Why You Should Never Pee In Pools (Even Though Michael Phelps Thinks It's Chill)

“I think everybody pees in the pool. It's kind of a normal thing to do for swimmers,” Michael Phelps said in a 2012 interview, adding, “Chlorine kills it, so it's not bad.” I hate to burst Phelps’s bubble, but he’s wrong: You should not pee in the pool. No, REALLY, you should not. It’s probably true that everyone does it, but there are legit scientific reasons that urinating in a swimming pool is bad for your health (and that of your fellow swimmers); it can result in skin issues and even major respiratory problems. (And also, come on, it’s gross.)

A video from Reactions, a YouTube channel from the American Chemical society, breaks it all down: As Phelps pointed out, pools are usually treated with chemicals like chlorine to prevent the growth of potentially harmful microorganisms. Chlorine doesn’t kill every harmful microbe, so it’s often paired with other disinfecting agents like ozone, bromine, and ultraviolet light. Together, these combos do a good job of keeping nasties from proliferating in the pool. However, they bring with them their own set of problems. When certain disinfectants interact with organic substances in the pool, like sweat, dirt, lotion, and — you guessed it — urine, they create chemicals known as “disinfection biproducts” (DBPs), and exposure to DBPs is not good for you.

The problem with peeing in the pool is thus not your exposure to urine itself — rather, it’s the chemical compounds that your pee produces when it reacts with the pool’s disinfectants. One of these chemicals is trichloramine. You know that classic, chemically “pool smell”? A lot of people thinks that odor means a pool is clean. Not so! Actually, that smell is trichloramine. Since trichloramine is created by the combo of chlorine with bodily fluids, a strong “pool smell” really means that your pool is full of bodily fluids.

Trichloramine is the stuff that makes your eyes burn and redden when you’re swimming, but it can also contribute to serious respiratory problems like asthma. Professional swimmers and other people who spend long periods of time at the pool daily (like lifeguards or other staff) are the most at risk.

Dirt and sweat contribute to DBPs (according to Chemical and Engineering News [C&EN], sweat is, unsurprisingly, a bigger issue for professional swimmers than casual pool-goers), but urine is the biggest problem. C&EN reports that, for every person in a pool, there is between 30 and 80 mL of pee in the water (That’s the equivalent of roughly 2 to 5.5 tablespoons). So a public pool with 10 people in it will have somewhere between about 1 and a quarter cups and nearly 3 and a half cups of urine in the water. I’ll give you a moment to imagine that. (Shudder.)

So how to can you help reduce the amount of DBP’s in your pool? Ernest R. (Chip) Blatchley III, an environmental engineer at Purdue University, explained to C&EN, “The best thing that swimmers could do to improve the swimming environment for themselves and for everybody else who uses the pool—the lifeguards and other people who are walking around on the pool deck—is to practice commonsense hygiene.” “Commonsense” here means two key things: Shower before hopping in the water, and, for the love of cheese, don’t pee in the pool.

Image: YouTube