Next time you find yourself in a public toilet, you might want to close the lid.
Researchers at Flinders University, Australia, reviewed research studying the volume and dispersal of aerosols released when a toilet is flushed, and how factors such as higher flush volumes can affect the distribution and concentration of disease-carrying microbes.
Warning: it’s not pretty. The results suggest particles can linger at heights equivalent to an adult’s breathing zone and remain suspended in the air for over 20 seconds.
While the review, published in Science of the Total Environment, suggests it’s not possible to eliminate the dispersal of aerosols entirely, there may be steps you can take to reduce your exposure to potentially harmful microbes, from regularly cleaning the toilet to choosing a model with a lower flush volume.
Read More: Squatting and Toilet Paper Won’t Protect You from Public Restroom Germs
What Happens When You Flush the Toilet
Flushing the toilet causes turbulence that flings tiny particles into the surrounding environment. The particles are often completely invisible to the human eye, measuring just nanometers or micrometers. However, once released, these particles (or aerosols) can remain suspended in the air for an extended period of time.
This can become an issue because aerosols can contain microorganisms deposited in the toilet bowl as well as those that may be lurking in the water itself. Both aerosols and bioaerosols (i.e., aerosols that contain biological material) can be inhaled and, thanks to their microscopic size, penetrate deep into the respiratory tract. This provides a potential route for disease transmission.
Explore All OptionsIndeed, bioaerosols have been linked to the spread of several infections — including coronaviruses, according to a study in the International Journal of Hygiene and Environmental Health.
Reviewing The Scientific Literature
The recently published research is a systematic review of 22 studies led by Lira Adiyani, a Ph.D. student in environmental health.
These studies were included because they met certain criteria: they investigated aerosols generated from toilet flushing, used data from air samples, and reported aerosol and bioaerosol concentrations.
Half the studies involved seeding, in which researchers purposefully placed viruses, bacteria, or fluorescent surrogates in the bowl before experiments took place, while the remaining half took place under unseeded conditions.
By combining the studies, Adiyani and colleagues analyzed data from different types of toilets (seated, squat, and urinal) and flushing volumes.
What The Evidence Shows
Aerosol concentrations varied significantly across studies, but certain trends emerged. For example, both higher seeding concentrations and larger flush volumes were linked to greater concentrations of aerosols. This would suggest that the generation of aerosols is primarily driven by what is in the bowl and the intensity of the flush.
Higher concentrations of aerosols were also typically found closer to the toilet and near seat height. However, aerosols were detected at distances up to 59 inches (150 centimeters) away and in one study, at heights of 64 inches (163 centimeters) above floor level.
This suggests particles can be found in the average adult’s breathing zone, though it is younger children who may be at greater risk of inhaling aerosols.
Encouraging Safer Toilet Hygiene
The team says the review highlights important gaps in current research but that determining where and how aerosols are distributed after flushing could help inspire safer toilet designs in the future.
In the meantime, the researchers note certain actions that could limit the spread of aerosols next time you flush. This includes regularly cleaning the toilet, ensuring the room has adequate ventilation, be that switching on an exhaust fan or opening a window, and selecting a model with lower flush volumes when possible.
The researchers weren’t able to draw any significant conclusions when it comes to the benefit of shutting the toilet lid due to limited data, but suggest it may influence dispersal and reduce the number of aerosols at breathing height.
“Based on the available evidence, I would recommend closing the toilet lid before flushing, where a lid is available, as a precautionary measure to [minimize] potential inhalation exposure —– while [recognizing] that it does not completely prevent aerosols from escaping,” Adiyani said in a statement.
This article is not offering medical advice and should be used for informational purposes only.
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in Science of the Total Environment: Aerosol and bioaerosol generation from toilet flushing: A systematic review and risk factor analysis
- This article references information from a study published in the International Journal of Hygiene and Environmental Health: Detection of SARS-CoV-2 RNA on contact surfaces within shared sanitation facilities
