Public toilets may act as hotbeds for COVID-19 infection

Toilet cleaning can produce large amounts of microbial aerosols, depending on the toilet design, water pressure, or cleaning power. Various pathogens are usually found not only in stagnant water, but also in urine, feces, and vomit. When widely spread by aerosolization, these pathogens can cause Ebola hemorrhagic fever, norovirus, which causes severe food poisoning, and COVID-19, which is caused by SARS-CoV-2.

Flügge droplets are the most prominent source of COVID-19 infection, but alternative pathways may exist given the small number of viable viruses found in urine and stool samples. Public toilets are of particular concern for COVID-19 infection, as they are relatively limited, have heavy traffic, and may not be well ventilated.

A team of scientists from the Faculty of Engineering and the School of Computer Science at the University of Florida Atlantic have tested fluid physics again to investigate the droplets that result from flushing the toilets and urinals of public toilets under normal ventilation conditions. .. To measure the droplets, they used particle counters placed at various heights in the toilet and urinal to capture the size and number of droplets generated during flushing.

The results of a study published in the journal Physics of Fluids show how public toilets can serve as a breeding ground for transmission of aerial infections, especially if there is insufficient ventilation or if the toilets do not have lids or covers. I will. Most public toilets in the United States often do not have a toilet seat lid, and the urinals are uncovered.

In this study, researchers obtained data from three different scenarios. Flushing covered toilets and urinals. They examined the data to determine the increased aerosol concentration, the behavior of droplets of various sizes, how high the droplets rose, and the effects of covering the toilet. Ambient aerosol levels were measured before and after the experiment.

After about 3 hours of testing with more than 100 flashes, aerosol levels measured in the ambient environment increased significantly, and the total number of droplets produced in each flash test was found to reach up to tens of thousands. I did. Both toilets and urinals produce large numbers of droplets less than 3 micrometers in size and contain infectious microorganisms, which poses a significant risk of infection.Due to their small size, these droplets can remain floating for extended periods of time... “

Siddhartha Verma, Ph.D, Study Co-Author and Assistant Professor, Department of Ocean and Mechanical Engineering, Florida Atlantic University

Droplets were detected at a height of up to 5 feet for more than 20 seconds after initiating the flash. Researchers have found that the number of droplets in the air is low when the toilet is flushed with a closed lid, but not so many. This suggests that the aerosolized droplets escaped through the small gap between the cover and the sheet.

“The significant accumulation of aerosolized droplets produced by the flash over time is not effective in removing them from the enclosed space, even if there is no perceptible shortage of airflow in the toilet. I suggest it wasn’t, “said Dr. Masoud Jahandar Lashaki. , Co-author and assistant professor of civil engineering, environment and geotechnical engineering at FAU. “In the long run, these aerosols can be elevated by updrafts created by people moving around in ventilation systems or toilets.”

There was a 69.5 percent increase for particles sized 0.3-0.5 micrometers, a 209 percent increase for particles sized 0.5-1 micrometers, and a 50 percent increase for particles sized 1-3 micrometers. Apart from the smallest aerosols, relatively large aerosols pose a risk in poorly ventilated areas, even when gravitational sedimentation is strong.

They often undergo rapid evaporation in the surrounding environment, and the resulting reduction in size and mass, or the final formation of droplet nuclei, can leave the microorganisms floating for several hours.

“This study suggests that incorporating adequate ventilation in the design and operation of public spaces can help prevent aerosol buildup in highly occupied areas such as public toilets,” said the FAU department. Co-author Dr. Manhar Dhanak said. Professor and director of marine and mechanical engineering, and SeaTech. “Fortunately, most buildings are designed based on specific code, so you don’t necessarily have to overhaul the entire system. It could just be a matter of redirecting airflow based on the toilet layout. “

During the 300 second sampling, the toilet and urinal were manually flushed 5 times with marks of 30 seconds, 90 seconds, 150 seconds, 210 seconds, and 270 seconds, and the flash handle was held down for 5 seconds. The toilet was thoroughly cleaned and closed 24 hours before the experiment and the ventilation system was working properly. The temperature and relative humidity in the toilet were 21 degrees Celsius (69.8 degrees Fahrenheit) and 52 percent, respectively.

“Aerosolated droplets play a central role in the transmission of various infectious diseases, including COVID-19. This latest study by our team of scientists is in a confined, poorly ventilated space. It provides additional evidence to support the risk of transmission of the disease, “says Stellabatalama. Ph.D., Dean of the Faculty of Engineering and Computer Science.