Chlorinated drinking water, cancers and adverse health outcomes in Gangtok, Sikkim, India.

Long-term impacts of drinking chlorinated water on the incidence of cancers and other adverse health outcomes were assessed in a population-based cross-sectional study. The study was conducted by comparing a group exposed to chlorinated drinking water for more than thirty years with control groups with less or no exposure to chlorine. A house-to-house survey was completed to gather information on residential history, age, education, income, source and extent of treatment of water and health characteristics. All residents below thirty years of age were excluded from the database used for analyses to ensure that the groups were comparable. Fourteen cancer cases were found in the long-term exposed groups of 1085 persons and 9 cancer cases in the two control populations of 725 persons. The odds ratio for cancers (OR) was 1.05 (95% CI = 0.43-2.65) and is not statistically significant. Reciprocal or inverse odds [corrected] ratios for gastrointestinal disorders, kidney problems and skin infections were statistically significant ranging from 2.06 (95% CI = 1.01-4.17) to 2.2 (95% CI = 1.45-3.33). These OR values indicate that there is no significant association between the incidence of cancer and exposure to chlorinated water while chlorinating drinking water significantly reduced the incidence of non-carcinogenic adverse health effects like gastrointestinal diseases, skin infections, and kidney diseases.