Chlorination, chlorination by-products, and cancer: a meta-analysis.
OBJECTIVE
Individual epidemiological investigations into the association between chlorination by-products in drinking water and cancer have been suggestive but inconclusive. Enough studies exist to provide the basis for a meaningful meta-analysis.


METHODS
An extensive literature search was performed to identify pertinent case-control studies and cohort studies. Consumption of chlorinated water, surface water, or water with high levels of chloroform was used as a surrogate for exposure to chlorination by-products. Relative risk estimates were abstracted from the individual studies and pooled.


RESULTS
A simple meta-analysis of all cancer sites yielded a relative risk estimate for exposure to chlorination by-products of 1.15 (95% CI: 1.09, 1.20). Pooled relative risk estimates for organ-specific neoplasms were 1.21 (95% CI: 1.09, 1.34) for bladder cancer and 1.38 (95% CI: 1.01, 1.87) for rectal cancer. When studies that adjusted for potential confounders were pooled separately, estimates of relative risks did not change substantially.


CONCLUSIONS
The results of this meta-analysis suggest a positive association between consumption of chlorination by-products in drinking water and bladder and rectal cancer in humans.
Morris
R D
RD
Division of Biostatistics, Medical College of Wisconsin, Milwaukee 53226.
Audet
A M
AM
Angelillo
I F
IF
Chalmers
T C
TC
Mosteller
F
F
D016022:Case-Control Studies; D015984:Causality; D002713:Chlorine / Q000009:adverse effects* / Q000378:metabolism; D002725:Chloroform / Q000009:adverse effects; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure; D004784:Environmental Monitoring; D062665:Epidemiological Monitoring; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D016015:Logistic Models; D008297:Male; D015201:Meta-Analysis as Topic; D009369:Neoplasms / Q000139:chemically induced / Q000453:epidemiology*; D016017:Odds Ratio; D012004:Rectal Neoplasms / Q000139:chemically induced / Q000453:epidemiology; D012680:Sensitivity and Specificity; D014481:United States / Q000453:epidemiology; D001749:Urinary Bladder Neoplasms / Q000139:chemically induced / Q000453:epidemiology; D014881:Water Supply / Q000592:standards*
D002713:Chlorine; D002725:Chloroform