Pleural plaques and cigarette smoking in asbestos workers

Our plain-English summary of Pleural plaques and cigarette smoking in asbestos workers, by W. Weiss, R. Levin, L. Goodman (Journal of Occupational Medicine., 1981).

The study

• Authors: W. Weiss, R. Levin, L. Goodman
• Journal: Journal of Occupational Medicine.
• Published: 1981;23(6):427-30
• Cited by: 19 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. 000781).

Abstract

In a survey of 45 men aged 40 or over who had worked five years or more in an asbestos manufacturing plant, the prevalence of pleural plaques was studied with respect to age, duration of asbestos exposure, estimated cumulative asbestos dose, and smoking habit. Plaques were found in 38 to 53% of the men, depending on the interpretation of the chest film reader. Cigarette habit appeared to be the most important factor; the prevalence was lowest in non-smokers, intermediate in current smokers, and particularly high in exsmokers. There was some confounding of this relationship by estimated cumulative asbestos dose but such confounding did not seem to be sufficient to explain fully the relationship between the prevalence of plaques and smoking habit. Both factors must be considered in studies of the risk of pleural plaques in asbestos workers.

In plain English

This study asked whether pleural plaques (thickened patches on the lining of the chest wall) were linked to cigarette smoking in workers at an asbestos products manufacturing plant. The plant used chrysotile asbestos throughout, and also used amosite from 1950 to 1964. The authors analyzed chest x-rays from 1977 and 1978 surveys of 45 men aged 40 or over who had worked at the plant for five years or more. Two of the authors read the films independently and often disagreed. Plaques were found in 38% to 53% of the men, depending on the reader. Age was not a factor. Plaques were least common in nonsmokers, more common in current smokers, and particularly common in ex-smokers. These differences were statistically significant for both readers. Ex-smokers had worked about eight years longer than the others and had higher estimated asbestos doses. The dose difference was not statistically significant. The authors concluded that these differences did not seem to fully explain the smoking link, and that both factors must be considered. They noted that the number of workers was small and the dose estimates were crude.

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: Cross-sectional chest x-ray survey of workers at one asbestos products plant, analyzing plaque prevalence by age, duration of exposure, estimated cumulative dose and smoking habit
• Who was studied: 45 men aged 40 or over who had worked five years or more at one asbestos products manufacturing plant (Plant B) and had chest films in 1977 and/or 1978. Of 69 eligible men, 56 had films, and 11 with less than five years at the plant were excluded.
• Exposure: Chrysotile asbestos in textiles, sheet packing, paper, millboard, molded insulation and asbestos cement boards. Amosite was added to chrysotile in molded insulation from 1950 to 1964. Fiber counts were not made until 1972 and have been generally under 2 per cubic centimeter in recent years. Cumulative dose was estimated with a semiquantitative job index.
• Main results:
  • Plaques were found in 38% to 53% of the 45 men, depending on which reader interpreted the films (53% for reader W.W., 38% for reader L.G.).
  • The readers disagreed on plaques in 31% of cases. In 11 (24%) of the 45 cases W.W. found plaques when L.G. did not.
  • Age was not a factor in plaque prevalence.
  • Duration of exposure and cumulative dose appeared to be factors, but three of the four comparisons were not statistically significant at the 0.05 level because of small numbers.
  • Plaque prevalence was lowest in nonsmokers, intermediate in current smokers and particularly high in ex-smokers. The differences were statistically significant for both readers.
  • Ex-smokers averaged eight years more work at the plant than nonsmokers and current smokers, a statistically significant difference.
  • Ex-smokers' average cumulative dose index was 40 to 55% higher than that of the other two groups. This was not statistically significant.
  • Among men in the two lower asbestos dose categories combined (W.W.'s readings), plaques were found in 6 of 21 nonsmokers and current smokers compared with 6 of 7 ex-smokers. This difference was statistically significant at the 0.05 level.
  • For L.G.'s readings, the cross-classified findings were similar but less clear-cut and not statistically significant at the 0.05 level.
• The authors' conclusion: The authors concluded that cigarette habit appeared to be the most important factor. Some confounding by estimated asbestos dose did not seem sufficient to fully explain the smoking relationship, and both factors must be considered in studies of pleural plaque risk in asbestos workers.
• Limitations the authors state:
  • Cross-classifying by dose and smoking left very small numbers in each group.
  • Estimates of asbestos dose were crude.
  • It was uncertain whether ex-smokers' greater asbestos exposure could account for their higher plaque prevalence.
  • A much larger study, preferably a cohort study, would be needed to tell whether the smoking-plaque association is spurious.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Pleural plaques and thickening.

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

Related studies

• Asbestosis: interstitial pulmonary fibrosis and pleural fibrosis in a cohort of asbestos insulation workers: influence of cigarette smoking — R. Lilis, I.J. Selikoff, et al. (1986)
• Railroad workers with pleural plaques: I. Spirometric and nitrogen washout investigation on smoking and nonsmoking asbestos-exposed workers — U. Hjortsberg, P. Orbaek, et al. (1988)
• Interaction of asbestos, age, and cigarette smoking in producing radiographic evidence of diffuse pulmonary fibrosis — K.H. Kilburn, R. Lilis, et al. (1986)
• Cigarette smoking, asbestos, and pulmonary fibrosis — W. Weiss (1971)
• Cigarette smoking and small irregular opacities — W. Weiss (1991)
• Clinical findings among asbestos workers in U.S.: influence of cigarette smoking — Y. Lerman, I.J. Selikoff, et al. (1986)

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