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Studies find DNA-damaging chemical byproducts in indoor pool water

A trio of studies published earlier this week in the journal Environmental Health Perspectives (here, here and here) has made a huge splash with indoor swimmers.

But not in a good way. The studies suggest that some of the chemicals used to disinfect indoor pools generate other chemicals that in turn may induce short-term respiratory effects and something called genotoxicity — damage to the DNA in cells. DNA damage can, of course, lead to cancer.

But don’t jump out of the pool — yet. As reporter Janet Raloff points out in her thorough review of the studies’ findings for Science News, the rates of DNA mutations in the 49 swimmers who participated in the research were low and might even be repaired by the body’s natural repair mechanisms.

The researchers identified, for the first time, about 100 different disinfection byproducts associated with pool water. (Only five had been known previously.) But, again, don’t panic. That number is nothing like the 600 known byproducts associated with the disinfection of drinking water.

“Once you start putting people in the water along with suntan oils and air-blown debris, you’re going to find disinfection byproducts,” a chemist told Raloff. The fact that pool water is being found to be no more mutagenic than drinking water is “fabulous,” he added.

The biggest sources of DNA-damaging byproducts in pool water are, apparently, skin, sweat and urine. “Swimmers need to be more aware of their personal hygiene,” another expert told Raloff. Taking a shower before you jump into the water helps enormously to improve everybody’s health. As does, ahem, taking bathroom breaks. “The urea in urine reacts with chlorine to produce some of these disinfection byproducts,” the expert explained. “In fact, it’s the constituents of human sweat and urine that are largely responsible for their formation.”

Why anybody over the age of 10 needs to be reminded to take bathroom breaks during swimming sessions is beyond me. But, then, earlier this year, in a journal article subtitled “Can we have both healthy pools and healthy people?” these same researchers felt it necessary to admonish the American public to “get past its acceptance of poor pool hygiene.” We have a culture, they wrote, “that seems to humorously ‘celebrate’ using the pool as a urinal. There is ample anecdotal evidence that young children and young adults on swim teams are discouraged from taking bathroom breaks during training. … Public education is needed regarding the immediate reporting of fecal incidents to pool operators and refraining from swimming while ill or while recovering from diarrheal illness.”

OK, now you can jump out of the pool.

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Comments (1)

  1. Submitted by Mary Ostrowski on 09/16/2010 - 06:21 pm.

    Chlorine disinfectants have been used safely for decades to protect swimmers from waterborne diseases and to provide a healthy form of exercise for people of all ages. As for the current studies, any science-based research that examines complex pool chemistry is a step forward and can help better manage chlorinated pools. As the authors themselves state, these studies rely on small numbers of swimmers in two Barcelona swimming pools with high bromine levels in the source water. Further research is needed to determine whether these results are applicable to swimming pools in the United States and other places where the bromine levels are lower. Nevertheless, the authors are correct in stating that “people need to work harder to reduce everyone’s exposure” to disinfection byproducts. The CDC encourages swimmers to play a key role in keeping pools healthy by showering before swimming and refraining from urinating in the pool. Ultimately, healthy pools are a shared responsibility. For more information, please see: http://bit.ly/9u4zVc


    Mary Ostrowski
    American Chemistry Council

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