A scenario that you might be all too familiar with:

You’re getting your cardio exercise on at the local pool — rec center, YMCA, country club, it doesn’t matter — and you swim through an alarmingly warm patch of water. Pee. You stop what you’re doing and glance around in all directions while treading water. Was it one of those teenagers canoodling in the shallow end? That ancient woman in the floral swim cap performing solo low-impact water aerobics in the slow lane? Is Michael Phelps present? Did you involuntarily lose bladder control while doing the backstroke?

Everyone pees. And a fair number of people — one in five Americans, apparently — have no qualms about doing so in a swimming pool. For rampant pool-peers, the general assumption/excuse tends to fall along the lines of this pool’s chock-full of chemicals, anyway no harm done, right? And isn’t urine sterile?

Yes, but not quite. In addition to being gross (and unhygienic), a new study published in the American Chemical Society journal Environmental Science & Technology has found that, in addition to the fact that pretty much every swimming pool has a bit of pee in it, the combination of urine and chlorine can be detrimental to human health.

Here’s the how and why, in simple terms, according to researchers from Purdue University and China Agricultural University in Beijing, who joined together to research and author the delightfully titled “Volatile Disinfection Byproducts Resulting from Chlorination of Uric Acid: Implications for Swimming Pools.”

Urine — and sweat — contains uric acid. Mix uric acid with chlorine and the resulting chemical reaction produces both trichloramine and cyanogen chloride, two dangerous — and “ubiquitous” — gases. Both chemicals have been linked to chronic health problems amongst swimmers: Exposure to trichloramine can lead to serious respiratory woes while cyanogen chloride has been linked to lung ailments and disorders of both the central nervous system and the cardiovascular system.

Overall, uric acid — pee, basically, as sweat doesn’t figure in too greatly — is responsible for 24 to 64 percent of cyangen chloride found in swimming pools; the figure is in the ballpark of 3 to 4 percent for trichloramine.

Concludes the study: "Because uric acid introduction to pools is attributable to urination, which is largely a voluntary process for most swimmers, opportunities exist for significant improvement of air and water quality in pools via changes in swimmer hygiene practices. Specifically, if swimmers avoided urinating in pools, then air and water quality would likely improve independent of other changes in water treatment or air circulation."

Translation: For the love of god, don’t do it. Finish that lap, drag yourself out of the pool, head to a bathroom, and do your business like a civilized person.

The Atlantic further picks the brain of study co-author and pool pee expert, Ernest Blatchley III:

Though there is uric acid in sweat, it’s a pretty small amount, and it’s really urine we should be worried about, Blatchley says. Which is comforting, since if you’re swimming hard, there’s not much you can do about sweating, but you can always, you know, not pee in the pool. Some people do and some people don’t, but on average, a person leaves about 30 to 80 milliliters of urine behind each time they visit the pool. A major concern, according to Blatchley, is times when there are a lot of people in one pool, such as at a swimming competition. In the presence of chlorine, cyanogen chloride in particular not only forms quickly, as shown in this study, but decays quickly as well. This means that if a lot of people are peeing in the pool, there’s the potential for a lot of cyanogen chloride to form, depleting the chlorine in the pool. While the cyanogen chloride would normally decay quickly, less chlorine means it might stick around longer, and that could be a real problem.
Blatchley also takes to task two highly decorated Speedo models who have taken a rather blasé — don’t worry about it! — stance on the topic of peeing in the pool: Michael Phelps and Ryan Loch. Blatchley tells the Atlantic: “There’s a lot of people in the swimming community who look up to these people and listen to what they have to say. [Phelps and Lochte] are not chemists and shouldn’t be making statements that are that false."

And if the fact that you may be inhaling hazardous gases formed by someone else’s pee isn't sobering enough, the Los Angeles Times has to go and throw poop into the mix by reminding us of a 2013 study conducted by the Centers for Disease Control and Prevention that found that fecal matter is waaay more common in swimming pools, both public and private, than we’d like to think.

Via [LA Times], [The Atlantic]

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Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.

Study finds chlorinated pools and pee are a match made in harmful gas heaven
While it ranks high on the gross scale, peeing in a pool has never been considered hazardous. A study, however, uncovers health effects.