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One in five Americans admit they have peed in a pool, and among Olympic swimmers, the practice is so widespread that a former US National team member said nearly 100 percent of competitive swimmers pee in the pool  regularly.1

Swimming in a urine-contaminated pool is certainly not the most pleasant thought, but is it really so bad?

Olympic swimmer Michael Phelps doesn’t think so, and famously said that “chlorine kills it [urine],” making peeing in the pool a non-issue. But it’s not the urine itself that you need to worry about.

Urine is virtually sterile when it leaves your body, so it doesn’t pose the risk of causing illness the way fecal matter in a pool does. In fact, urine is a valuable source of nutrients that is now being used as an effective and natural fertilizer.

So it’s not the urine that is the problem  it’s what happens when urine mixes with pool chemicals, including chlorine, that is catching researchers’ attention.

Peeing in the Pool Creates a Chemical Warfare Agent

Highly toxic disinfection byproducts (DBPs) form from reactions between pool disinfectants and organic matter, including hair, skin, sweat, dirt and  urine. In a new study, researchers mixed uric acid from human urine with chlorine and found it creates two DBPs: cyanogen chloride (CNCl) and trichloramine (NCl3).2

The former, CNCI, is classified as a chemical warfare agent and is a known toxicant to your lungs, heart, and central nervous system. NCl3 is linked to lung damage.

As for how dangerous this is, practically speaking, the researchers found that, in a worst-case scenario, urine in a pool might lead to about 30 parts per billion (ppb) of cyanogen chloride, which is well below the 70 ppb used as the maximum cyanogen concentration allowed in drinking water, according to the World Health Organization (WHO).3