An invisible danger lurks in your bathroom.
Bathroom hygiene often focuses on what you touch — wash your hands properly, clean your towels and bathmats often and consider investing in a bidet.
Recent research, though, has unveiled a horrifying threat that’s unleashed into the air every time you flush.
Researchers at Flinders University reviewed 22 previously published studies of aerosols released when a toilet is flushed.
When water rushes around the bowl, turbulence throws microscopic droplets up into the air that contain bacteria, viruses and other biological material, such as fecal matter, from the toilet water.
Some of the studies included in the review detected these particles more than five feet above the floor — within many people’s breathing zones — and found some even remain airborne for at least 20 seconds after a flush.
And more microbial “loading,” or higher levels of bacteria in the toilet water, meant more amounts of invisible bacterial spray in the air.
Every tenfold increase in microbial concentration in the water was linked to around 2.6 times asmuch bacteria the amount in the air.
Many of the particles ranged in size from 0.3 to 10 micrometers, with a majority under 3 micrometers, remaining small enough to stay airborne and potentially be inhaled.
The review also found that flushing energy, or the amount of water in the bowl that’s being flushed down, contributed to the presence of bacteria in the air, with an additional liter of water associated with roughly a 1.3-fold increase.
Previous studies have even made the invisible spray visible to demonstrate just how far it can reach.
A 2022 study from the University of Colorado used a laser exhibit to create a visual representation of a commercial toilet launching aerosols to a height of about 1.5 meters in a matter of eight seconds.
However, closing the lid may not make too much of a difference.
A 2024 study in the American Journal of Infection Control found that although putting the lid down before flushing trapped larger particles, it did nothing for more microscopic ones, allowing them to escape through gaps between the lid, seat and bowl.
The more recent review also found limited evidence that the lid position made a difference in the air plume.
Researchers still recommend closing the lid as a precautionary measure to help somewhat prevent toilet “loading” from ending up in the air.
Additionally, regular toilet cleaning, handwashing and using the lower-volume option on dual-flush toilets can reduce the spread of germs.
While these are all feasible in a private home bathroom, the flush plume is concerning in public restrooms, with further research needed to develop interventions to reduce toilet-generated aerosols.
