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Meta-analysis of studies on individual consumption of chlorinated drinking water and bladder cancer
  1. C M Villanueva1,2,
  2. F Fernández1,
  3. N Malats1,
  4. J O Grimalt3,
  5. M Kogevinas1
  1. 1Respiratory and Environmental Health Research Unit, Municipal Institute of Medical Research (IMIM), Barcelona, Spain
  2. 2Universitat Autònoma de Barcelona, (UAB), Spain
  3. 3Department of Environmental Chemistry, Chemical and Environmental Research Institute, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
  1. Correspondence to:
 Dr M Kogevinas, Respiratory and Environmental Health Research Unit, Institut Municipal d’Investigació Médica, IMIM, 80 Doctor Aiguader Road, 08003-Barcelona, Spain;


Study objective: To evaluate whether consumption of chlorinated drinking water is associated with bladder cancer.

Design: A bibliographic search was conducted and the authors selected studies evaluating individual consumption of chlorinated drinking water and bladder cancer. The authors extracted from each study risk estimates for intermediate and long term (>40 years) consumption of chlorinated water, stratified by sex when possible, and performed meta-analysis for the two exposure levels. A meta-analysis was also performed of the dose-response regression slopes.

Setting: Populations in Europe and North America.

Participants: Those included in six case-control studies (6084 incident bladder cancer cases, 10 816 controls) and two cohort studies (124 incident bladder cancer cases) fulfilling the inclusion criteria.

Main results: Ever consumption of chlorinated drinking water was associated with an increased risk of bladder cancer in men (combined OR=1.4, 95%CI 1.1 to 1.9) and women (combined OR=1.2, 95%CI 0.7 to 1.8). The combined OR for mid-term exposure in both genders was 1.1 (95% CI 1.0 to 1.2) and for long term exposure was 1.4 (95%CI 1.2 to 1.7). The combined estimate of the slope for a linear increase in risk was 1.13 (95% CI 1.08 to 1.20) for 20 years and 1.27 (95% CI 1.15 to 1.43) for 40 years of exposure in both sexes.

Conclusions: This meta-analysis of the best available epidemiological evidence indicates that long term consumption of chlorinated drinking water is associated with bladder cancer, particularly in men. The observed relative risk is only moderately high, but the population attributable risk could be important as the vast majority of the population of industrialised countries is potentially exposed to chlorination byproducts for long time periods.

  • bladder cancer
  • chlorination
  • meta-analysis

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  • Funding: CM Villanueva has a fellowship from the Department of University, Research and Society of the Information, of the Generalitat de Catalunya (Government of Catalonia). This project is partially funded by the CIRIT grant no 1999SGR 00241 (Generalitat de Catalunya), by FIS contract 01/1326E, and by the DG SANCO Project 2001/CAN/112.

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