We now know how much urine there is in swimming pools

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Then they tracked the levels of this sweetener in two public swimming pools over a period of three weeks.

Lindsay Blackstock, a graduate student at the University of Alberta, Edmonton, and lead author of the research, said, somewhat unsurprisingly: "Our study provides additional evidence that people are indeed urinating in public pools and hot tubs". Whether we like it to or not it seems to be one of those social acts that people think they can get away with.

In order to "apply the concept of using this artificial sweetener as an indicator of urine input", they investigated how much of it really lurked in public pools.

Why artificial sweetener? Well you'll be pleased to hear that many processed foods contain acesulfame-K (ACE) and that it completely passes through the body before being excreted in your urine.

The concentration of ACE in the pools and hot tubs ranged from 30 to 7,110 nanograms per liter of water - up to 570 times more than the levels found in the tap water samples.

In a large swimming pool (around a third of an Olympic swimming pool) the team discovered around 75 litres of urine present.

The researchers want to raise awareness about the risks of peeing in the pool. Ace is not found in the tap water that filled those pools.

Although the researchers were unable to confirm exactly what fraction of visitors were choosing to quietly relieve themselves in the water rather than making the shivery trip to the changing rooms, the results suggest that the urine content was being topped up several times each day. The team also tested a handful of hot tubs and found concentrations of the sweetener even higher in those. These include trichloramines, which can cause eye irritation and respiratory problems. To stay safe, she says all swimmers need to be vigilant about showering before entering and exiting pools, but most importantly, to "be considerate of others and make sure to exit the pool to use the restroom when nature calls". 'Chlorine kills it, so it's not bad'. But recent studies have shown that urine and sweat can react with the chlorine to form other harmful disinfection byproducts.

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