The St. Louis air quality forecast for Thursday, July 17 is ORANGE
For over a decade the News 4 Storm Team has provided the official daily EPA ozone forecast for the St. Louis region. The forecast we produce here in the 4 Warm Storm Center is distributed to newspapers, radio stations and even other TV stations. It's a unique challenge for us and one we take very seriously.
This year our responsibilities have been expanded to include the air quality forecast for the region. What's the difference? The ozone forecast attempts to predict the level of low level ozone alone while the air quality forecast includes the ozone and particulate matter combined. Particulate matter, sometimes referred to as aerosols, includes fine dust or other solid matter that may be contained in the air we breathe.
Obviously dust is an irritant but why is ozone so bad? We've all seen the stories about how holes in the ozone form over the antarctic and we're told that's a bad thing. Well it turns out ozone resides in two different levels of our atmosphere. The upper level ozone helps to filter out harmful UV rays from the sun. This is beneficial to us by limiting our exposure to these rays which have been proven to cause skin cancer. So a hole in the stratospheric ozone layer is a bad thing. This reduction in upper level ozone is believed to be caused primarily by use of chlorofluorocarbons (CFCs). Use of these CFCs are now controlled and in some cases even forbidden. Some examples of CFC producing compounds include halon and freon which are commonly used in fire retardents and refrigerants. Bottom line: stratospheric or upper level ozone is good.
Down here on terrafirma ozone is produced through a number of sources. The largest of which is automobile exhaust and the burning of fossil fuels. Volatile organic compounds (VOCs) and nitrous oxides react with sunlight and heat to produce ozone here at ground level. That's why we only produce an ozone forecast in the warm season. Breathing elevated levels of ozone has been proven to irritate your respiratory system, reduce lung function and aggravate asthma among other things. So needless to say: low level ozone is bad, especially for the chronically ill, the very young and the elderly.
Ironically the high pressure that has been providing our sunny weather this week is also acting to allow low level ozone to be produced and continue to accumulate. For more information about ozone from the St. Louis Regional Clean Air Partnership click here.