Electricians' chrysotile asbestos exposure from electrical products and risks of mesothelioma and lung cancer

Our plain-English summary of Electricians' chrysotile asbestos exposure from electrical products and risks of mesothelioma and lung cancer, by J.E. Goodman, M.K. Peterson, L.A. Bailey, et al (Regulatory Toxicology and Pharmacology, 2014).

The study

• Authors: J.E. Goodman, M.K. Peterson, L.A. Bailey, L.E. Kerper, D.G. Dodge
• Journal: Regulatory Toxicology and Pharmacology
• Published: 2014;68(1):8-15
• Type of article: Review
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Both mechanistic and epidemiology studies indicate chrysotile asbestos has a threshold below which it does not cause mesothelioma or lung cancer. We conducted a critical review to determine whether electricians are at increased risk for these cancers and, if so, whether their exposure to chrysotile in electrical products could be responsible. We found that most, but not all, epidemiology studies indicate electricians are at increased risk for both cancers. Studies that evaluated electricians' exposure to asbestos during normal work tasks have generally reported low concentrations in air; an experimental study showed that grinding or drilling products containing encapsulated chrysotile resulted in exposures to chrysotile fibers far below the OSHA permissible exposure limit and the cancer no observed adverse effect level. Studies of other craftsmen who often work in the vicinity of electricians, such as insulators, reported asbestos (including amphibole) exposures that were relatively high. Overall, the evidence does not indicate that exposure to chrysotile in electrical products causes mesothelioma or lung cancer in electricians. Rather, the most likely cause of lung cancer in electricians is smoking, and the most likely cause of mesothelioma is exposure to amphibole asbestos as a result of renovation/demolition work or working in the proximity of other skilled craftsmen.

Copyright © 2013 Elsevier Inc. All rights reserved.

In plain English

This was a critical review, not new research. The authors searched PubMed, Scopus and TOXLINE through April 2013 for studies of mesothelioma or lung cancer in electricians. They also reviewed measurements of electricians' airborne asbestos exposure, including from encapsulated-chrysotile electrical products. Most reviewed epidemiology studies reported elevated mesothelioma risks (most estimates below 3) and small elevated lung cancer risks (mostly 1 to 2). However, none measured airborne asbestos levels or allowed assessment of risk from chrysotile or amphibole, and only three of sixteen smoking-adjusted studies reported increased lung cancer risk. Exposure studies generally found low airborne levels during routine work, except among power generation electricians revising steam turbines. Grinding chrysotile-containing resin plaques for about 4 to 5 minutes produced up to 1.2 fibers per cubic centimeter (f/cc). A cited review reported that insulators removing amphibole asbestos were exposed to up to 3021 f/cc. The authors concluded the evidence does not indicate chrysotile in electrical products causes mesothelioma or lung cancer in electricians. They considered smoking the most likely cause of electricians' lung cancer and amphibole asbestos the most likely cause of their mesothelioma.

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: Critical review of published epidemiology and exposure-measurement literature, searched in PubMed, Scopus and TOXLINE through April 2013
• Who was studied: Published studies of electricians, mostly in Europe and the US. For mesothelioma: eight case-control, five cohort and 10 proportionate mortality (PMR) studies. The review also covered air-sampling studies of electricians' work.
• Exposure: Chrysotile asbestos in electrical products: wire insulation contained 24–40% chrysotile, and resin circuit board and motor controller products contained 1–31%, generally encapsulated in resin or plastic. The review also considered electricians' general airborne asbestos exposure and bystander exposure to amphibole asbestos.
• Main results:
  • Among the mesothelioma studies of electricians, the majority reported elevated risks (most risk estimates below 3). These studies did not allow an assessment of risk from asbestos.
  • The authors identified 19 case-control, eight cohort and six PMR studies of lung cancer in electricians. The majority reported small elevated risks, mostly ranging from 1 to 2.
  • None of the epidemiology studies allowed an assessment of risk from chrysotile or amphibole asbestos, because airborne levels were not measured.
  • Only three of the sixteen epidemiology studies that adjusted for smoking reported an increase in lung cancer risk among electricians.
  • Of those three smoking-adjusted studies, one (Bovenzi et al., 1993) assessed asbestos exposure qualitatively through a job exposure matrix. The other two did not evaluate asbestos exposure in any way.
  • The authors judged that electricians' exposure to any asbestos, and particularly chrysotile, was generally low during routine work tasks.
  • In one reviewed study of power industry workers, power generation electricians involved in steam turbine revision had estimated exposures of 33 f/cc-yr (SD 132 f/cc-yr). Power distribution electricians had an estimated 2.8 f/cc-yr (SD 23 f/cc-yr).
  • Power grinding of resin plaques containing 0.8% to 18% chrysotile, for about 4 to 5 minutes, produced airborne concentrations ranging from below the limit of detection to 1.2 f/cc, measured by phase-contrast microscopy (PCM).
  • In another study, sawing, sanding and drilling of phenolic molding material containing 31% chrysotile gave estimated 8-hour time-weighted averages of 0.006 to 0.08 f/cc.
  • A literature review the authors relied on (Williams et al., 2007) reported that insulators removing amphibole asbestos were exposed to up to 3021 f/cc in one study.
• The authors' conclusion: The authors concluded that the evidence does not indicate that chrysotile in electrical products causes mesothelioma or lung cancer in electricians. They concluded that the most likely cause of lung cancer in electricians is smoking, and the most likely cause of mesothelioma is amphibole asbestos exposure.
• Limitations the authors state:
  • The epidemiology studies generally classified occupation at a single time point, such as the last job held at death, and collected little information on other jobs.
  • The authors stated that the epidemiology studies cannot show whether any elevated mesothelioma risk was due to any particular exposure.
  • The electrician air-sampling studies did not typically distinguish amphibole from chrysotile fibers.
  • Comparing historical air measurements is complicated because different sampling and measurement methods were used.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Asbestos Exposure, Mesothelioma, Lung Cancer, Epidemiology, Permissible Exposure Limit (PEL), Insulator, Amphibole Group.

Related studies

• Comparison of Calidria chrysotile asbestos to pure tremolite: inhalation biopersistence and histopathology following short-term exposure — D.M. Bernstein, J. Chevalier, et al. (2003)
• Minimising health hazards associated with derogated products and in-situ materials containing chrysotile contaminated with amphibole asbestos fibres — R.M. Howie (1999)
• Health risk of chrysotile revisited — D. Bernstein, J. Dunnigan, et al. (2013)
• A review and critique of U.S. EPA's risk assessments for asbestos — S.H. Moolgavkar, E.L. Anderson, et al. (2014)
• Chamber for testing asbestos-containing products: validation and testing of a re-created chrysotile-containing joint compound — P.J. Sheehan, G.P. Brorby, et al. (2011)
• Sumas Mountain chrysotile induces greater lung fibrosis in Fischer344 rats than Libby amphibole, El Dorado tremolite, and Ontario ferroactinolite — J.M. Cyphert, A. Nyska, et al. (2012)

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