{"data":{"id":"us/40-cfr-52.1921","jurisdiction":"us","citation":"40 CFR 52.1921","heading":"Classification of regions.","body":"The Oklahoma plan was evaluated on the basis of the following classifications:\nAir quality control region Pollutant\nParticulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Ozone\nCentral Oklahoma Intrastate I III III III I\nNortheastern Oklahoma Intrastate I III III III I\nSoutheastern Oklahoma Intrastate III III III III III\nNorth Central Oklahoma Intrastate III III III III III\nSouthwestern Oklahoma Intrastate III III III III III\nNorthwestern Oklahoma Intrastate III III III III III\nMetropolitan Fort Smith Interstate II III III III III\nShreveport-Texarkana-Tyler Interstate II III III III III","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER C—AIR PROGRAMS","PART 52—APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS","Subpart LL—Oklahoma"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"a01eba2b5deee9383cfd9f8d91cfba256126a66e5706cdb2db192f11bae4707f","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-52.1920","next":"us/40-cfr-52.1922"},"notice":"GroundRules: Original legal text. Not legal advice."}