Toilet Flushes in Public Restrooms May Pose a Risk

A new study out of Florida Atlantic University might give people even more pause before entering dingy, poorly ventilated restrooms. Researchers found that toilet flushes, as well as urinal flushes, generate tiny aerosol droplets that linger and can be inhaled, per a university release. This goes beyond the gross factor—these droplets have the potential to spread bacteria and diseases such as Ebola and, yes, COVID-19, reports Science Alert. Closing the toilet lid before flushing helps, "although not by much" because droplets escape through the gap between lid and toilet, say the researchers. They also point out that the risk is diminished if the restroom is properly ventilated, which can be achieved through relatively modest tweaks. If not, such restrooms "could serve as hotbeds for airborne disease transmission."

"After about three hours of tests involving more than 100 flushes, we found a substantial increase in the measured aerosol levels in the ambient environment," says co-author Siddhartha Verma. "Both the toilet and urinal generated large quantities of droplets smaller than 3 micrometers in size, posing a significant transmission risk if they contain infectious microorganisms." Because the droplets are so small, they can stay in the air for awhile. The team found them at heights of up to 5 feet for 20 seconds or more after a flush, per the Miami Herald. The newspaper notes that the coronavirus has been detected in urine and feces samples of those infected, though it quotes an expert who says more study is needed. "COVID- risk of bathroom exposure is largely theoretical—possible, but not proven,” says Dr. John Ross of Brigham and Women’s Hospital in Boston. (More toilets stories.)