Flushing toilets to release virus: Study
Aerosol droplets can last long to be breathed in by others
Beijing, June 17: Flushing a toilet can create a large and widespread cloud of virus-containing aerosol droplets that last long enough to be breathed in by others, according to a simulation study that raises the possibility of Covid-19 being transmitted with the use of toilets.
Researchers from Yangzhou University in China noted that recent studies show the novel Coronavirus that causes Covid-19 can survive in the human digestive tract and show up in faeces of the infected. Toilet flushing creates a great deal of turbulence, and qualitative evidence suggests this can spread both bacteria and viruses, they said.
The study, published in the journal Physics of Fluids, used computer models to simulate water and air flows in a flushing toilet and the resulting droplet cloud.
The researchers used a standard set of fluid dynamic formulas, known as the Navier-Stokes equations, to simulate flushing in two types of toilet — one with a single inlet for flushing water, and another with two inlets to create a rotating flow. They also used a discrete phase model to simulate movement of the numerous tiny droplets likely to be ejected from the toilet bowl into the air.
A similar model was used recently to simulate the movement of aerosol droplets ejected during a human cough, the researchers said. As water pours into the toilet bowl from one side, it strikes the opposite side, creating vortices, the explained. These vortices continue upward into the air above the bowl, carrying droplets to a height of nearly three feet, where they might be inhaled or settle onto surfaces, according to the researchers.
These droplets are so small they float in the air for over a minute. A toilet with two inlet ports for water generates an even greater velocity of upward flowing aerosol particles, they said. “One can foresee that the velocity 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,” said study co-author JiXiang Wang, of Yangzhou University. The simulations show that nearly 60 per cent of the ejected particles rise high above the seat for a toilet with two inlet ports, the researchers said. —