of heavy exposure unless enclosure and ventilation are efficient. They noted that the factories were not randomly chosen and that sampling was done only in summer.

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 air-sampling (exposure measurement) survey, with personal and stationary sampling repeated between 1982 and 1989
• Who was studied: Three small factories (A, B, C) in Nagoya, Japan, reprocessing automobile brakes and clutches. In 1983 they had 57 workers, of whom 27 directly handled friction materials. A total of 295 air samples were taken: 198 personal and 97 stationary.
• Exposure: Airborne chrysotile asbestos from reprocessing brakes and clutches. The operations were stripping worn linings and facings, gluing, drilling, riveting, grinding new linings, and inspection and packing. The friction materials were labeled as 50% asbestos.
• Main results:
  • Workers reprocessing brakes and clutches were exposed to asbestos concentrations of 0.025-76.4 fibers/cm3.
  • The highest personal-sample geometric mean, 44.2 fibers/cm3, was found when grinding brake linings with a band grinder, even though a local exhaust ventilator was in use. This operation was done only in factory A.
  • In personal samples, the geometric mean was 0.859 fibers/cm3 for attaching linings to brake shoes and 0.780 fibers/cm3 for attaching facings to clutch disks.
  • The geometric mean was 0.484 fibers/cm3 for stripping worn brake linings and 0.382 fibers/cm3 for stripping worn clutch facings.
  • Personal-sample geometric means exceeded the 0.15 fibers/cm3 reference value of the Japan Society for Occupational Health during four processes: stripping worn brake linings, stripping worn clutch facings, reassembling brakes, and reassembling clutches.
  • Factory C always had the lowest geometric mean for the same operation, except for stripping worn brake linings. Factory C had local exhaust ventilators on most grinders and drills and was frequently vacuum-cleaned.
  • In stationary sampling, five areas were measured repeatedly, giving 15 unit work area assessments. Of these, 14 were classified as Control Class 3, compared against the 0.15 fibers/cm3 administrative control level amended in 2004.
  • A locker room in factory B, located close to where brakes were reassembled, had an asbestos concentration of 1.72 fibers/cm3.
  • Over time, exposure levels decreased in factories A and C but fluctuated in factory B.
  • Personal-sample concentrations tended to be higher than stationary-sample concentrations.
• The authors' conclusion: Drawing on their own results and previous reports, the authors concluded that machine grinding and beveling of new brake-lining surfaces can become sources of heavy asbestos exposure unless enclosure and local ventilation are efficient.
• Limitations the authors state:
  • The results may not represent all Japanese brake- and clutch-reprocessing workers, because the factories were not randomly selected and the number of subjects was small.
  • Sampling was done only in summer. Concentrations may be higher in winter, when doors and windows are kept closed.
  • No time study was done, so time-weighted average exposures are unavailable.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, phase contrast microscopy (PCM), Chrysotile, Brake Lining.

Related studies

• Airborne asbestos exposures associated with work on asbestos fire sleeve materials — C.L. Blake, S.C. Harbison, et al. (2011)
• Personal exposures to asbestos fibers during brake maintenance of passenger vehicles — M.F. Cely-García, M. Sánchez, et al. (2012)
• Evaluation of the size and type of free particulates collected from unused asbestos-containing brake components as related to potential for respirability — M.A. Atkinson, M. O'sullivan, et al. (2004)
• Re: Evaluation of the size and type of free particulates collected from unused asbestos-containing brake components as related to potential for respirability — D.J. Paustenbach, B.L. Finley, et al. (2006)
• Exposure to chrysotile asbestos associated with unpacking and repacking boxes of automobile brake pads and shoes — A.K. Madl, L.L. Scott, et al. (2008)
• A study of airborne chrysotile concentrations associated with handling, unpacking, and repacking boxes of automobile clutch discs — G.C. Jiang, A.K. Madl, et al. (2008)

Browse more research in International Journal of Occupational and Environmental Health, or return to medical research.