Toilet seat up or down? The truth about flushing and germs

A new study shows that flushing with the lid open might not make any difference to the spread of some germs — but there are implications for cleaning.

It’s an ongoing argument in many houses — should you flush with the seat up and down? Conventional wisdom has been that flushing with the seat down may prevent the spread of infection, but a new study from the US suggests this isn’t necessarily the case.

Previous studies concluded that having the lid down stops a “bacterial plume” from casting nasty germs onto nearby surfaces. These studies have driven a discussion about public toilets design and the perils of lidless bowls. But a research team from the University of Arizona has shown that closing the lid does not prevent the spread of smaller viral particles on flushing.

The study, published in the American Journal of Infection Control, concludes that these microscopic viral particles spread to the floor and neighbouring surfaces even when the lid is down. These findings highlight the importance of thorough cleaning, as the only meaningful way to prevent the spread of pathogens such as the norovirus is to frequently disinfect the toilet and all surrounding surfaces.

Norovirus outbreaks are common in contained settings such as an aeroplane or cruise ship, where facilities are shared by a large number of people. Microbiologist and study author Charles Gerba told USA Today there was only one way to reduce the impact of these outbreaks — a regular and thorough cleaning and maintenance routine.

“You really have to make sure you always clean the toilet seat and other areas in the restroom,” Gerba said.

The study demonstrated that toilet bowls cleaned with a brush and a disinfectant had less contamination than those cleaned with just a brush. Cleaning the bowl with a disinfectant also reduced contamination of nearby surfaces such as the bathroom floor and the toilet brush caddy, the study said. The conclusion was that “disinfection of all restroom surfaces may be necessary after flushing or after toilet brush use” to reduce viral spread.

For toilets at home, Gerba recommends disinfecting the toilet and other frequently touched bathroom surfaces at least twice a day if a household member has diarrhoea – indicating possible exposure to norovirus or salmonella.

There is still a good argument for keeping the lid down in most settings, however. One earlier study involving a hospital toilet showed that bacterial particles were still floating in the air half an hour after the toilet had been flushed with the lid up. In a healthcare environment, this could see patients who are immunocompromised put at risk of bacterial infection such as Clostridioides difficile.

Photo by Giorgio Trovato on Unsplash

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