This report presents a summary of air quality data collected throughout the State of Illinois during calendar year 2015. 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 compounds, and toxic compounds. Monitoring was conducted at 65 different site locations collecting data from more than 140 instruments.
In terms of the Air Quality Index (AQI), air quality during 2015 was either good or moderate 98% of the time throughout Illinois. There was one day when air quality was considered unhealthy (category red). This compares with zero unhealthy days in 2014. The unhealthy day was due to elevated PM2.5 concentrations occurring in the vicinity of firework displays between July 4th and July 5th. There were five days (two for ozone and three for PM2.5) when air quality in some part of Illinois was considered Unhealthy for Sensitive Groups (category orange). This compares with seven Unhealthy for Sensitive Groups days reported in 2014. Air quality trends for the criteria pollutants are continuing to show downward or stable trends well below the level of the standards. Examples of percentage changes over the ten year period 2006-2015 are as follows: annual particulate matter (PM2.5) 20% decrease, 1-hour sulfur dioxide 65% decrease, annual nitrogen dioxide 32% decrease, 8-hour carbon monoxide 56% decrease, and 8-hour ozone 6% decrease.
Stationary point source emission data has again been included. The data in the report reflects information contained in the Integrated Comprehensive Environmental Management System (ICEMAN) as of December 31, 2015. Emission estimates are for the calendar year 2014 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 2014. There has been a trend toward decreasing emissions over this time period.