What We're Really Swimming In

I was a lifeguard as a teenager and we used to tell kids that a chemical in the water would turn purple if they peed in the pool. Of course, there was no chemical and they probably called my bluff. Now, fast forward five decades and scientists finally found a way to tell just how much urine is in a pool.

Pools are treated with chemicals such as chlorine to kill microbes that swimmers bring in, because contrary to popular belief, urine is not sterile. And these chemicals can interact with organic materials such as dirt, insects, and swimmers' hair, and skin to form DBPs, disinfection byproducts. These byproducts are toxic and laws regulate a minimum amount of pool water that must be replaced daily to prevent a buildup. Here's where urine comes in; it's the biggest contributor to DBPs.

Each swimmer, even Olympians, is responsible for contributing up to one-third cup of urine while in the pool. Urine contains nitrogen rich urea that reacts with chlorine to form a DBP called trichloramine which is responsible for that unique indoor pool smell. Urine consumes between thirty to forty-five percent of chlorine in a pool to form DBPs.

The new urine test is now able to tell the amount of urine in an average pool. The test screens for a ubiquitous artificial calorie free sweetener called acesulfame-potassium or Ace-K. It's in many common foods such as Jello, candy, and sodas and is excreted in urine.

One hundred percent of the pools tested were positive for Ace-K and pools with one hundred ten thousand gallons of water held eight gallons of urine. This is proof positive people do pee, a lot, in pools and they should stop.