Abstract: The Environmental Protection Agency (EPA) compiles data on emission tonnages of air pollutants for US counties.  US Air Quality Gradebook ("AirGrades") source sheets such as this one for Placer County, California, and

Plumas County, California, give the percentage contributions from specific air pollution sources.  The Placer County Seat is Auburn, California, and the Plumas County Seat is Quincy, California.