Scientists Shine Laser on What Spews Up When You Flush Down Human Waste

Laser toilet
Laser light illuminates what comes up when you flush a public toilet.University of Colorado Boulder

Trust us, what happens when you flush a commercial toilet is worse than you thought.

It turns out there is something worse to fear than just sitting on a public toilet. Flushing it spews a whole host of airborne gunk.

Scientists at the University of Colorado Boulder used laser lights to document what comes bubbling up when you flush a commercial toilet to send your business down.

The study illuminated that when flushed, public toilets spew airborne particles at speeds of up to 6 feet per second. 

In eerie, green-lit videos, researchers turned on lasers and shut off the lights, then flushed a commercial toilet with no lid. Like an erupting volcano, the surge of water spewed human waste high into the air, which could make you sick.

“If it’s something you can't see, it’s easy to pretend it doesn’t exist,” said the study's co-author John Crimaldi, an engineer at the university, in a statement. “But once you see these videos, you’re never going to think about a toilet flush the same way again.”

The researchers said they hope their findings will help the spread of diseases associated with human waste including noroviruses, E. coli and C. difficile, a potentially deadly infection.

Pathogens expelled by flushing can make their way into the lungs of people using the bathroom, according to the study.

The laser-lit videos showed particles rising to the ceiling, and spreading across the room, researchers said.

The study noted that designers of public restrooms could combat spreading disease by installing increased ventilation systems and equipping toilets with disinfectant measures. Using laser technology would enable designers to track how well the new measures are working, scientists said.

“Being able to see this invisible plume is a game-changer,” Crimaldi said. “None of those improvements can be done effectively without knowing how the aerosol plume develops and how it’s moving.”

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