What's in the Water?: Swimming pools may be bad for your health. Jason Regan

Do you smell chlorine when you swim in an indoor pool? Maybe it's not chlorine after all.

Researchers at Purdue University have identified "volatile disinfection byproducts" that can form when chlorine in pool water reacts with sweat and urine. When enough of these byproducts form, they can cause problems for breathing, skin and eyes.

Health experts at the federal Centers for Disease Control have documented cases where people became sick after breathing contaminants at indoor pools. And last summer, officials had to interrupt the U.S. National Swimming Championships because some swimmers were having trouble breathing.

Now the Purdue researchers are trying to learn more about the chemistry of swimming pools. It's not just sweat and urine. Chlorine may react with other additives, such as cosmetics and deodorants.

Future research will focus on figuring out how to break down the unhealthy byproducts that form in pools. Or better yet, prevent their formation. Our suggestion: Insist that everyone take a shower before hitting the pool. And make it a warm one.