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Coronavirus can spread from toilet flushing, study says

Published Jun 17th, 2020 10:52AM EDT
coronavirus toilet
Image: New Africa/Shutterstock

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  • Study says toilets can spread coronavirus by sending particles into the air after flushing.
  • Researchers say that particles continue to come out of a recently-flushed toilet for as long as a minute after the flush, creating a cloud of aerosols that could carry the virus if a person was infected. 
  • Closing the toilet before flushing and washing your hands are the best lines of defense.

Ever since the coronavirus pandemic began, scientists have been working hard to determine how the virus spreads. We all know that being near someone with the virus without face protection is bad news, but highlighting ways that you can become infected with the virus without realizing it is also incredibly important.

Now, a new study seems to support previous research that indicated a route of transmission related to toilets. As it turns out, toilets can be big ole’ poop particle bombs if flushed with the lid open, and since we know that the coronavirus can survive in feces, that makes bathrooms a potential avenue of infection. This is especially concerning in light of the fact that businesses across the country are reopening and many public restrooms are filled with toilets that have no lids.

The study, which was published in the journal Physics of Fluids, examines how particles are blown out of a toilet bowl when it is flushed. It’s already well-known that the act of flushing can create aerosols or airborne particles which can then be inhaled to land on other surfaces. If an individual is infected with the coronavirus, those aerosols may contain the virus, and anyone who uses the bathroom afterward is at risk of becoming infected themselves.

“It is clear from daily experience that flushing a toilet generates strong turbulence within the bowl,” the researchers write. “Will this flushing-induced turbulent flow expel aerosol particles containing viruses out of the bowl? This paper adopts computational fluid dynamics to explore and visualize the characteristics of fluid flow during toilet flushing and the influence of flushing on the spread of virus aerosol particles.”

Earlier research out of China seemed to suggest that the airborne particles from a flushed toilet were a viable route of transmission for the virus. The study pointed out that fecal-oral (particles landing in the mouth) and fecal-respiratory (breathing in tiny particles containing the virus) were both possible in a typical bathroom situation.

This latest round of research supports that notion, revealing that particles can remain in a large cloud around the toilet bowl after flushing, and those aerosols can continue to travel from the bowl to the air for a minute or so after the flush is initiated. That’s a whole lot of tiny particles in the air.

The scientists lay out their observations as follows:

• Strong turbulence has been observed to be generated by both flushing methods.

• An upward velocity of as much as 5 m/s is produced, which is certainly capable of expelling aerosol particles out of the toilet bowl.

• Some 40%–60% of the total number of particles can rise above the toilet seat to cause large-area spread, with the height of these particles reaching 106.5 cm from the ground.

• Even in the post-flushing period (35 s–70 s after the last flushing), the upward velocity of the diffused particles can reach 0.27 cm/s–0.37 cm/s, and they continue to climb.

The best way to prevent this from happening? Simply closing the toilet lid before flushing is a great way to mitigate the spread, as well as cleaning the toilet seat and nearby surfaces. Washing hands is also a major factor and should continue to be a top priority, the researchers say.