Retrospective exposure assessment to airborne asbestos among power industry workers

Our plain-English summary of Retrospective exposure assessment to airborne asbestos among power industry workers, by M.K. Felten, L. Knoll, C. Eisenhawer, et al (Journal of Occupational Medicine and Toxicology, 2010).

The study

• Authors: M.K. Felten, L. Knoll, C. Eisenhawer, D. Ackermann, K. Khatab, J. Hüdepohl, W. Zschiesche, T. Kraus
• Journal: Journal of Occupational Medicine and Toxicology
• Published: 2010;5:15
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: A method of individually assessing former exposure to asbestos fibres is a precondition of risk-differentiated health surveillance. The main aims of our study were to assess former levels of airborne asbestos exposure in the power industry in Germany and to propose a basic strategy for health surveillance and the early detection of asbestos related diseases.

Methods: Between March 2002 and the end of 2006, we conducted a retrospective questionnaire based survey of occupational tasks and exposures with airborne asbestos fibres in a cohort of 8632 formerly asbestos exposed power industry workers. The data on exposure and occupation were entered into a specially designed computer programme, based on ambient monitoring of airborne asbestos fibre concentrations. The cumulative asbestos exposure was expressed as the product of the eight-hour time weighted average and the total duration of exposure in fibre years (fibres/cubic centimetre-years).

Results: Data of 7775 (90% of the total) participants working in installations for power generation, power distribution or gas supply could be evaluated. The power generation group (n = 5284) had a mean age of 56 years, were exposed for 20 years and had an average cumulative asbestos exposure of 42 fibre years. The occupational group of "metalworkers" (n = 1600) had the highest mean value of 79 fibre years. The corresponding results for the power distribution group (n = 2491) were a mean age of 45 years, a mean exposure duration of 12 years and an average cumulative asbestos exposure of only 2.5 fibre years. The gas supply workers (n = 512) had a mean age of 54 years and a mean duration of exposure of 15 years.

Conclusions: While the surveyed cohort as a whole was heavily exposed to asbestos dust, the power distribution group had a mean cumulative exposure of only 6% of that found in the power generation group. Based on the presented data, risk-differentiated disease surveillance focusing on metalworkers and electricians from the power generating industry seems justified. That combined with a sensitive examination technique would allow detecting asbestos related diseases early and efficiently.

In plain English

This German study estimated how much airborne asbestos power industry workers had been exposed to in the past. From 2002 to 2006 the authors surveyed 8632 current and former employees of a major power provider who had stated they were exposed to asbestos, using questionnaires on their jobs and tasks. A computer program based on historical workplace air measurements turned the answers into cumulative exposure in "fibre years". Exposure after 1992 was not counted. Usable data were available for 7775 workers. Power generation workers (5284) averaged 42 fibre years and 20 years of exposure. Metalworkers among them (1600) averaged 79 fibre years, the highest average of any job group. Power distribution workers (2491) averaged 2.5 fibre years and 12 years of exposure, about 6% of the power generation figure. Fibre years were not calculated for 512 gas supply workers. Company records showed exposure to both chrysotile and crocidolite for 40% of all participants. The authors concluded that health surveillance focusing on metalworkers and electricians in power generation seemed justified. They noted that selection and recall bias could not be ruled out.

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: Retrospective, questionnaire-based exposure assessment in a cohort of asbestos-exposed workers. Cumulative exposure was calculated with standardized software based on historical air monitoring data.
• Who was studied: 8632 formerly or still active employees of a major German electrical power provider who had signed a statement that they were exposed to asbestos. Survey ran March 2002 to end of 2006. Breakdown: 5622 power generation workers (mostly in eight power plants, six conventional and two nuclear), 2498 power distribution workers and 512 gas supply workers. 28 were women.
• Exposure: Occupational airborne asbestos exposure, expressed as cumulative fibre years (8-hour time-weighted average fibre concentration multiplied by duration of exposure). Tasks included turbine revisions, removal of asbestos insulation, spraying of asbestos pulp, gaskets and packings, and drilling or sawing asbestos cement sheets. Exposure periods after 1992 were excluded.
• Main results:
  • 7775 of the 8120 power generation and power distribution workers (96%) gave enough data to calculate individual cumulative exposure.
  • Power generation workers (n = 5284) had a mean age of 56 years, a mean exposure of 20 years and a mean cumulative exposure of 42 fibre years.
  • Within power generation, metalworkers (n = 1600) averaged 79 fibre years, far higher than any other job group.
  • In power generation, 75% of metalworkers had been actively involved in turbine revisions.
  • Power distribution workers (n = 2491) had a mean age of 45 years, a mean exposure of 12 years and a mean cumulative exposure of 2.5 fibre years.
  • Power distribution workers' mean cumulative exposure was about 6% of the power generation group's.
  • In power distribution, 77% of electricians had drilled asbestos cement sheets.
  • Gas supply workers (n = 512) had a mean age of 54 years and a mean exposure of 15 years. Their cumulative exposure was not calculated.
  • Fibre type was recorded for 5637 of the 8632 participants. As shares of all 8632: 40% (3479) were exposed to both chrysotile and crocidolite, 18% (1545) to chrysotile only and 7% (613) to crocidolite only.
• The authors' conclusion: The authors concluded that risk-differentiated disease surveillance focusing on metalworkers and electricians in power generation seemed justified. They considered power generation metalworkers a high-risk group, based on the assumption that higher cumulative exposure leads to higher risk of asbestos-associated disease.
• Limitations the authors state:
  • Because of the long and varied time between exposure and the survey, general conclusions about the original exposed workforce and its work standards should be drawn with caution.
  • The fibre-year approach still needs validation against disease rates.
  • Job titles were assigned to exposure groups without considering job changes over time, which partly explains the large spread of values.
  • Selection bias or recall bias could not be ruled out. The return rate of usable questionnaires was 70% in the power generation group.
  • Detailed exposure data and job tasks for gas supply workers could not be included.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Cumulative Exposure.

Related studies

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