Look at the microbial water droplets coming out of the toilet

University of Colorado researchers used laser imaging to show how tiny

water droplets invisible to the naked eyequickly released into the air when the toilet is flushed without a lid. Scientists analyzed how the speed and distribution of particles within the flow changes. This is important to reduce the risk of infection through disinfection and ventilation strategies, or to improve toilet and flush design.

The study showed that aerosol particlesquickly fly out with an initial speed of 2 m / s. Gradually slowing down, they reach a height of 1.5 m above the toilet within 8 seconds. The largest droplets settle on surfaces within seconds, while small aerosol particles (less than 5 microns in size) remain in the air for several seconds or longer.


Emission of aerosol from the toilet. Video: University of Colorado Boulder

In their work, scientists used two lasers:one continuously shone on and over the toilet, while the other sent rapid pulses of light into the same area. A constant laser showed where the particles were in the air, while a pulsed laser measured their speed and direction. The entire experiment was filmed using two high resolution cameras.

For the study, scientists chose a toilet without a lidwith a cylindrical flush mechanism. This model is common in public toilets in North America and several other countries around the world. In the experiment, a new, clean toilet was filled with only water. The researchers note that the addition of waste products and paper can further alter the distribution of the aerosol spray and microparticles.

Emission of aerosol from the toilet. Image: John P. Crimaldi et al., Scientific Reports

Aerosol droplets can carry pathogens,such as Escherichia coli (E. coli), clostridia (C. difficile), noroviruses and adenoviruses. Understanding the trajectories and velocities of these particles is important to reduce the risk of infection through disinfection and ventilation strategies or improve toilet and flush design, the scientists explain. They note that when visiting public toilets, people are exposed not only to their own bacteria, but also to germs from previous visitors, which can remain in the toilet even after 10 flushes.

Emission of aerosol from the toilet. Image: John P. Crimaldi et al., Scientific Reports

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On the cover: scheme of the experiment. Image: John P. Crimaldi et al., Scientific Reports