In the dark early days of the pandemic, when we knew almost nothing and feared almost everything, there was a moment when people became very, very worried about toilets. More specifically, they were worried about the possibility that the cloud of particles toilets spew into the air when flushed—known in the scientific literature as “toilet plume”—might be a significant vector of COVID transmission. Because the coronavirus can be found in human excrement, “flushing the toilet may fling coronavirus aerosols all over,” The New York Times warned in June 2020. Every so often in the years since, the occasional PSA from a scientist or public-health expert has renewed the scatological panic.
In retrospect, so much of what we thought we knew in those early days was wrong. Lysoling our groceries turned out to not be helpful. Masking turned out to be very helpful. Hand-washing, though still important, was not all it was cracked up to be, and herd immunity, in the end, was a mirage. As the country shifts into post-pandemic life and takes stock of the past three years, it’s worth asking: What really was the deal with toilet plume?
The short answer is that our fears have not been substantiated, but they weren’t entirely overblown either. Scientists have been studying toilet plume for decades. They’ve found that plumes vary in magnitude depending on the type of toilet and flush mechanism. Flush energy plays a role too: The greater it is, the larger the plume. Closing the lid (if the toilet has one) helps a great deal, though even that cannot completely eliminate toilet plume—particles can still escape through the gap between the seat and the lid.
Whatever the specifics, the main conclusion from years of research preceding the pandemic has been consistent and disgusting: “Flush toilets produce substantial quantities of toilet plume aerosol capable of entraining microorganisms at least as large as bacteria … These bioaerosols may remain viable in the air for…
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