On July 25, 2013, the EPA identified or “designated” 29 areas in 16 states as “nonattainment” for the 2010 SO2 standard. Air quality monitors in each of these areas measured violations of the standard based on 2009 – 2011 data. State plans demonstrating how these areas will meet the SO2 standard are due to the EPA by April 4, 2015. At that time, EPA indicated that it intended to address designation for the remainder of the country in separate future actions.

On March 2, 2015, the U.S. District Court for the Northern District of California accepted, as an enforceable order, an agreement between the EPA and Sierra Club and Natural Resources Defense Council to resolve litigation concerning the deadline for completing the designations. The court’s order directs EPA to complete designations for all remaining areas in the country in up to three additional rounds: the first round by July 2, 2016, the second round by December 31, 2017, and the final round by December 31, 2020.

• Fact Sheet - Status and Next Steps: Area Designations for the SO2 2010 Standard (PDF)(3 pp, 79 K)
• Remaining SO2 Designations Schedule (PDF)(1 pg, 218 K)