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The Effects of Chlorination in Public Water

The chlorination of public drinking water has been an established practice for more than 100 years to minimize the public's exposure to pathogenic bacteria. Only since 1991 have water-quality studies focused on the long-term effects of consuming chlorinated water. Although results are limited, due to the difficulty of monitoring large groups of people for extended periods, some studies have shown that long-term consumption can have very detrimental effects.

  1. Chlorinated Water and Cancer

    • Many municipalities throughout the world use chlorination as the primarily method to disinfect drinking water. A study published in the July 1998 issue of "Environmental Research" investigated the correlation between water chlorination and the risk of cancer in 28 urban areas in Taiwan. The researchers found that chlorination was positively correlated to the increased incidence of rectum, lung, bladder and kidney cancers. However, the authors cautioned that the results must be interpreted cautiously due to the limited sample sizes used in the study.

    Long-term Consumption and Bladder Cancer

    • A study appearing in the January 1999 issue of "Epidemiology" was designed to compare cancer rates with drinking water sources in men from various areas in Iowa. The researchers interviewed more than 3,000 male residents and their respective water utility companies and found a strong relationship between water chlorination and the risk of bladder cancer. The study also concluded that the incidence of bladder cancer increased along with the number of years that a person consumed chlorinated water.

    Incidence of Diarrhea in Children

    • Pathogenic, or disease-causing, bacteria can often contaminate wells in rural areas. To prevent human illness, rural residents in Saudi Arabia are encouraged to treat well water with calcium hypochloride, to rid the water of bacteria that causes diarrhea, especially in children. An April 1995 study in "The Journal of Tropical Medicine and Hygiene" stated that children from families consuming untreated water had twice the risk for contracting diarrhea-causing bacteria.

    Preterm Pregnancy

    • Studies on the effects of water chlorination and the risk of pregnancy complications or premature delivery have been relatively inconclusive. However, a large sample-sized, long-term study was included in the May 2004 issue of "Toxicology." The researchers evaluated more than 180,000 women from more than 120 municipalities in Taiwan, who gave birth to only one child between 1994 and 1996. The study found a slight, but significant, increase of 2 percent in premature delivery in women consuming chlorinated water compared to those with alternative water sources.

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