Evaluation of asbestos exposure during brake repair and replacement

Our plain-English summary of Evaluation of asbestos exposure during brake repair and replacement, by H. Kakooei, M. Hormozy, H. Marioryad (Industrial Health, 2011).

The study

• Authors: H. Kakooei, M. Hormozy, H. Marioryad
• Journal: Industrial Health
• Published: 2011;49(3):374-80
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Occupational exposure to asbestos fiber of brake repair job (auto mechanics) has seldom been evaluated in Iran. Accordingly, we evaluated asbestos fiber concentrations in the breathing zone of auto mechanics between July 2008 and December 2008. The asbestos fiber concentrations of 60 personal air samples collected from 30 cars and trucks brake replacement and they were analyzed by phase-contrast optical microscopy (PCM) and scanning electron microscopy (SEM) by energy-dispersive X-ray analysis. The geometric means of the personal monitoring fiber concentrations were 0.92 PCM f/ml and 0.46 PCM f/ml respectively in car and passenger heavy truck auto shops. There was a significant differences in the asbestos fiber concentrations between the car and truck auto shops (p=0.006). Based on these findings, auto mechanics who worked with asbestos containing brake may have been exposed to asbestos concentrations approximately 7 times higher than the current occupational safety and health agency (OSHA) permissible exposure limit (PEL) of 0.1 f/ml. Fiber morphology and energy dispersive X-ray analysis by SEM revealed that amphibole fibers such as tremolite and actinolite existed in the brakes dust and that the vast majority (>30%) of the airborne chrysotile fibers were greater than 1 μm in diameter. It can be concluded that the imported chrysotile asbestos contains trace amounts of tremolite and actinolite fibers and they are responsible for the high airborne asbestos levels and occupational exposure to amphibole asbestos in auto mechanics job in Iran. Thus, it is to be expected that the auto mechanics will suffer negative health effects due to exposure to the serpentine and amphibole asbestos fibers.

In plain English

This study measured airborne asbestos fiber concentrations in the breathing zone of auto mechanics during brake repair and replacement in 30 car and truck auto shops in Zahedan, south-east Iran, between July and December 2008. Sixty personal air samples, two per shop, were counted by phase-contrast optical microscopy (PCM). Scanning electron microscopy with X-ray analysis was used to identify fiber types. The geometric mean was 0.92 fibers per milliliter (f/ml) in car shops and 0.46 f/ml in truck shops, a statistically significant difference (p=0.006). The overall geometric mean of 0.67 f/ml was described as more than 7 times the US OSHA limit of 0.1 f/ml. Summer levels (1.27 f/ml) were significantly higher than autumn levels (0.29 f/ml). Of 2,435 fibers counted, the authors reported chrysotile 70%, tremolite 10% and actinolite 10%. The authors concluded that the imported chrysotile contains trace tremolite and actinolite. They noted that the PCM method cannot tell asbestos from non-asbestos fibers. The printed fiber-type percentages do not match the article's own counts, which work out to about 73%, 14% and 14%.

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: cross-sectional workplace air-sampling (exposure measurement) study
• Who was studied: 30 brake repair and replacement auto shops (cars and trucks) in Zahedan, south-east Iran, sampled July to December 2008. The shops employed 75 people (45 workers and 30 auto mechanics), with a mean age of 29 years (range 18 to 40) and a mean employment period of 11.5 years (range 2 to 25).
• Exposure: Asbestos-containing brake dust released while removing, cleaning (often with a small brush), grinding and installing brake linings and pads on cars and trucks. It was measured as 60 personal breathing-zone samples of 45 minutes each, counted by PCM. Fiber types were identified by scanning electron microscopy as chrysotile, tremolite and actinolite.
• Main results:
  • The geometric mean fiber concentration was 0.92 PCM f/ml in car auto shops (32 samples) and 0.46 PCM f/ml in truck auto shops (28 samples). The car shops were significantly higher (p=0.006).
  • The overall geometric mean personal concentration was 0.67 PCM f/ml, which the authors described as more than 7 times the OSHA PEL of 0.1 f/ml.
  • Concentrations ranged from 0.116 to 2.48 f/ml in car shops and from 0.117 to 1.93 f/ml in truck shops.
  • The geometric mean was significantly higher in summer (1.27 PCM f/ml; 22 car and 10 truck samples) than in autumn (0.29 PCM f/ml; 10 car and 18 truck samples), with p less than 0.001.
  • Of 2,435 counted fibers, the authors reported chrysotile 70% (n=1,769), tremolite 10% (n=334) and actinolite 10% (n=332). The counts sum to 2,435, but the printed percentages sum to 90%.
  • More than 30% of airborne chrysotile fibers were greater than 1 micrometer in diameter, and about half (50%) of the fibers were of respirable width (less than 1 micrometer).
• The authors' conclusion: The authors concluded that the imported chrysotile asbestos contains trace amounts of tremolite and actinolite fibers, and that these are responsible for the high airborne asbestos levels and the amphibole exposure of auto mechanics in Iran.
• Limitations the authors state:
  • The PCM method used to measure concentrations does not distinguish asbestos fibers from non-asbestos fibers.
  • The scanning electron microscopy used for fiber identification usually images only fibers 0.25 micrometer or more in diameter.

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, Occupational Exposure, Scanning Electron Microscopy (SEM), OSHA, Permissible Exposure Limit (PEL), Fiber Morphology, Amphibole Group, Tremolite.

Related studies

• Evaluation of exposure to the airborne asbestos in an automobile brake and clutch manufacturing industry in Iran — H. Kakooei, H. Marioryad (2010)
• 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)
• Asbestos exposure among transmission mechanics in automotive repair shops — N. Salazar, M.F. Cely-García, et al. (2015)
• Evaluation of the fate and pathological response in the lung and pleura of brake dust alone and in combination with added chrysotile compared to crocidolite asbestos following short-term inhalation exposure — D.M. Bernstein, R.A. Rogers, et al. (2015)
• Evaluation of the deposition, translocation and pathological response of brake dust with and without added chrysotile in comparison to crocidolite asbestos following short-term inhalation: interim results — D.M. Bernstein, R. Rogers, et al. (2014)

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