While there were trace amounts of artificial sweeteners in the tap water itself, the amount was 570 times higher in the pool water, confirming that people had been secretly peeing in public.
One swimming pool, which was about a third the size of an Olympic-sized one, had an astonishing 75 litres - 132 pints - of urine, while a smaller pool had 30 litres.
Analysis of more than 250 samples from 31 pools and tubs from two Canadian cities showed ACE in all samples.
The test works by detecting a substance called acesulfane potassium (ACE), a widely consumed sweetener found in many processed and baked foods.
The sweetener doesn't break down easily and is created to be excreted through urine.
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Try not to think of this the next time you accidentally swallow swimming pool water. "Additionally, we should all be considerate of others and make sure to exit the pool to use the restroom".
In a 2012 survey cited by the Guardian, 19 per cent of adults anonymously admitted to urinating in a swimming pool on at least one occasion.
The researchers hypothesized that it could be a good indicator of urine levels in pools. Because ammonia in urine and the chemicals in chlorine don't mix well, they may be producing a potentially harmful reaction that could irritate your eyes and lungs.
Then they tracked the levels of this sweetener in two public swimming pools over a period of three weeks.
The results were even grosser for hot tubs.
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The study specifically looked at the amount of artificial sweeteners found in public pools, which they hypothesized could be an indication of urine in the water. 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.
"The benefits of keeping active through swimming outweigh the potential risks we use as rationale for the study", said Blackstock to Gizmodo. "Chlorine kills it, so it's not bad".
The research was published on Wednesday in the Environmental Science and Technology Letters journal.
"However, we do have many compounds in urine, for example urea and nitrogen-content compounds, which can react with chlorine disinfectants that can produce by-products we don't want to be exposed to."
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