Chlorination, chlorination by-products, and cancer: a meta-analysis

Am J Public Health. 1992 Jul;82(7):955-63. doi: 10.2105/ajph.82.7.955.


Objectives: 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.

Publication types

  • Meta-Analysis

MeSH terms

  • Case-Control Studies
  • Causality
  • Chlorine / adverse effects*
  • Chlorine / metabolism
  • Chloroform / adverse effects
  • Cohort Studies
  • Confounding Factors, Epidemiologic
  • Dose-Response Relationship, Drug
  • Environmental Exposure
  • Environmental Monitoring
  • Epidemiological Monitoring
  • Female
  • Health Status Indicators
  • Humans
  • Logistic Models
  • Male
  • Meta-Analysis as Topic
  • Neoplasms / chemically induced
  • Neoplasms / epidemiology*
  • Odds Ratio
  • Rectal Neoplasms / chemically induced
  • Rectal Neoplasms / epidemiology
  • Sensitivity and Specificity
  • United States / epidemiology
  • Urinary Bladder Neoplasms / chemically induced
  • Urinary Bladder Neoplasms / epidemiology
  • Water Supply / standards*


  • Chlorine
  • Chloroform