Change in prevalence of asbestos-related disease among sheet metal workers 1986 to 2016

Our plain-English summary of Change in prevalence of asbestos-related disease among sheet metal workers 1986 to 2016, by G.H. West, R.K. Sokas, L.S. Welch (American Journal of Industrial Medicine, 2019).

The study

• Authors: G.H. West, R.K. Sokas, L.S. Welch
• Journal: American Journal of Industrial Medicine
• Published: 2019;62(7):609-615
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: A medical screening program began in 1986 for sheet metal workers exposed to asbestos, primarily while working alongside insulators applying spray-on asbestos materials, a practice banned in 1973. Exposure continues during maintenance, renovation, and repair.

Methods: Radiographic abnormalities among 26 397 sheet metal workers examined from 1986 to 2016 were analyzed by year of entry into the trade. Logistic regression was used to examine risk factors for parenchymal and pleural abnormalities among the overall study population and among the subcohort who entered the trade after 1973.

Results: Prevalence of parenchymal disease was 17.4% for those starting work before 1950 compared with 0.8% for those starting work after 1973 (adjusted prevalence odds ratio [pOR] = 26.65, 95% confidence interval [CI] = 18.46-38.46). For each calendar year after 1973, entering the trade 1 year later was associated with an estimated 12.7% decreased odds of acquiring asbestos-related disease (adjusted pOR = 0.873, 95% CI = 0.832-0.916).

Conclusion: Sheet metal workers who began work after the US implemented environmental and occupational regulations develop asbestos-related disease at much reduced rates, consistent with regulatory projections made for nonmalignant asbestos-related disease by the Occupational Safety and Health Administration at the time. Cancer remains a concern among this cohort, and lung cancer screening recommendations should consider year of entry into the trade. This study highlights the importance of regulatory intervention and of continued surveillance.

© 2019 Wiley Periodicals, Inc.

In plain English

This brief report analyzed chest X-rays from a screening program for sheet metal workers in the US and Canada. It covered 26 397 workers whose latest exam was between 1986 and 2016. Workers became eligible 20 years after starting in the trade. The authors grouped workers by the year they entered the trade and adjusted for years worked and smoking. Overall, 8.4% had abnormalities in the lung tissue (parenchymal) and 18.6% had pleural abnormalities. Parenchymal abnormalities appeared in 17.43% of those who started before 1950 and 0.84% of those who started after 1973. Compared with the after-1973 group, the adjusted prevalence odds ratio for the before-1950 group was 26.65 (95% CI 18.46 to 38.46). Among workers who started after 1973, each later year of entry was associated with an estimated 12.7% lower odds of asbestos-related abnormalities (odds ratio 0.873, 95% CI 0.832 to 0.916). The authors concluded that workers who entered after US regulations had much lower rates, but that the disease has not been eliminated and cancer remains a concern. They noted they had no direct exposure measures.

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: Brief report: cross-sectional analysis of chest X-ray results from a medical screening program, using logistic regression
• Who was studied: 26 397 sheet metal workers in the United States and Canada whose most recent screening exam occurred between 1986 and 2016. Workers were eligible if they first began sheet metal work at least 20 years before the invitation to screening.
• Exposure: Asbestos exposure in the sheet metal trade, assessed indirectly by calendar year of entry into the trade (before 1950, 1950-1959, 1960-1973, after 1973) and by duration of sheet metal work. The authors describe the 1973 ban on spray-on asbestos as reducing bystander exposure. They say later entrants still had exposure to other products such as pipe-covering. No fiber types are named, and there were no direct exposure measurements.
• Main results:
  • Among all 26 397 workers, 2218 (8.4%) had X-ray findings consistent with parenchymal disease and 4896 (18.6%) had pleural abnormalities.
  • Parenchymal disease (ILO score 1/0 or higher) by year of entry into the trade: 856 (17.43%) before 1950, 873 (10.82%) in 1950-1959, 456 (4.8%) in 1960-1973, and 33 (0.84%) after 1973.
  • Pleural disease by year of entry: 1736 (35.35%) before 1950, 2043 (25.33%) in 1950-1959, 1052 (11.07%) in 1960-1973, and 65 (1.66%) after 1973.
  • Adjusted prevalence odds ratios for parenchymal disease compared with workers entering after 1973: 26.65 (95% CI 18.46 to 38.46) for entry before 1950, and 9.17 (95% CI 6.46 to 13.01) for entry in 1950-1973.
  • Adjusted prevalence odds ratios for pleural disease compared with workers entering after 1973: 32.33 (95% CI 24.84 to 42.07) for entry before 1950, and 12.17 (95% CI 9.47 to 15.63) for entry in 1950-1973.
  • Among the 3920 workers who entered the trade after 1973, 2.45% had abnormalities consistent with asbestos-related disease (96 workers).
  • In the after-1973 group, entering the trade one year later was associated with an estimated 12.7% decreased odds of asbestos-related disease (adjusted pOR 0.873, 95% CI 0.832 to 0.916).
  • Smoking had a small but statistically significant association with parenchymal disease (pOR 1.060, 95% CI 1.050 to 1.070 per 5 pack-years) and with pleural disease (pOR 1.020, 95% CI 1.015 to 1.025 per 5 pack-years).
• The authors' conclusion: The authors concluded that sheet metal workers who entered the trade after US environmental and occupational regulations develop X-ray abnormalities consistent with nonmalignant asbestos-related disease at much reduced rates compared with those who entered before 1973. They also noted that the after-1973 prevalence is higher than in the general population, so asbestos-related disease has not yet been eliminated. They stated that cancer remains a concern.
• Limitations the authors state:
  • Screening required 20 years since first exposure, which limited the authors' ability to assess the effect of latency; further follow-up may be needed.
  • There were no direct measures of exposure.
  • The analysis cannot tell whether disease reflects relatively high exposures in a subset of workers or less intense exposures across a broad group.
  • The association between smoking and pleural changes may be confounded by asbestos exposure that the models could not control for.

Topics

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

Medical terms in this study, explained in our Lexicon: Insulator, Odds Ratio, confidence interval, Low-Dose CT Screening.

Related studies

• Change in prevalence of asbestos-related disease among sheet metal workers 1986 to 2004 — L.S. Welch, E. Haile, et al. (2007)
• Asbestos-related disease among sheet metal workers 1986-2004: radiographic changes over time — L.S. Welch, E. Haile (2009)
• The National Sheet Metal Worker Asbestos Disease Screening Program: radiologic findings. National Sheet Metal Examination Group — L.S. Welch, D. Michaels, et al. (1994)
• Asbestos-related disease among sheet-metal workers. Preliminary results of the National Sheet Metal Worker Asbestos Disease Screening Program — L.S. Welch, D. Michaels, et al. (1991)
• Asbestos disease in sheet metal workers: II. Radiologic signs of asbestosis among active workers — D. Michaels, S. Zoloth, et al. (1987)
• Prevalence of Asbestos-Related Disease Among Workers in Sri Lanka — B.A. Wickramatillake, M.A. Fernando, et al. (2019)

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