The Environmental Protection Agency (EPA) is proposing to approve revisions to the Iowa State Implementation Plan (SIP) to include recent changes to the Polk County Board of Health Rules and Regulations in addition to revisions from past submittals. The proposed revisions update definitions and references to the effective dates of Federal rules approved into the State's SIP, prohibit burning of demolished buildings, update references to methods and procedures for performance test/stack test and continuous monitoring systems, and revise permitting exemptions.

The Environmental Protection Agency (EPA) is withdrawing its proposed rule to approve Missouri's revisions to the state's open burning rule, as published in the Federal Register on January 13, 2020. By a letter to the EPA dated May 26, 2021, Missouri withdrew its request for approval of revisions to this rule in the state implementation plan (SIP).

The Environmental Protection Agency (EPA) is proposing to approve in part and disapprove in part portions of a state implementation plan (SIP) revision submitted by the State of California to meet Clean Air Act (CAA or ``Act'') requirements for the 1997 annual fine particulate matter (PM<INF>2.5</INF>) national ambient air quality standards (NAAQS or ``standards'') in the San Joaquin Valley PM<INF>2.5</INF> nonattainment area. Specifically, the EPA is proposing to approve the 2013 base year emissions inventories in the submitted SIP revisions.

The Environmental Protection Agency (EPA) is amending several New Source Review (NSR) regulations by making the following types of changes: Correcting typographical and grammatical errors, removing court vacated rule language, removing or updating outdated or incorrect cross references, conforming certain provisions to changes contained in the 1990 Clean Air Act (CAA or Act) Amendments, and removing certain outdated grandfathering or transitional exemptions.