Several California cities appear on all three lists of most polluted cities in the United States for unhealthy ozone days, unhealthy spikes in particle pollution, and annual particle pollution levels.
Among those cities are Fresno, Tulare, Madera, Hanford, Visalia and Bakersfield in Central California.
Fresno, Visalia and Bakersfield, were listed in the top five of the most ozone-polluted cities in the nation.
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However, all three improved to their fewest number of ozone days since the first State of the Air report released in 2000.
Los Angeles, Sacramento, and San Francisco were also among those listed.
According to the report, more than 135 million Americans live in counties that have unhealthy levels of pollution. It's nearly 15 million fewer people in the country who are breathing unhealthy air compared to last year.
Read the full report here.