Environmental Progress - Winter 2002

Chicago Area Years Ahead On Meeting Ozone Levels

State will seek removal from "severe non-attainment" designation.

Chicago has cleaned up an ozone problem years before its deadline.

In early November, Illinois EPA Director Renee Cipriano announced that the Agency plans to petition the U.S. EPA for formal redesignation of the Chicago non-attainment area. Monitoring data collected over the past three years indicates the area measured attainment of the one-hour standard for ozone. This achievement makes Chicago the largest metropolitan area in the nation to go from a severe non-attainment designation to measuring attainment. The feat was accomplished six years ahead of the federal deadline.

The Chicago metropolitan area received the original designation of severe non-attainment in response to the 1990 Clean Air Act Amendments. Numerous ozone monitors in the area recorded exceedances in the prior three years. An exceedance occurs when ozone levels surpass the federal health standard of 125 parts per billion. U.S. EPA regulations state that Illinois must meet the attainment standard by November 2007. Illinois' petition will demonstrate that the standard was achieved six years ahead of the federal requirement.

Area's 21 monitors showed no exceedances.

Air monitoring measures air quality gains.

To qualify for attainment, none of the individual monitoring sites can measure more than three exceedances within three years. The Chicago area completed a successful 2001 ozone season with none of the 21 ozone monitors located in Illinois recording exceedances. "This is a great milestone that has been achieved because of the efforts of business, individual citizens and government to reduce the pollutants that can cause ozone," said Gov. George H. Ryan.

Illinois is expected to petition for formal redesignation of the area in spring 2002. Director Cipriano cautioned, "We must remember our work is not done. Together, we face more challenges in maintaining our compliance with the one-hour standard and addressing the new eight-hour standard for ozone."

State officials continue to develop a maintenance plan for the one-hour standard, and will face additional challenges in working toward the eight-hour standard of 85 parts per billion for ozone. U.S. EPA has not determined regulations to address the eight-hour standard.