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Sept. 13, 2010 -- Swimming in indoor pools may result in respiratory effects and induce DNA damage that could lead to cancer, according to new research that examined the impact of byproducts of pool disinfection.
But the researchers emphasize they are not suggesting anyone get out of the pool. "We do not say stop swimming," says researcher Manolis Kogevinas, MD, PhD, professor of epidemiology at the Centre for Research in Environmental Epidemiology in Barcelona. "We should keep a clear message that swimmers should keep swimming."
The research findings, he tells WebMD, are a message to the industry that ''the positive effects of swimming could be increased by reducing the chemicals."
Industry experts and pool researchers agree. "It's good that research is being done in this area,'' says Thomas Lachocki, CEO of the National Swimming Pool Foundation, an educational nonprofit organization based in Colorado Springs, Colo. ?The research is published online in the journal Environmental Health Perspectives.
''We have been doing research on chemicals in water -- not swimming pools -- for quite some time," Kogevinas says. More recently, he and his colleagues have focused more intently on indoor swimming pool water.?"Chemicals are produced when you put chlorine in water," he says. Chlorine reacts, for instance, to urine, cosmetics, and other substances typically found in swimming pools.
The researchers wanted to characterize these disinfection byproducts, or DBPs, in an indoor pool environment. Other studies have linked DBP exposure in drinking water to a risk of bladder cancer and other problems.
In the first of three new studies published in the journal, the researchers evaluated 49 healthy adults after they swam for 40 minutes in an indoor chlorinated pool, looking for biomarkers linked to cancer.
"What we found is by analyzing blood samples and urine samples, we have an increase in risk markers related to cancer," Kogevinas tells WebMD.
Exposure to the pool water was associated with a five-fold increase in one of the markers, he says. But that does not mean swimmers are doomed to get cancer, he stresses.
"This doesn't mean at all that swimmers have a five times increased cancer risk," he says. "It simply means that after swimming for 40 minutes in a chlorinated pool, you get an increase in this marker in the blood that in other studies has been associated with future cancer risk."
In a second study, Kogevinas and his colleagues focused on respiratory effects of exposure to indoor pool water.
"We compared markers of lung injury before and after swimming," he says, evaluating 48 swimmers this time, from the same group as in the first study.
They found changes in just one blood marker, a slight increase in one known as CC16. The increase, the researchers say, is due to the exercise itself in addition to the DBP exposure.
''Some studies have suggested a link with swimming and asthma," Kogevinas says. "We found one of many biomarkers a small increase."