In 2011 the U.S. EPA finalized the Cross-State Air Pollution Rule (CSAPR) in response to a 2008 court decision remanding the Clean Air Interstate Rule (CAIR) to EPA. CSAPR requires some states (not including Connecticut) to reduce annual SO₂ emissions, annual NOx emissions and/or ozone season NOx emissions to assist in attaining the 1997 ozone and fine particulate matter (PM_2.5) and 2006 PM_2.5 National Ambient Air Quality Standard (NAAQS). For more information on CSAPR, its successor, the CSAPR Update, and subsequent actions by EPA and states, visit EPA’s Cross-State Air Pollution Rule web page.