You probably think pools smell clean. People often mistake the summery smell for chlorine. But the amount of chlorine added to a pool shouldn’t smell on its own. That familiar pool odor actually comes from a toxic gas called trichloramine (try-KLOR-uh-meen). This gas forms when chlorine and water mix with a compound called uric acid.
Uric acid is found in our sweat and urine. Scientists like Ernest Blatchley from Purdue University in Indiana study water quality to find compounds like this. Blatchley’s team discovered uric acid in every pool they studied.
The trichloramine gas made during the chemical reaction with uric acid can be bad for people—especially in indoor pools. “When someone breathes in the chemical, their eyes might water and they might cough,” says Blatchley.
He says the solution is easy: Shower the sweat off before swimming, and don’t pee in the pool! “It doesn’t take a lot of effort,” he added.