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Is it safe to use an indoor pool?

MIT Medical answers your COVID-19 questions. Got a question about COVID-19? Send it to us at CovidQ@mit.edu, and we’ll do our best to provide an answer.

I am looking for some guidance about swimming in an indoor pool in the fall. Are there any recommendations at this point?

Illustration of three people swimming in separate lanes in a lap pool

Come on in, the water’s fine!

We’re serious. The pool itself is a low-risk space, assuming you’re able to maintain proper distancing from other swimmers. According to the Centers for Disease Control and Prevention (CDC), there’s no evidence that SARS-CoV-2, the virus that causes COVID-19, can spread through water in pools. While we don’t yet have data showing how this particular coronavirus responds to chlorine, we do know that chlorine effectively inactivates similar viruses, including SARS-CoV. With proper pool operation and maintenance, including disinfection with chlorine and bromine, most experts believe that transmission of the virus through water is virtually impossible.

But going to a public pool involves more than swimming, and that’s where the risk can be found.

Assessing that out-of-water risk involves looking at several variables. The Japanese government’s very effective COVID-19 messaging advises people to avoid the “three C’s”closed spaces with poor ventilation, crowded places with many people nearby, and close-contact settings, such as close-range conversation.

To those three C’s we would add an important fourth — continuous exposure. Your risk of contracting COVID-19 in a closed space, crowded place, or close-contact setting increases steadily as long as you remain in that situation. In other words, 60 seconds in a crowded, indoor space is relatively low risk; 20 minutes in that same situation raises the risk level to “yikes.”

Applying these considerations to your question, we can say that as long as the pool is in a large, airy space, and patrons are using the facility for exercise — as opposed to, say, raucous games of Marco Polo — lap swimming is a low-risk activity. Make sure to maintain physical distance from other people around the pool before and after your swim, and wear a mask when you’re not in the water. But take it off before you start to swim. As the CDC helpfully notes, “Masks can be difficult to breathe through when they’re wet.”

Then there’s the locker room. Small, windowless, probably not well ventilated — exactly the kind of place one should avoid during a pandemic.

Check to make sure your pool facility has, and is enforcing, locker-room occupancy limits. And even so, do everything you can to get in and out quickly. If a shower is required before you hit the pool, make it fast.  Put on your swimsuit before you leave home, so you can hop out of your clothes and wet yourself down quickly when you get to the locker room at the pool. After your swim, either head home in your wet suit or, if that’s not practical, mask up and use the locker room to change into dry clothes as quickly as you can. In either case, wait until you get home to take a proper shower and wash that chlorine out of your hair. If possible, go to the pool early in the day so you can be one of the first people in and out.

Finally, when assessing the relative safety of any activity, it’s important to consider your unique circumstances. If community spread is currently high in your area, that increases the potential risk of any activity that puts you in contact with people outside of your household or “bubble.” The Testing Trends Tool from Johns Hopkins School of Medicine can help you keep up with the numbers in your area.

And then there’s your own individual risk of complications from the COVID-19 illness. If your age or a chronic medical condition puts you at increased risk, you should factor that into any decision you make about participating in activities outside of your home.

All that said, swimming is great exercise, and exercise is important to our physical and mental health — now more than ever. While outdoor pools present the fewest risks for COVID-19 transmission, many of us don’t live in a place where outdoor swimming is possible year round. But with the right precautions, your cold-weather exercise program should go swimmingly.

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