As the world is eyeing for a relaxation of lockdown measures in the summer, many are considering swimming pools for a quick dip. But while the water itself is unlikely to pose a threat, we should be careful about reopening pools, researchers warn.

Chlorinated water is probably safe

At the moment, there’s no clinical trial to analyze COVID-19 and its transmission in swimming pools, so we have to rely on indirect or incomplete information.

According to the Centers for Disease Control, there is “no evidence” that the virus can be spread to people through the water in any type of environment, be it hot tubs, spas, or swimming pools.

The main reason for this is that the water is routinely disinfected. The most common such disinfectant is chlorine, and chlorine almost certainly destroys the virus.

Chlorine is thought to destroy microorganisms in as little as 30 minutes, and bromine, ozone, or other types of pool disinfectants have a similar effect. Based on what we know about SARS-CoV-2, the virus that causes COVID-19, it should be destroyed by chlorine. It’s even possible that the virus is particularly vulnerable to chlorine since it has an enveloped structure, which means its relatively fragile to chemical stress (which is why, for instance, soap destroys it easily).

“Proper operation, maintenance and disinfection with chlorine and bromine should remove or inactive the virus that causes COVID-19,” the CDC said in a statement.

Again, this has not been formally tested in a controlled environment, but based on all the evidence we have available at this point in time, chlorinated water should be very effective at killing the virus. But this doesn’t necessarily give us a green light to open up the pools.

In a COVID-19 white paper commissioned by Myrtha Pools (a swimming pool contractor in Italy), Vicenzo Romano Spica, Professor of Hygiene at the University of Rome “Foro Italico” says we should still be cautious.

“At another time, I would have said yes, it is a guarantee of safety that the water is disinfected and appropriately treated according to current regulations. Today I have to say ‘yes, but …’”. He explained:

“Yes, because – what you say is right – various disinfectants including chlorine act on viruses and therefore also on a Coronavirus; but it is also true that this “new” virus is still little known and has already given us unwanted surprises. Therefore, in the absence of epidemiological evidence and dedicated experimental studies, it is necessary to be very cautious.”

Spica, who is currently carrying out a study on pool water coronavirus safety, makes a case for caution and regular disinfection of the pool — not just the water, but all surfaces there as well.

More than just the swimming water

Imagine a regular visit to the swimming pool. You don’t just jump into the water. First you check your bag somewhere and change into your swimming outfit, take a shower, and only then you go into the water. After that, you wash up and maybe dry your hair, take your clothes and go outside.

This means that unless they are regularly disinfected, changing cabins and storage facilities can pose a risk of transmitting the disease. Saunas and hot baths are also another potential way through which the virus could propagate, and simply walking by someone who is breathing heavily into a droplet-rich environment raises the potential for viral transmission.

So when considering a reopening of pools, it’s not just the water that has to be considered — but the entire environment. Disinfecting surfaces for everything that is routinely touched must be considered, and this is not an easy feat, particularly when it comes to things such as pool rails.

Several changes will have to be incorporated into the overall layout of a swimming pool. Drinking fountains, common in many pools, are an absolute no-no. Cabins will need to be redesigned or cleaned more often. Air circulation (which is oftentimes a challenge in swimming pools) needs to be analyzed with extra care, particularly as air recirculation has been linked to the coronavirus. Lastly, the rules that go outside the pool also go inside the pool: distancing is crucial.

Social distancing — inside the pool and out

Most health agencies recommend a distance of two meters between individuals to reduce the risk of transmission. The two-meter margin is a general estimate; it’s not like you’re perfectly safe at 2.01 meters and unsafe at 1.99 meters. But there are a few clear things: if you’re closer than 1 meter to someone, you’re doing it wrong. If that person were to sneeze, there’s no way you could dodge or avoid the droplets, and you would have a substantial risk of infection.

This is something that also needs to be considered for swimming pools.

People tend to breathe heavily in swimming pools. They cough and sneeze a lot, and saliva and nasal secretions tend to flow more often than normal.

While the chlorinated water can kill the virus, it doesn’t necessarily do so instantly. If you’re sitting right next to someone (or say, swimming behind them), there could be a risk of transmission. The science is a little lacking in this area, but generally speaking, the farther you are from someone, the more any potential virus gets dissipated into the water, and the safer everyone will be. Of course, maintaining a steady distance in a swimming pool is not an easy task, which is why a healthy margin might be recommended.

Needless to say, the same social distancing guidelines go outside of the pool as well.

Interactions should be kept to an absolute minimum and a distance of at least two meters should be established — in all directions.

Is it safe to swim?

Unfortunately, things are not clear. In a vacuum, chlorinated pools should be safe to reopen. But in the real world, there are no guarantees yet.

Absolute zero risk does not exist, especially in an environment such as a swimming pool. Adequate prevention measures must be ensured, and it is advisable to only open pools when the number of cases drops to an acceptable level. Then, special precautions must be taken regarding air circulation, disinfection, and social distancing — both inside the water and out.

Spica also believes that we should make a distinction between leisure swimming pools and sports swimming facilities. It is much more dangerous to ensure safety in the former, whereas, given a careful disinfection strategy, the latter could be done in a reasonable fashion.

“It is necessary to distinguish between the sport-physical activity or rehabilitative use of swimming pools from the play-recreational one, which comes more within the sphere of beaches and fun spaces. In fact, it becomes more difficult to foresee a control over social distancing or compliance with stringent regulations on an open beach or in a pool where elderly and children play freely and without rules.

“At the time of the new Coronavirus, these situations should wait for a substantial reduction in the epidemic before they can be reopened safely, and in any case always in compliance with shared rules.

“For sports swimming facilities, on the other hand, clear regulations, preventive measures, technical solutions and user discipline can encourage the achievement of higher levels of safety to counter the possible transmission of Covid-19.”