Chlorinated Pools Increases Risk of Cancer

"Parents send their children to pools because they want to do something good for them," said toxicologist Alfred Bernard of the Catholic University of Louvain in Brussels, Belgium, who was not involved in the study. "But we actually don't know the long-term effects."

Prior studies have raised concerns that chlorine in pools can react chemically with sweat, skin cells and other organic material to produce chemicals linked with asthma and bladder cancer. In one of the new studies, researchers analyzed water from a public swimming pool and identified more than 100 such byproducts, including many toxins.

The researchers then tested the blood, urine and breath of 50 healthy adults both before and after they swam laps for 40 minutes. They found an increase in a marker for respiratory distress, suggesting a decreased resistance of the lung lining to foreign substances. They also found a sevenfold increase in several markers of DNA damage that have been associated with cancer risk.

Chlorine is a known toxic chemical, and health advocates have been raising concerns about its use in pools for a long time.

"Chlorine causes scarring of the arteries," write Kevin Gianni and Annmarie Colameo in their book The Busy Person's Fitness Solution.

"When the arteries scar, cholesterol now has something to attach itself to," they write. "This is what clogs arteries. So basically tap water, pools, and hot tubs help you clog your arteries."

"We have good evidence that you have to be careful with these chemicals," Bernard said. "Maybe chlorine is not the best choice for disinfecting swimming pools."