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 Hill County, Texas, and

Hockley County, Texas, give the percentage contributions from specific air pollution sources.  The Hill County Seat is Hillsboro, Texas, and the Hockley County Seat is Levelland, Texas.