Asbestos exposure among transmission mechanics in automotive repair shops

Our plain-English summary of Asbestos exposure among transmission mechanics in automotive repair shops, by N. Salazar, M.F. Cely-García, P.N. Breysse, et al (The Annals of Occupational Hygiene, 2015).

The study

• Authors: N. Salazar, M.F. Cely-García, P.N. Breysse, J.P. Ramos-Bonilla
• Journal: The Annals of Occupational Hygiene
• Published: 2015;59(3):292-306
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: Asbestos has been used in a broad variety of industrial products, including clutch discs of the transmission system of vehicles. Studies conducted in high-income countries that have analyzed personal asbestos exposures of transmission mechanics have concluded that these workers are exposed to asbestos concentrations in compliance with the US Occupational Safety and Health Administration (US OSHA) occupational standards. Clutch facings are the friction component of clutch discs. If clutch facings are sold separated from the support, they require manipulation before installation in the vehicle. The manipulation of asbestos containing clutch facings is performed by a group of mechanics known as riveters, and includes drilling, countersinking, riveting, sanding, and occasionally grinding, tasks that can potentially release asbestos fibers, exposing the mechanics. These manipulation activities are not reported in studies conducted in high-income countries. This study analyzes personal asbestos exposures of transmission mechanics that manipulate clutch facings.

Methods: Air sampling campaigns in two transmission repair shops (TRS) were conducted in November 2012 and July 2013 in Bogotá, Colombia. Four workers employed in these TRS were sampled (i.e. three riveters and one supervisor). Personal samples (n = 39), short-term personal samples (n = 49), area samples (n = 52), blank samples (n = 8), and background samples (n = 2) were collected in both TRS during 3-5 consecutive days, following US National Institute for Occupational Safety and Health (US NIOSH) methods 7400 and 7402. Asbestos samples were analyzed by an American Industrial Hygiene Association accredited laboratory.

Results: On at least one of the days sampled, all riveters were exposed to asbestos concentrations that exceeded the US OSHA permissible exposure limit or the Colombian permissible limit value. Additionally, from the forty-seven 30-min short-term personal samples collected, two (4.3%) exceeded the US OSHA excursion limit of 1 f cm(-3).

Conclusions: In this study, we identified that the working conditions and use of asbestos containing transmission products expose transmission mechanics to asbestos concentrations that exceed both the Colombian and OSHA standards. The potential consequences for the health of these workers are of great concern.

© The Author 2014. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

In plain English

This study measured airborne asbestos in two transmission repair shops in Bogotá, Colombia, in November 2012 and July 2013. Three 'riveters', who drill, sand and grind clutch facings to fit clutch plates, and a supervisor were sampled. Chrysotile was the only asbestos type found, and two clutch facing brands tested contained 20% chrysotile. On the first day, the two riveters in the first shop had 8-hour average exposures of 0.108 and 0.111 fibers per cubic centimetre. Both exceeded the US OSHA limit of 0.1 and the Colombian limit. The second shop's riveter exceeded both limits on two of five days: 8-hour averages of 0.153 and 0.193, and 9-hour averages (used for the Colombian limit) of 0.136 and 0.172. Overall, 4 of 14 worker-day averages exceeded both limits. Two of 49 short 30-minute samples (the abstract says 47), both in the second shop, exceeded the US OSHA 30-minute limit of 1. The supervisor stayed below both limits but was still exposed. The authors concluded that these mechanics are at excess risk of asbestos-related disease. The study measured air levels, not illness.

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: Occupational exposure assessment (personal and area air sampling) in two transmission repair shops, analysed by phase contrast and transmission electron microscopy (US NIOSH methods 7400 and 7402)
• Who was studied: Four workers in two transmission repair shops in Bogotá, Colombia: two riveters (R1, R2) and a supervisor (W1) in the first shop (TRS1), and one riveter (R3) in the second shop (TRS2); sampled in November 2012 and July 2013
• Exposure: Chrysotile asbestos released while riveters manipulated clutch facings sold detached from the clutch plate (drilling, countersinking, riveting, sanding, occasionally grinding). Two brands believed by workers to contain asbestos had 20% chrysotile. Chrysotile was the only asbestos type identified in the air samples.
• Main results:
  • 150 samples were collected in total: 39 personal, 49 short-term personal, 52 area, 8 blank and 2 background samples.
  • In TRS1, both riveters exceeded the US OSHA PEL and the corrected Colombian limit on Day 1. R1 had an 8-h TWA of 0.108 f/cm3 and an 8.5-h TWA of 0.103. R2 had 0.111 and 0.107. The limits were 0.1 for the 8-h TWA and 0.091 for the 8.5-h TWA.
  • In TRS2, riveter R3 exceeded both standards on Days 1 and 2. The 8-h TWAs (compared with the US OSHA PEL of 0.1) were 0.153 and 0.193 f/cm3. The 9-h TWAs (compared with the corrected Colombian limit of 0.083) were 0.136 and 0.172.
  • Across all workers, 4 of 14 8-h TWA personal estimates (29%) exceeded both the US OSHA PEL and the corrected Colombian limit.
  • Of the 30-min short-term personal samples, 2 of 49 (4.1%) exceeded the US OSHA excursion limit of 1 f/cm3, according to the discussion and Table 4. The abstract instead gives 2 of 47 (4.3%). Both exceedances came from R3 in TRS2, whose highest value was 1.653 f/cm3. All TRS1 short-term PCME samples were below the excursion limit.
  • The supervisor (W1) was below both standards on all days, with 8-h TWAs of 0.006 to 0.014 f/cm3. The authors noted that his samples still showed exposure to asbestos fibers.
  • In TRS2, an area sample 2 m from the manipulation equipment had an 8-h TWA PCME concentration of 0.183 f/cm3 on Day 2. One 30-min area sample there measured 1.715 f/cm3, compared with 1.653 f/cm3 on the riveter at the same time.
  • Two short-term samples taken while workers handled clutch facings they reported as asbestos-free still contained asbestos fibers.
• The authors' conclusion: The authors concluded that this group of transmission mechanics is at excess risk of developing asbestos-related diseases, and that workers who do not manipulate clutch facings may also be exposed. Their conclusion is based on measured air concentrations; the study did not examine workers' health.
• Limitations the authors state:
  • The number of short-term area samples was small, and no clear pattern linking concentration to distance from the equipment was seen.
  • Area samples cannot be used to judge regulatory compliance.
  • The authors stated that more studies are needed to understand exposures among mechanics who manipulate asbestos-containing products.

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: Asbestos Exposure, OSHA, Air Sampling, Personal Breathing Zone Sample, NIOSH, Industrial Hygiene, Permissible Exposure Limit (PEL), Excursion Limit.

Related studies

• Personal exposures to asbestos fibers during brake maintenance of passenger vehicles — M.F. Cely-García, M. Sánchez, et al. (2012)
• Evaluation of asbestos exposure during brake repair and replacement — H. Kakooei, M. Hormozy, et al. (2011)
• 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)
• Cumulative asbestos exposure for US automobile mechanics involved in brake repair (circa 1950s-2000) — B.L. Finley, R.O. Richter, et al. (2007)
• 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)
• 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)

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