FRESNO, Calif. -

Cities in California's Central Valley dominate the American Lung Association's annual rankings of the nation's worst air pollution, though traditional dirty-air leader Los Angeles still tops key categories.

The report released Wednesday says California cities have cleared their air and seriously reduced pollution in recent decades, but still lag behind the rest of the country in cleanliness.

Fresno, Visalia and Bakersfield rank 1-2-3 in the country for short-term spikes in fine particle pollution, with Los Angeles fourth.

LA is still on top in one category, violating federal standards for ozone in the air 122 days a year.

The Central Valley and the Los Angeles Basin have stagnant weather and a bowl shape make smog-cutting especially challenging.

The rankings came in the Lung Association's 15th annual "State of the Air" report.