Should You Flush With Toilet Lid Up Or Down? Study Says It Doesn't Matter

doc1623 shares a report from Ars Technica: Scientists at the University of Arizona decided to investigate whether closing the toilet lid before flushing reduces cross-contamination of bathroom surfaces by airborne bacterial and viral particles via 'toilet plumes.' The bad news is that putting a lid on it doesn't result in any substantial reduction in contamination, according to their recent paper published in the American Journal of Infection Control. The good news: Adding a disinfectant to the toilet bowl before flushing and using disinfectant dispensers in the tank significantly reduce cross-contamination.

The scientists conducted their experiment with E. coli (as a host bacteria) and coliphage MS2; the latter is not a human or animal pathogen but serves as a useful model. The public toilet used in the experiment was located in a stall in the restroom of an office building. That toilet was tankless, relying on water-line pressure for flushing, with no lid and a U-shaped seat with a gap in the front. The home toilet was a standard siphonic toilet with a tank and lid in a private residence; there was no gap on the center of the seat. Toilet bowls were seeded with MS2 and flushed. After one minute, samples were taken from various restroom surfaces: the top and bottom of toilet seats, the bowl rim, three locations on the floor, and the right and left walls. The team also conducted a similar experiment involving cleaning the bowls with toilet brushes, both with and without Lysol toilet bowl cleaner. All those samples were then tested for MS2 contamination.

The results: both the tops and bottoms of the lidless public toilet seats had more contamination compared to household seats, but otherwise, there was no statistical significance in the degree of contamination between lidless public toilets and household toilets with lids. And the surface contamination did indeed persist even after repeated flushes. The toilet seat was the worst offender with the greatest degree of contamination, which the authors suggest 'reflects the airflow that occurs during toilet flushing, i.e., largely around the top and bottom of the toilet seat.' That same airflow is likely a factor in spreading the contamination to restroom floors and walls. Perhaps the least surprising finding is that rigorous cleaning with a toilet bowl brush and Lysol reduced the contamination by 99.99 percent compared to cleaning with just a brush. Therefore, 'The most effective strategy for reducing restroom cross-contamination associated with toilet flushing include the addition of a disinfectant to the toilet bowl before flushing and the use of disinfectant/detergent dispensers in the toilet tank,' the authors concluded. They also recommend regularly disinfecting all restroom surfaces after flushing or cleaning with a toilet brush in health care facilities -- which often have a lot of immunocompromised people -- and if someone in your house has an active infection like norovirus. The findings have been published in the journal American Journal of Infection Control.

Slashdot reader doc1623 writes: 'This headline brought me joy today, so I thought I would share (I could honestly care less about reading the article but joy is joy, I take it where I can find it.)'

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