U.S. Code of Federal Regulations
Regulations most recently checked for updates: Aug 28, 2025
The South Dakota plan evaluated on the basis of the following classifications:
| Air quality control region | Pollutant | ||||
|---|---|---|---|---|---|
| Particulate matter | Sulfur oxides | Nitrogen dioxide | Carbon monoxide | Photochemical oxidants (hydrocarbons) | |
| Metropolitan Sioux City Interstate | III | III | III | III | III |
| Metropolitan Sioux Falls Interstate | II | III | III | III | III |
| Black Hills—Rapid City Intrastate | III | III | III | III | III |
| South Dakota Intrastate | III | III | III | III | III |
