The CDC reports that nearly 60 percent of public pools tested positive for bacteria found in human feces that can cause rashes and infections.

A refreshing dip in your local public pool might not be so appealing now that the U.S. Centers for Disease Control (CDC) report that more than half of public pools contain a detectible amount of human fecal matter.

Researchers with the CDC collected samples from indoor and outdoor public pools in the Atlanta, Ga., region during last summer’s busy swimming season and tested them for bacteria. They discovered a high percentage of bacteria found in the human digestive system, suggesting that the pool water was contaminated with human feces.

CDC scientists found that 58 percent of the water samples tested positive for E. coli, bacteria that lives in the human gut and makes headlines during food poisoning outbreaks.

The pools also had a high percentage—59 percent—of pseudomonas aeruginosa, a common bacterium that can cause rashes, infection, and in the worst case scenario, sepsis and death. About two percent of the pool samples tested positive for Cryptosporidium and Giardia, two germs that can cause diarrhea and are spread by contact with feces.

Though the pool samples tested positive for these germs and bacteria, the testing did not indicate whether the germs were alive and capable of causing infection and disease.

The CDC noted that their study only addressed public pools and did not include other types of recreational water parks, such as private pools and water theme-parks.

Not only is it gross, the presence of fecal matter in pools poses a major health risk because chlorine and other pool cleaning chemicals don’t kill bacteria immediately.

“Swimming is an excellent way to get the physical activity needed to stay healthy,” Michele Hlavsa, chief of the CDC’s Healthy Swimming Program, said in a press release. “However, pool users should be aware of how to prevent infections while swimming.”

To reduce your risk of getting sick and to honor Recreational Water Illness and Injury Prevention Week next week, the CDC offers the following guidelines for maximizing your summer pool safety:

  • Do not swallow the water you swim in.
  • Keep feces and other contaminants out of the water by showering with soap before swimming, washing your hands properly after using the restroom or changing a baby’s diapers, and never swimming when you have diarrhea.
  • Keeping chlorine levels at 1 to 3 mg/L or parts per million and the pH at 7.2 to 7.8 to maximize its germ-killing power.
  • Children should be taken to use the bathroom every 60 minutes and diapers should be checked every 30 minutes while at the pool.

For more information, visit the CDC’s Healthy Swimming information page.

Of course, if you see something brown in the water, don’t automatically assume someone pulled the ol’ Baby Ruth gag.