Illinois Annual Air Quality Report 2011

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A Message from the Director

The 2011 Annual Air Quality Report was developed to provide a thorough, unbiased assessment of air quality in Illinois. The data compiled in this report was collected from the extensive air monitoring network operated throughout the state. The report includes monitoring data for criteria pollutants (particulate matter, ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide and lead), as well as some heavy metals (e.g., mercury), nitrates, sulfates and volatile organic compounds.

Illinois’ air monitoring network underwent a number of changes from 2010 to 2011 and has met U.S. EPA regulatory criteria. Sites and monitors have been discontinued in areas where ambient air quality concentrations have not shown exceedances over the course of five years and with values significantly below National Ambient Air Quality Standards (NAAQS). Overall, Illinois had nine fewer monitoring site locations and 41 fewer monitors in 2011.  Additional information on these changes is contained in the report.

Although meteorology often has a significant impact on air quality, and hot weather resulted in more than 40 temperature records tied or broken in 2011, overall air quality for the year was either good or moderate 92 percent of the time, a slight increase from 2010.  As with previous years, the 10-year air quality trends continue to show decreases in all criteria pollutants.  In addition to providing this report, the Agency also provides air quality data to the public on a daily basis through the Agency’s website.

Significant progress has been made in terms of air quality in the state.  The Illinois EPA continues work to meet NAAQS, even as standards continue to be tightened.  The Agency also strives to provide the most accurate information to residents about our air quality.  Please contact the Illinois EPA with any comments and/or questions regarding the 2011 Annual Air Quality Report or air pollution control programs.


John J. Kim
Interim Director

Executive Summary

This report presents a summary of air quality data collected throughout the State of Illinois during the calendar year - 2011.  Data is presented for the six criteria pollutants (those for which air quality standards have been developed - particulate matter (PM10 and PM2.5), ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead) along with some heavy metals, nitrates, sulfates, volatile organic and toxic compounds.  Monitoring was conducted at 75 different site locations collecting data from more than 170 instruments.

In terms of the Air Quality Index (AQI) air quality during 2011 was either good or moderate 92 percent of the time throughout Illinois. There were no days when air quality in some part of Illinois was considered Unhealthy (category Red). This compares with zero Unhealthy days in 2010. There were 31 days (25 for 8-hour ozone, 4 for PM2.5 and 2 for both 8-hour ozone and PM2.5) when air quality in some part of Illinois was considered Unhealthy for Sensitive Groups (category Orange). This compares with 32 Unhealthy for Sensitive Groups days reported in 2010. Air quality trends for the criteria pollutants are continuing to show downward trends or stable trends well below the level of the standards. Percentage changes over the ten year period 2002 - 2011 are as follows: 24-hour Particulate Matter (PM10) 15 percent decrease, annual Particulate Matter (PM2.5) 20 percent decrease, 1-hour Sulfur Dioxide 47 percent decrease, annual Nitrogen Dioxide 29 percent decrease, 8-hour Carbon Monoxide 48 percent decrease, Lead 33 percent decrease, and 8-hour Ozone 5 percent decrease.

Stationary point source emission data has again been included. The data in the report reflects information contained in the Emission Inventory System (EIS) as of December 31, 2011. Emission estimates are for the calendar year 2011 and are for the pollutants: particulate matter, volatile organic material, sulfur dioxide, nitrogen oxides and carbon monoxide. Emission trends of these pollutants have been given for the years 1998 to the present.  Emissions reported with the Annual Emissions Report have been provided starting with 1998 and are currently available through 2010. In general there has been a trend toward decreasing emissions over this time period.

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