Public swimming pools are more dangerous than you might think, a new study suggests. When sweat and urine, among other organics, mix with the disinfectants in pool water, the result can be hazardous to health.
The findings, announced this week, link the application of disinfectants in recreational pools to genetic cell damage that has been shown to be linked with adverse health outcomes such as asthma and bladder cancer.
Pool water represents extreme cases of disinfection that differ from the disinfection of drinking water as pools are continuously exposed to disinfectants. But with so many people cooling off and exercising in pools and water parks (339 million visits across the United States each year), the disinfectants are a must to prevent outbreaks of infectious disease.
Chlorine and pee don't mix
The problem occurs when the sanitizers mix with organic matter.
"All sources of water possess organic matter that comes from decaying leaves, microbes and other dead life forms," said study researcher Michael Plewa, University of Illinois professor of genetics. "In addition to organic matter and disinfectants, pool waters contain sweat, hair, skin, urine [1 in 5 adults admits peeing in the pool] and consumer products such as cosmetics and sunscreens from swimmers."
These consumer products are often nitrogen-rich, and when mixed with disinfectants, these products may become chemically modified and converted into more toxic agents.
Long-term exposure to these disinfection byproducts can mutate genes, induce birth defects, accelerate the aging process, cause respiratory ailments, and even induce cancer, according to the researchers. While the new study did not examine actual effects on humans, it suggests such research might be warranted.
Pool samples
In this study, researchers evaluated water samples from public pools and a control sample of tap water. They tested whether the byproduct chemicals in the samples could induce gene mutations using a so-called systematic mammalian cell genotoxicity analysis.
This sensitive DNA technology can detect genomic damage in mammalian cells, allowing researchers to investigate damage at the level of each nucleus within each cell.
Results proved that all disinfected pool samples had more genomic DNA damage than the source tap water, Plewa said.
The findings are published in the journal Environmental Science & Technology. The work was supported by grants from the National Science Foundation.
Cleaner pools
All this doesn't mean you need to ditch your pool plans. Plewa offers recommendations for pool operators and swimmers to reduce hazardous chemicals and make for safer pool water.
"Care should be taken in selecting disinfectants to treat recreational pool water," Plewa advised. "The data suggest that brominating agents should be avoided as disinfectants of recreational pool water. The best method to treat pool waters is a combination of UV treatment with chlorine as compared to chlorination alone."
In addition, organic carbon should be removed prior to disinfection when the pool water is being recycled, Plewa said.
Swimmers can also help by showering before entering the water, which would mean fewer organics and so reduce the genotoxicity of the pool water. One recommendation that may seem obvious: Don't pee in the pool. Plewa suggests pool owners remind patrons about the potential harm caused by urinating in a pool.
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