Cigarette smoking, asbestos, and pulmonary fibrosis

Our plain-English summary of Cigarette smoking, asbestos, and pulmonary fibrosis, by W. Weiss (The American Review of Respiratory Disease, 1971).

The study

• Author: W. Weiss
• Journal: The American Review of Respiratory Disease
• Published: 1971;104(2):223-7
• Cited by: 53 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. 001381).

In plain English

This pilot study examined 100 workers at an asbestos (chrysotile) textile mill using chest X-rays and a questionnaire on age, sex, smoking and years of asbestos exposure. Another 42 workers refused. The author read the X-rays for pulmonary fibrosis (lung scarring) without knowing the questionnaire answers. Among the 98 workers with complete smoking information, fibrosis was seen in 24 per cent of 25 nonsmokers and 40 per cent of 73 smokers. Adjusting for age had almost no effect on this difference. None of 11 nonsmokers exposed under 20 years had fibrosis, against 6 of 14 nonsmokers exposed 20 years or more. In smokers, fibrosis rose from 29 per cent of 45 exposed under 20 years to 57 per cent of 28 exposed 20 years or more. Among people smoking a pack or more a day, it ranged from 28 per cent of 18 with under 20 years of both smoking and exposure to 74 per cent of 19 with 20 years or more of both. The author concluded that smoking asbestos workers had more fibrosis but could not say whether the effects were additive or synergistic, partly because the groups were small.

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: Pilot cross-sectional survey (prevalence study) using chest X-rays read without knowledge of smoking or exposure histories, plus a questionnaire
• Who was studied: 100 workers (16 women) at one asbestos textile mill, aged 18 to 68 years. 42 further workers refused examination. The mill's location and the study dates are not stated.
• Exposure: Work in a chrysotile asbestos textile mill, measured as years of exposure (under 20 vs 20 or more), together with cigarette smoking (amount per day and years smoked)
• Main results:
  • Pulmonary fibrosis was seen in 24 per cent of the 25 nonsmokers and 40 per cent of the 73 smokers.
  • Age adjustment had almost no effect on the difference between nonsmokers and smokers.
  • None of the 11 nonsmokers with under 20 years of asbestos exposure showed fibrosis on X-ray.
  • 6 (43 per cent) of 14 nonsmokers with 20 or more years of exposure had fibrosis.
  • Among smokers, fibrosis was seen in 29 per cent of 45 with under 20 years of exposure and 57 per cent of 28 with 20 or more years of exposure.
  • The author reported these differences as highly significant (p less than 0.005, chi square).
  • Among smokers, fibrosis was seen in 23 per cent of 13 who smoked under one pack a day and 43 per cent of 60 who smoked one pack or more a day.
  • Among smokers of a pack or more a day, the lowest prevalence was 28 per cent of 18 people who had smoked under 20 years and been exposed under 20 years.
  • The highest prevalence was 74 per cent of 19 people who had smoked a pack or more a day for 20 years or more and been exposed for 20 years or more.
  • Among the 16 women, 2 of 8 nonsmokers had fibrosis compared with 5 of 8 smokers.
  • Among workers aged 50 or older, fibrosis was seen in 30 per cent of 20 exposed under 20 years and 65 per cent of 26 exposed 20 years or more.
• The authors' conclusion: The author concluded that asbestos workers who smoke cigarettes had a higher prevalence of pulmonary fibrosis than those who do not. The author stated it was uncertain whether the effects of the two factors were additive or synergistic.
• Limitations the authors state:
  • 42 of the plant's 142 workers refused examination. The plant then closed and its records became inaccessible, so examined and unexamined workers could not be compared for possible bias.
  • Reading pulmonary fibrosis on X-rays is subject to error. The author argued that a single reader who was blind to smoking and exposure would make errors evenly across groups.
  • Duration of smoking was tied to age in groups this small, so the prevalences by smoking duration could not be age-adjusted. A similar, lesser problem applied to duration of asbestos exposure.
  • Whether the effect was additive or synergistic could not be decided because the groups were too small. The comparison survey of 999 people presumed unexposed to asbestos was not strictly comparable (it used 70-mm films).

Topics

Medical terms in this study, explained in our Lexicon: Pulmonary Fibrosis.

Related studies

• Interaction of asbestos, age, and cigarette smoking in producing radiographic evidence of diffuse pulmonary fibrosis — K.H. Kilburn, R. Lilis, et al. (1986)
• 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)
• Cigarette smoking does not produce or enhance the radiologic appearance of pulmonary fibrosis — K.H. Kilburn (1981)
• Smoking-associated fibrosis and pulmonary asbestosis — J.R. Bledsoe, D.C. Christiani, et al. (2015)
• Radiographic abnormalities in asbestos insulators: effects of duration from onset of exposure and smoking. Relationships of dyspnea with parenchymal and pleural fibrosis — R. Lilis, A. Miller, et al. (1991)
• Association of cigarette smoking and asbestos exposure with location and histology of lung cancer — B.W. Lee, J.C. Wain, et al. (1998)

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