Australian researchers have confirmed what many of us have believed for years: flushing the toilet releases aerosols and bioaerosols that can end up in our nose, throat, and mouth.
The Flinders University research team have systematically reviewed the scientific literature to learn more about the generation and distribution of aerosols (fine liquid or solid particles that are suspended in air) and bioaerosols (aerosols of biological origin, containing microorganisms and other biological materials – like urine and faeces) after flushing the toilet.
“Toilet flushing creates turbulence that can release aerosols into the surrounding air. Some studies detected these aerosols at adult breathing height, indicating a potential pathway for inhalation exposure,” said Lira Adiyani, a PhD student and the lead author on the research.
“The microbes can originate both from contamination of the toilet bowl during use, or from the water used for flushing. The more microbes present in the toilet, the more bioaerosols may be released. Therefore, larger flush volumes generally produce more aerosols.”
The findings were published in Science of The Total Environment.
After searching the literature – and making sure to include studies that focused on latrines, lavatories, washrooms, water closets, and bidets – the research team managed to find 22 studies that explored which factors influenced aerosol and bioaerosol concentrations after toiled flushing.
“The reviewed studies employed a range of experimental setups, resulting in notable variations,” the researchers noted. “Toilets included seated and squat types, with some studies also examining urinals. Flushing systems were generally grouped into gravity-fed (11 studies), flushometers (six studies), and vacuum systems (one study). Three studies did not clearly report the flushing mechanism, while one directly compared a gravity-fed system with a flushometer.”
After flushing, particles could be detected as far as 150cm horizontally from the toilet, and as high as 163cm above it. This latter figure was the perfect height for an adult’s breathing zone, according to the researchers.
“As most measurements were conducted at within this lower height range, approximately corresponding to adult waist level, reported concentrations likely reflect near-source conditions. This sampling height may also be relevant for certain groups, particularly young children (e.g., four to six years old), whose breathing zone is closer to this level and may increase their exposure risk,” the researchers noted.
But take note – the boffins also found that closing the lid and having good ventilation in your throne room did not change the post-flush aerosol concentrations, even if they might change how the nasty stuff dispersed from the toilet bowl to the surrounding area. And if that wasn’t not enough, aerosol particles could remain suspended in the air for a minimum of 20 seconds after the flush.
Ms Adiyani had the following advice for minimising the spread of poo particles.
“Based on the available evidence, I would recommend closing the toilet lid before flushing, where a lid is available, as a precautionary measure to minimise potential inhalation exposure – while recognising that it does not completely prevent aerosols from escaping,” she told media.
If you have a way to flush the toilet without being in the same room as it, let Holly@medicalrepublic.com.au know.
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