Exposures and mortality among chrysotile asbestos workers. Part II: mortality

Our plain-English summary of Exposures and mortality among chrysotile asbestos workers. Part II: mortality, by J.M. Dement, R.L. Harris, M.J. Symons, et al (American Journal of Industrial Medicine, 1983).

The study

• Authors: J.M. Dement, R.L. Harris, M.J. Symons, C.M. Shy
• Journal: American Journal of Industrial Medicine
• Published: 1983;4(3):421-33
• Cited by: 113 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000603).

Abstract

A retrospective cohort mortality study was conducted among a cohort of 1,261 white males employed one or more months in chrysotile asbestos textile operations and followed between 1940 and 1975. Statistically significant excess mortality was observed for all causes combined (standardized mortality ratio [SMR] = 150), lung cancer (SMR = 135), diseases of the circulatory system (SMR = 125), nonmalignant respiratory diseases (SMR = 294), and accidents (SMR = 134). Using estimated fiber exposure levels in conjunction with detailed worker job histories, exposure-response relationships were investigated. Strong exposure-response relationships for lung cancer and asbestos related non-malignant respiratory diseases were observed. Compared with data for chrysotile miners and millers, chrysotile textile workers were found to experience significantly greater lung cancer mortality at lower lifetime cumulative exposure levels. Factors such as differences in airborne fiber characteristics may partially account for the large differences in exposure response between textile workers and miners and millers.

In plain English

This retrospective cohort study followed 1,261 white men who had worked at least one month in textile production at a U.S. plant processing chrysotile asbestos. Each had at least one month of employment between 1940 and 1965, and deaths were tracked through 1975. Deaths were compared with numbers expected from U.S. death rates. There were 308 deaths against 205.66 expected (SMR 150). Lung cancer caused 35 deaths against 11.10 expected (SMR 315). Asbestosis or pulmonary fibrosis was the underlying cause of 17 deaths. One peritoneal mesothelioma was confirmed by autopsy. The authors also analyzed men who had reached at least 15 years since first employment. In this group, the lung cancer SMR rose with cumulative fiber exposure, from 140 in the lowest exposure group to 1,818 in the highest, which was based on 2 deaths. Death rates from asbestosis or pulmonary fibrosis also rose with exposure. Smoking rates among 292 workers with smoking data were close to U.S. rates. The authors concluded that smoking alone could not explain the excess. They found that these textile workers had greater lung cancer mortality at lower exposures than chrysotile miners and millers, possibly because of differences in airborne fiber characteristics.

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 cohort mortality study, with expected deaths based on U.S. death rates and exposure-response analysis using estimated cumulative fiber exposure
• Who was studied: 1,261 white males employed one or more months in textile production operations at a chrysotile asbestos plant in the United States, with at least one month of employment between January 1, 1940 and December 31, 1965, followed through December 31, 1975 (33,141 person-years)
• Exposure: Chrysotile asbestos in textile operations. Exposures were estimated by job for 1930 to 1975 as fibers longer than 5 micrometers per cubic centimeter of air, and summed for each worker as cumulative exposure in fibers/cc times days.
• Main results:
  • All causes of death, whole cohort: 308 deaths observed versus 205.66 expected (SMR 150, p less than 0.05).
  • Lung cancer, whole cohort: 35 deaths observed versus 11.10 expected (SMR 315, p less than 0.05). No lung cancers occurred before 10 years since first employment, and 17 of the 35 occurred after 30 or more years.
  • Nonmalignant respiratory diseases, whole cohort: 28 deaths versus 9.53 expected (SMR 294). Of these, 24 were 'other respiratory diseases', and asbestosis or pulmonary fibrosis was the underlying cause for 17.
  • Mesothelioma: only one was observed in the cohort. It was a peritoneal mesothelioma confirmed by autopsy, 34 years after first employment.
  • Lung cancer among men who had reached 15 or more years since initial employment (latency): the SMR increased with cumulative exposure. It was 140 (5 observed versus 3.58 expected) in the lowest stratum and 1,818 (2 observed versus 0.11 expected) in the highest stratum, above 100,000 fibers/cc times days.
  • Deaths with asbestosis or pulmonary fibrosis as underlying cause, among men with 15 or more years since initial employment: 0.32 per 1,000 person-years in the lowest exposure stratum and 15.87 per 1,000 person-years in the highest, about 50 times higher.
  • Smoking among the 292 white male workers with smoking data: 52.4% current smokers, 22.3% past smokers and 25.3% nonsmokers. US white adult males in 1965: 51.5%, 22.1% and 26.4%.
  • Compared with the Quebec chrysotile miners and millers studied by McDonald et al, these textile workers had much larger lung cancer SMRs in every duration-of-employment group.
• The authors' conclusion: The authors concluded that chrysotile textile workers had significantly greater lung cancer mortality at lower lifetime cumulative exposure than chrysotile miners and millers. They suggested that differences in airborne fiber characteristics, such as length and diameter, may partly account for this. They also concluded that smoking independent of asbestos could not explain the excess, and that their data predict significantly elevated lung cancer and asbestosis risk at a cumulative exposure of 100 fibers/cc times years in the textile industry.
• Limitations the authors state:
  • Smoking histories were not available for all cohort members.
  • Historic exposure levels are hard to estimate, and imprecision may explain part of the difference from the miners and millers study.
  • The shape of the asbestosis and pulmonary fibrosis exposure-response curve is tentative, because only two cases were in the highest exposure group.
  • Lung cancer death rates in the plant's county were 75% higher than U.S. rates. The authors used U.S. rates and estimated that contiguous-county rates would have raised expected lung cancer by only about 15%.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, standardized mortality ratio (SMR), Lung Cancer, Cumulative Exposure.

Related studies

• Exposures and mortality among chrysotile asbestos workers. Part I: exposure estimates — J.M. Dement, R.L. Harris, et al. (1983)
• Follow-up study of chrysotile asbestos textile workers: cohort mortality and case-control analyses — J.M. Dement, D.P. Brown, et al. (1994)
• Increased lung cancer mortality among chrysotile asbestos textile workers is more strongly associated with exposure to long thin fibres — D. Loomis, J.M. Dement, et al. (2012)
• Cause-specific mortality in a Chinese chrysotile textile worker cohort — X. Wang, S. Lin, et al. (2013)
• Lung cancer mortality in North Carolina and South Carolina chrysotile asbestos textile workers — L. Elliott, D. Loomis, et al. (2012)
• Cancer mortality among Chinese chrysotile asbestos textile workers — X.R. Wang, I.T. Yu, et al. (2012)

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