A new study, which found genetic fragments from the fecal germ E. coli in 58 percent of public pools, might have you thinking twice about taking a dip this summer.
But experts say there's no cause for alarm.
"The study did not test for living bacteria," said ABC News' chief health and medical editor Dr. Richard Besser. "It's possible and likely that many of these germs were dead. That's why we put disinfectants in swimming pools in the first place. Our bodies are covered with bacteria, some harmful and some not."
For the study, researchers from the U.S. Centers for Disease Control and Prevention performed genetic testing on samples scraped from the filters of 161 Atlanta-area public pools. Ninety-three of the samples came back positive for E. coli genetic fragments, which could have come from living germs or germs killed off by chlorine and other disinfecting chemicals.
Either way, the fragments came from bacteria that probably came from human poop - a fact that might be unsettling for some. Nevertheless, Michele Hlavsa, chief of CDC's Healthy Swimming Program, stressed that swimming is still a great way to get exercise and stay healthy.
"However, pool users should be aware of how to prevent infections while swimming," she said in a statement. "That's why it's important for swimmers to protect themselves by not swallowing the water they swim in and to protect others by keeping feces and germs out of the pool by taking a pre-swim shower and not swimming when ill with diarrhea."
E. coli wasn't the only germ floating around in the tested pools. Ninety-five of the pools tested contained DNA belonging to Pseudomonas aeruginosa, a bug that can cause skin rashes and ear infections. Sixty-seven of the pools contained DNA from both bacteria, according to the study, but none of the pools were the source of a disease outbreak.
"Although this sounds alarming, we need to be careful here," said Besser, explaining how the findings should come as no surprise considering that the average swimmer, according to the CDC, has 0.14 grams of fecal material on his or her body that could rinse off into the water. "The only way to remove this is with a vigorous shower using soap and water. And most public pools only provide outdoor showers that let people rinse off while keeping their bathing suits on."
To make a splash safely this summer, the CDC offers the following tips:
Swimmers can also check the chlorine and pH levels before getting into the water. Chlorine levels should be in the range of 1 to 3 milligrams per liter or parts per million, and the pH of the water should be between 7.2 and 7.8 to maximize germ-killing power, according to the CDC.
"The rules for safely using swimming pools that the CDC lays out make a lot of sense, but it is no surprise that this study found evidence of bacteria," said Besser. "After all, he added, "our bodies contain more bacteria than human cells."