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Chlorination by-products may increase cancer risk

A series of studies published in the January issue of the American Journal of Epidemiology shows that there is a link between drinking water that has been treated with chlorine and an increased risk of bladder, colon and rectal cancers. However, the increased risk is primarily prevalent among people whose lifestyles put them at risk regardless of their drinking water source.

According to Epidemiology, chlorination byproducts are found in drinking water disinfected with chlorine. This sterilization process has been around since the turn of the 20th century, but it was not until the 1970s that it was discovered that chlorine reacts with naturally occurring organic matter to form trihalogenated methanes, which have been linked with cancer.

In the case of bladder cancer, the increased risk was found among people who are classified as smokers, while there was no elevated risk among non-smokers, according to Epidemiology.

The study on the relationship between chlorinated by products in surface water and colon and rectal cancers found that there was an increased risk in people who live an unhealthy lifestyle and have low-fiber diets. Both physical activity and high-fiber diets result in quick stool transit time, thus giving the carcinogens less time to come into contact with both the rectum and colon.

Given the results of this study, the American Water Works Association, a water safety group, has issued a statement that says although tap water often contains chlorination disinfection by-products resulting from chlorine's reaction with organic matter during the water treatment process, the World Health Organization notes that the risks to health from DBPs are extremely small in comparison to the risks associated with inadequate disinfection and water treatment.

The AWWA is working with the EPA to research the issue of carcinogens in drinking water and microbial removal processes. Water utilities have committed to a $180 million investment to learn about and solve this problem.

The use of chlorine to disinfect drinking water is vital in the fight against microbial diseases such as typhoid and cholera. Potentially harmful levels of DBPs are extremely rare in drinking water.

However, those who lead a unhealthy lifestyle that includes a lack of exercise, a low-fiber diet, or smoking ought to take precautions when drinking surface drinking water that has been treated.

For more information, contact Elizabeth Muslim, AWWA, (303)347-6140. Copyright 1998, Environmental News Network, All Rights Reserved

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