Every summer, thousands of Floridians take to the water in public swimming pools for relief from the subtropical heat in the Sunshine State. But what many swimmers might not know is that over half of all public swimming pools contain fecal matter, according to a study published by the U.S. Centers for Disease Control and Prevention.
The CDC collected samples of water from pool filters from public pools and tested the samples for genetic material (for example, DNA) of multiple microbes. The study found that 58 percent of the pool filter samples tested were positive for E. coli, bacteria normally found in the human gut and feces. The E. coli is a marker for fecal contamination.
The CDC says that finding a high percentage of E. coli-positive filters indicates swimmers frequently contaminate pool water when they have "a fecal incident" in the water or when feces rinse off of their bodies because they do not shower thoroughly before getting into the water.
Pseudomonas aeruginosa, which can cause skin rashes and ear infections, was detected in 59 percent of samples. Finding Pseudomonas aeruginosa in the water indicates natural environmental contamination or contamination introduced by swimmers. Cryptosporidium and Giardia, germs that are spread through feces and cause diarrhea, were found in less than 2 percent of samples. The tests used in the study do not indicate whether the detected germs were alive or able to cause infections. Both indoor and outdoor public pools were sampled.
The study did not address water parks such as those found at the Orlando-area theme parks, residential pools or other types of recreational water. The study does not allow CDC to make conclusions about all pools in the United States. However, the CDC says it is unlikely that swimmer-introduced contamination, or swimmer hygiene practices, differ between pools in the study and those in the rest of the country.
“Swimming is an excellent way to get the physical activity needed to stay healthy,” said Michele Hlavsa, chief of CDC’s Healthy Swimming Program. “However, pool users should be aware of how to prevent infections while swimming. Remember, chlorine and other disinfectants don’t kill germs instantly. 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.”