Artificial sweetener key component in University of Alberta pee-in-pool research

Lindsay Blackstock never expected to leave her mark on the scientific community by researching people who pee in public pools.

But the University of Alberta student is happy to use this golden opportunity to educate the public about her team's unique methodology in studying the taboo topic.

"In general, no one's going to admit to peeing in a pool," Blackstock said in an interview with CBC Radio's Edmonton AM.

When Blackstock, a PhD student of analytical and environmental toxicology, set out to test urine levels in public pools, hot tubs and diving tanks, she wasn't looking for urine itself, but for an artificial sweetener called acesulfame potassium, or Ace K.

The compound is consumed in all sorts of processed foods such as soft drinks and cookies and, unlike most components of urine, it doesn't decompose in chlorinated water.

"There's really no other logical explanation as to why we're finding this in pools and hot tubs, so people must be peeing in there," Blackstock said.

Armed with that knowledge, Blackstock and her team determined that a pool of about of 830,000-litres — one-third the size of an Olympic pool — had on average 75 litres of urine.

"It can be very difficult to measure urine in swimming pools, because it breaks down. "So if we look at this artificial sweetener, we can use to estimate because we know that it's excreted exclusively in urine."

'Keep swimming, stop peeing'

The researchers took more than 250 samples from 31 pools and hot tubs in two undisclosed Canadian cities, and determined the problem is pervasive. They didn't divulge the locations, because they promised the pool owners anonymity.

The team found significant volumes of the sweetener in all pools and hot tubs they tested, while only trace amounts were found in the tap water used to fill them.

The results are nothing to turn your nose up at, said Blackstock. Pee can cause some serious public health problems.

Though chlorine kills most harmful bacteria that makes its way into public waters, the chemical can cause some problems of its own.

Urine can react with chlorine to form disinfection byproducts. These compounds can cause irritation to eyes and lungs, and research suggests a link between long-term exposure and elevated rates of asthma found in professional swimmers and pool workers.

While she acknowledged the ick factor of the results, Blackstock said the presence of pee in swimming pools was "quite dilute" and the public health risks are relatively low.

She suggested swimmers shower well after a swim, and be sure to exit the pool when nature calls. 

"We really don't want to scare people away from swimming. It's a great way to stay healthy," she said. "But we want to raise awareness that people are still peeing in the pools, and be considerate of your neighbours who are also using the facilities.

"Keep swimming, stop peeing."