TIME Chemistry

Here’s Why You Shouldn’t Pee in the Pool

Besides being icky, it could also be very bad for you.

Now that summer is here, there’s a good chance you might spend some of your time cooling off in a swimming pool. But, given that the average swimmer leaves behind 30 to 80 ml of urine when they go swimming, there might be more than just refreshment waiting for you in the water.

A recent study published in the American Chemical Society journal Environmental Science & Technology shows that mixing chlorine and uric acid — the latter of which is “almost entirely attributable to human urine” — can result in “volatile disinfection by-products.”

Those by-products include trichloramine, which can affect the respiratory system and lead to irritation of the skin and eyes, as well as cyanogen chloride, which has been used in the past as a chemical-warfare agent.

There isn’t enough chlorine or urine in a pool to produce quite that level of destruction, but what is there can still find its way into your body, so science just gave swimmers another reason to hold it until you can get out.

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