Peeing in the Pool Isn’t Just Gross, It’s Unhealthy

Bad things can happen when you pee in the pool. The pool could turn green, for instance, which is what happened at the Olympics this week. (Just kidding—the green Olympic pool was actually caused by excess hydrogen peroxide.) But like hydrogen peroxide, urine also interacts with chlorine and, while the pool won't turn green, the results are still pretty nasty.

This video by Reactions, a series from the American Chemical Society, explains how organic matter from our bodies such as dirt, sweat, lotion, and urine affect the pool chemicals meant to keep it clean and free of dangerous microorganisms.

Chlorine, sodium hypochlorite, and calcium hypochlorite—the chemicals added to public pools for sanitation—react with water to create a disinfectant called hypochlorous acid. Pools are also kept clean with ultraviolet light, ozone, and bromine, which tackle chemicals that are immune to chlorine.

The problem with these disinfectants is that when they come into contact with organic materials, especially urine, they create unhealthy byproducts called disinfection byproducts, or "DBPs".

Public pools contain a whopping 30 to 80 milliliters of urine per person (gross!), and that urine contains a chemical called urea which reacts with chlorine to create trichloramine. Trichloramine causes the classic pool smell, as well as a burning sensation in the eyes and in some cases asthma—a serious problem, especially for professional athletes who spend much of their time in public pools.

Urine also contains chemicals from new and existing drugs on the market, and scientists don't yet know how these chemicals will interact with those already in the pool.

If this story hasn't completely turned you off from swimming in public pools, remember next time to shower off before and after you dive in. And for everyone's sake, pee in the toilet. Nobody swims in there.