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 Allegan County, Michigan, and

Alpena County, Michigan, give the percentage contributions from specific air pollution sources.  The Allegan County Seat is Allegan, Michigan, and the Alpena County Seat is Alpena, Michigan.