Do you use a public toilet? Hide!

Think you don’t need to worry about COVID-19 when using a public toilet? A group of researchers from Yangzhou University in China recently reported that flushing public toilets can release clouds of virus-laden aerosols that you can potentially inhale.

If that’s not interesting enough, after running additional computer simulations, they concluded that flushing urinals does the same. In Fluid physics, the group shares its work of simulating and monitoring the movements of virus-laden particles when rinsing urinals.

Researchers’ work clearly shows that public toilets can be dangerous places to potentially be infected with a virus, especially during the COVID-19 pandemic. Other work has shown that virus transmission through both faeces and urine is possible.

“To do this, we used a computational fluid dynamics method to model the movement of particles that occurs with the act of flushing,” Xiangdong Liu said. “The specific models are the fluid volume model and the discrete phase model.”

Flushing a urinal, like flushing a toilet, involves an interaction between the gas and liquid interfaces. The result of the flushing causes the release of a large dispersion of aerosol particles from the urinal, which the researchers simulated and tracked.

What the simulations revealed is worrying. The trajectory of the tiny particles ejected by flushing a urinal “manifests a type of external spread, with more than 57% of the particles moving away from the urinal,” Liu said.

But that’s not all. When men use urinals in public toilets, these tiny particles can reach their thighs in 5.5 seconds compared to the toilet flush, which takes 35 seconds to reach a little higher. The particles from the urinals, however, “show a more violent escalation tendency,” Liu said. “The climb speed is much faster than the toilet flush.”

Urinals are used more frequently in densely populated areas, and the researchers stress that particles will travel faster and farther, posing a serious public health concern.

This work underlines how important it is to wear a mask in public places but especially in the toilets.

“From our work, we can deduce that flushing urinals does indeed promote the spread of bacteria and viruses,” says Liu. “Face masks should be mandatory in public washrooms during the pandemic, and anti-release improvements are urgently needed to prevent the spread of COVID-19.”