52.1171—Classification of regions.

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

Air quality control region	Pollutant
Air quality control region	Particulate matter	Sulfur oxides	Nitrogen dioxide	Carbon monoxide	Ozone
Metropolitan Detroit-Port Huron Intrastate	I	I	III	III	III
Metropolitan Toledo Interstate	I	I	III	III	I
South Central Michigan Intrastate	II	II	III	III	III
South Bend-Elkhart (Indiana)-Benton Harbor (Michigan) Interstate	I	IA	III	III	III
Central Michigan Intrastate	II	III	III	III	III
Upper Michigan Intrastate	III	III	III	III	III

Code of Federal Regulations

[37 FR 10873, May 31, 1972, as amended at 39 FR 16346, May 8, 1974; 45 FR 29801, May 6, 1980]