The COVID-19 pandemic has likely taught us some interesting knowledge. For example, does everyone know what “aerosol” means? These are tiny water particles in suspension that can linger in the air.
When you sneeze or cough, you will disperse a cloud of aerosol into the environment. That cloud can carry flu viruses and even the SARS-CoV-2 virus that causes the COVID-19 pandemic. However, there are also some beneficial aerosol dispersing devices, such as nasal sprays that carry medication deep into your sinus membranes. Insect sprays disperse chemicals toxic to mosquitoes or cockroaches in aerosol form.
Can you guess what else?
In a new study published in the journal Fluid Physics, scientists from Florida Atlantic University reported that a toilet can disperse more than 10,000 aerosol particles after you flush.
It goes without saying, but you probably know what these aerosol particles carry: your waste, possibly from previous users, along with bacteria and countless pathogens!
So, the tip here is to wait at least 20 seconds if someone just used the toilet before you enter the room. When you flush the toilet, be sure to close the toilet lid. For urinals with automatic sensors in men’s restrooms, they need to be programmed with a certain delay to avoid flushing and spraying aerosol particles onto someone still standing there.
A toilet flush disperses more than 10,000 aerosol particles
This is what researchers at Florida Atlantic University discovered after spending 3 hours and conducting over 100 flushes under various scenarios in a public restroom at a university.
This restroom was of average size, with 6 urinals for men and 3 stalls with standard toilets. Each flush of the urinal used 3.8 liters of water, while the toilet used 4.8 liters.
24 hours prior, they had deep cleaned the entire restroom, turned on the ventilation system 24/7, and temporarily closed it to eliminate all stray aerosol particles. In the experiment the following day, an aerosol counter was placed in front of a urinal and a toilet stall to measure the difference in particles before and after flushing.
“After about 3 hours of experimentation with over 100 flushes, we measured a significant increase in aerosol concentration in the surrounding environment. The total number of droplets dispersed in each flush reached tens of thousands,” said Professor Siddhartha Verma from the Department of Mechanical Engineering at Florida Atlantic University.
The height of the spray from the urinal reached 69 cm, while the standard toilet with a seat reached 109 cm. The particles dispersed most strongly ranged from 0.5 to 1 micrometer, which is 100 times smaller than a human hair. Their density increased by more than 200% after flushing. Particles sized 0.3-0.5 micrometers increased by nearly 70%, while the largest particles sized 1-3 micrometers increased by 50%.
The measurement results also showed that most aerosol droplets in the restroom take 20 seconds to settle down. Therefore, this could be the safe time you need to wait before entering a restroom where someone just flushed.
In addition, researchers indicated that closing the toilet lid (if available) can help. This polite action may reduce the density of aerosol dispersal, but they warn that droplets can still escape through gaps.
Therefore, waiting remains a safer strategy before you enter a restroom where someone has just exited.
Risk of infection from multiple pathogens, including COVID-19
“Both toilets and urinals produce a large amount of droplets smaller than 3 micrometers. They pose a significant risk of disease transmission if they contain infectious microorganisms,” Professor Verma stated. “Due to their small size, these water droplets can linger in the air for a long time.”
We know that pathogens lurk in stagnant water, urine, feces, and vomit from humans. Studies show that the SARS-CoV-2 virus can survive in feces longer than in respiratory secretions.
Previously, the Ebola virus was also found in toilet waste, and outbreaks of norovirus causing food poisoning, gastroenteritis, and Legionnaire’s disease from public restrooms are not uncommon.
Previous mathematical models have also indicated that flushes in restrooms can disperse germs up to several meters away, and at heights that can reach human respiratory pathways.
During the COVID-19 pandemic, the issue becomes even more concerning. The research team at Florida Atlantic University indicated that most public restrooms today are small and poorly ventilated.
High daily service traffic and infrequent cleaning can increase the risk of COVID-19 transmission.
Therefore, this is a recommendation for building owners to improve the ventilation systems in their restrooms and to clean them at least twice a day.
For users, scientists advise that they should wait at least 20 seconds before entering a restroom where someone has just flushed. After that, please close the toilet lid, flush, and exit as soon as possible.
Source: Sciencealert