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A mixture of urine and chlorine in swimming pools forms dangerous chemicals


The claim: urinating in a swimming pool is dangerous for your heart and lungs

A Facebook post from April 26 (direct link, archive link) warns of inappropriate behavior in swimming pools.

“Peeing in a swimming pool is dangerous for your heart? Urine and chlorine create dangerous chemicals when combined,” the post reads. “One of those chemicals, cyanogen chloride, is classified as a chemical warfare agent and can damage your heart and lungs.”

The post was shared more than 400 times in a week.

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Experts say urine mixes with chlorine, creating toxic chemicals that can damage internal organs. However, experts say the level of risk depends on the amount of harmful chemicals in the pool.

Urine in combination with pool chemicals poses a risk

Using a pool as a toilet is a bad idea on several fronts, although serious health consequences are unlikely with limited exposure, experts say.

A 2014 study in the journal Environmental Science and Technology found that uric acid in urine mixes with chlorine in pool water, creating toxic cyanogen chloride and trichloramine. Cyanogen chloride “can affect multiple organs via inhalation, including the lungs, heart and central nervous system,” and trichloramine “has been associated with acute lung injury during accidental, occupational, or recreational exposure to chlorine-containing disinfectants,” the study said.

And according to the National Institutes of Health, cyanogen chloride is indeed used as a chemical warfare agent.

Ernest Blatchley, co-author of the study and professor of environmental engineering at Purdue University, told USA TODAY that both chemical compounds escape from the liquid into the air, which is how people inhale them. Blatchley said it is normal to see adverse health effects from the compounds in the respiratory tract, but other organs can also be affected.

“It is possible to see effects in other organs as these chemicals are transferred from the lungs into the blood supply and then circulate,” Blatchley said. “There is potential for acute effects and chronic effects. Both have been documented in swimmers.”

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The amount of toxic exposure in the air around a swimming pool can only be estimated, said Ludmilla Aristilde, associate professor of civil and environmental engineering at Northwestern University. She said that while the combination of certain pool chemicals and urine is dangerous, it is rare for someone to have an acute reaction after one exposure.

“Only in rare cases would a single exposure to a pollutant cause such an acute toxicological effect, unless there is a very high dose exposure or the pollutant is very toxic such that a very small dose is the consequence,” said Aristilde.

Blatchley said it’s important to shower before getting into a pool to prevent these chemicals from building up. He also reiterated that people should get out of the pool to urinate.

Aristilde suggested swimming in outdoor pools where the wind helps the toxins escape and warned against high-traffic pools where hygiene is not regulated.

“Less than 30 minutes of swimming in such pools may be advisable,” she said.

USA TODAY reached out to the Facebook user who shared the post for comment but did not immediately receive a response.

Our fact-checking resources:

  • Ernest Blatchley, May 1, Phone interview and email exchange with USA TODAY
  • Ludmilla Aristilde, May 1-3, email exchange with USA TODAY
  • ACS Publications, February 25, 2014, Volatile Disinfection Byproducts Due to Uric Acid Chlorination: Implications for Swimming Pools
  • National Institutes of Health, accessed May 3, cyanogen chloride
  • ACS, August 30, 2016, Molecule of the Week Archive: Trichloramine

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