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]