Asbestos-related disease among sheet metal workers 1986-2004: radiographic changes over time

Our plain-English summary of Asbestos-related disease among sheet metal workers 1986-2004: radiographic changes over time, by L.S. Welch, E. Haile (American Journal of Industrial Medicine, 2009).

The study

• Authors: L.S. Welch, E. Haile
• Journal: American Journal of Industrial Medicine
• Published: 2009;52(7):519-25
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: 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 (SMOHIT) to examine the health hazards of the sheet metal industry. Between 1986 and 2004 18,211 individuals were examined. At the time of the first examination 9.6% of all participants (1,745) had findings consistent with parenchymal disease (ILO > 1/0), and 21% (3,827) had pleural scarring.

Methods: 2181-Two thousand hundred eighty-one who had no radiographic evidence of pneumoconiosis on baseline examination underwent a second examination.

Results: By the second examination, 5.3% had developed parenchymal disease on chest radiograph; an additional 12.4% had developed pleural scarring without parenchymal disease. Factors that predicted new cases of pneumoconiosis on radiograph were the calendar year the worker entered the sheet metal trade, smoking, and shipyard work. Forty-seven percent of those smoking at the time of initial exam reported having quit smoking by the second examination.

Conclusions: Asbestosis is still occurring 50 years after first exposure. Exposed workers benefit from medical screening programs that incorporate smoking cessation.

In plain English

This study followed up sheet metal workers in a United States screening program for asbestos-related disease. The authors analyzed 2,181 workers whose first chest X-ray showed no signs of pneumoconiosis and who had a second X-ray an average of about 10 years later. By the second examination, 115 (5.3%) had developed changes in the lung tissue (parenchymal disease), and another 270 (12.4%) had pleural changes without parenchymal changes. Workers who began in the trade before 1950 developed changes more often (9% parenchymal, 15.8% pleural) than those who began between 1950 and 1970 (4.6% and 11.7%). Entering the trade earlier, smoking and shipyard work were associated with new changes. Age and years worked were not significant predictors. Of 472 workers who smoked at the first exam, 221 (47%) had quit by the second. The authors concluded that asbestosis is still occurring 50 years after first exposure, and that exposed workers benefit from screening that includes help to stop smoking. They noted that each X-ray was classified by a single reader, and that the two X-rays were not read side by side.

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: Longitudinal study comparing first and repeat chest X-rays from a medical screening program for sheet metal workers
• Who was studied: 2,181 United States sheet metal workers (all male in Table II) first screened in rounds 1 or 2, with no X-ray evidence of pneumoconiosis at first exam, at least two exams, and both X-rays classified by B readers; drawn from 9,890 eligible workers
• Exposure: Asbestos exposure in sheet metal work (fiber types not specified). The authors grouped workers by the calendar year they entered the trade (before 1950, 1950 to 1969, 1970 or later), on the assumption that exposure was highest for the earliest group. They also examined years worked, shipyard work and smoking.
• Main results:
  • Of the 2,181 workers, 115 (5.3%) had parenchymal disease, with or without pleural disease, on the second examination, and 270 (12.4%) had pleural disease without parenchymal disease.
  • Pleural disease without parenchymal disease was found in 270 (12.4%) on the second examination.
  • Among workers who began before 1950, 9% developed parenchymal disease and 15.8% developed pleural disease, compared with 4.6% and 11.7% among those who began between 1950 and 1970.
  • In regression models, workers with asbestos-related disease on the second exam had entered the trade earlier, were more likely to be current or former smokers, and were more likely to have worked in a shipyard. Age and years worked were not significant predictors.
  • Shipyard work had an odds ratio of 5.08 (95% CI 1.91 to 13.49) for parenchymal disease and 2.70 (1.17 to 6.23) for pleural disease only, compared with no disease. Few workers had shipyard work: 4 of 115 with parenchymal disease, 4 of 270 with pleural disease only, and 3 of 1,796 with no disease.
  • Of the 472 workers who were active smokers at the first exam, 221 (47%) had quit by the second exam.
  • Compared with all eligible workers, those who returned for a second exam were younger, had entered the trade somewhat later, had fewer years worked, and were less likely to have worked in a shipyard.
• The authors' conclusion: The authors concluded that asbestosis is still occurring 50 years after first exposure, and that exposed workers benefit from medical screening programs that incorporate smoking cessation.
• Limitations the authors state:
  • Each X-ray was classified by a single reader. The first and later X-rays were not read side by side and were not classified by the same reader. The authors considered differential misclassification unlikely.
  • Latency and cumulative exposure were highly correlated, and the range of years worked was narrow, so the authors could not separate their effects.
  • Only workers with a normal X-ray were invited back, so improvement (regression) could not be measured. The authors did not think this affected interpretation.

Topics

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

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

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. 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)
• Mortality among sheet metal workers participating in a respiratory screening program — L. Welch, J. Dement, et al. (2015)
• Asbestos disease in sheet metal workers: proportional mortality update — D. Michaels, S. Zoloth (1988)
• 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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