40 CFR 52.1921: Classification of regions.

The Oklahoma plan was evaluated on the basis of the following classifications:

Air quality control region Pollutant

Particulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Ozone

Central Oklahoma Intrastate I III III III I

Northeastern Oklahoma Intrastate I III III III I

Southeastern Oklahoma Intrastate III III III III III

North Central Oklahoma Intrastate III III III III III

Southwestern Oklahoma Intrastate III III III III III

Northwestern Oklahoma Intrastate III III III III III

Metropolitan Fort Smith Interstate II III III III III

Shreveport-Texarkana-Tyler Interstate II III III III III