Bakersfield had the worst level of fine-particle pollution in the nation last year -- a toxic mix of soot, diesel exhaust, chemicals, metals and aerosols that contribute to heart attack, stroke and lung disease, according to the American Lung Assn.'s annual State of the Air report.
The San Joaquin Valley city displaced Los Angeles, which fell to the third spot in the category of year-round particle pollution, behind second-place Pittsburgh-New Castle, Pa.
The lung association report is based on data from local governments' air monitoring stations and statistics gathered by the U.S. Environmental Protection Agency.
Los Angeles-Long Beach retained its spot as the worst ozone-polluted metropolitan area, despite a slight improvement in its air in the last year. San Bernardino ranked as the nation's worst county for ozone pollution. Ozone causes wheezing and asthma attacks, and can shorten lives.