How to monitor urine in pools, by testing sweetness

Recent studies have shown that nitrogenous compounds (e.g., urea) in urine and sweat react with chlorine to form disinfection byproducts (DBPs), including trichloramine, that can cause eye irritation and respiratory problems. Xing-Fang Li, Lindsay K. Jmaiff Blackstock and colleagues say this evidence has highlighted the need for improved understanding of pool chemistry to raise awareness and educate the public on the importance of swimming hygiene practices.

To estimate how much urine -- and potentially DBPs -- might be in a given pool, Li's team needed to identify what compound might consistently be present in urine. So the researchers turned to the artificial sweetener, acesulfame potassium (ACE), which is marketed as Sunett and Sweet One. The sweetener, which is often used in processed foods like sodas, baked goods and even in other sweeteners, is widely consumed, chemically stable and passes right through the digestive tract and into consumers' urine.

The researchers developed a rapid, high-throughput analytical technique to test more than 250 water samples from 31 actively used pools and hot tubs in two Canadian cities, and more than 90 samples of clean tap water used to initially fill the basins. 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. Based on the concentrations of the sweetener, the researchers estimated that swimmers released more than 7 gallons of urine -- enough to fill a medium-size trash bin -- in a 110,000-gallon pool in one instance, and nearly 20 gallons in a 220,000-gallon pool (one-third the size of an Olympic-size pool) in another instance.