Relation between exposure to asbestos and smoking jointly and the risk of lung cancer

Our plain-English summary of Relation between exposure to asbestos and smoking jointly and the risk of lung cancer, by P.N. Lee (Occupational and Environmental Medicine, 2001).

The study

• Author: P.N. Lee
• Journal: Occupational and Environmental Medicine
• Published: 2001;58(3):145-53
• Type of article: Review
• Cited by: 96 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: To review evidence about the joint relation of exposure to asbestos and smoking on the risk of lung cancer to answer three questions: (1) does asbestos increase risk in non-smokers; (2) are the data consistent with an additive model; and (3) are the data consistent with a multiplicative model?

Methods: Analysis of 23 studies reporting epidemiological evidence on the joint relation. Comparison of risk of lung cancer in subjects unexposed to asbestos or smoking, exposed to asbestos only, to smoking only, or to both. Estimation of the relative risk associated with asbestos exposure in non-smokers and of statistics testing for additivity and multiplicativity of risk.

Results: Eight of the 23 studies provided insufficient data on the risk of lung cancer in non-smokers to test for possible effects of asbestos. Asbestos exposure was associated with a significantly (p<0.05) increased risk in non-smokers in six of the remaining studies and with a moderately increased, but not significant, increase in a further six. In two of the three studies that found no increase, asbestos exposure was insufficient to increase risks in smokers. In 30 of 31 data sets analysed, risk in the combined exposure group was greater than predicted by the additive model. There was no overall departure from the multiplicative model, the proportional increase in risk of lung cancer with exposure to asbestos being estimated as 0.90 (95% confidence interval (95% CI) 0.67 to 1.20) times higher in smokers than non-smokers. For two studies significant (p<0.05) departures from a multiplicative relation were found in some, but not all, analyses. Reasons are presented why these may not indicate true model discrepancies.

Conclusions: Asbestos exposure multiplies risk of lung cancer by a similar factor in non-smokers and smokers. The extent to which it multiplies risk varies between studies, no doubt depending on the type of asbestos involved, and the nature, extent, and duration of exposure.

In plain English

This single-author review analysed 23 published epidemiological studies of how asbestos exposure and smoking together relate to lung cancer risk. Twelve were conducted in Europe, seven in North America, three in Asia and one in Australia. They included asbestos products workers exposed to chrysotile, amosite, or crocidolite and chrysotile. Of the studies with enough data on non-smokers, six found a significantly increased lung cancer risk with asbestos exposure in non-smokers, and six more found a moderate increase that was not statistically significant. In 30 of 31 data sets, risk in people exposed to both asbestos and smoking was higher than an additive model predicted. Pooling 16 estimates, the proportional increase in risk from asbestos was 0.90 (95% CI 0.67 to 1.20) times as high in smokers as in non-smokers. The author concluded that asbestos increases lung cancer risk in non-smokers and that the joint effect is much better described by a multiplicative model than by an additive model. The author noted few lung cancers in some studies and possible confounding by other lung carcinogens.

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: Review with statistical re-analysis (model testing and meta-analysis) of 23 published epidemiological studies: case-control, cohort and occupational studies
• Who was studied: 23 studies: nine case-control studies, seven cohort/occupational studies with internal comparison groups, and seven cohort/occupational studies compared with external references. Twelve were in Europe, seven in North America, three in Asia and one in Australia.
• Exposure: Asbestos exposure combined with smoking. The populations included asbestos products workers exposed to chrysotile (two studies), amosite (two), crocidolite and chrysotile (one) or unstated asbestos type (two). Other studies covered miners and millers, insulation workers, railway workers and people in shipbuilding and industrial areas.
• Main results:
  • Among the studies with enough data on non-smokers, asbestos exposure was associated with a significantly (p less than 0.05) increased lung cancer risk in non-smokers in six studies, and with a moderate, not statistically significant increase in a further six.
  • In 30 of 31 data sets, lung cancer risk in the group exposed to both asbestos and smoking was greater than the additive model predicted.
  • A meta-analysis of 16 study estimates of the multiplicativity statistic gave 0.90 (95% CI 0.67 to 1.20), with no significant heterogeneity between estimates. This means the proportional increase in lung cancer risk from asbestos was estimated as 0.90 times as high in smokers as in non-smokers.
  • Only four estimates showed any indication of departure from the multiplicative model.
  • In one study of insulation workers (Hammond et al), taken at face value and ignoring confounding by other exposures, the author calculated that among insulation workers who smoked, about 90% of lung cancers could have been avoided by not smoking and about 80% by not being insulation workers.
• The authors' conclusion: The author concluded that asbestos exposure increases lung cancer risk in non-smokers. The author also concluded that the joint relation of asbestos and smoking to lung cancer risk is much better described by a multiplicative model than by an additive model.
• Limitations the authors state:
  • Few lung cancers in some studies led to unreliable risk estimates, particularly in non-smokers.
  • Studies failed to account for confounding by other lung carcinogens, so increased risks in asbestos-exposed groups may not be due entirely to asbestos.
  • Many studies relied on death certificate data, which are known to be inaccurate.
  • Asbestos exposure assessment was often only an educated guess.
  • Some studies relied on data from proxy respondents.

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer, Relative Risk, Asbestos Exposure, confidence interval.

Related studies

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• Risk of human health by particulate matter as a source of air pollution--comparison with tobacco smoking — M. Enomoto, W.J. Tierney, et al. (2008)
• Combined effect of asbestos exposure and tobacco smoking on Finnish anthophyllite miners and millers — L.O. Meurman, R. Kiviluoto, et al. (1979)
• Occupational cancer of the lung and smoking — (1970)
• Asbestos and smoking as risk factors for idiopathic retroperitoneal fibrosis: a case-control study — M. Goldoni, S. Bonini, et al. (2014)

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