January 6, 2026, 2:31 pm | Read time: 3 minutes
Toddlers do it without thinking, adults sometimes do it secretly but intentionally: peeing in the pool. But is it actually harmful? Yes, say experts–because human urine in swimming pools can be hazardous to health.
Chlorine is known to kill bacteria. Still, one should not even think about relieving themselves in a pool. Not only because it’s simply gross for all fellow swimmers in the relatively small pool, but also because it can have potentially harmful health effects if everyone pees in the pool. This has been discovered by scientists from the China Agricultural University in Beijing and Purdue University in Indiana.
Chlorine and Uric Acid–Not a Good Mix
In their study published in the journal “Environmental Science & Technology,” the experts conclude that mixing chlorine and uric acid can form so-called “volatile disinfection byproducts.” According to the scientists, these byproducts include trichloramine, which can damage the respiratory system and cause eye and skin irritation. Chlorine cyanide is also formed, a substance that has been used as a chemical warfare agent in the past. Although the amounts of these unwanted byproducts are very small, they still find their way into the body.
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This Much Urine Is in the Water
The amount of urine in pools is anything but negligible, as shown in an illustrative video by the Washington-based American Chemical Society: 30 to 80 milliliters are distributed in each swimming pool–per person.
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According to experts, the urine in the pool and the resulting disinfection byproducts are also responsible for the typical swimming pool smell that we loved as children. At the end of the video, the scientists offer a clear piece of advice to all pool visitors. “Now that you know, it’s your duty to use the toilets and shower every time before you go into the pool!”
But: Definitely Pee in the Ocean!
While one should restrain themselves in the pool and even in the lake, peeing in the ocean is perfectly fine. Another study by the American Chemical Society shows that the minuscule amounts of human urine do no harm to the oceans. On the contrary, the nitrogen in urea actually benefits the growth of marine plants.
What should also not be forgotten: Every tiny creature in the sea also pees in its habitat every day. A whale, for example, releases up to 970 liters of urine into the ocean–every day! “If that doesn’t cause any harm, then you certainly won’t either,” states another video released by the American Chemical Society on the topic.