Absence of multiplicative interactions between occupational lung carcinogens and tobacco smoking: a systematic review involving asbestos, crystalline silica and diesel engine exhaust emissions

Our plain-English summary of Absence of multiplicative interactions between occupational lung carcinogens and tobacco smoking: a systematic review involving asbestos, crystalline silica and diesel engine exhaust emissions, by M. El Zoghbi, P. Salameh, I. Stücker, et al (BMC Public Health, 2017).

The study

• Authors: M. El Zoghbi, P. Salameh, I. Stücker, P. Brochard, F. Delva, A. Lacourt
• Journal: BMC Public Health
• Published: 2017;17(1):156
• Type of article: Systematic review
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Tobacco smoking is the main cause of lung cancer, but it is not the sole causal factor. Significant proportions of workers are smokers and exposed to occupational lung carcinogens. This study aims to systematically review the statistical interaction between occupational lung carcinogens and tobacco smoking, in particular asbestos, crystalline silica and diesel engine exhaust emissions.

Methods: Articles were identified using Scopus, PubMed, and Web of Science, and were limited to those published in English or French, without limitation of time. The reference list of selected studies was reviewed to identify other relevant papers. One reviewer selected the articles based on the inclusion and exclusion criteria. Two reviewers checked the eligibility of articles to be included in the systematic review. Data were extracted by one reviewer and revised by two other reviewers. Cohorts and case-control studies were analyzed separately. The risk of bias was evaluated for each study based on the outcome. The results of the interaction between the tobacco smoking and each carcinogen was evaluated and reported separately.

Results: Fifteen original studies were included for asbestos-smoking interaction, seven for silica-smoking interaction and two for diesel-smoking interaction. The results suggested the absence of multiplicative interaction between the three occupational lung carcinogens and smoking. There is no enough evidence from the literature to conclude for the additive interaction. We believe there is a limited risk of publication bias as several studies reporting negative results were published.

Conclusion: There are no multiplicative interactions between tobacco smoking and occupational lung carcinogens, in particular asbestos, crystalline silica and diesel engine exhaust emissions. Even though, specific programs should be developed and promoted to reduce concomitantly the exposure to occupational lung carcinogens and tobacco smoking.

In plain English

This was a systematic review, not a new study of workers. The authors searched PubMed, Scopus and Web of Science (English or French articles, latest search June 30, 2016) for cohort and case–control studies measuring statistical interaction between smoking and occupational asbestos, crystalline silica or diesel engine exhaust emissions on lung cancer. They included 15 asbestos studies, seven silica and two diesel, and did not pool them in a meta-analysis. The asbestos studies included chrysotile miners and millers in Quebec and China and crocidolite workers at Wittenoom, Australia. Most found no multiplicative interaction, and one Swedish case–control study found a negative one. The authors stated that only one of five asbestos studies examining additive interaction, of asbestos workers in Great Britain, showed a significant positive additive interaction. However, their table gives a Dutch case-cohort study an additive measure of 1.94 (0.13-4.89) while marking it as showing no interaction. The two diesel studies found no multiplicative interaction. The silica studies disagreed on the additive scale. The authors concluded that, in general, there is no multiplicative interaction between these exposures and smoking, and that the evidence was insufficient to conclude on the additive scale.

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: Systematic review of cohort and case–control studies (no meta-analysis performed)
• Who was studied: Published studies found in PubMed, Scopus and Web of Science, limited to English or French, with the most recent search on June 30, 2016. Included: 15 asbestos-smoking studies (6 cohorts, 1 case-cohort, 8 case–control), 7 silica-smoking studies and 2 diesel-smoking studies.
• Exposure: Occupational exposure to asbestos (including chrysotile and crocidolite workers in some included studies), crystalline silica, and diesel engine exhaust emissions, each in combination with tobacco smoking, with lung cancer as the outcome
• Main results:
  • In three asbestos cohorts (chrysotile workers of Qinghai mine, China; crocidolite workers of Wittenoom, Australia; asbestos factory workers of East London), the relative asbestos effect indicated no multiplicative interaction.
  • In the Great Britain asbestos workers cohort, there was a positive additive interaction but no multiplicative interaction.
  • In the Quebec chrysotile miners and millers cohort, neither additive nor multiplicative interaction was found.
  • Seven of the eight asbestos case–control studies found no multiplicative interaction. A Swedish case–control study found no additive interaction and a negative multiplicative interaction (interaction term OR = 0.31, 0.11-0.86).
  • The authors stated that, of the five asbestos studies in the review that examined additive interaction, only one showed a significant positive additive interaction.
  • For the Dutch case-cohort study (Offermans 2014), the table reports an additive measure, RERI = 1.94 (0.13-4.89), an interval that does not include zero. The authors nonetheless interpreted it as showing no additive interaction.
  • Both diesel-smoking studies showed no multiplicative interaction. For silica, the original studies disagreed, so no conclusion on additive interaction was possible.
• The authors' conclusion: The authors concluded that, in general, there is no multiplicative interaction between asbestos, crystalline silica or diesel engine exhaust emissions and tobacco smoking, and that the evidence is not sufficient to conclude on the additive scale. They recommended programs to reduce both occupational exposures and smoking at the same time.
• Limitations the authors state:
  • The authors did not perform a meta-analysis, and they suggested that a new asbestos-smoking meta-analysis using stricter inclusion criteria should be considered.
  • Their finding on additive asbestos-smoking interaction differed from a 2015 meta-analysis. The authors attributed this mainly to their stricter selection criteria for studies.
  • In the original studies, data from employment records and questionnaires may have been affected by record quality and recall bias.
  • Use of job-exposure matrices in original studies could cause misclassification of exposure and underestimated risks.
  • Case–control studies can estimate only odds ratios. Using odds ratios instead of risk ratios could wrongly suggest a positive interaction.

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: Systematic Review, Crystalline, Lung Cancer.

Related studies

• Phenotypes of lung cancer and statistical interactions between tobacco smoking and occupational exposure to asbestos and crystalline silica from a large case-only study: The CaProMat study — M. El Zoghbi, P. Salameh, et al. (2017)
• Workplace exposure to diesel and gasoline engine exhausts and the risk of colorectal cancer in Canadian men — L. Kachuri, P.J. Villeneuve, et al. (2016)
• Prevalence of occupational exposure to asbestos and crystalline silica according to phenotypes of lung cancer from the CaProMat study: A case-only study — M. El Zoghbi, P. Salameh, et al. (2018)
• Occupational exposure to diesel motor exhaust and risk of lung cancer by histological subtype: a population-based case-control study in Swedish men — A. Ilar, N. Plato, et al. (2017)
• Diesel exhaust and coal mine dust: lung cancer risk in occupational settings — B. Hoffmann, K.H. Jöckel (2006)
• Occupational exposure to diesel and gasoline emissions and lung cancer in Canadian men — P.J. Villeneuve, M.É. Parent, et al. (2011)

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