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article imageCoronavirus: Is it safe to use public swimming pools?

By Tim Sandle     Jun 24, 2020 in Science
As society starts to open up in relation to the coronavirus pandemic, how safe are public swimming areas? Is the virus killed by the addition of chlorine and are there any other risk factors?
Viruses are a major cause of recreationally-associated waterborne diseases linked to pools, lakes, ponds, thermal pools/spas, rivers, and hot springs. With swimming pools, this is especially so with poorly maintained pools. However, is the SARS-CoV-2 coronavirus a greater risk than other viruses? Evidence suggests not.
Survival in water
A study using surrogate coronaviruses - transmissible gastroenteritis and mouse hepatitis - found that viruses of these types remained infectious in water for periods stretching from days to weeks, at a temperature of 25 °C. The time taken for a 99 percent reduction in water was between 17 and 22 days. This study is titled "Survival of surrogate coronaviruses in water" (journal: Water Research). A different study "Survival of Coronaviruses in Water and Wastewater" showed viral recovery at 10 days.
Examination of wastewater have shown that coronavirus is present ("Making Waves: Coronavirus detection, presence and persistence in the water environment: State of the art and knowledge needs for public health") and examining wastewater samples serves as a reliable detection method. In fact, the analysis of library wastewater samples showed that Italy had cases of coronavirus far earlier than was originally reported.
While coronaviruses can survive in wastewater, what is the risk to people using public swimming pools? To assess this, chlorine levels (the chemical added to swimming pool water) need to be considered.
Studies indicate that concentrations of sodium hypochlorite at 1000 ppm (parts per million) are effective against viruses capable of causing human infections.
This finding however does not help with respect to swimming pools, where the recommended range for chlorine in residential pools is 1 – 3 ppm, which relates to the levels of 'free chlorine'. This is a balance between killing germs and maintaining safety to pool users (higher levels of free chlorine cause the 'red eye itching' sometimes experienced by swimmers).
However, the data available suggests that the infectious coronavirus has a low stability in the environment and is very sensitive to oxidants, like chlorine. This tallies with advice issued by U.S. CDC.
Swimming pool risks
While coronavirus does not survive in swimming pools that are correctly chlorinated, this does not mean there are not other risks. But that doesn’t mean you can’t get COVID-19 while in a swimming pool. Coronavirus is a respiratory illness, and the main vector is as droplets from the mouth or nose are carried through the air. This means a risk exists with talking, coughing, or sneezing, plus the use of communal changing areas.
These risks assume that the quality of swimming pool water is expected to be similar to that of drinking water and that the water is chemically treated on a regular basis. All of the major swimming pool viral outbreaks in history have been associated with pool water with inadequate levels of chlorine.
More about Swimming Pool, Chlorine, coronavirus
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