Arsenic, tobacco smoke, and occupation: associations of multiple agents with lung and bladder cancer

Our plain-English summary of Arsenic, tobacco smoke, and occupation: associations of multiple agents with lung and bladder cancer, by C. Ferreccio, Y. Yuan, J. Calle, et al (Epidemiology, 2013).

The study

• Authors: C. Ferreccio, Y. Yuan, J. Calle, H. Benítez, R.L. Parra, J. Acevedo, A.H. Smith, J. Liaw, C. Steinmaus
• Journal: Epidemiology
• Published: 2013;24(6):898-905
• Cited by: 86 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Millions of people worldwide are exposed to arsenic in drinking water, and many are likely coexposed to other agents that could substantially increase their risks of arsenic-related cancer.

Methods: We performed a case-control study of multiple chemical exposures in 538 lung and bladder cancer cases and 640 controls in northern Chile, an area with formerly high drinking water arsenic concentrations. Detailed information was collected on lifetime arsenic exposure, smoking, secondhand smoke, and other known or suspected carcinogens, including asbestos, silica, and wood dust.

Results: Very high lung and bladder cancer odds ratios (ORs), and evidence of greater than additive effects, were seen in people exposed to arsenic concentrations >335 µg/L and who were tobacco smokers (OR = 16, 95% confidence interval = 6.5-40 for lung cancer; and OR = 23 [8.2-66] for bladder cancer; Rothman Synergy Indices = 4.0 [1.7-9.4] and 2.0 [0.92-4.5], respectively). Evidence of greater than additive effects were also seen in people coexposed to arsenic and secondhand tobacco smoke and several other known or suspected carcinogens, including asbestos, silica, and wood dust.

Conclusions: These findings suggest that people coexposed to arsenic and other known or suspected carcinogens have very high risks of lung or bladder cancer.

In plain English

This case-control study in northern Chile, where drinking water once had high arsenic, compared 538 lung or bladder cancer patients with 640 controls. Arsenic exposure was estimated from residence history; participants also reported smoking, asbestos, silica, wood dust and other exposures. The reference group was never-smokers in the lowest quarter of average arsenic exposure up to 1971 (below 11 µg/L). Against them, people in the highest quarter (above 335 µg/L) smoking over 10 cigarettes daily for at least six months had odds ratios of 23 (95% CI 8.2–66) for bladder and 16 (6.5–40) for lung cancer. A synergy index above 1 suggests more-than-additive combined effects; it was 4.0 (1.7–9.4) for lung and 2.0 (0.92–4.5) for bladder cancer. Among men, the lung cancer odds ratio for high arsenic plus asbestos exposure was 16 (2.8–95), based on 6 cases and 3 controls, against men with low arsenic and no asbestos exposure; the synergy index was 2.7 (0.52–14). The authors wrote that the findings suggest people exposed to arsenic plus some other known or suspected carcinogens have risks over ten times those of unexposed people. They noted possible exposure misclassification.

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: case-control study
• Who was studied: 538 lung and bladder cancer cases (306 lung, 232 bladder) and 640 controls chosen at random from the Chilean Electoral Registry, in regions I and II of northern Chile; cases were first diagnosed between October 2007 and December 2010
• Exposure: Lifetime arsenic in drinking water, estimated from residence history; direct smoking; secondhand smoke; and other self-reported known or suspected carcinogens, including asbestos (fiber type not specified), silica, wood dust, welding fumes, coke oven emissions, soot, fiberglass and solvents
• Main results:
  • In the smoking analyses, low and high arsenic exposure were the lower (below 11 µg/L) and upper (above 335 µg/L) quartiles of average lifetime drinking-water arsenic up to 1971
  • Heavier smokers were those smoking an average of more than 10 cigarettes per day for at least 6 months
  • Bladder cancer: heavier smokers with high arsenic exposure had OR = 23 (95% CI 8.2–66), compared with never-smokers with low arsenic exposure
  • Bladder cancer synergy index for arsenic and smoking was 2.0 (95% CI 0.92–4.5)
  • Lung cancer: heavier smokers with high arsenic exposure had OR = 16 (95% CI 6.5–40)
  • Lung cancer synergy index for arsenic and smoking was 4.0 (95% CI 1.7–9.4)
  • The analyses of asbestos and other agents covered lung cancer in men only; women and people with proxy interviews were excluded
  • Lung cancer in men, with men who had low arsenic exposure and no asbestos exposure as the reference: asbestos with low arsenic, 1 case and 7 controls, OR 1.6 (0.15–18); high arsenic without asbestos, 40 cases and 57 controls, OR 6.0 (2.9–12); both exposures, 6 cases and 3 controls, OR 16 (2.8–95); synergy index 2.7 (0.52–14)
  • Synergy indices with arsenic for lung cancer were 2.7 for asbestos, 2.0 for silica and 3.1 for wood dust
  • Synergy indices for arsenic combined with agents not known to cause lung cancer, such as benzene and solvents, were mostly near 1.0
  • In never-smokers, the synergy index for arsenic and childhood secondhand smoke was 2.6 (95% CI 0.77–8.5) for bladder cancer
  • In never-smokers, the synergy index for arsenic and childhood secondhand smoke was 2.1 (95% CI 0.25–17) for lung cancer
• The authors' conclusion: The authors wrote that the findings suggest people exposed to arsenic in drinking water combined with some other known or suspected carcinogen, including tobacco smoke, asbestos, silica and wood dust, have lung and bladder cancer risks more than 10 times higher than unexposed people
• Limitations the authors state:
  • Exposure information was collected retrospectively, so some exposure misclassification is likely
  • Because many exposures were assessed, some findings could be due to chance or to correlations between exposures
  • Self-reported exposures to agents such as asbestos or silica could have been misclassified
  • Confounding from other factors such as diet or radon is possible
  • Specific hobbies were not asked about, so some exposures may have been missed

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: Case-Control Study, Odds Ratio, confidence interval, Lung Cancer.

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