Combined effect of asbestos and smoking on mortality from lung cancer and mesothelioma in factory workers

Our plain-English summary of Combined effect of asbestos and smoking on mortality from lung cancer and mesothelioma in factory workers, by G. Berry, M.L. Newhouse, P. Antonis (British Journal of Industrial Medicine, 1985).

The study

• Authors: G. Berry, M.L. Newhouse, P. Antonis
• Journal: British Journal of Industrial Medicine
• Published: 1985;42(1):12-8
• Cited by: 86 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000459).

Abstract

The mortality of over 1250 male and 420 female asbestos factory workers was observed over the period 1971-80. Smoking habits were obtained from the subjects in 1971 before the start of the follow up period. Mortality due to lung cancer and to mesothelioma was related to smoking habits. After allowing for the effect of smoking on lung cancer the relative risk due to asbestos was highest for those who had never smoked, lowest for current smokers, and intermediate for ex-smokers; the trend was statistically significant (p less than 0.05). There was no significant association between smoking and deaths due to mesothelioma. Data from several studies are reviewed, and although overall non-smokers have a relative risk of lung cancer due to asbestos that is 1.8 times that of smokers, there is some uncertainty on the accuracy of this figure because of possible biases and sampling variation. Overall the evidence is that mesothelioma risk is independent of smoking.

In plain English

This study followed 1253 men and 423 women who had worked at an asbestos factory in east London and whose smoking habits were recorded in 1971. Deaths were tracked to 1980. There was no unexposed comparison group, so lung cancer deaths were compared with numbers expected from death rates in the general population of the region, adjusted for smoking. After this adjustment, the asbestos-related lung cancer risk (men and women combined) was highest in those who had never smoked (7.3 times expected), intermediate in ex-smokers (4.0) and lowest in current smokers (2.2). This trend was statistically significant. Combining men and women, mesothelioma death rates did not differ significantly between smoking groups. The authors also reviewed six studies, two from this factory. They estimated that non-smokers' relative lung cancer risk from asbestos was 1.8 times that of smokers (95% confidence interval 1.1 to 2.8), but said this interval was too narrow and that some recorded never-smokers may have smoked. The authors concluded this was not established, though the data suggested it may be so, and that mesothelioma risk appeared independent of smoking.

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: Prospective mortality (cohort) study of factory workers whose smoking habits were recorded before follow-up, plus a review and combined analysis of similar published studies
• Who was studied: Workers from an asbestos factory in the east end of London. Men were born 1900 to 1930, first employed 1 April 1933 to 31 December 1955, and were not laggers. Women were first employed 1936 to 1942. Of 1543 men and 538 women traced alive on 1 July 1971, the 1253 men and 423 women with smoking habits recorded in 1971 were analysed. Follow-up ran to 31 December 1980 (men) and 30 June 1980 (women).
• Exposure: Employment at an asbestos factory (fiber type not specified for this factory), classified as light or moderate versus severe exposure, and as less or more than two years' duration; smoking habit (never smoked, ex-smoker, smoker) as reported in 1971
• Main results:
  • Men: the ratio of observed to expected lung cancer deaths (after allowing for smoking) was 6.2 for never smoked (1 observed, 0.16 expected), 4.7 for ex-smokers (11 observed, 2.32 expected) and 2.0 for smokers (52 observed, 25.92 expected). The trend was statistically significant (p less than 0.05), as was the ex-smoker versus smoker difference.
  • Women: the lung cancer ratio was 12.5 for never smoked (3 observed, 0.24 expected), 3.4 for ex-smokers and 4.3 for smokers. The difference between never smoked and those who had smoked at some time was not significant.
  • Men and women combined, standardised for sex and exposure: relative risk of lung cancer due to asbestos was 7.3 for never smoked, 4.0 for ex-smokers and 2.2 for smokers. The trend was significant (p less than 0.05), but neither never versus ever smoked nor ex-smokers versus smokers was significant.
  • Mesothelioma in men: ex-smokers had the highest rate (477 per 100 000 subject-years, 10 deaths), significantly (p less than 0.05) higher than smokers (201 per 100 000, 16 deaths). There were no mesotheliomas in men who had never smoked, which the authors said was not significant because of few subject-years.
  • Mesothelioma, men and women combined and adjusted for sex and asbestos exposure: no significant differences between smoking groups
  • Checking smoking habits recorded at death against those given in 1971 (114 people): of 12 who said in 1971 they had never smoked, eight were recorded as never smoked at death, two as ex-smokers and two as smokers
  • Review of six studies (including two from this factory): the relative risk of lung cancer due to asbestos was estimated as 1.8 times greater in non-smokers than in smokers (95% confidence interval 1.1 to 2.8), with little evidence of difference between studies
• The authors' conclusion: The authors concluded that it is not established that non-smokers have a higher relative lung cancer risk from asbestos than smokers, although overall the data suggest this may be the case. They also concluded that in absolute terms smokers have the higher lung cancer risk, and that mesothelioma risk appears independent of smoking.
• Limitations the authors state:
  • Some people recorded as never having smoked may have smoked, and this could explain the trend seen
  • Confidence intervals in the combined review assumed expected deaths were known without error, so they will be too narrow
  • Smoking adjustments used relative risks from British doctors, whose smoking patterns may differ from the factory workers'
  • Only four lung cancer deaths occurred in non-smokers in this study
  • Misdiagnosis on death certificates can bias comparisons between smoking groups

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer, Mesothelioma, Habit, Relative Risk.

Related studies

• Combined effect of asbestos exposure and smoking on mortality from lung cancer in factory workers — G. Berry, M.L. Newhouse, et al. (1972)
• Mortality of factory workers in east London 1933-80 — M.L. Newhouse, G. Berry, et al. (1985)
• Mortality from all cancers of asbestos factory workers in east London 1933-80 — G. Berry, M.L. Newhouse, et al. (2000)
• The combined effects of smoking and occupational or urban factors in relation to lung cancer — R.E. Waller (1972)
• Predictions of mortality from mesothelial tumours in asbestos factory workers — M.L. Newhouse, G. Berry (1976)
• The effect of smoking on the risk of lung cancer mortality for asbestos workers in Great Britain (1971-2005) — G. Frost, A. Darnton, et al. (2011)

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