Evaluation of Airborne Asbestos Concentrations Associated with the Operation and Maintenance of Brakes and Clutches on Nonautomated Heavy Equipment

Our plain-English summary of Evaluation of Airborne Asbestos Concentrations Associated with the Operation and Maintenance of Brakes and Clutches on Nonautomated Heavy Equipment, by J. Sahmel, H. Avens, T. Ferracini, et al (Journal of Environmental and Public Health, 2022).

The study

• Authors: J. Sahmel, H. Avens, T. Ferracini, A. Banducci, K. Rickabaugh
• Journal: Journal of Environmental and Public Health
• Published: 2022;2022:9831883
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

This study evaluated the potential for chrysotile asbestos exposure during maintenance and operation of older, nonautomated heavy equipment with chrysotile-containing brake and clutch linings. Recent reports indicate that such equipment may be in current use in the U.S. and other locations, including developing countries, due to its lower cost and ease of maintenance compared to newer equipment. Personal and area airborne fiber concentrations were measured for cranes with draglines during brake and clutch repair, equipment operation, shop cleanup, and clothes handling of the mechanic's coveralls over a period of three days. The range of airborne chrysotile concentrations during the complete friction band replacement process, including band removal from the equipment, friction lining replacement, and reinstallation, ranged from 0.0053 to 0.0273 f/cc (phase contrast microscopy-equivalent or PCME) over 3.3 to 6.2 hours. Additional bench work tasks, including electric wire brushing, hand sanding, riveting, and compressed air use were also performed. Full shift airborne chrysotile concentrations (6.1-8.5 hours) for all combined maintenance activities were 0.0093, 0.0414, and 0.0445 f/cc (PCME), on days 1, 2, and 3, respectively. Personal short-term samples (14-36 minutes) for lining removal, installation, wire brushing, hand sanding, and compressed air use ranged from nondetect (ND) to 0.238 f/cc (PCME), below the U.S. Occupational Safety and Health Administration's (OSHA's) 30-minute excursion limit of 1 f/cc. Short-term samples during crane operation, shop cleanup, and simulated laundry activities with the mechanic's coveralls ranged from ND to 0.01 f/cc (PCME; 15-36 minutes). The results indicated that full-shift measured airborne chrysotile concentrations during the brake and clutch maintenance activities evaluated remained below the U.S. 8-hour time-weighted average (TWA) permissible exposure limit (PEL) for asbestos of 0.1 f/cc. The results are likely to be relevant to farmers, construction workers, and vehicle maintenance workers historically, as well as today for those who choose to continue using and maintaining such equipment.

Copyright © 2022 J. Sahmel et al.

In plain English

Air was sampled in a Pennsylvania garage while a mechanic removed, relined and reinstalled brake and clutch bands on one crane, removed both from a second crane and relined its clutch band, and did extra bench tasks. The linings contained 22 to 41% chrysotile; no amphibole fibers were found in the air. The mechanic's full-shift chrysotile (PCME) levels were 0.0093, 0.0414 and 0.0445 fibers per cubic centimeter (f/cc) on days 1 to 3, averaging 0.0317 f/cc. His reported 14- to 36-minute personal task samples ranged from not detected to 0.238 f/cc. A 60-minute woven-lining installation measured 0.260 f/cc. A pneumatic sanding task gave just over 1 f/cc over 30 minutes, but the authors excluded it as not representative. During 30 minutes of outdoor crane operation, the operator's average was 0.005 f/cc (PCME). The person handling the coveralls had a measured 15-minute average of 0.0022 f/cc. Assuming no further exposure that workday, the authors calculated an 8-hour average of 0.000069 f/cc. The authors concluded that all full-shift levels were below the U.S. OSHA 8-hour limit of 0.1 f/cc.

