The most polluted cities in the U.S. — A 2014 report ranks cities that have the worst air quality. San Francisco, California, is among them. George Rose/Getty Images/File The most polluted cities in the U.S. — Downtown El Paso, Texas Visions of America/Getty Images/File The most polluted cities in the U.S. — A plume of exhaust rises from a coal-fired power plant located 20 miles southwest of Pittsburgh, in New Eagle, Pennsylvania. Jeff Swensen/Getty Images/File The most polluted cities in the U.S. — Los Angeles, California, seen through smog before sunset. David McNew/Getty Image The most polluted cities in the U.S. — Fairbanks, Alaska Erick Pasquier/Getty Images/File Prev Next
