Attention Men: Using a Urinal Can Spread the Coronavirus

If you thought just flushing a toilet was a problem, urine for a surprise.

Herrentoiletten und Pissoir aus Nilpferdköpfen
Herrentoiletten und Pissoir aus Nilpferdköpfen.

 Getty Images

If our earlier post, Close That Toilet Lid or the Air Might Be Flush with Coronavirus, had you running from the washroom as quickly as you could, urine for a shock. The same researchers who modeled the toilet flushing (and determined that "the simulation results are alarming in that massive upward transport of virus particles is observed, with 40%–60% of particles reaching above the toilet seat, leading to large-scale virus spread") are at it again, this time looking at the spread that comes from using urinals.

The results from the latest exercise, published in the Physics of Fluids Journal, are in some ways scarier than the earlier ones. The researchers write:

Similar to the toilet-induced flushing, results indicate that the trajectory of the particles triggered by the urinal flushing manifests an external spread type. Even more alarmingly, the particle can reach [2.75'] 0.84 m (man’s thigh) in 5.5 seconds when compared with the diffusion performance of the toilet-induced one (around [3'] 0.93 m in 35 s). 

A statement on the research notes:

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% of the particles traveling away from the urinal," said Liu ... "From our work, it can be inferred that urinal flushing indeed promotes the spread of bacteria and viruses," says Liu. "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."

But Not So Fast

standing at imaginary urinal
Man in front of urinal.  Ji-Xiang et al

We had some issues with the previous research, and do with this study as well. The first point is that no water was wasted or urinals flushed in the latest research. It's all done by simulation; it's a mathematical model using computational fluid dynamics.

Unlike toilets which are all pretty similar, namely bowls that you sit on with water supplies, urinals come in all shapes and sizes, with varying amounts of water depending on their efficiencies. Many now are completely waterless. Some are big wide-open floor standing models and some are little round things. So I think it is fair to question whether a mathematical model based on a Chinese urinal is going to be valid for every urinal.

Secondly, when I wrote about the first study, I noted that there was a long history of research showing how bacteria and viruses are transferred by the fecal-oral route and can be launched airborne through flushing. Charles Gerba wrote about it in 1975. There has never been as much worrying about what is transferred in urine.

There is research that shows that the SARS-CoV-2 virus that causes COVID-19 can be found in urine, as documented in a letter, Isolation of infectious SARS-CoV-2 from urine of a COVID-19 patient. The researchers conclude: "These findings raise the importance of using appropriate precautions to avoid transmission from urine." A Korean study of confirmed COVID-19 patients found SARS-CoV-2 RNA in 10.1% of poop samples, but only 0.8% of pee. Those are both studies of people who are already sick and in the hospital, not the general population that you will find in a public washroom.

Many urinals are terrible, splashing back when men pee or spraying them when they flush. It's always a good idea to get away from them as fast as possible, notwithstanding the virus. And they are in terrible bathrooms. It is probably good practice to wear a mask in the washroom in any case, given what might be floating around in the air from the toilets, the blower hand dryers, and the guy standing at the next urinal, well within six feet. As I noted in the last post, "our current public and private bathrooms are a design disaster, and the fixtures that go in them are just as pathetic."

France, Paris, pissoir along the wall of La Santé Prison
France, Paris, pissoir along the wall of La Santé Prison.  Guy Bouchet, Getty Images

But do I find this new study "alarming" and "disturbing?" No. It's a mathematical model examining a mathematical improbability when the person peeing is already standing in the middle of a petri dish. On top of all of this, it is trivial. Whatever you are doing in the loo, wear a mask, wash your hands, and get out fast. Or, if you are in Paris, use the Pissoir.