St. Louis region under an 'Orange Air Quality Alert'; here's what that means

ST. LOUIS — The air St. Louisans breathe may pose health risks to thousands around the area.

5 On Your Side meteorologists called for an "Orange" Air Quality Alert on Wednesday, to stay in effect from 10 a.m. to 8 p.m. The causes are mostly ozone air pollutants aided by wildfire smoke from Canada and the western portion of the nation. The alert includes the following counties:

Missouri

• St. Louis City
• St. Louis County
• St. Charles County
• Jefferson County
• Franklin County

Illinois

• Madison County
• Saint Clair County
• Monroe County

READ MORE: Poor air quality Wednesday and spotty showers, storms into the weekend

What does an 'orange' air quality alert mean?

The air quality alert warns groups sensitive to air quality changes may experience health effects.

"An Orange air quality forecast means that maximum ozone concentrations are expected to reach levels that pose a health risk," the National Weather Service said in its alert. "Adverse health effects increase as air quality deteriorates. Ground-level ozone is an air contaminant which can cause breathing difficulties for children, older adults, as well as persons with respiratory problems."

Meteorologists recommended reducing outdoor physical activity and to telecommute, carpool or use public transit while going to work in order to reduce ozone in the affected areas. People should also avoid excessive idling and to not top off when refueling vehicles.

"Orange" is the fourth most severe air quality warning on the National Weather Service's scale. The more severe levels include:

1. Maroon - Hazardous air quality should be considered an emergency as everyone will be affected.
2. Purple - Very unhealthy air quality that causes increased health effects for everyone.
3. Red - Unhealthy air quality will cause some members of the general public to experience health effects while members of sensitive groups will experience more serious health effects than Orange.