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 Broward County, Florida, and

Calhoun County, Florida, give the percentage contributions from specific air pollution sources.  The Broward County Seat is Fort Lauderdale, Florida, and the Calhoun County Seat is Blountstown, Florida.