Flushing public toilets can spread Covid-19: Study

Chinese researchers have recently reported that flushing public restroom toilets or urinals can spew clouds of particles carrying viruses, including Covid-19.

The study, published in the journal 'Physics of Fluids', found that Covid-19 particles from a flushing urinal can rise to two feet in the air in less than six seconds "potentially infecting the unsuspecting urinal user".

The researchers' work shows public restrooms can be dangerous places for potentially becoming infected with a virus, especially during the Covid-19 pandemic.

Other studies have shown that both faeces and urine-based virus transmission is possible.

"To do this, we used a method of computational fluid dynamics to model the particle movement that occurs with the act of flushing," said study researcher Xiangdong Liu from Yangzhou University in China.

"The specific models are the volume-of-fluids model and the discrete-phase model," Liu added.

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

What the simulations revealed is disturbing. The trajectory of the tiny particles ejected by flushing a urinal "manifests an external-spread type, with more than 57 per cent of the particles travelling away from the urinal," said Liu.

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But that's not all. When men use urinals within a public restroom, these tiny particles can reach their thigh within 5.5 seconds as compared to the toilet flush, which takes 35 seconds to reach slightly higher, the researchers wrote.

"Particles from urinals, however, show a more violent climbing tendency. The climbing speed is much faster than toilet flushing," Liu said.

Urinals are used more frequently within densely populated areas and the researchers point out that particles will travel faster and farther, which poses a serious public health challenge. This work underscores how important it is to wear a mask within public places, especially restrooms.

"From our work, it can be inferred that urinal flushing promotes the spread of bacteria and viruses," Liu added.

"Wearing a mask should be mandatory within public restrooms during the pandemic and anti-diffusion improvements are urgently needed to prevent the spread of Covid-19," the study author noted.