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 San Juan County, New Mexico, and

San Miguel County, New Mexico, give the percentage contributions from specific air pollution sources.  The San Juan County Seat is Aztec, New Mexico, and the San Miguel County Seat is Las Vegas, New Mexico.