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 Monterey County, California, and

Napa County, California, give the percentage contributions from specific air pollution sources.  The Monterey County Seat is Salinas, California, and the Napa County Seat is Napa, California.