The toilet seat had the most contamination, while walls had little.
Contrary to previous study findings, closing the toilet lid before flushing doesn't stop aerosolized viruses from contaminating bathroom surfaces, scientists from the University of Arizona and Reckitt Benckiser LLC, the company that makes the disinfectant used in the study, report in the American Journal of Infection Control.
The researchers added a bacteriophage (virus that targets and kills bacteria) to household and public toilet bowls as a proxy for human intestinal viruses. After they flushed the toilets (with the lid open or closed in case of the household toilets), they measured viral contamination of the toilet and bathroom floor and walls.
"Research has demonstrated that people with COVID-19, even those who are asymptomatic, excrete severe acute respiratory syndrome coronavirus (SARS-CoV-2) in fecal matter and other excretions," the researchers wrote. "Viruses contaminating urine and feces can be aerosolized in building restrooms during toilet flushing."
The resulting toilet aerosol plumes, they said, can land on surfaces more than 5 feet away.
Mythbusters busted this myth long before studies. Turns out that air pressure is enough to push the particles flying from the bowl despite the lid, because the toilet lid isn't a good air tight seal, and the air is pushed out due to water volume increase.
Ok it doesn't 100 percent stop it or it doesn't help at all? Because I always assumed something as small as a poop bacteria could get through the little cracks but I also assumed having it go through the cracks was better than having it go through the massive entire open bowl where it seemed like more would spray out. Did they comparison test the amount of bacteria on surfaces or just prove that some gets through?
Edit: obviously I could be wrong but it also seems like having the lid down would direct more bacteria to lower surfaces whereas having it open would give an easier path to higher surfaces where we tend to keep things like toothbrushes.