40 CFR 52.821: Classification of regions.

The Iowa plan was evaluated on the basis of the following classification:

Air quality control region Pollutant

Particulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Photochemical oxidants (hydrocarbons)

Metropolitan Omaha-Council Bluffs Interstate I II III III III

Metropolitan Sioux Falls Interstate II III III III III

Metropolitan Sioux City Interstate III III III III III

Metropolitan Dubuque Interstate I III III III III

Metropolitan Quad Cities Interstate I III III III III

Burlington-Keokuk Interstate I I III III III

Northwest Iowa Intrastate III III III III III

North Central Iowa Intrastate IA III III III III

Northeast Iowa Intrastate I III III III III

Southwest Iowa Intrastate III III III III III

South Central Iowa Intrastate I III III III I

Southeast Iowa Intrastate III III III III III