Charles Teves
A new study published in the Physics of Fluids suggests that flushing toilets can send droplets from the bowl three feet into the air which is where viruses could be aloft for around a minute.
“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,” says Ji-Xiang Wang from Yangzhou University in China.
The authors of the study used computational fluid dynamics to simulate how droplets in a toilet jump out when flushed carrying various pathogens with them.
The researchers looked at two common types of flushing toilets in their simulations: one with a single inlet that fills up the toilet bowl from just one source of water, and one with two symmetrical inlets, to simulate the annular flushing toilet where the water enters the bowl from the entire underside of the rim.
“The volume-of-fluid (VOF) model is used to simulate two common flushing processes (single-inlet flushing and annular flushing), and the VOF–discrete phase model (DPM) method is used to model the trajectories of aerosol particles during flushing,” the team said in their paper.
“The simulation results are alarming in that massive upward transport of virus particles is observed, with 40 percent to 60 percent of particles reaching above the toilet seat.”
The team only experimented with simulated fluids and aerosols but never tested whether a viral particle that flies up in the air and lands on the toilet seat is enough to make someone sick.
One good practice would be to close the lid before flush to avoid having poop droplets scatter, but public restrooms usually do not have this feature.
“The daily flow of people in a public washroom is stunningly large: thus, a confirmed case may cause a massive number of infections. For these reasons, investigation of toilets in the context of epidemic prevention is imperative,” the authors write.
When using public toilets it is best to clean the seat before using it, flush with the lid closed if there is one, and wash hands carefully afterwards.
