40 C.F.R. § 52.421
Classification of regions.
Cite as 40 C.F.R. § 52.421 (2026)
The Delaware 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) Metropolitan Philadelphia Interstate I I III I I Southern Delaware Intrastate III III III III III [37 FR 10856, May 31, 1972, as amended at 39 FR 16345, May 8, 1974]