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 Isanti County, Minnesota, and

Itasca County, Minnesota, give the percentage contributions from specific air pollution sources.  The Isanti County Seat is Cambridge, Minnesota, and the Itasca County Seat is Grand Rapids, Minnesota.