Tougher pollution controls, including inspections of car emissions control systems and gasoline vapor recovery program, have substantially reduced ozone levels. But, despite these programs, the St. Louis area has been unable to meet the one-hour ozone standard. Since the 1977 amendments to the Clean Air Act, the East-West Gateway Coordinating Council has been the lead air quality planning agency for the St. Louis metropolitan region. The natural ozone layer of the upper atmosphere shields the earth from harmful ultraviolet radiation. However, the manmade ozone which occurs at ground level creates a variety of health problems.
Weather plays an important role in ozone formation.
Days when ozone may form are indicated by high pressure weather systems with high temperatures in the '90s or above and low winds. Temperature inversions during the warm summer months can trap pollutants close to the ground, stopping them from dispersing during the night. These systems are common in the St. Louis area during the months of May through early September. They are the result of incomplete combustion of fossil fuels and vapors escaping from volatile organic compounds. In large doses, ozone can cause headaches, fatigue, shortness of breath, coughing, wheezing and eye, nose and respiratory tract irritation.