Los Angeles may be the most polluted city in the state and in the nation, but which California county is the most polluted? That dubious honor goes to San Bernardino County, followed by Riverside, Kern, and Tulare counties.
Even though some counties are less polluted than others, 36 of California's 58 counties received a failing grade from the American Lung Association because of high pollution levels.
Source: American Lung Association. The highlighted counties received a failing grade for high pollution levels, according to the Association. Counties in gray received either an “A” or “B” score, or were not represented in the study. See the ALA website for details.
