Western Nevada County is designated as an "isolated rural non-attainment area" under the 8-hour ozone National Ambient Air Quality Standards (NAAQS), effective June 15, 2004.

Isolated rural non-attainment areas are required to demonstrate air quality conformity when federal approval is required on a regionally significant non-exempt transportation project. A regional emission analysis must show that the project, in addition to the other regionally significant federal and non-federal transportation projects, does not create new violations of the NAAQS, increase the severity of NAAQS, or delay timely attainment.