Regulations last checked for updates: Feb 12, 2026

Title 40 - Protection of Environment last revised: Dec 22, 2026
§ 52.2721 - Classification of regions.

The Puerto Rico plan was evaluated on the basis of the following classifications.

Air quality control region Pollutant
Particulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Photochemical oxidants (hydrocarbons)
Puerto RicoIAIAIIIIIIIII
[37 FR 10905, May 31, 1972]
cite as: 40 CFR 52.2721