{"data":{"id":"us/40-cfr-52.1121","jurisdiction":"us","citation":"40 CFR 52.1121","heading":"Classification of regions.","body":"The Massachusetts plan was evaluated on the basis of the following classifications:\nAir quality control region Pollutant\nParticulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Ozone\nMetropolitan Boston Intrastate I I III I I\nMerrimack Valley-Southern New Hampshire Interstate I I III III III\nMetropolitan Providence Interstate I I III III III\nCentral Massachusetts Intrastate I II III III III\nHartford-New Haven-Springfield Interstate I I III I I\nBerkshire Intrastate 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 W—Massachusetts"],"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":"206ba99b1acb9d9f67d410768fa6045edddb2ac668286ad3db5111332e5e354f","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-52.1120","next":"us/40-cfr-52.1122"},"notice":"GroundRules: Original legal text. Not legal advice."}