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

Our plain-English summary of Combined effect of asbestos exposure and smoking on mortality from lung cancer in factory workers, by G. Berry, M.L. Newhouse, M. Turok (Lancet, 1972).

The study

• Authors: G. Berry, M.L. Newhouse, M. Turok
• Journal: Lancet
• Published: 1972;2(7775):476-8
• Cited by: 129 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. 002418).

In plain English

This study followed workers from an asbestos factory in the East End of London to see how cigarette smoking and asbestos exposure together related to deaths from lung cancer. The groups were 1834 men born 1900 to 1930 and 658 women, all alive on 1 January 1960. Deaths up to 31 March 1970 were examined. Smoking histories came from questionnaires to survivors and, for those who had died, from hospital records, family doctors and relatives. Lung-cancer deaths were compared with the numbers expected from general-population rates adjusted for smoking. Workers with low-to-moderate exposure showed no significant excess, whether they smoked or not. Among severely exposed smokers the excess was highly significant, and it stayed significant when pleural mesothelioma deaths were left out. For the women, the data clearly followed a multiplicative pattern, where the two risks multiply rather than add. The authors judged this 6 to 1 more likely, although the additive pattern could not be firmly rejected (P=0.06). The results for the men were not clear enough to decide. Smoking information was gathered differently for the dead and the living.

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: Cohort mortality study comparing observed with expected lung-cancer deaths, with expected numbers adjusted for smoking habits. Smoking histories came from a retrospective inquiry for those who had died and a survey of survivors.
• Who was studied: Workers from an asbestos factory in the East End of London. There were 1834 men born 1900 to 1930, alive on 1 January 1960 and first employed between 1 April 1933 and 31 December 1955. There were 658 women alive on 1 January 1960 who were first employed 1936 to 1942. The study period ran from 1 January 1960 to 31 March 1970, during which 180 men and 98 women died.
• Exposure: Mixed types of asbestos at the factory, grouped as light/moderate or severe exposure, combined with cigarette smoking (smoking habits as of 1960). The fiber types are not named individually. Women worked chiefly in textile departments.
• Main results:
  • Smoking histories were obtained for 73% of male and 70% of female survivors, and for 72% of the men and 91% of the women who died.
  • 30% of the women who completed questionnaires had never smoked, compared with 6% of the men.
  • Among men with low-to-moderate exposure, smokers had a slight excess of lung-cancer deaths, which disappeared after adjustment for bias. Women in this exposure group had only 1 lung-cancer death.
  • Among severely exposed workers who smoked, the excess of lung-cancer deaths was highly significant.
  • Even with pleural mesothelioma deaths excluded, deaths from bronchogenic carcinoma in severely exposed smokers remained significantly raised.
  • Among the deceased, 4 of 58 deaths (7%) without smoking histories were from lung cancer, compared with 63 of 220 deaths (29%) with known smoking habits. This indicated bias in which smoking information was available, and the authors adjusted for it.
  • For severely exposed men, the results were not clear-cut enough to choose between the additive and multiplicative hypotheses.
  • For severely exposed women, the data clearly followed the multiplicative hypothesis. Rejecting the additive hypothesis on these data alone might be premature (P=0.06), but the relative likelihood was 6 to 1 in favour of the multiplicative hypothesis.
  • Severely exposed women smokers had a greater excess mortality than similarly exposed male workers. The authors described the explanation as speculative.
• The authors' conclusion: The authors concluded that the data on women support the multiplicative hypothesis, in which the risks of smoking and asbestos multiply rather than add. They noted that this agrees with findings in New York insulation workers. They drew no conclusion for men.
• Limitations the authors state:
  • Smoking information was obtained in different ways for the deceased and the survivors, a potential source of bias.
  • A higher proportion of the deceased were recorded as non-smokers, which suggests inaccurate reporting.
  • Ex-smokers' 1960 smoking habits depended on how accurately they remembered when they had quit.
  • The lung-cancer rates for women used to adjust the expected numbers were not very accurate.
  • Too few men were non-smokers to draw any conclusion for men.
  • Results are preliminary. Retrospective and prospective data were combined because a purely prospective study would give no valid results for ten years.

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: Asbestos Exposure, Lung Cancer.

Related studies

• Combined effect of asbestos and smoking on mortality from lung cancer and mesothelioma in factory workers — G. Berry, M.L. Newhouse, et al. (1985)
• Predictions of mortality from mesothelial tumours in asbestos factory workers — M.L. Newhouse, G. Berry (1976)
• Mortality of factory workers in east London 1933-80 — M.L. Newhouse, G. Berry, et al. (1985)
• Occupational lung cancer and smoking: a review in the light of current theories of carcinogenesis — A.C. Chovil (1979)
• 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)
• Mortality from all cancers of asbestos factory workers in east London 1933-80 — G. Berry, M.L. Newhouse, et al. (2000)

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