Flushing the toilet may release germ plume at adult face height
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Flushing the toilet may release germ plume at adult face height
Flushing the toilet may release germ plume at adult face height
Mary Van Beusekom, MSToday at 2:33 p.m.
Misc Emerging Topics
Toilet flushing can propel aerosols into bathroom air at adult breathing height, creating a potential pathway for inhalation of airborne pathogens, say Australian researchers in a meta-analysis of 22 studies published in Science of The Total Environment.
The authors, from Flinders and Adelaide universities in Australia, assessed factors influencing aerosol and bioaerosol concentrations after toilet flushing, focusing on toilet design, target microorganisms, and relevant air-sampling methods. Some of the included studies added microorganisms or surrogate organisms into toilet water rather than evaluating unseeded aerosols.
“Toilet flushing creates turbulence that can release aerosols into the surrounding air,” lead and corresponding author Lira Adiyani, a PhD student at Flinders, said in a university news release. “The microbes can originate both from contamination of the toilet bowl during use, or from the water used for flushing.”
Does closing the lid help?
Aerosols remained airborne, some reaching adult heights, for at least 20 seconds after flushing. In general, higher seeding concentrations and larger flush volumes were tied to greater aerosol and bioaerosol concentrations, which the authors said indicates that pathogen levels and flushing energy are the main drivers of aerosol generation.“The more microbes present in the toilet, the more bioaerosols may be released,” Adiyani said. “Therefore, larger flush volumes generally produce more aerosols.”
In studies using seeded microorganisms, higher microbial levels in toilet water were linked to higher concentrations in aerosols, which were often reported closer to the toilet, especially at seat height. But evidence of the independent effects of flushing pressure, lid position, and ventilation was limited and inconsistent.
The findings, the authors said, suggest that regular cleaning of the toilet and surrounding surfaces, together with handwashing after use and the use of toilets with lower flush volumes, may help minimize microbial contamination and exposure to airborne pathogens.
Although ventilation and lid position weren’t significantly associated with aerosol concentrations, the researchers said they may still influence how aerosols disperse.
Thus, they said, adequate ventilation may help disperse and remove aerosols, while evidence from individual studies suggests that closing the lid can force aerosols to escape through gaps between the lid and bowl rather than wafting directly upward. A 2024 study, though, found that the amount of virus collected from surfaces on the toilet or floor didn’t differ significantly whether the lid was open or closed.
“Overall, the findings highlight the central role of toilet design and source microbial loading in shaping bioaerosol exposure, with important implications for risk assessment, building design, and infection control in an era of water security pressures and emerging infectious diseases,” the researchers concluded.