The Environmental Protection Agency (EPA) is taking final action to disapprove a specific part of a state implementation plan (SIP) revision that was previously approved by EPA. On May 19, 2019, EPA fully approved certain parts of a SIP revision submitted by the Commonwealth of Pennsylvania to address reasonably available control technology (RACT) for the 1997 and 2008 ozone national ambient air quality standards (NAAQS), and conditionally approved other parts of that submission. The U.S. Court of Appeals for the Third Circuit vacated EPA's approval of a portion of the SIP revision, as discussed below. EPA is now disapproving the portion of the SIP submission addressed by the court's decision. This action is being taken under the Clean Air Act (CAA).