{"data":{"id":"us/40-cfr-52.1321","jurisdiction":"us","citation":"40 CFR 52.1321","heading":"Classification of regions.","body":"The Missouri plans were evaluated on the basis of the following classifications:\nAir quality control region Pollutant\nParticulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Photochemical oxidants (hydrocarbons)\nMetropolitan Kansas City Interstate I III III I I\nSouthwest Missouri Intrastate I III III III III\nSoutheast Missouri Intrastate III III III III III\nNorthern Missouri Intrastate II III III III III\nMetropolitan St. Louis Interstate I I III I I","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER C—AIR PROGRAMS","PART 52—APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS","Subpart AA—Missouri"],"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":"e3568aef4c760161e8d59c1bc96926f95698d13a780d192fba4f04d77f73d392","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-52.1320","next":"us/40-cfr-52.1322"},"notice":"GroundRules: Original legal text. Not legal advice."}