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 Mecosta County, Michigan, and

Menominee County, Michigan, give the percentage contributions from specific air pollution sources.  The Mecosta County Seat is Big Rapids, Michigan, and the Menominee County Seat is Menominee, Michigan.