{"data":{"id":"us/40-cfr-52.421","jurisdiction":"us","citation":"40 CFR 52.421","heading":"Classification of regions.","body":"The Delaware plan was 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 Philadelphia Interstate I I III I I\nSouthern Delaware Intrastate III 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 I—Delaware"],"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":"271e9f3516bf194d2f1bfd0d7de4e5a3e8ef97bb2052bfe89bd14f632d730491","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-52.420","next":"us/40-cfr-52.422"},"notice":"GroundRules: Original legal text. Not legal advice."}