The United States Environmental Protection Agency (USEPA) promulgated the revised primary annual National Ambient Air Quality Standards (NAAQS) for particulate matter less than 2.5 microns (PM2.5). The primary annual PM2.5 NAAQS was revised from 15.0 µg/m3 to 12.0 µg/m3 as the other existing PM2.5 standards were retained. Per the requirements of the Clean Air Act (CAA), the Illinois Environmental Protection Agency (IEPA) submitted the area designation recommendations for the 2012 primary annual fine PM2.5 NAAQS to USEPA on December 12, 2013. 

The USEPA has reviewed these area designations along with other supplemental information and the 2011-2013 air quality data. Technical audits of Illinois’ monitoring program were also conducted during which it was discovered by the USEPA that the majority of the data submitted was invalid. This was due to lack of appropriate equipment that is needed for determining if all requirements for proper collection of monitoring data were satisfied and this led to data quality issues. Thereafter, USEPA concluded that there was insufficient data and as a result will modify the recommended areas for designation and also designate the State of Illinois as “Unclassifiable”. A letter was sent by USEPA to Illinois’ Governor Pat Quinn on August 19, 2014 along with supporting documentation

The state can submit additional data by October 29, 2014. All future proposed designation decisions and documentations will be available for public review and comment. A 30–day public comment period will be announced shortly in the Federal Register and USEPA plans on promulgating the final annual PM2.5 designations in December 2014.