How Do Germs Get into the Swimming Pool? You Might Not Want to Know

Scientific American

As the summer winds down and Labor Day weekend approaches in the U.S., beaches and public pools will be filling up with swimmers looking to take one last dip outdoors before the season ends. Most people will hit the water without worrying about the microscopic organisms they’ll be swimming with. Maybe that’s for the best, considering what those organisms are and how they’re introduced to swimming holes.

The protozoan organism Cryptosporidium, one of the most frequent causes of waterborne disease, has become a major problem in swimming pools, says Charles Gerba, a microbiologist at the University of Arizona who’s spent decades studying how pathogens are transmitted. Crypto is a microscopic parasite with a tough outer shell that allows it to survive for days even in properly chlorinated pools.

The germ generally causes prolonged bouts of diarrhea if swimmers drink contaminated water. How crypto contaminates the water in the first place is another matter. “Besides what the average person puts in the pool when they go swimming such as sweat, sunscreen and even urine there is also the problem of AFR’s, or accidental fecal releases, by bathers, which occur on a regular basis in pools which have children in them,” Gerba says.

But such accidents are not the only way water becomes contaminated. One of Gerba’s studies from a decade ago revealed that bathers naturally shed an estimated 0.14 gram of fecal matter during a swim. Another Gerba study indicated the average bather releases 50 milliliters of urine and a liter of sweat per hour into the water during a recreational swim.

Although Cryptosporidium outbreaks in swimming pools certainly are not a new phenomenon, one area of central Idaho reported 21 cases over 10 days earlier this month and late July. That same region normally sees maybe 10 cases annually, according to the state’s Central District Health Department (CDHD).

Overall, a well-maintained pool poses no major infection risk to healthy individuals. Still, there are ways to cut down on crypto in swimming areas. One is for parents to take their kids out of the water frequently for bathroom breaks and to check diapers for infant AFRs. The U.S. Center for Disease Control and Prevention also recommends that all swimmers wash themselves thoroughly with soap and water prior to entering the pool. Swimmers should also check the pool water for signs of trouble before jumping in. If you can’t see the bottom of the pool, or if the edge of the pool is foamy, you might want to find an alternate way of cooling off.

Image courtesy of Slobodan Vasic, via iStockphoto.com

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