As extreme heat continues to impact people across the nation, jumping into pools, lakes and ponds to cool off probably seems more attractive than ever. However, there could be danger lurking in the refreshing water.
Natural bodies of water and man-made recreational water features alike can harbor disease. According to the U.S. Centers for Disease Control and Prevention, there were a total of 208 outbreaks associated with treated recreational water reported to CDC between 2015 and 2019.
One recent example was an outbreak last March in Maine, according to the CDC. There, 23 people who were swimming in a hotel pool developed ear pain, rash, or pain or swelling in their feet or hands due to the Pseudomonas aeruginosa bacteria.
In the past, Audacy has reported on a brain-eating amoeba such as one lurking in a Texas water park. While those are particularly alarming cases, contaminants in swimming water are actually pretty common.
“Do you think your eyes turn red after swimming because of irritating chlorine? Wrong. Experts say urine and sweat are the actual culprits,” said the Cleveland Clinic. “Yep, you read that right. They bind to chlorine and create chemical irritants.”
If that is happening, it means that the chlorine is doing its job to neutralize contaminants. Here are some ways to tell if it’s not.
First, be aware of how crowded the pool is. Since many contaminants come from people, the more there are, the more risk there is of getting an infection. Per Prevention, other danger signs are algae in the water, several babies in the same pool, improperly stored pool ladders and a lack of safety fences.
“Skin, ear, nose, throat, and respiratory disease have been linked to swimming,” said the County of Los Angeles Public Health Department.
San Diego Pools advice quoted by USA Today said that pool water should be crystal clear to be swim safe. Public pools are required by law to maintain a certain level of disinfectant when in operation. Attendees should make sure they see employees regularly testing the water at their favorite pools, according to Prevention.
Still, some pathogens might get through. For example, County of Los Angeles Public Health said the Cryptosporidium parasite “envelopes itself in a tough outer covering called a cyst,” and that “disinfectants can’t readily get past this barrier to kill the parasite.”
Someone who swallows water at a public pool might become infected with this parasite. When swimming in natural bodies of water, the chances of this and other infections increase.
“There’s so many unknowns,” said Primrose Freestone, a clinical microbiologist at the University of Leicester in the United Kingdom who writes about recreational water safety, per USA Today. “There’s a risk with swimming in all wild waters.”
Swimmer’s itch is a common infection swimmers face when they enter natural bodies of water. It “appears as a skin rash caused by an allergic reaction to certain microscopic parasites that infect some birds and mammals.
These parasites are released from infected snails into fresh and salt water (such as lakes, ponds, and oceans).”
Some ways to tell if a natural body of water is particularly risky include checking for pipes along river banks. Freestone those might be carrying human sewage and that they are a sign to get out of the water immediately. She also warned swimmers about lakes without an inlet or outlet, as fecal matter, bacteria, algae or other pollutants could sit stagnant in those bodies of water for some time.
“Lakes would hold on to the pollution longer, whereas in an ocean, there would be more mixing with the larger volume of ocean water,” said Mara Dias, senior water quality manager at the Surfrider Foundation, an environmental preservation group with more than 80 chapters nationwide.
Before heading out to swim, it is a good idea to check the weather report and look for any notices about water contamination. Swimmers can also ask life guards about water quality.
“Wherever you go swimming, research done ahead of time goes a long way to ensuring your safety. Dias recommends checking the water quality at your favorite swim spot the same way you’d check the weather forecast,” said USA Today. Dias also noted that most bodies of water are polluted 24 to 48 hours after heavy rain.
For extra safety, people should avoid swimming while sick and shower both before and after they go swimming.