The Michigan plan was evaluated on the basis of the following classifications: ----------------------------------------------------------------------------------------------------------------
Pollutant
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Air quality control region Particulate Sulfur Nitrogen Carbon
matter oxides dioxide monoxide Ozone----------------------------------------------------------------------------------------------------------------Metropolitan Detroit-Port Huron Intrastate................ I I III III IIIMetropolitan Toledo Interstate............................ I I III III ISouth Central Michigan Intrastate......................... II II III III IIISouth Bend-Elkhart (Indiana)-Benton Harbor (Michigan) I IA III III III
Interstate...............................................Central Michigan Intrastate............................... II III III III IIIUpper Michigan Intrastate................................. III III III III III---------------------------------------------------------------------------------------------------------------- [37 FR 10873, May 31, 1972, as amended at 39 FR 16346, May 8, 1974; 45 FR 29801, May 6, 1980]