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42 U.S.C. 7401 et seq.
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Nomenclature changes to part 52 appear at 81 FR 74586, Oct. 26, 2016.
The District of Columbia plan was evaluated on the basis of the following classifications:
| Air quality control region | Pollutant | ||||
|---|---|---|---|---|---|
| Particulate matter | Sulfur oxides | Nitrogen dioxide | Carbon monoxide | Ozone | |
| National Capital Interstate | I | I | III | I | I |
[37 FR 10857, May 31, 1972, as amended at 39 FR 16346, May 8, 1974; 46 FR 61263, Dec. 16, 1981]