Smog over the city of Chicago


Private: Ann Jaworski

Fighting Bad Ozone in the Midwest

Summer in Chicago is the season of outdoor music festivals, fireworks at Navy Pier, and an invisible menace looming in the air—ozone.

While stratospheric ozone (the “ozone layer”) protects Earth from UV rays, ground level ozone is a dangerous air pollutant that harms humans and vegetation. Unfortunately, EPA hasn’t been doing its job to protect human health and the environment by requiring all areas that contribute to Chicago’s ozone problem to clean up their act. So, ELPC has sued EPA.

Infographic shows NOx and VOC from cars and factories become ozone through chemical reaction

Emissions become ozone through a chemical reaction in the sun. Source:, 2014

Ozone levels are higher in the summer because ozone forms in a chemical reaction when certain emissions from factories, power plants, and cars combine in the air with the heat of the summer sunlight. Chicago’s weather patterns cause these emissions to swirl out over Lake Michigan, where this chemical reaction occurs. Then the cool lake breezes carry ozone back toward the City where it harms human and environmental health. Both trees and domestic crops are negatively affected by ozone, which can stunt plant growth and turn leaves yellow by interfering with photosynthesis. In humans, ozone has been shown to increase asthma attacks, heart attacks, and mortality. It can also multiply the health effects of particulate matter pollution and increase allergic responses in people with pollen allergies. It can even decrease lung function in healthy individuals, with recent studies suggesting air pollution may be as harmful to your lungs as smoking cigarettes.

The Clean Air Act requires EPA to review the latest science every five years and set new “National Ambient Air Quality Standards” for six dangerous air pollutants, including ozone. In 2015, EPA strengthened the ozone standard, lowering it to 70 parts per billion, based on evidence that the earlier standard of 75 parts per billion wasn’t adequately protective. After EPA sets the standards, the Clean Air Act requires EPA to designate every area across the country. Each area is either in “attainment” (if air quality meets the standard), or “nonattainment” (if it “does not meet” or “contributes to ambient air quality in a nearby area that does not meet” the standard). Nonattainment areas are subject to stricter federal regulations on air pollution. Any state with a nonattainment area has to create a State Implementation Plan, which EPA must approve, containing measures designed to improve air quality in the state.

EPA’s air monitors showed ozone levels above 70 parts per billion in Cook and Lake Counties in Illinois, and Kenosha County, Wisconsin. Therefore, EPA had to designate at least those areas as nonattainment for the 2015 standard. EPA also had to analyze “nearby” areas—which EPA defines as all counties in the Chicago metropolitan area. To determine whether these nearby counties “contribute” to the air pollution at the violating monitors, EPA looks at factors like the counties’ populations, commuting patterns, emission sources, wind patterns, and geographic features that affect the way pollution moves around the region. For the prior two ozone standards (1997 and 2008), EPA designated Lake and Porter Counties in Indiana and McHenry County, Illinois as nonattainment because emissions from those counties contributed to the Chicago area’s ozone violations. Both EPA’s proposed designations and Illinois EPA’s recommendations for the 2015 ozone standard were consistent with the prior designations and included those counties in the Chicago nonattainment area.

But something changed between EPA’s proposed designations and the final designations issued in 2018. The final designation determined that McHenry, Lake, and Porter didn’t “contribute.” EPA also shrank Kenosha County’s nonattainment area to a narrower slice near the lakefront monitor that showed an ozone violation. What changed? Not the data on emissions, population, transportation, and other factors. And not EPA’s analysis of that data, which was essentially identical in EPA’s proposed and final “technical support documents” that provide the basis for the designations. But EPA still came to opposite conclusions for these counties.

Freedom of Information Act (FOIA) requests to Illinois EPA and U.S. EPA have further revealed the impropriety behind the scenes of the 2018 designation process. As justification for McHenry County’s final “attainment” designation, EPA’s final technical support document for the Chicago area cites seven times to a letter it received from Illinois EPA. This letter contained no new data or analysis, and merely says that “it would seem appropriate to consider a designation of attainment for the Illinois counties of McHenry and Monroe.” The FOIA request revealed that this letter was sent after U.S. EPA requested a “5 minute phone call” a few days before the final designations were due. Another FOIA request revealed emails exchanged by EPA scientists about the final designations for several Wisconsin counties. The staff say that they “do not see a sound technical basis” for the designations and that the decisions are “hard to digest and support.”

ELPC, on behalf of both our members and members of Respiratory Health Association, sued EPA in 2018, because the designations for the 2015 ozone standard were not supported by the data and were contrary to the law. This lawsuit in the D.C. Circuit Court of Appeals was consolidated with four other lawsuits challenging designations across the country. That includes the City of Chicago and State of Illinois, who are also challenging the Chicago area designations. In briefing, EPA declined to defend its designations for ten of the seventeen counties that were challenged, including McHenry, Porter, and Kenosha. They essentially agreed to a re-do because they hadn’t done a proper job of justifying those designations. But EPA continues to defend its designations for a number of Midwestern counties.

The D.C. Circuit Court of Appeal set the date for oral arguments in this case to be held November 6. It will be at least several more months after that before the court issues its decision. In the meantime, vulnerable populations, including people with lung disease, children, and the elderly continue to be exposed to the dangers of ozone. There were 23 days in 2018 on which metropolitan Chicago’s ozone levels were “unhealthy for sensitive groups” or “unhealthy” overall. Reducing this number will require all areas contributing to Chicago’s ozone problem to do their part to clean up the air.

Private: Ann Jaworski,

Staff Attorney

Ann Jaworski is a staff attorney at ELPC, joining in 2018.

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