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 Lake County, California, and

Lassen County, California, give the percentage contributions from specific air pollution sources.  The Lake County Seat is Lakeport, California, and the Lassen County Seat is Susanville, California.