Swimming pool
March 3, 2017

How much pee is in your local swimming pool?

We’ve all heard and possibly snickered about the amount of urine in the typical swimming pool or hot tub.

Well, in a new study published in the Environmental Science and Technology Letters, researchers said they have determined the average percentage of urine in any given pool: .01 percent.

While that may not sound like much, it’s equivalent to 20 gallons of urine in a 220,000-gallon pool, which is about one-third the size of an Olympic swimming pool. The study team said that’s enough urine to be a public health concern.

“Our study provides additional evidence that people are indeed urinating in public pools and hot tubs,” Lindsay Blackstock, a graduate researcher at the University of Alberta, told The Guardian.

Testing for Sweeteners

To reach their conclusion, researchers sampled 31 different pools and hot tubs in two unnamed Canadian cities over the course of three weeks. The scientists tested for acesulfame potassium (ACE), a sweetener in processed food that passes unchanged through the body. The study team found evidence of urine in every single pool or hot tub they tested.

Given the standard practice of cycling fresh water into pools, the study observations suggest urine levels in the pools were being replenished regularly.

“We did not monitor the number of pool users over the three week time period ... so there is no way we could estimate the number of individual urination events per day,” Blackstock said.

Incidentally, eight hot tubs in the study were found to contain far higher concentrations of urine than the average swimming pool.

Urine in hot tubs and swimming pools is more than just a chilling thought. It is also a health hazard. When urine combined with the chlorine commonly used in pools and hot tubs, it can lead to "disinfection byproducts" that can cause eye irritation and respiratory problems, including asthma in severe cases. Sweat and hair care products that make their way into the water can also contribute to the creation of these irritants.

In their paper, the researchers said they knew going in that they would find urine in pools.

"Although considered a taboo, 19 percent of adults have admitted to having urinated in a swimming pool at least once," the team wrote in the study.

The study team went on to recommend a public health campaign that emphasizes good pool hygiene practices, like showering before jumping in and not using a pool as a toilet.

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