What’s the big deal, you ask? Can’t the chemicals just deal with it? Well, sort of—but those same chemicals plus your pee can make a whole new set of dangerous chemicals.
According to a study published in Environmental Science and Technology, human urine is the culprit behind a couple of deadly chemicals commonly found in pools. Most pools add chlorine to their water—it kills microbes and bacteria. However, researchers behind the study also note that pools are commonly found to contain trichloramine (NCl3) and cyanogen chloride (CNCl); trichloramine is thought to cause lung disorders, and cyanogen chloride is a toxic blood agent also known to injure respiratory organs and the eyes. Actually, it’s also listed in the Chemical Weapons Convention.
Anyway, people certainly aren’t adding trichoramine or cyanogen chloride to their pools, so researchers attempted to create some by adding uric acid to chlorine—and sure enough, it worked. Some uric acid gets into pools via sweat, but it’s thought that over 90% is from urine.
All things considered, there probably isn’t enough trichloramine or cyanogen chloride in pools to be causing serious damage (although the former is associated with youth asthma), but at the same time, this is why we skip pools with a lot of kids. It’s also why we don’t pee in the pool.