The Environmental Protection Agency (EPA) is approving rules submitted by the Wisconsin Department of Natural Resources (WDNR) as a revision to its State Implementation Plan (SIP). The submitted rules incorporate the 2015 primary and secondary National Ambient Air Quality Standards (NAAQS) for ozone. In addition, WDNR included several updates to ensure implementation of the ozone NAAQS, in areas currently or formerly designated as nonattainment for any ozone standard, in a manner consistent with Clean Air Act (CAA) requirements.

The Environmental Protection Agency (EPA) is finalizing a program to further reduce air pollution, including ozone and particulate matter (PM), from heavy-duty engines and vehicles across the United States. The final program includes new emission standards that are significantly more stringent and that cover a wider range of heavy-duty engine operating conditions compared to today's standards; further, the final program requires these more stringent emissions standards to be met for a longer period of when these engines operate on the road.

The Environmental Protection Agency (EPA) is approving, under the Clean Air Act (CAA), a request submitted by the Michigan Department of Environment, Great Lakes, and Energy (EGLE) on December 18, 2020, to revise the Michigan State Implementation Plan (SIP). EGLE's submittal addresses the emissions inventory and statement requirements for the Allegan County, Berrien County, Detroit (Livingston, Macomb, Monroe, Oakland, St. Clair, Washtenaw, and Wayne Counties) and Muskegon County nonattainment areas under the 2015 ozone National Ambient Air Quality Standard (NAAQS or standard).

The EPA is taking final action finding that the state of California has failed to submit state implementation plan (SIP) revisions for the Sacramento Metro nonattainment area to satisfy certain requirements of the Clean Air Act (CAA) for the 2008 8-hour ozone National Ambient Air Quality Standards (NAAQS). Specifically, these requirements pertain to the assessment and collection of fees under CAA section 185. This action triggers certain CAA deadlines for the imposition of sanctions if California does not submit the required SIP revisions within the specified timeframes.