The Iowa plan was evaluated on the basis of the following classification: ----------------------------------------------------------------------------------------------------------------
Pollutant
----------------------------------------------------------
Air quality control region Photochemical
Particulate Sulfur Nitrogen Carbon oxidants
matter oxides dioxide monoxide (hydrocarbons)----------------------------------------------------------------------------------------------------------------Metropolitan Omaha-Council Bluffs Interstate......... I II III III IIIMetropolitan Sioux Falls Interstate.................. II III III III IIIMetropolitan Sioux City Interstate................... III III III III IIIMetropolitan Dubuque Interstate...................... I III III III IIIMetropolitan Quad Cities Interstate.................. I III III III IIIBurlington-Keokuk Interstate......................... I I III III IIINorthwest Iowa Intrastate............................ III III III III IIINorth Central Iowa Intrastate........................ IA III III III IIINortheast Iowa Intrastate............................ I III III III IIISouthwest Iowa Intrastate............................ III III III III IIISouth Central Iowa Intrastate........................ I III III III ISoutheast Iowa Intrastate............................ III III III III III---------------------------------------------------------------------------------------------------------------- [37 FR 10865, May 31, 1972, as amended at 39 FR 16346, May 8, 1974]