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Close the Lid! Flushing Toilets Spreads Coronavirus: Study

TUESDAY, June 16, 2020 -- A large cloud of virus-laden droplets can be released high into the air when you flush a toilet -- and it can hang around long enough to be inhaled by others, a new study says.

The new coronavirus that causes COVID-19 can be found in the feces of infected people, and this finding suggests it could be transmitted through the use of toilets, according to the authors. The study was published June 16 in the journal Physics of Fluids.

"One can foresee that the velocity [of upward-flowing aerosol particles] will be even higher when a toilet is used frequently, such as in the case of a family toilet during a busy time or a public toilet serving a densely populated area," study co-author Ji-Xiang Wang, of Yangzhou University in China, said in a journal news release.

For the study, Wang and colleagues created computer simulations of how water and air flows in flushing toilets create droplet clouds that can contain viruses and bacteria. The simulations included two types of toilets -- one with a single inlet for flushing water, and another with two inlets for water to create a rotating flow.

The simulations showed that as water pours into the toilet bowl from one side, it strikes the opposite side, creating vortexes that send droplets nearly 3 feet into the air, where they can be inhaled or settle onto surfaces. These droplets float in the air for more than a minute, the researchers found.

The upward velocity of droplets is higher in toilets with two inlet ports than in those with one, and nearly 60% of ejected droplets rise high above the seat when a toilet with two inlet ports is flushed, according to the study.

While a simple solution is to close the toilet lid before flushing, many toilets in public restrooms don't have lids, the researchers noted. They said that can be a serious hazard.

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Posted: June 2020