Change in prevalence of asbestos-related disease among sheet metal workers 1986 to 2004

Our plain-English summary of Change in prevalence of asbestos-related disease among sheet metal workers 1986 to 2004, by L.S. Welch, E. Haile, J. Dement, et al (Chest, 2007).

The study

• Authors: L.S. Welch, E. Haile, J. Dement, D. Michaels
• Journal: Chest
• Published: 2007;131(3):863-869
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In 1985, the Sheet Metal Workers International Association and the Sheet Metal and Air Conditioning National Association formed The Sheet Metal Occupational Health Institute Trust to examine the health hazards of the sheet metal industry in the United States and Canada. Between 1986 and 2004, 18,211 individuals were examined. The mean age of this cohort was 57.9 years, and the participants had worked for a mean (+/- SD) duration of 32.9 +/- 6 years in the sheet metal trade. Twenty-three percent of participants were current smokers, 49% were former smokers, and 28% were never-smokers. A total of 9.6% of participants (1,745 participants) had findings that were consistent with parenchymal disease (International Labor Organization [ILO] score, >/= 1/0); 60% of those with an ILO score >/= 1/0 were classified as 1/0, 34% as 1/1 to 1/2, and 6% as >/= 2/1. A total of 21% of participants (3,827 participants) had pleural scarring. There was a lower prevalence of nonmalignant asbestos-related disease among those who began to work after 1970, when compared to workers who began to work before 1949; those who began to work between 1950 and 1969 had a prevalence between the other two groups. The strongest predictor of both parenchymal and pleural disease on a chest radiograph was the calendar year in which the worker began sheet metal work; work in a shipyard was also an important risk. The results of this study suggest that the efforts to reduce asbestos exposure in the 1980s through strengthened Occupational Safety and Health Administration regulation have had a positive public health impact.

In plain English

This study analyzed chest X-rays from a screening program, run by the Sheet Metal Occupational Health Institute Trust, for sheet metal workers in the United States and Canada who had entered the trade at least 20 years earlier. The analysis included 18,211 workers examined between 1986 and 2004; only 17 were women. Overall, 1,745 workers (9.6%) had X-ray findings consistent with parenchymal (lung tissue) disease, scored 1/0 or higher on the International Labor Organization scale. Pleural scarring was found in 3,827 workers (21%). Statistical models for 14,530 men took account of age, years worked, shipyard work, smoking and type of X-ray reader. In these models, workers who began before 1949 had higher odds than those who began after 1970 of parenchymal disease (odds ratio 2.43, 95% confidence interval 2.03 to 2.90) and of pleural disease (2.55, 95% confidence interval 2.26 to 2.88). Shipyard work was also a strong predictor of disease. The authors concluded that their results suggest reduced asbestos exposure in the 1980s, through strengthened OSHA regulation, has had a positive public health impact. They noted that years worked and starting year were hard to separate.

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: Analysis of chest radiograph results from a standardized occupational screening program (prevalence study), using logistic regression to find predictors of disease
• Who was studied: 18,211 sheet metal workers in the United States and Canada examined between 1986 and 2004, all first employed in the industry at least 20 years earlier. Mean age was 57.9 years and only 17 were women. The regression models were restricted to men (n 14,530).
• Exposure: Occupational asbestos exposure in sheet metal work; no fiber type is specified. Exposure was studied through the calendar year of entering the trade (before 1949, 1950 to 1969, after 1970), years worked in the trade (mean 32.9 years), and any history of shipyard work.
• Main results:
  • Among all 18,211 workers screened, 1,745 (9.6%) had findings consistent with parenchymal disease (ILO score 1/0 or higher). Of these, 60% were classified 1/0, 34% 1/1 to 1/2, and 6% 2/1 or higher.
  • 21% of all participants (3,827 workers) had pleural scarring.
  • In adjusted models for 14,530 men, workers who began sheet metal work before 1949 had an odds ratio of 2.43 (95% CI 2.03 to 2.90) for parenchymal disease and 2.55 (95% CI 2.26 to 2.88) for pleural disease, compared with those who began after 1970. Workers who began in 1950 to 1969 had odds ratios of 1.32 (95% CI 1.14 to 1.53) for parenchymal disease and 1.39 (95% CI 1.26 to 1.53) for pleural disease, compared with those who began after 1970.
  • Shipyard work was a strong predictor of radiographic disease: odds ratio 1.97 (95% CI 1.61 to 2.40) for parenchymal disease and 1.85 (95% CI 1.57 to 2.17) for pleural disease. 13% of those who began before 1949 had worked in a shipyard, compared with 3.6% of those beginning 1950 to 1969 and 2% of those beginning in or after 1970.
  • In the main adjusted models, age, shipyard work, reading by an A reader and pack-years of smoking were significant predictors, while the number of years of sheet metal work was not.
  • In alternative models adjusted for age and smoking, each year of sheet metal work was a significant predictor of parenchymal disease if it fell before 1950 (OR 1.023; 95% CI 1.009 to 1.038) or between 1950 and 1969 (OR 1.045; 95% CI 1.033 to 1.058). Years of work after 1970 were not a significant predictor.
  • A readers were more likely than B readers to report parenchymal abnormalities (16.4% vs 7.8%) and pleural abnormalities (32.3% vs 20.0%).
• The authors' conclusion: The authors concluded that their results suggest that reduced asbestos exposure in the 1980s, through strengthened OSHA regulation, has had a positive public health impact. They also concluded that the calendar year of starting sheet metal work was the strongest predictor of both parenchymal and pleural disease on X-ray, with shipyard work also an important risk.
• Limitations the authors state:
  • Years worked in the trade were inversely correlated with the year work began, making it difficult to separate the effects of these two factors.
  • Because the program required 20 years of sheet metal work, even the comparison group had significant exposure. This limited the ability to detect the true effect of work duration.
  • The number of disease cases among those who worked after 1970 gave limited statistical power to detect trends by work duration for that period.
  • The data do not allow the effects of latency and cumulative exposure to be separated, and cumulative exposure could not be assigned to individual workers.
  • A reading was correlated with shipyard work and with the calendar year of entering the trade, because earlier radiographs were more often read by A readers.
  • Additional disease may appear in future years among workers who began in the 1960s and 1970s, given the long latency of asbestos disease.

Topics

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

Medical terms in this study, explained in our Lexicon: Chest X-Ray, Asbestos Exposure.

Related studies

• Asbestos-related disease among sheet metal workers 1986-2004: radiographic changes over time — L.S. Welch, E. Haile (2009)
• 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)
• Change in prevalence of asbestos-related disease among sheet metal workers 1986 to 2016 — G.H. West, R.K. Sokas, et al. (2019)
• Asbestos disease in sheet metal workers: proportional mortality update — D. Michaels, S. Zoloth (1988)
• Mortality among sheet metal workers participating in a respiratory screening program — L. Welch, J. Dement, et al. (2015)
• The National Sheet Metal Worker Asbestos Disease Screening Program: radiologic findings. National Sheet Metal Examination Group — L.S. Welch, D. Michaels, et al. (1994)

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