When it comes to toilet etiquette, do you put the lid down before you flush or leave it up? If you said leave it up, the results of a new study by researchers at the Asan Medical Center in South Korea might have you questioning your practices.
Scientists have known for a while that flushing a toilet can spread small particles of water, urine, feces, and pathogens. To see just what a flush was capable of, in 2022, University of Colorado Boulder researchers used lasers to measure the normally invisible aerosol plume created by a commercial toilet without a lid. They found that flushing produced a plume that travelled faster than 2 m/second (6.6 ft/s) and reached a height of 1.5 m/4.9 ft within eight seconds. They captured a video of the icky process.
Shining a light on what comes up when you flush
With hospital patients in mind and determined to keep whatever bugs are in the bowl in there and nowhere else, Asan Medical Center researchers developed an automated toilet flushing device that only works when the lid is closed.
“Human feces can contain a number of disease-causing bacteria, including E. coli, Staphylococcus, and Campylobacter,” said Jihye Park, the study’s lead author. “Any potential means of infection control must be applied to keep patients, especially the most vulnerable, as safe and healthy as possible.”
To analyze the spread of bugs caused by toilet flushing, they fitted their device to four hospital toilets used by patients. Four toilets without the device acted as a control. Eight agar plates used to culture microorganisms were placed strategically on top, in front, to the sides, and behind the bowl.
Each toilet was flushed once when the toilets were clean. Airborne particles were allowed 90 minutes to settle on the surface of the agar plates. The plates were incubated for two days, and then the researchers examined what bacterial colonies had grown. On average, across all locations, less than half as many – six versus 14 – bacterial colonies were found on the surfaces around the toilets fitted with automatic flushing devices compared to those without.
Sung-han Kim et al
“Our study underscores the importance of closing the lid before flushing and fitting automatic flushing devices to reduce the contamination of the bathroom surfaces,” Park said. “We are now going to install automatic flushing devices in all hospital bathrooms along with automatic UV disinfection to reduce the spread of infection.”
This research only considered bacteria. A study published in February 2024 in the American Journal of Infection Control found that putting the lid up or down prior to flushing household or public toilets of US design had no significant effect on viral contamination of restroom surfaces. This is likely because viruses are smaller in size than bacteria. The study found that the most effective method of reducing cross-contamination associated with toilet flushing included adding a disinfectant to the bowl before flushing, using disinfectants or detergents in the toilet tank, and disinfecting all restroom surfaces.
The current study’s findings will be presented later this month at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID 2024) in Barcelona, Spain. There’s no published paper at this stage.
Source: Asan Medical Center via Scimex
