The five most ozone-polluted cities in the United States are all in California. Los Angeles is number one and the other four are in the Central Valley. The survey results are not much better for the state's particulate pollution, either. Bonnie Holmes-Gen is Senior Policy Director with the American Lung Association in California. She says the state has a challenging set of conditions that contribute to poor air quality.
BONNIE HOLMES-GEN: "...with our large population, our huge number of vehicles, our increasing number of vehicles miles traveled. And our ports and a large number of diesel sources."
Holmes-Gen says there is a bright side however, the state has seen a dramatic reduction in pollution in recent years, especially in Los Angeles, Sacramento and in the Bay Area.