Everyone's been losing their shit about a recent study from the University of Alberta, which reported that up to 75 litres of urine were present in a standard public swimming pool in a Canadian city—about the equivalent volume of "20 large milk jugs," as The National Post memorably reported. That's a lot of pee. But how bad is it, really?
The first thing graduate student Lindsay Blackstock, lead author of the paper, told me when I called her was: "It's really not bad at all."
In a public swimming pool, harmful bacteria are zapped by a boatload of chlorine. It's even possible to filter and drink human pee (astronauts do this on the International Space Station). The American Chemical Society has previously endorsed peeing in the ocean. Plus, Blackstock said, most of the gross stuff "that could be harmful in water is broken down in a wastewater treatment plant," and that happens well before the water gets to our sinks or pools.
Aside from a resounding "ew" from the media, the only thing scientists are worried about is that some nitrogenous compounds present in pee—such as urea or ammonia—can interact with a swimming pool's chlorine to create disinfection byproducts (DBPs), as reported in a 2014 paper. These DBPs, like trihalomethanes, have been shown to potentially cause lung irritation, eye irritation and occupational asthma. Potentially. Occupational. These are keywords—you're not going to drop dead in a puff of pee-coloured steam the next time you enter a hot tub.
So with the reader's best interest in mind, I asked Blackstock: If the real problem here is DBP, should we just stop putting chlorine in our swimming pools?
"Goodness, no," she said. "There are water-born pathogens that can be introduced into the swimming pool, but the chlorine or disinfectants used are an extremely effective way of eliminating these dangerous pathogens."
Basically, pee is the least of your problems.
Blackstock and her team measured the urine in pools by sampling 29 hot tubs, as well as indoor and outdoor pools, across two Canadian cities that they wouldn't name. They tested for acesulfame potassium, or Ace-K, a sweetener that's commonly consumed but not metabolized by the body—the Ace-K you drink is the same Ace-K you pee.
Equipped with a good average of how much Ace-K is present in recreational bodies of water, in the next phase of their test, Blackstock and her team got that "75 litres of urine" number from the largest of the two pools they tracked for three weeks. Ace-K levels rose over the three-week period, leading to a conclusion that more pee was present. Cue the freakout.
"Keep in mind how diluted that [pee] would be in 870,000 litres" of total pool water, she said. The pool water in question was 0.0086 per cent urine.
The thought of swimming in pee is undeniably gross (even though some people have been known to wash their faces with it). But activity of swimming is much better for you than the damage any pool water pee could do, Blackstock added. Plus, there are some very easy fixes.
"We want people to keep swimming but quit peeing," she said. "Make sure to rinse off in the showers provided to rinse off any personal care products that could also interact with chlorine … and leave the swimming pool to go to the restroom when nature calls."
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