U.S. Code of Federal Regulations
Regulations most recently checked for updates: Aug 28, 2025
The air quality control region which encompasses the Reservation of the Stillaguamish Tribe is classified as follows for purposes of episode plans:
| Pollutant | Classification |
|---|---|
| Carbon monoxide | I |
| Nitrogen dioxide | III |
| Ozone | I |
| Particulate matter (PM10) | I |
| Sulfur oxides | IA |
