Special Report

The 10 Most Polluted Cities in America

3. Visalia-Porterville-Hanford, CA
> Average year-round particle pollution:
17.0 ug/M3
> People with asthma: 52,749
> Population: 605,103
> High ozone days per year: 82.7

Visalia is located almost directly in between San Francisco and Los Angeles. The city had had an average of nearly 83 high-ozone days a year, the second highest rate in the country. The Visalia metro area was one of six California metros to break the top 10 for ozone pollution, ranking second in the nation despite this year reporting the fewest days of unhealthy ozone levels in its reporting history. On the other hand, the city, like many other Valley cities, experienced its worst year for particulate pollution.

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2. Bakersfield, CA
> Average year-round particle pollution:
17.3 ug/M3
> People with asthma: 75,406
> Population: 864,124
> High ozone days per year: 69.7

Bakersfield residents have endured nearly 70 high-ozone level days a year, the third highest rate compared with other U.S. cities. Still, this was a considerable improvement for the area when compared to years past since the ALA began reporting on air quality. As in other California metro areas, however, particularly those in the state’s Central Valley, annual particle pollution worsened last year, partly due to the severe drought conditions in the region. Also, the topography and industrial composition of the Valley is conducive to air pollution problems. Adding to the region’s especially poor air quality is pollution generated by cars and trucks travelling through the region’s major throughways and the toxic gases from manure on the millions of acres of the area’s farmland.

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1. Fresno-Madera, CA
> Average year-round particle pollution:
18.1 ug/M3
> People with asthma: 96,760
> Population: 1,107,661
> High ozone days per year: 68

Air pollution improved in Fresno-Madera, but the metro area is still the most polluted in the country, as it was in the ALA’s 2014 report. As in other parts of California, the statewide, multi-year drought has likely worsened air quality in the area over the past several years. Hot and dry weather can promote dust storms and wildfires, which trap particulates generated by power plants and other carbon emitters. Fresno residents have experienced an average of 68 high-ozone days a year, the sixth highest rate in the country.