Personal exposures to asbestos fibers during brake maintenance of passenger vehicles

Our plain-English summary of Personal exposures to asbestos fibers during brake maintenance of passenger vehicles, by M.F. Cely-García, M. Sánchez, P.N. Breysse, et al (The Annals of Occupational Hygiene, 2012).

The study

• Authors: M.F. Cely-García, M. Sánchez, P.N. Breysse, J.P. Ramos-Bonilla
• Journal: The Annals of Occupational Hygiene
• Published: 2012;56(9):985-99
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: Brake linings and brake pads are among the asbestos-containing products that are readily available in Colombia. When sold separated from their support, brake linings require extensive manipulation involving several steps that include drilling, countersinking, riveting, bonding, cutting, beveling, and grinding. Without this manipulation, brake linings cannot be installed in a vehicle. The manipulation process may release asbestos fibers, which may expose brake mechanics to the fibers.

Methods: Three brake repair shops located in Bogotá (Colombia) were sampled for 3 or 4 consecutive days using US National Institute for Occupational Safety and Health (NIOSH) methods 7400 and 7402. Standard procedures for quality control were followed during the sampling process, and asbestos samples were analyzed by an American Industrial Hygiene Association accredited laboratory. Personal samples were collected to assess full-shift and short-term exposures. Area samples were also collected close to the brake-lining manipulation equipment and within office facilities. Activities were documented during the sampling process.

Results: Using Phase Contrast Microscopy Equivalent counts to estimate air asbestos concentrations, all personal samples [i.e. 8-h time-weighted averages (TWAs) and 30-min personal samples] were in compliance with the US Occupational Safety and Health Administration standards. Personal asbestos concentrations based on transmission electron microscopy counts were extremely high, ranging from 0.006 to 3.493 f cm(-3) for 8-h TWA and from 0.015 to 8.835 f cm(-3) for 30-min samples. All asbestos fibers detected were chrysotile. Cleaning facilities and grinding linings resulted in the highest asbestos exposures based on transmission electron microscopy counts. There were also some samples that did not comply with the NIOSH's recommended exposure limits.

Conclusion: The results indicate that the brake mechanics sampled are exposed to extremely high asbestos concentrations (i.e. based on transmission electron microscopy counts), suggesting that this occupational group could be at excess risk of asbestos-related diseases.

In plain English

The authors measured airborne asbestos in three brake repair shops in Bogotá, Colombia, between May and August 2010. In these shops, loose brake linings for passenger vehicles were drilled, riveted, cut, beveled and ground. Each shop was sampled for 3 or 4 consecutive days, giving 57 air samples. The only asbestos type found was chrysotile. Counted by transmission electron microscopy, 8 of 11 full-shift worker samples exceeded 0.1 fibers per cubic centimeter (median 0.189, range 0.006 to 3.493), and 30-minute samples ranged from 0.015 to 8.835. Using the optical-equivalent counts that US OSHA limits use, the worker samples that could be counted were within OSHA limits. However, several overloaded filters could not be counted this way, so compliance could not be checked for those. Three samples at one shop exceeded the NIOSH recommended limit. Some of the highest short-term levels occurred during cleaning such as dry sweeping. No worker used protective equipment recommended for asbestos. The authors concluded that this occupational group could be at excess risk of asbestos-related diseases. They noted that the shops were about 4% of those operating in Bogotá.

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 assessment) study, using personal, area, office and background samples analyzed by phase contrast microscopy (NIOSH 7400) and transmission electron microscopy (NIOSH 7402)
• Who was studied: Three brake repair shops in Bogotá, Colombia, working mostly on passenger cars and light vehicles. Of 70 shops listed in telephone directories, 3 agreed to sampling. Six workers (riveters and brake mechanics) are described. Sampling took place May to August 2010, and 57 samples were collected: 19 long-term personal, 15 short-term personal, 10 area, 10 office and 3 background.
• Exposure: Chrysotile asbestos released while preparing asbestos-containing brake linings for installation (drilling, countersinking, riveting, bonding, cutting, beveling, grinding, and grinding old shoes), and during cleaning such as dry sweeping
• Main results:
  • By transmission electron microscopy counts, 8 of 11 full-shift (8-hour time-weighted average) personal samples exceeded 0.1 f cm-3
  • Personal concentrations by transmission electron microscopy ranged from 0.006 to 3.493 f cm-3 for 8-hour averages (median 0.189) and from 0.015 to 8.835 f cm-3 for 30-minute samples
  • The authors reported that personal samples complied with US OSHA standards using phase contrast microscopy equivalent counts. However, overloaded filters prevented this calculation for several samples, so compliance could not be checked directly for those.
  • Compared against the NIOSH recommended exposure limit, three samples at shop BRS1 (two personal, one area) had phase contrast microscopy equivalent concentrations above the limit
  • Some of the highest 30-minute concentrations by electron microscopy were linked to cleaning activities rather than direct handling of linings
  • BRS2 had the highest concentrations for all sample types, which the authors attributed to its largest workload and worst ventilation
  • A sample collected while a worker handled non-asbestos brake linings contained chrysotile, below the OSHA short-term limit
  • The authors stated that concentrations found in office and other shop areas indicate that administrative staff and customers were also exposed
  • No worker used the personal protective equipment recommended for asbestos
• The authors' conclusion: The authors concluded that the brake mechanics sampled were exposed to extremely high asbestos concentrations based on transmission electron microscopy counts, suggesting this occupational group could be at excess risk of asbestos-related diseases
• Limitations the authors state:
  • Many filters were overloaded, so a high fraction of phase contrast microscopy samples could not be counted, making those results difficult to interpret
  • Filters had to be re-deposited for electron microscopy analysis, which added uncertainty to those concentrations
  • The three shops were about 4% of brake shops in Bogotá and were sampled only 3 or 4 days each. The authors nonetheless argued the shops represent a range of workloads and facilities.
  • Results are limited to the activities on the days sampled
  • No health assessments of workers were conducted

Topics

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

Medical terms in this study, explained in our Lexicon: Brake Lining, NIOSH, Industrial Hygiene, Personal Breathing Zone Sample, Short-Term Exposure, phase contrast microscopy (PCM), Time-Weighted Average (TWA), Transmission Electron Microscopy (TEM).

Related studies

• Asbestos exposure among transmission mechanics in automotive repair shops — N. Salazar, M.F. Cely-García, et al. (2015)
• Personal exposure to asbestos and respiratory health of heavy vehicle brake mechanics — M.F. Cely-García, C.A. Torres-Duque, et al. (2015)
• Estimation of personal exposure to asbestos of brake repair workers — M.F. Cely-García, F.C. Curriero, et al. (2017)
• Exposure to asbestos during brake maintenance of automotive vehicles by different methods — T. Kauppinen, K. Korhonen (1987)
• Asbestos exposures during reprocessing of automobile brakes and clutches — K. Sakai, N. Hisanaga, et al. (2006)
• Evaluation of asbestos exposure during brake repair and replacement — H. Kakooei, M. Hormozy, et al. (2011)

Browse more research in The Annals of Occupational Hygiene, or return to medical research.