Here’s How Gross Your Gym Pool ~Really~ Is

Hot days are on the horizon (we promise!). And you’re probably going to take your workout to the water if you haven’t already.

Not so fast, Missy Franklin. A new study published in the journal Environmental Science & Technology shows the water in the swimming pools and hot tubs you love to frequent isn’t nearly as clean as you likely thought.

Most pools and hot tubs are filled with disinfectants like chlorine, which you know to be a good thing. It becomes not so good when that disinfectant-filled water mixes with sweat, sunscreen, lotion, pee, and whatever else people bring into the pool. That’s when disinfection byproducts are created, and those have the power to cause genetic damage to your cells, according to the study’s researchers.

The researchers analyzed 28 water samples from seven different sites, which included a mix of public and private pools and hot tubs. The lab results showed over 100 disinfection byproducts (ick!) in the water samples. Pool samples were 2.4 times more mutagenic (or filled with the gene-altering agents), and the hot tub water was 4.1 times more mutagenic than straight-from-the-tap H2O.

The study also mentioned that serious swimmers and those who work in and around pools are more likely to develop respiratory issues and bladder cancer.

This part should come as no surprise: Researchers found that the more often the water gets used, the more likely it is to contain harmful byproducts. So if you’re constantly fighting people for a lane in your gym’s swimming pool, there are likely many, many of these byproducts swimming in there with all the people.

Not ready to give up your daily swims? You shouldn’t—swimming has a ton of health benefits. The Centers for Disease Control and Prevention suggests only diving into pools where you can clearly see the bottom and don’t give off a heavy scent of chlorine (that’s actually a bad thing). If it looks iffy, ask the pool staff how often they check chlorine and pH levels. Correct answer: at least two.

You can also do your part by showering before jumping in to clear off lotion and sweat. Choose pools that enforce this as a rule.