Flushing toilets release particles into the “breathing zone” of adults and can remain suspended in the air for at least 20 seconds, a new study has found. And closing the lid might not be enough to avoid a “plume” of potential pathogens. Meanwhile, previous research has shown public toilets are an inescapable hotbed of microbes.
Flinders University researchers reviewed 22 studies of toilet-generated aerosols, publishing the results in the Science of the Total Environment journal. They found microbes from the water used for flushing or from contamination of the bowl ended up as aerosols, with more “turbulent” flushing releasing more particles. That included bioaerosols – aerosols that contain biological material and can transmit pathogens including legionella, influenza and norovirus.
There are differing reports about whether Covid spreads through toilet aerosols. The researchers found higher levels of aerosols in the water and higher levels of turbulence during the flush increased the volume of particles suspended in the air, but the effects of bathroom ventilation and whether the lid was up or down were unclear. Despite that, lead author and PhD student Lira Adiyani said she would still recommend putting the lid down after using the toilet.
Therefore, larger flush volumes generally produce more aerosols.” Adiyani said “based on the available evidence” she would still recommend closing the lid as a precautionary measure, “while recognising that it does not completely prevent aerosols from escaping”. In the report, the researchers wrote that the effects of indoor aerosols had been “understudied” despite the risk of infection. This had “important implications for risk assessment, building design, and infection control in an era of water security pressures and emerging infectious diseases”, they wrote.
She said the team was working on “protecting the most vulnerable through good design” in places such as hospitals and aged care environments. They are increasingly concerned about “opportunistic pathogens” that can be present in water, particularly recycled or rainwater. Dr Lotti Tajouri, an associate professor in molecular genetics at Bond and Murdoch universities wasn’t involved in the research but warned bathroom dangers go well beyond the toilet.
His own research is particularly focused on public toilets and mobile phone use in toilets. The door will have microbes on it, as will the floor – so you should never put anything on it, he said. Then you might touch the lid, after which you flush with the lid up or down.
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