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St. Louis Metro Area in Violation of Federal Air Quality Standards

Release Date: 12/22/2008
Contact Information: David Bryan, 913-551-7433,

Environmental News


(Kansas City, Kan., Dec. 22, 2008) - The U.S. Environmental Protection Agency officially notified the state of Missouri today that areas of the St. Louis metropolitan area in Missouri do not meet the Agency's daily standard for fine particle pollution, also known as fine particulate matter, or PM 2.5.

Franklin, Jefferson, St. Charles and St. Louis counties, along with the city of St. Louis, are included in EPA's designation for Missouri. For portions of the metro area in Illinois, the determination also includes Madison, Monroe and St. Clair counties, and part of Randolph County. EPA Region 5 officials in Chicago will address the determination issues for the Illinois counties.

To protect public health, in 2006 EPA strengthened the 24-hour fine particle standards from 65 micrograms per cubic meter of air to 35 micrograms per cubic meter of air. Fine particles can either be emitted directly, or they can form in the atmosphere from reactions of sulfur dioxide and nitrogen oxides. Exposure to fine particle pollution can cause serious health problems, including respiratory and cardiovascular difficulties, as well as premature death.

The four Missouri counties and the city of St. Louis were determined to be contributing to violations of the air quality standards in Madison County, Ill. The Clean Air Act requires the designation of all areas in violation, as well as nearby areas that contribute to the violation.

EPA closely reviewed recommendations from the Missouri Department of Natural Resources along with public comments before making its determination. The nonattainment areas include those where air monitors indicate violations of standards, and nearby areas that contribute to the violations. Missouri's DNR will be required to develop a plan and take steps to reduce the emissions that contribute to fine particle pollution.

EPA weighs nine factors to help determine the boundaries of a nonattainment area, including pollutant emissions, air quality data, population density and degree of urbanization, traffic and community patterns, growth, meteorology, geography, jurisdiction, and the sophistication of emission controls already installed and operating on pollution sources in the area.

In EPA's technical analysis of the metro area, it was determined that the Missouri counties are responsible for approximately 50 percent of the locally emitted direct particle matter, about 57 percent of the nitrogen oxide, and 74 percent of the sulfur dioxide. The Agency also considered that the area in Missouri is already part of a nonattainment area for existing ozone and annual particulate matter violations.