Estimation of personal exposure to asbestos of brake repair workers

Our plain-English summary of Estimation of personal exposure to asbestos of brake repair workers, by M.F. Cely-García, F.C. Curriero, M. Sánchez-Silva, et al (Journal of Exposure Science & Environmental Epidemiology, 2017).

The study

• Authors: M.F. Cely-García, F.C. Curriero, M. Sánchez-Silva, P.N. Breysse, M. Giraldo, L. Méndez, C. Torres-Duque, M. Durán, M. González-García, P. Parada, J.P. Ramos-Bonilla
• Journal: Journal of Exposure Science & Environmental Epidemiology
• Published: 2017;27(4):417-426
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Exposure assessments are key tools to conduct epidemiological studies. Since 2010, 28 riveters from 18 brake repair shops with different characteristics and workloads were sampled for asbestos exposure in Bogotá, Colombia. Short-term personal samples collected during manipulation activities of brake products, and personal samples collected during non-manipulation activities were used to calculate 103 8-h TWA PCM-equivalent personal asbestos concentrations. The aims of this study are to identify exposure determinant variables associated with the 8-h TWA personal asbestos concentrations among brake mechanics, and propose different models to estimate potential asbestos exposure of brake mechanics in an 8-h work-shift. Longitudinal-based multivariate linear regression models were used to determine the association between personal asbestos concentrations in a work-shift with different variables related to work tasks and workload of the mechanics, and some characteristics of the shops. Monte Carlo simulations were used to estimate the 8-h TWA PCM-Eq personal asbestos concentration in work-shifts that had manipulations of brake products or cleaning activities of the manipulation area, using the results of the sampling campaigns. The simulations proposed could be applied for both current and retrospective studies to determine personal asbestos exposures of brake mechanics, without the need of sampling campaigns or historical data of air asbestos concentrations.

In plain English

This study measured asbestos exposure in 28 brake riveters, who drill, rivet, bevel, grind and cut brake products. Sampled from 2010 at 18 brake repair shops in Bogotá, Colombia, they yielded 103 eight-hour average exposures. The mean was 0.151 f/cm3 in passenger-vehicle shops (43 averages) and 0.042 f/cm3 in heavy-duty-vehicle shops (60 averages). Chrysotile was the only asbestos type in personal samples, aside from traces of crocidolite, tremolite and actinolite in a few. In the authors' Model 1, exposure was 5.25 times higher in shifts with beveling, grinding or electric-saw cutting of asbestos-containing products than without (log-scale 95% confidence interval 0.772 to 2.547). It was 2.52 times higher when the worker stayed inside rather than outside the manipulation area during other work (log-scale interval 0.206 to 1.640). Dry cleaning of the work area was not statistically significant. A simulation estimated shift exposure from sets of asbestos-containing brake products handled, plus other work and, in one version, dry cleaning. Its estimates correlated with measured values, though the authors said it underestimated real exposures. The authors concluded that "controlled or safe use" of asbestos-containing brake products is not being achieved.

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 study using personal air sampling, longitudinal-based linear regression models and Monte Carlo simulations
• Who was studied: 28 riveters (brake mechanics) from 18 brake repair shops in Bogotá, Colombia: 13 riveters in 9 passenger-vehicle shops and 15 riveters in 9 heavy-duty-vehicle shops, sampled since 2010
• Exposure: Asbestos released during three kinds of work: manipulation of brake products (drilling, countersinking, riveting, beveling, grinding, cutting), dry cleaning of the manipulation area, and non-manipulation periods. Chrysotile was the only asbestos type in personal samples, with traces of crocidolite, tremolite and actinolite in a few. Bulk analysis of 18 duplicate brake-product samples from 12 brands, also reported in the group's earlier paper, found 15 pairs containing 5 to 15% asbestos, all chrysotile.
• Main results:
  • Passenger-vehicle shops: 43 eight-hour TWA PCM-equivalent asbestos concentrations for 13 riveters. Mean 0.151 f/cm3, median 0.048 f/cm3, range 0.00 to 0.61 f/cm3.
  • Heavy-duty-vehicle shops: 60 eight-hour TWA concentrations for 15 riveters. Mean 0.042 f/cm3, median 0.021 f/cm3, range 0.00 to 0.31 f/cm3.
  • Thirty-minute personal samples taken during manipulation with beveling and grinding of asbestos-containing products (66 samples): mean 0.853 f/cm3, median 0.459 f/cm3.
  • Multivariate Model 1 (without cleaning): exposure was 5.25-fold higher in shifts with at least one manipulation of asbestos-containing products involving beveling, grinding and/or cutting with an electric saw, compared with shifts without it. Log-scale coefficient 1.659, P = 0.001, 95% CI 0.772 to 2.547.
  • Multivariate Model 1: exposure was 2.52-fold higher when the worker stayed inside rather than outside the manipulation area during non-manipulation activities. Log-scale coefficient 0.923, P = 0.014, 95% CI 0.206 to 1.640.
  • Model 2: dry cleaning of the manipulation area was associated with a 10% increase that was not statistically significant (P = 0.755).
  • The Monte Carlo simulation without dry cleaning estimated a mean 8-hour TWA of 0.85 f/cm3 (95% interval 0.08 to 3.46) for a worker handling 16 sets of asbestos-containing brake products.
  • Simulated exposures correlated with actual measured shift exposures. Across all 103 shifts, the Spearman coefficients were 0.73 (Scenario 3) and 0.72 (Scenario 4).
• The authors' conclusion: The authors concluded that their models can estimate brake mechanics' asbestos exposures for current and retrospective studies without sampling. They recommended the simulation for shifts without cleaning but noted that it underestimates real exposures. They also concluded that "controlled or safe use" of asbestos-containing brake products is not being achieved in Bogotá and supported stopping use of the material.
• Limitations the authors state:
  • The authors stated that the models underestimate real full-shift asbestos exposure.
  • The models have not been externally validated with other exposure data.
  • The dry cleaning exposure factor needs more sampling to improve its predictive value.
  • The authors excluded 32 non-manipulation samples from one shop with an unusually high workload and said this could limit the generalizability of the results.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Personal Breathing Zone Sample.

Related studies

• Personal exposures to asbestos fibers during brake maintenance of passenger vehicles — M.F. Cely-García, M. Sánchez, et al. (2012)
• Personal exposure to asbestos and respiratory health of heavy vehicle brake mechanics — M.F. Cely-García, C.A. Torres-Duque, et al. (2015)
• Asbestos exposure among transmission mechanics in automotive repair shops — N. Salazar, M.F. Cely-García, et al. (2015)
• Exposure of UK industrial plumbers to asbestos, Part I: Monitoring of exposure using personal passive samplers — G. Burdett, D. Bard (2007)
• Personal and static sample measurements of asbestos fibres during two abatement projects — A. Dufresne, C. Dion, et al. (2009)
• Asbestos exposure during brake lining maintenance and repair — A.N. Rohl, A.M. Langer, et al. (1976)

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