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What is ozone and why are air quality alerts issued for high concentrations of it?

"Very simply put, it's kind of like a sunburn on your lung," Susannah Fuchs, with the Clean Air Partnership, said.

ST. LOUIS — During Memorial Day weekend and the start of the work week, the St. Louis area has been under an "Orange - Unhealthy for Sensitive Groups" Air Quality Alert.

The rating is from the U.S. Environmental Protection Agency's Air Quality Index. The 5 On Your Side Weather First team reported on the air quality issues all weekend. 

Tuesday after lunchtime, the air quality again rose into the orange category through the evening hours. Wednesday should be similar with another Ozone action day for the St. Louis metro area.

Yes, air quality in the area is currently rated as "sensitive for some groups," but Director of Clean Air Partnership, Susannah Fuchs, said that's more people than you would expect.

"You would think that's just a few people, it's actually lots of people -- children, the elderly, anybody who works outside, anyone who is sensitive to air pollution and then everybody with any kind of lung disease."

Because air quality affects a large chunk of the population, the mobile weather app is showing the hazard icon to signal the air quality alert. 

It's clear ... why has the air quality diminished? The answer is too much ozone. 

"There's a fun little saying, 'Good up high, bad nearby.' Right now, there's too much ozone at the ground level," Fuchs said. 

So how does that happen? Let's get scientific. 

Ozone is a gas molecule made up of oxygen. When oxygen molecules come into contact with pollutants -- like exhaust -- and are then hit by sunlight, a chemical reaction takes place and ozone smog is formed. Ozone smog is typically close to the surface and dangerous for people to breathe in.   

"Very simply put, it's kind of like a sunburn on your lungs," Fuchs added. 

Regardless of sensitivity, Fuchs said poor air quality affects everyone.

"You have to be mindful of what the air pollution forecast is, even though you can't see it, it can be harmful for your lungs," she said. 

Download the free 5 On Your Side app to get the latest watches and warnings and track conditions live with our interactive radar. Use the links below to download now.

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