A public toilet flushes more feces than you might expect
Engineers from the University of Colorado Boulder used laser lights to see what happens when you flush a public toilet.
Just like the big debate over which way the toilet paper roll goes, there’s a similar debate over flushing: Is the lid open or closed?
Scientists have come to their own sad conclusion: There is no solution to stop the spread of dangerous germs.
Microbiologist Charles Gerba and his research team at the University of Arizona determined that leaving the lid up or down made little difference. Closing the lid on a residential toilet does not prevent the spread of viral particles from a violent cough in a flushed toilet.
In a study published Thursday in the American Journal of Infection Control, researchers concluded that when a person flushes the toilet, tiny virus particles are transferred to the floor and nearby toilets, regardless of whether the lid is up or down. The only meaningful way to reduce the spread of viral pathogens such as norovirus is to disinfect the toilet, toilet water and nearby surfaces, the study found.
“A lot of people just close the lid and that’s it,” says Gerba, who has been studying toilet germs for nearly half a century. “All that air goes somewhere when you flush, and it pulls the viruses out of the toilet bowl.”
Previous studies have shown that a closed lid reduces the risk of bacterial contamination on nearby surfaces, and researchers have tried to raise awareness of how lidless toilets can flush out germ-ridden pipes in public restrooms. But Gerban’s team studied whether the same was true for tiny virus particles found in residential toilets and found little change.
Previous studies have linked norovirus outbreaks on airships and flights, and in schools, from toilet flushes. In a bad outbreak on a cruise ship, Gerba said, half of the toilets tested contained norovirus particles.
“You really have to make sure you’re always cleaning the toilet seat and other areas in the toilet,” Gerba said.
How was the research done?
Gerba’s team studied public toilets and residential toilets in an office building. The public toilet was tankless, installed in the tent and flushed with a piped water line. The house toilet had a tank in a small toilet.
The team included researchers from UK-based Reckitt Benckiser, which sells consumer products including Lysol.
The researchers added the viral particles to the toilet and after one minute measured the contamination in the toilet and the adjacent toilet.
Because public toilets usually do not have lids, researchers only measured data on lid clogging from home toilets. The study found no difference in overall viral contamination if a residential toilet lid was opened or closed before flushing, but noted that a closed lid may change the “direction of aerosol plume contamination.”
When the lid was closed before flushing, researchers measured slightly higher pollution to the left and in front of the toilet, but slightly lower pollution to the right of the toilet.
Toilet bowls cleaned with a brush and disinfectant, hydrochloric acid, had less contamination than those cleaned with a brush alone. Cleaning the bowl with disinfectant also reduces contamination of nearby surfaces such as the toilet floor and toilet brush caddy, the study found.
According to the study, the results “show that closing the toilet lid before flushing does not reduce the risk of contamination of the bathroom and that it is important to disinfect all toilet surfaces after the toilet brush” to reduce the spread of germs.
In other words, you need to clean the toilet with germ-killing chemicals and a brush every time. Then wash your hands.
Hospital patients exposed to toilet germs
Other researchers have found that there is little doubt that particles can be forcefully ejected from the toilet bowl after being flushed.
Matthew Nonenman, a professor in the College of Public Health at the Nebraska Medical Center, sees the importance of closing the lid when one is present.
“This is kind of a personal question. Have you ever flushed while sitting on the toilet?” Nonenman said. “You feel the effects of the particles on your skin.”
Nonenman’s group studied particles and bioaerosols from flushing hospital toilets during routine patient care. His Research These contaminants found can remain in the toilet for 30 minutes after flushing.
Healthy people with a strong immune system may be able to avoid such pathogens. However, immunocompromised patients in the hospital may be more susceptible to bacterial infections such as Clostridioides difficile, also known as C. diff.
Keeping the lid closed – along with common disinfectants and hand washing – helps keep things clean.
“If you close the lid, you reduce some of the larger particles that fly out of the toilet,” Nonenman said.
What steps can I take to reduce bathroom germs?
Although the UA-Rickitt Benckiser study did not recommend how often toilets should be cleaned, Gerba said homeowners should clean toilets and nearby surfaces regularly.
To clean the toilet handle after use, it is recommended to keep disinfectant next to the toilet and also to carry disinfectant wipes. People should always wash their hands thoroughly and use hand sanitizer, especially if someone in the family is infected with the virus, Gerba said.
If a family member has diarrhea — indicating possible exposure to norovirus or salmonella — Gerba recommends disinfecting toilet seats, sinks and other high-touch bathroom surfaces twice a day.
Of course, users have less control over how often public restrooms are cleaned, but people can still protect themselves by hand washing and sanitizing.
In addition to washing your hands and disinfecting the bathroom, Nonenman recommends putting away your toothbrush and facial makeup. People should avoid holding their phones while using the toilet.
Phones in the bathroom? There is an argument ripe for the new generation.
Ken Alltucker is at X, formerly on Twitter, @kalltucker, or can be emailed at alltuck@usatoday.com.