A recent study might make you more wary about your toilet.
Researchers from Flinders University in Australia examined the scientific literature on what happens after we flush a toilet. The very act of flushing can shoot up aerosols loaded with potentially dangerous microbes, they found—even high enough to reach our airways. The team’s work could help us design safer and less stomach-churning toilets, the researchers say.
“From a practical perspective, these findings suggest several implications for sanitation design and operation,” they wrote in their paper, published last month in the journal Science of The Total Environment.
Flushing dangers
It’s well established that toilet flushing can generate aerosols, particularly aerosols loaded with microbes like viruses and bacteria, which are also called bioaerosols. And specific outbreaks of diseases have been linked to flushing, including of the original SARS virus. According to the researchers, however, stronger empirical evidence is needed to understand the public health risks of toilets and flushing.
The team reviewed 22 studies covering toilet flushing and aerosol generation. These studies included flushing experiments in the lab as well as real-world toilets, and some involved potentially disease-causing microorganisms like Escherichia coli and Salmonella bacteria.
The researchers found that aerosol concentrations could vary widely from study to study, depending on the type of toilets used, the experimental conditions, or how the aerosols were sampled for analysis. But they did isolate two factors that seemed most important to a higher risk of disease transmission: the amount of microbes left in the toilet bowl and the volume of water being flushed. Unnervingly, they also found that at least some toilets can generate aerosols capable of being breathed in when flushed.
“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 lead study author Lira Adiyani, a PhD student at Flinders, in a statement from the university.
What should this mean for your flushing?
There are some positives to take away from this research, the authors say. Though it’s not conclusive, for instance, better ventilated bathrooms might help reduce the risk of poo-scattered germs lingering in the air. And there are things you can personally do to mitigate this risk further, according to Adiyani, though probably not entirely.
“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,” she said.
Ultimately, though, systematic changes in toilet and sanitation design are truly needed to make the bathroom safer after going number two, particularly in higher-risk environments like hospitals, the authors say. This could include things like reducing the microbial load that ends up in the toilet, particularly in systems that use recycled water, and finding the optimal balance for a toilet flush so that it doesn’t kick up too many aerosols but is still strong enough for all our hygiene needs.
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