LOS ANGELES, April 28 (UPI) -- Smog has decreased significantly in Southern California in the last decade but the region still has the highest ozone levels in the country, a study found.
Los Angeles ranks second in the country behind Bakersfield, Calif., for the highest year-round levels of toxic particles or soot and the region still violates federal health standards an average of 137 days a year, the Los Angeles Times reported Thursday.
The rankings were contained in an annual report by the American Lung Association, based on federal and state data, which said more than 90 percent of Californians live in counties with unhealthful air.
Unlike the East and Midwest, where coal-fired power plants are the largest source of air pollution, Southern California's shroud is the product of tailpipe emissions from cars and pollution from diesel trucks, trains and ships linked to the ports of Los Angeles and Long Beach, the report said.
"There has been tremendous progress in California," Jane Warner of the lung association's California branch said, but pollution levels remain "a critical public health issue."
"It is not just a nuisance that burns your eyes or stings your throat," she said.
Nationally, the lung association said, more than half the U.S. population lives in areas with dirty air.