Before you flush……


by Mila McManus, MD

A group of engineers from the University of Colorado Boulder used laser lights to expose the otherwise invisible spray that is sent into the air by flushing a toilet with the lid up. It became visibly evident that pathogens from human waste spread up into the air, potentially exposing people to contagious disease.

The research was done using a typical commercial toilet, showing how the flush generates a strong upward jet of air that can rapidly carry particles up to 5 feet above the bowl within a few seconds of the start of the flush.

Respiratory diseases such as influenza are smaller particles that remain longer in the air and can be easily contracted through inhalation. Larger particles that settle faster on surfaces can spread intestinal diseases by contact with hands and mouth.

While toilet bowls generally have concentrations of pathogens even after dozens of flushes, the risk of disease transmission from toilet aerosol plumes is still unclear.

In any case, it never hurts to put the lid down before flushing :-/


*Closing the Toilet Lid Before Flushing Is Important – Medscape- Feb 14, 2023.

*Toilets spew in invisible aerosol plumes with every flush – here’s the proof, captured by high powered lasers,” published in The Conversation on December 16, 2022,

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