A toilet plume is the invisible to the naked eye, cloud-like dispersal of potentially infectious sewage particles as a result of flushing a toilet. Flush particles rapidly rise out of the bowl and several feet into the air after flushing. Aerosolized droplets can remain suspended in the air for tens of minutes between users. These invisible particles go on to coat and spread onto surfaces like floors and counters; or objects like hand towels, bathmats or even toothbrushes. Daily use of a toilet by healthy individuals is considered to pose a lower health risk in terms of infection. However, if an individual is immunocompromised and the previous user was sick and shed out quantities of an infectious virulent pathogen (virus or bacteria) in their urine, feces or vomitus that would be sufficient for infection, a significantly greater risk may arise to the immunocompromised individual.
Aerosolization of the toilet bowl contents allows infectious particles to free-float haphazardly, then potentially be inhaled and/or land on surfaces. There is evidence that specific pathogens such as norovirus or SARS coronavirus can be spread by toilet aerosols. It has been hypothesized that dispersal of pathogens may be reduced by closing the toilet lid before flushing, and by using toilets with lower flush energy. A 2024 study showed evidence that even closing the lid may still lead to small viral particles escaping through gaps under the lid, resulting in viral cross contamination of the air and surfaces in a washroom.