Meta-analysis of studies on individual consumption of chlorinated drinking water and bladder cancer.
OBJECTIVE
To evaluate whether consumption of chlorinated drinking water is associated with bladder cancer.


METHODS
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.


METHODS
Populations in Europe and North America.


METHODS
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.


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.
Villanueva
C M
CM
Respiratory and Environmental Health Research Unit, Municipal Institute of Medical Research (IMIM), Barcelona, Spain.
Fernández
F
F
Malats
N
N
Grimalt
J O
JO
Kogevinas
M
M
D002713:Chlorine / Q000009:adverse effects*; D004781:Environmental Exposure / Q000009:adverse effects; D005260:Female; D006801:Humans; D008297:Male; D016017:Odds Ratio; D018570:Risk Assessment; D012307:Risk Factors; D017678:Sex Distribution; D013997:Time Factors; D001749:Urinary Bladder Neoplasms / Q000139:chemically induced*; D018508:Water Purification; D014881:Water Supply
D002713:Chlorine