(WSVN) - When we’re at the mall, the airport or taking a long road trip, there’s a good chance we’ll need to stop and use a public restroom, but there could be a “Hidden Hazard” there. Kevin Ozebek has tonight’s special assignment report.

Kevin Ozebek: “Shall we open the seal?

Dr. Masoud Lashaki, professor, Florida Atlantic University: “Sure.”

Professor Masoud Lashaki is turning a public restroom at Florida Atlantic University into his lab.

The mission: to find out how many microscopic droplets are pushed up into the air when a toilet is flushed.

Dr. Masoud Lashaki: “What we looked at here was an unconventional type of aerosol.”

The world “aerosol” entered our everyday vocabulary last year. We breathe out these microscopic respiratory droplets, and if a person is COVID-positive, these droplets spread the disease.

Turns out toilets pump out aerosol, too.

Dr. Masoud Lashaki: “In fact, human waste may contain coronavirus long before the person is testing positive. Because of flushing, it can get into the air.”

That means public restrooms could serve as hotbeds for the transmission of COVID-19 and other airborne diseases.

Kevin Ozebek: “I see nothing in the air right now, but is there aerosol as we speak from all these flushes?”

Dr. Masoud Lashaki: “Sure. If you want, I can run this counter.”

Using a particle counter, we can see, in the middle of this restroom, there are hundreds of aerosol particles floating by the sensor.

Next, we move into a stall.

Dr. Masoud Lashaki: “Now I am going to flush for five seconds.”

The counter can pick up different sizes of particles. After the flush, we see the number of the tinniest aerosol particles soar above 1,000.

Graduate student Jesse Schreck repeats the experiment in front of a men’s urinal.

Jesse Schreck, graduate student, Florida Atlantic University: “And we see our jump there.”

The counter detects more than 900 aerosol particles. These micro droplets can linger in the air for up to 12 hours, so the more flushes, the more aerosol is floating around a public restroom.

Dr. Masoud Lashaki: “That was really the main thing that surprised me: that over time, over a few hours, the count, the number of these aerosols in a large place like a bathroom can double or triple.”

Professor Lashaki did repeat the experiment with a toilet that has a lid. He found the lid does not eliminate aerosol being pumped into the air, though it does lower it.

But most public toilets don’t have lids.

Dr. Masoud Lashaki: “So that could be a new design consideration, I would say, for future renovations, for building new bathrooms.”

FAU researchers say the data is striking, but engineering professor Manhar Dhanak says there are precautions you can take.

Kevin Ozebek: “What should we do next time we have to use a public restroom?”

Manhar Dhanak, director, SeaTech – the Institute for Ocean and Systems Engineering: “Wear a mask. Secondly, don’t linger.”

So, smart and simple advice is all you need to best protect yourself from this hidden hazard.

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