Report Places Los Angeles At Top Of List For City With Worst Traffic And Smog

LOS ANGELES, CA - APRIL 25: Heat waves emanate from the exhaust pipe of a city transit bus as it passes an American flag hung on the Los Angeles County Hall of Justice by workers renovating the historic structure on April 25, 2013 in Los Angeles, California. The nation's second largest city, Los Angeles, has again been ranked the worst in the nation for ozone pollution and fourth for particulates by the American Lung Association in it's annual air quality report card. Ozone is a component of smog that forms when sunlight reacts with hydrocarbon and nitrous oxide emissions. Particulates pollution includes substances like dust and soot. (Photo by David McNew/Getty Images)