Research claims that bioaerosols produced in public toilets may cause the spread of COVID-19
A scientist in the School of Engineering and Computer Science at Florida Atlantic University The team tested the physics of the fluid again and studied the droplets produced by flushing toilets and urinals in public toilets under normal ventilation conditions. To measure these droplets, they used particle counters placed at different heights in the toilet and urinal to capture the size and number of droplets produced during flushing.
The results of this study published in the journal Fluid Physics indicate that public toilets may become “hot beds” for airborne diseases, especially if public toilets do not have adequate ventilation or toilets are not covered. The case of the lid. Most public toilets in the United States are often not equipped with toilet lids, and urinals do not have lids.
In this study, the researchers obtained data for three different scenarios: toilet flushing; toilet flushing with lid and urinal flushing. They checked the data to determine the increase in aerosol concentration, the behavior of droplets of different sizes, the height of droplets rising, and the effect of covering the toilet. The environmental aerosol level was measured before and after the experiment.
“After about 3 hours The test involved more than 100 washes. We found that the measured aerosol levels in the environment have risen sharply, and the total number of droplets produced in each wash test is as high as tens of thousands. Assistant Professor Siddhartha Verma said. “Both toilets and urinals produce a large number of droplets less than 3 microns in size. If they contain infectious microorganisms, they will pose a huge risk of transmission. Because of their small size, these droplets can be suspended in the air for a long time.”< /p>
These droplets were detected at an altitude of up to 5 feet within 20 seconds or more after the start of the flush. The researchers detected that when the toilet was flushed with the lid closed, the amount of droplets in the air was small, although not many, but this indicated that the aerosol droplets escaped through the small gap between the lid and the seat.
“Over time, the significant accumulation of aerosol droplets produced by flushing indicates that even if there is no obvious lack of airflow in the toilet, the ventilation system cannot effectively remove them from the enclosed space. “Dr. Masoud Jahandar Lashaki said he is a co-author and an associate professor in the Department of Civil, Environmental and Geomathematical Engineering at Florida Atlantic University. “In the long term, these aerosols may rise with the updraft generated by the ventilation system or people moving in the bathroom.”
The measurement level of droplets with a size of 0.3 to 0.5 microns has increased. 69.5%, the particle size of 0.5 to 1 micron increased by 209%, and the particle size of 1 to 3 micron increased by 50%. In addition to the smallest aerosols, relatively large aerosols can also pose a hazard in poorly ventilated areas, although their gravity sedimentation is stronger. They usually evaporate quickly in the surrounding environment, and the resulting volume and mass decrease, or eventually form droplet nuclei, which will allow microorganisms to suspend for several hours.
“This study shows that adding adequate ventilation to the design and operation of public spaces will help prevent the accumulation of aerosols in high-occupancy areas (such as public toilets),” co-author, Said Dr. Manhar Dhanak, Professor and Director of the SeaTech Department of Marine and Mechanical Engineering, Florida Atlantic University. “The good news is that it may not always be necessary to thoroughly inspect the entire system, because most buildings are designed according to certain specifications. It may just be a matter of redirecting the airflow according to the layout of the restroom.”
< p>During the 300-second sampling process, the researchers performed 5 different manual flushes of the toilet and urinal at 30, 90, 150, 210, and 270 seconds, and kept pressing the flush button. ,5 seconds. The toilet was deeply cleaned and closed 24 hours before the experiment, and the ventilation system was operating normally. The temperature and relative humidity in the bathroom are 21°C and 52% respectively.
“Aerosol droplets play a central role in the spread of various infectious diseases, including COVID-19. This latest study by our team of scientists provides more evidence to support the The risk of infection spread in confined and poorly ventilated spaces,” said Dr. Stella Batalama, Dean of the School of Engineering and Computer Science.