Unlike most other pollutants, ozone is not significantly emitted directly into the air by specific sources. Ozone is generated when heat and sunlight "cook up" Nitrogen Oxides and Volatile Organic Compounds (VOC) to create ozone.
Ozone and its precursors can travel with the wind. Because of this, ozone cannot be viewed as a strictly local problem, but more as a regional issue that must be dealt with not only by the people in the highly urbanized St. Louis area, but also by people throughout the Bi-State region.
Developed by East-West Gateway Council of Governments | Source: IEPA and MDNR data
Typically, ozone pollution is a problem in the St. Louis area in the hot summer months (from late May to early September) when the sun is strong and can cause the chemical reaction to take place. Ozone levels tend to rise in mid-morning, several hours after the rush-hour and onset of emissions-generating business operations (as many businesses only operate one shift per day) and peak in the late afternoon.
Missouri State plans to reduce emissions from a range of sources are required under the Clean Air Act Amendments of 1990.