Chlorinated Pools May Increase Cancer Risk

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THE GIST

- Chemicals in chlorinated swimming pools may cause asthma, respiratory problems and even cancer.

- There are alternatives to chlorine and methods for using less of it.

- You can do your part to help by taking a shower before you swim.

Swimming in a chlorinated pool may increase your risk of developing cancer, suggest a new suite of studies, which identified more than 100 chemical byproducts in pools that use chlorine as a disinfectant.

The work is too preliminary to suggest that people should stop swimming, said Manolis Kogevinas, an epidemiologist at the Center for Research in Environmental Epidemiology in Barcelona. The studies were small, and they found a rise in blood markers that have been associated with cancer -- not a rise in cancer itself.

Still, Kogevinas said, the findings suggest that people need to work harder to reduce everyone's exposure to chlorine.

"People should not be afraid of swimming, but we should get more research on whether there are better practices for disinfecting pools," Kogevinas said. "It's all a matter of costs and benefits."

Chlorine is really good at killing microbes in swimming pools. Over the years, though, scientists have become concerned about its possible health effects. In water, chlorine reacts with sweat, urine, skin cells and other organic materials to produce all sorts of chemical byproducts. In animal studies, some of those chemicals have been linked with asthma and bladder cancer.

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In a new study -- one of three just published in Environmental Health Perspectives -- chemists for the first time analyzed exactly what was in chlorinated water from a public swimming pool in Barcelona. They identified more than 100 chemical byproducts in the water. Many were toxic. Some had never been found in swimming pools or in chlorine-treated drinking water.

For the other two studies, 50 healthy adults swam laps for 40 minutes. The researchers measured levels of a number of substances in the blood, urine and breaths of the swimmers, both before they got in the pool and after they emerged. Each measurement looked at a marker, or sign of what was happening in the body.

The scientists expected to find some sign of respiratory distress. Previous studies have shown higher rates of asthma in lifeguards and competitive swimmers, as well as higher rates of eye, nose and throat irritation in pool workers.