Asbestos exposure from gaskets during disassembly of a medium duty diesel engine

Our plain-English summary of Asbestos exposure from gaskets during disassembly of a medium duty diesel engine, by L.R. Liukonen, F.W. Weir (Regulatory Toxicology and Pharmacology, 2005).

The study

• Authors: L.R. Liukonen, F.W. Weir
• Journal: Regulatory Toxicology and Pharmacology
• Published: 2005;41(2):113-21
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Diesel engines have historically used asbestos-containing gaskets leading to concerns of fiber release and mechanic exposure. Other published studies regarding asbestos fiber release during gasket removal have reported on short-duration events; were conducted under simulated work conditions; or had other limitations. There are no comprehensive studies relating to diesel engine gaskets under conditions similar to those reported herein, evaluating asbestos fiber release from gaskets during all facets of a complete disassembly and cleaning of a medium duty diesel engine in a busy repair and service shop by a journeyman mechanic. Asbestos content of all gaskets was identified; all disassembly tasks were described and timed; and personal and area air monitoring was conducted for each task. Twenty seven of thirty three gaskets contained chrysotile asbestos in concentrations that ranged from 5 to 70%. All but one air monitoring sample reported results below the limit of reliable detection even though plumes of visible dust were evident during various removal, cleaning, and buffing procedures. The detection limit for airborne asbestos fibers in this investigation was influenced by the presence of other shop dust in the air. Our investigation demonstrates that using shop-standard procedures in an established repair facility, a journeyman mechanic has very little potential for exposure to airborne asbestos fibers during disassembly of an engine, approximately 10% or less than that currently considered to be acceptable by OSHA.

In plain English

This field study sampled air while a senior mechanic dismantled a 1982 diesel engine over three days in a working shop. Using his usual methods, he scraped off gaskets and cleaned surfaces with a power wire brush or abrasive pad. Chrysotile asbestos, at 5 to 70%, was found in 27 of 33 gaskets. Air was sampled at the mechanic's lapel and 10 ft downwind. Most samples were below detection. Of two personal samples with detectable fiber concentrations, electron microscopy found no asbestos in one and 0.012 f/cm3 chrysotile in the other. A third was too overloaded with dust to analyze. Visible dust plumes from some brushing and buffing stayed next to the mechanic, about 1.5 ft from the source. The authors calculated daily 8-hour averages assuming undetected samples were at the detection limit or half of it. Under the first, the mechanic's highest was 0.0137 f/cm3, below the OSHA limit of 0.1 f/cm3. The authors concluded the mechanic had very little potential for exposure. They noted that shop dust limited detection and the low counts were probably biased high.

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: Field industrial hygiene exposure study (air and bulk sampling) during an actual engine overhaul in a working shop. Personal, area, observer and outdoor background air samples were analyzed by PCM, with TEM for samples showing fibers.
• Who was studied: One senior journeyman mechanic with over 25 years of experience disassembling one mid-sized, turbocharged, six-cylinder, in-line diesel engine built in 1982. The work took place at a privately operated independent repair facility, over three days in early August.
• Exposure: Chrysotile-containing engine gaskets were removed with a scraper. Residue was cleaned with a rotary wire brush or a Scotch Brite pad on a hand-held air-operated grinder.
• Main results:
  • 27 of 33 gaskets contained chrysotile asbestos at 5 to 70%
  • Most air samples were below their detection limits, although several had nonzero fiber densities. Two personal samples (A-7 and A-28) had fiber concentrations above their detection limits by PCM. The Task 9 personal sample (A-22) was overloaded with particulate and not analyzed.
  • One Task 10 personal sample (A-28) measured 0.017 f/cm3 by PCM, of which 0.012 f/cm3 was chrysotile asbestos by TEM (NIOSH 7402)
  • A Task 4 personal sample (A-7) read 0.032 f/cm3 by PCM, but TEM found no detectable asbestos fibers
  • The authors calculated 8-hour TWAs two ways. With non-detects set at the detection limit, the mechanic's TWAs were 0.0084, 0.0137 and 0.0096 f/cm3 on days 1 to 3; at half the detection limit they were 0.0042, 0.0069 and 0.0048. For the bystander area sample they were 0.0052, 0.018 and 0.0055 f/cm3 (0.0026, 0.0092 and 0.0027 at half). All were well below the OSHA PEL of 0.1 f/cm3.
  • Area samples (bystander, 10 ft downwind) and observer samples were always non-detectable
  • Visible dust plumes formed during some wire brushing and pad buffing but never extended beyond the area immediately adjacent to the mechanic, approximately 1.5 ft from the source
• The authors' conclusion: The authors concluded that, using shop-standard procedures, a journeyman mechanic has very little potential for exposure to airborne asbestos fibers during engine disassembly, with all measured concentrations well below the OSHA PEL
• Limitations the authors state:
  • Other non-fibrous shop dust on the filters made detection limits less than optimal
  • Fiber densities of 10.8 f/mm2 or less, below the NIOSH optimal 100 to 1300 f/mm2, meant greater variability, and counts were probably biased high
  • Exposures could be shown to be below a given level, but an actual finite value could not be determined

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, Gasket, Fiber Release, Air Sampling, Chrysotile, OSHA.

Related studies

• Assessment of airborne asbestos exposure during the servicing and handling of automobile asbestos-containing gaskets — C.L. Blake, G.S. Dotson, et al. (2006)
• Fiber release during the removal of asbestos-containing gaskets: a work practice simulation — W.E. Longo, W.B. Egeland, et al. (2002)
• Workplace exposure to diesel and gasoline engine exhausts and the risk of colorectal cancer in Canadian men — L. Kachuri, P.J. Villeneuve, et al. (2016)
• Absence of multiplicative interactions between occupational lung carcinogens and tobacco smoking: a systematic review involving asbestos, crystalline silica and diesel engine exhaust emissions — M. El Zoghbi, P. Salameh, et al. (2017)
• Airborne asbestos concentration from brake changing does not exceed permissible exposure limit — C.L. Blake, D.R. Van Orden, et al. (2003)
• 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 Regulatory Toxicology and Pharmacology, or return to medical research.