Researchers say hot tubs and swimming pools may not be as clean as people think.
The study reveals that disinfectants added to the water of swimming pools and hot tubs release byproducts when they react with users' sweat, urine, and other compounds, and that these have the potential to cause damage to DNA.
What is more, the team found that the more swimming pools and hot tubs are used, the more potent the byproducts.
Study co-author Susan D. Richardson, of the Department of Chemistry and Biochemistry at the University of South Carolina, and colleagues publish their findings in the journal Environmental Science & Technology.
It is well established that chlorine and other substances used to disinfect pools and hot tubs react with organic matter - including urine and sweat from humans - to create disinfection byproducts (DBPs).
"Although disinfection is important to inactivate harmful pathogens, adverse health effects associated with exposure to DBPs, such as asthma and bladder cancer, have been noted in human epidemiologic studies," say the authors.
However, they note that there have been no studies on the mutagenicity of such byproducts - that is, how capable these byproducts are of altering the DNA of an organism and increasing the risk of genetic mutations.
Mutagenicity of pools, hot tubs increased fourfold with human use
To investigate, the researchers analyzed 28 water samples retrieved from private and public swimming pools and hot tubs - both before and after intense use - across seven locations in the United States.
The pools and hot tubs were disinfected using chlorine, bromine, ozone, or ozone-chlorine.
The researchers also tested the tap water used to fill the hot tubs and pools, enabling them to better determine how the disinfectants and their reaction with user substances affected the mutagenicity of DBPs.
The team identified more than 100 DBPs from the pool and hot tub samples, and extracts of these DBPs were tested for their mutagenicity.
They found that, compared with the original tap water used to fill the pools and hot tubs, the DBP samples of swimming pools were 2.4 times more mutagenic, while the hot tub DBP samples were 4.1 times more mutagenic.
Additionally, the researchers found that the more the pools and hot tubs were used, the more mutagenic the DBP samples were.
The researchers say their results indicate that the mutagenicity of swimming pools and hot tubs in increased with human use, adding:
"Thus, encouraging practices that reduce these inputs, such as frequent cleaning of spas, more frequent exchange of water in pools, showering before entering pools/spas, and not urinating or wearing personal care products while in pools/spas, should have a beneficial effect on public health.
Positive health effects gained by swimming could be increased, and potential health risks reduced, by implementation of these practices."
Tips for healthy use of hots tubs and pools
The research is particularly timely; May 23rd represents the beginning of Healthy and Safe Swimming Week, and the Centers for Disease Control and Prevention (CDC) recently released a report revealing that every year, thousands of public pools and hot tubs are closed as a result of serious health and safety violations.
- Check the latest inspection results of the pool
- Use pH test strips to ensure the pool has the correct disinfectant levels
- Stay out of the water if you have diarrhea or an open wound that is not covered with a waterproof bandage
- Shower before entering the water
- Do not swallow hot tub water or let it enter the mouth.