40 CFR 52.1121 - Classification of regions.

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

Air quality control region	Pollutant					Particulate matter	Sulfur oxides	Nitrogen dioxide	Carbon monoxide	Ozone	Metropolitan Boston Intrastate	I	I	III	I	I	Merrimack Valley-Southern New Hampshire Interstate	I	I	III	III	III	Metropolitan Providence Interstate	I	I	III	III	III	Central Massachusetts Intrastate	I	II	III	III	III	Hartford-New Haven-Springfield Interstate	I	I	III	I	I	Berkshire Intrastate	II	III	III	III	III

[37 FR 10872, May 31, 1972, as amended at 39 FR 16346, May 8, 1974; 45 FR 61303, Sept. 16, 1980; 84 FR 29383, June 24, 2019]