Next time you're climbing into a pool, know this: You might be swimming in gallons of pee.
That's according to a new study from our neighbors up north at the University of Alberta. Researchers developed a way to test urine levels in water, and took over 250 samples from 31 pools and hot tubs in two Canadian cities.
They were looking for substance called acesulfame K or ACE – it's an artificial sweetener that passes through the body in our urine and is "an ideal urinary marker," according to the study. The sweetener is in a ton of food and drinks, and even products like toothpaste and mouthwash, so it's hard to avoid consuming it.
And if you find the sweetener in a pool, it means you've found urine. So how much did researchers find?
Well, first of all, pee was found in ALL OF THE SAMPLES they took. Every single one.
The concentration levels varied. After studying samples for over three weeks, researchers determined the average amount of pee in a 220,000-gallon, commercial-size swimming pool is 75 liters – roughly 20 gallons.
Vice points out that's not really a lot of pee, percentage-wise, when you compare it to the overall amount of water in the pool (about 0.009 percent). But still, it is 20 gallons of pee.
What about a smaller pool in your friend's backyard? NPR crunched the numbers and found it translates to about two gallons of urine in a residential pool (20-by-40-foot, five-feet deep).
And when you consider how much smaller a hot tub is than a pool... ew.
Is it bad for you?
As kids, a lot of us were taught to not pee in pools – because it's gross. Some of us even fell for that myth that a special chemical added to pools would turn the water blue when pee was introduced, humiliating the offender.
But clearly people are doing it anyway – even Olympic swimmers like Michael Phelps pee in the pool. So do we need to be worried about it?
The researchers at University of Alberta say it could be a public health concern. Although urine itself is sterile, it can mix with pool chemicals to harm swimmers' health, the study says.
Science News explains that urinating in a chlorinated pool creates a toxic chemical called cyanogen chloride. It forms when chlorine from the pool reacts with nitrogen in urine, and it can irritate the eyes, nose, and lungs.
So it's not going to kill you (hypothetically, this is how much it would take), but it's something that we wouldn't have to worry about if people would just get out of the pool to use the restroom.
"I view it like secondhand smoke," Ernest Blatchley III, an environmental engineer at Purdue University, told NPR. "It's disrespectful and potentially dangerous."