Flushing a Toilet Throws a ‘Plume’ of Droplets Into the Air, Raising Questions About COVID-19 Risk

Korin Miller
·5 min read
Flushing a Toilet Throws a ‘Plume’ of Droplets Into the Air, Raising Questions About COVID-19 Risk

You already know that public bathrooms are pretty disgusting—but recent research sheds light on just how germy they can be.

For a study published in the journal Physics of Fluids in February, researchers measured the size and number of droplets generated by flushing toilets and urinals in a public bathroom. They discovered that droplets can be thrown up to five feet in the air, “similar to the height at which many people breathe,” says study co-author Masoud Jahandar Lashaki, Ph.D., an assistant professor at Florida Atlantic University.

While aerosol levels went up right after the toilet flushed, the researchers found there was a “notable rise” in the levels of aerosols in the area due to an accumulation of droplets from multiple flushes done during testing.

Why does this matter now? Jahandar points out that, while respiratory droplets are the main driver of the spread of COVID-19, there may be other sources of transmission to pay close attention to, given that SARS-CoV-2 (the novel coronavirus) can be found in urine and poop samples.

“Our results indicate that ensuring adequate ventilation in public restrooms is essential,” Jahandar says. “These relatively confined areas often experience heavy foot traffic and could pose a risk for widespread community transmission of various gastrointestinal and respiratory illnesses.”

But infectious disease experts say you shouldn’t panic about your COVID risk within a bathroom just yet. Here’s what to keep in mind next time you have to use a public toilet.

First, this connection isn’t exactly new when it comes to germs.

It’s well known among public health experts that aerosols shoot into the air when you flush. It’s called the “toilet plume,” and the concept has been around since 1975 when microbiologist Charles Gerba wrote in the journal Applied and Environmental Microbiology that “there is a possibility that a person may acquire an infection from an aerosol produced by a toilet.”

But while the toilet plume has been studied—including how far it can spread in a bathroom—research hasn’t “clearly demonstrated or refuted toilet plume-related disease transmission,” so the significance of the risk is still unclear, per the Centers for Disease Control and Prevention (CDC).

There have been some associations, though. “Airborne dispersion is suspected to have played a key role in the outbreak of viral gastroenteritis aboard a cruise ship, where infection was twice as prevalent among passengers who used shared toilets compared to those who had private bathrooms,” Jahandar says. However, it’s hard to say for sure if poor hand hygiene or contaminated aerosols drove the spread of illness in this case.

Is it possible to get COVID-19 from a public bathroom or toilet?

There are some things to consider. Research has found that SARS-CoV-2 can cause digestive issues like diarrhea and vomiting. The coronavirus has also been detected in toilet bowls and sinks in rooms used by people who have been diagnosed with COVID-19.

Theoretically, then, if someone had COVID-19 and used the bathroom before you got there, there’s a chance that particles from their pee or poop could go into the air with their toilet plume. “Owing to their small size, these droplets can remain suspended for long periods of time,” Jahandar says.

But while the theory is there, public bathrooms haven’t been concretely linked to COVID-19 outbreaks so far. “It’s only theoretical at this point,” says William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine. “If there were a major concern about public restrooms, we wouldn’t have them.”

Public bathrooms are still pretty gross. How can I take extra precautions?

Given the amount of germs that circulate in public bathrooms, it’s understandable that you might want to do everything you can to stay safe until COVID-19 case numbers dip to much lower levels.

Richard Watkins, M.D., an infectious disease physician and professor of internal medicine at the Northeast Ohio Medical University, agrees that the risk of transmission from a toilet plume is likely low, but still recommends lowering the toilet seat before you flush, if one is available.

It’s also a good idea to keep your face mask on while you use the bathroom, he says. Approach public restrooms in the same way you would any indoor space—so if you can, avoid using a stall right next to someone to maintain some distance.

Above all, good hand hygiene is crucial: “By all means, wash your hands,” Dr. Schaffner says. That means thoroughly lathering with soap and water for at least 20 seconds—or the amount of time it takes to hum “Happy Birthday” from beginning to end twice.

This article is accurate as of press time. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus develops, some of the information may have changed since it was last updated. While we aim to keep all of our stories up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news. Always talk to your doctor for professional medical advice.

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