You really should put the toilet seat down.
And while it may also put some household arguments to rest, the real reason to close the toilet lid is a phenomenon known as a "toilet plume."
When you flush a toilet, the swirling water that removes your waste from the bowl also mixes with small particles of that waste, shooting aerosolized feces into the air.
Low-flow toilets have decreased this risk — they don't gush or blast as much as other types of johns — but countless old toilets are still in use today and can really spew.
Philip Tierno, a microbiologist at New York University, says that aerosol plumes can reach as high as 15 feet.
"It is a good idea to lower the seat, especially if the bathroom is used by multiple people," Tierno told Tech Insider.
A study published in the journal Applied Microbiology in 1975 (before the adoption of low-flow toilets) found that whatever you put in your toilet can stay there long after you flush. After seeding a toilet bowl with potentially infectious bacteria and viruses, the researchers found that the toilet dispersed the microbes far enough to settle on other bathroom surfaces, like the floor, the sink, and even your toothbrush.
The microbes also remained on the toilet bowl's porcelain surface after multiple flushes, and while the number of microbes decreased after the first few flushes, the population leveled out and remained until it was scrubbed off (with or without a detergent).
A more recent scientific review article found similar dispersion results, although it didn't find any evidence supporting or denying that disease could be transferred through a toilet plume. More disgusting research is needed to truly gauge the danger of these aerosolized fecal particles.
So don't worry — too much — if you come into contact with the contents of a toilet plume.
"If you have [unbroken] skin, you're likely to be okay," says Tierno. He notes, however, that bacteria like salmonella and shigella and viruses like norovirus and hepatitis A, are transmitted when fecal particles enter the mouth. But it's best to be wary even if you plan on keeping your mouth away from your toilet.
Even with your seat down, Tierno says, it's probably a good idea to store your mouth related items in the cabinet. "Make sure your cups and toothbrushes are tucked away."
And what about the public toilets, which rarely have lids? Tierno suggests that you "exit at the time of the flush."
Yet as gnarly as toilet plumes may be, Tierno insists that proper hygiene is more crucial than any toilet-plume prevention. "It's most important to wash your hands before you exit the toilet," he says.
by Sean Kane