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Florida Atlantic University tests what lingers after you flush

Scientists see spike in aerosols after 100 flushes in public restroom
Florida Atlantic University public bathroom toilet bowl
Posted at 3:38 PM, Apr 29, 2021
and last updated 2021-04-29 23:50:33-04

BOCA RATON, Fla. — South Florida scientists tested the physics of flushing and how it impacts the air in a public bathroom. The College Of Engineering and Computer Science at Florida Atlantic University looked at how flushing could cause virus droplets to float in the air.

The team tested 100 flushes in a public restroom on campus with a toilet and urinal, using a partial counter to track the aerosols in the air after each flush. The particle counter could track different sized aerosols.

"For all these size ranges, from very small to large, we saw a spike in these numbers," Dr. Masoud Lashaki said.

AeroTrak device used to trace particles after flushing
Dr. Masound Lashaki uses this device to track the aerosols in the air after each flush.

Lashaki said the results show the spike in numbers could cause microbe-containing aerosols to increase. Many aerosols contain respiratory droplets, or pathogens, and when dispersed widely through aerosolization after a toilet flush, Lashaki said, those pathogens can cause the spread of viruses like norovirus that results in food poisoning and viruses like COVID-19.

The team tested different height levels from 3 to 5 feet and found 3 feet had the biggest increase in aerosols, but 5 feet also has a significant amount.

Dr. Manhar Dhanak said the results show the increase in aerosols means there is a potential risk after each flush.

"There is a good chance of areal transmission of the disease," Dhanak said.

He said viruses like COVID-19 could be hanging in the air after the flush and could be inhaled by someone using the bathroom.

toilet bowl flushing in public bathroom at Florida Atlantic University
"There is a good chance of areal transmission of the disease," Dr. Manhard Dhanak says.

"Don't panic," Lashaki said, noting there are changes and ways to reduce the number of aerosols in a bathroom.

He said a good ventilation system is required, and even wearing a mask in the bathroom can help reduce risk.

"If the ventilation system is not sufficient, that's where from the beginning of the day to the end of the day, the level in the bathroom is double or triple," Lashaki added.

He said the team did test putting a toilet seat down and found it does help reduce the number of aerosols, but there were still some that escaped the sides.