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 exposure-measurement study: brake and clutch maintenance, crane operation and clothes handling were performed over three days while personal and area air samples were collected
• Who was studied: One career heavy-equipment mechanic worked on a Bucyrus-Erie 22B crane (1953) and a 15B crane (1960). On the 22B he removed, relined and reinstalled a clutch band and a brake band. On the 15B he removed the clutch and brake bands and relined the clutch band. A heavy equipment operator also ran a 22B crane outdoors.
• Exposure: Chrysotile-containing brake and clutch linings (22 to 41% chrysotile; a woven lining contained 31 to 35% chrysotile). They were handled during removal, relining, reinstallation, grinding, wire brushing, sanding and compressed-air blow-off. Exposure was also measured during crane operation and the handling of coveralls.
• Main results:
  • Mechanic, full shift: chrysotile (PCME) concentrations were 0.0093, 0.0414 and 0.0445 f/cc on days 1, 2 and 3, over 6.1 to 8.5 hours, with an overall average of 0.0317 f/cc
  • Mechanic, routine crane maintenance only (excluding the additional bench tasks): 0.0053 to 0.0273 f/cc PCME over 3.3 to 6.2 hours
  • Mechanic, short-term personal task samples reported in the results, about 30 minutes or less (14 to 36 minutes): not detected to 0.238 f/cc. The highest, 0.238 f/cc, was during hand sanding of brake linings followed by compressed air. This range does not include the excluded pneumatic sanding task.
  • Mechanic, 60-minute personal sample during installation of woven brake linings: 0.260 f/cc (PCM and PCME)
  • A nonstandard task, pneumatic sanding of the whole surface of a used clutch band, gave a 30-minute personal level of just over 1 f/cc and a 30-minute area level of 0.5 f/cc (PCME) at 1.5 m
  • The mechanic said he would never perform the pneumatic sanding task, and the authors did not include it in the study results or tables
  • Crane operator, during a single 30-minute outdoor operation session: one lapel sample was 0.010 f/cc PCME, and the average of the two lapel samples was 0.005 f/cc PCME. This was not a full-shift measurement.
  • Person handling the mechanic's coveralls, two 15-minute personal samples: not detected and 0.0044 f/cc PCME, with an average of 0.0022 f/cc
  • Person handling the coveralls: the authors calculated an 8-hour average of 0.000069 f/cc PCME, assuming no exposure during the rest of the workday. This was a calculation, not an 8-hour measurement.
  • Full-shift area samples at 4.6 and 9.6 m from the workbench were described as indistinguishable from the baseline air measurements
  • No amphibole fibers were detected in any air sample
• The authors' conclusion: The authors concluded that full-shift PCM and PCME concentrations for all activities evaluated were below the current OSHA 8-hour time-weighted average limit for asbestos of 0.1 f/cc
• Limitations the authors state:
  • The personal cleanup sample on day 3 is uncertain because the sampling pump shut off before the sampling period ended

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Asbestos Exposure, phase contrast microscopy (PCM), OSHA, Excursion Limit, Time-Weighted Average (TWA), Permissible Exposure Limit (PEL).

Related studies

• Airborne concentrations of chrysotile asbestos during operation of industrial crane controls and maintenance of associated arc chutes — M.J. McCoy, R.C. Lewis, et al. (2021)
• Airborne asbestos concentration from brake changing does not exceed permissible exposure limit — C.L. Blake, D.R. Van Orden, et al. (2003)
• Heavy equipment maintenance exposure assessment: using a time-activity model to estimate surrogate values for replacement of missing data — F.W. Boelter, J.W. Spencer, et al. (2007)
• Safety and health of heavy equipment operators at Ground Zero — B.E. Lippy (2002)
• Evaluation of exposure to the airborne asbestos in an automobile brake and clutch manufacturing industry in Iran — H. Kakooei, H. Marioryad (2010)
• A study of personal and area airborne asbestos concentrations during asbestos abatement: a statistical evaluation of fibre concentration data — J.H. Lange, P.R. Lange, et al. (1996)

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