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SAN DIEGO — The San Diego metropolitan area has the 13th worst ozone pollution in the nation, but is not among the regions with the most short-term and annual particle pollution, according to a report released Wednesday by the American Lung Association.

The association’s “State of the Air 2016” study noted that 16 of the nation’s most-polluted cities showed their lowest levels of particle pollution in the 17-year history of the report.

California cities, however, dominated the top-10 lists of worst offenders in all three categories. Bakersfield ranked worst in the nation for short-term and annual particle pollution, and second for ozone pollution behind Los Angeles-Long Beach. The Visalia-Porterville-Hanford region ranked among the worst three in all three categories. Fresno-Madera ranked among the worst four across the board.

The report is based on readings taken at monitoring sites across the country from 2012-14.

“Thanks to California’s cleaner vehicles and fuels and other innovated clean-air policies, we’re seeing steady progress in our fight for cleaner air,” said Olivia J. Diaz-Lapham, president/CEO of the American Lung Association in California. “However, more than 80 percent of Californians — 32 million residents — still live in counties with unhealthy air during certain parts of the year. We simply must do more to protect the health of Californians.”

According to the ALA, the prolonged drought and frequent heat waves caused by climate change are making it more difficult to clean up the air in San Diego.

Despite an uptick in ozone days, San Diego has experienced an overall drop of 71 percent in unhealthy ozone days since 2000, and unhealthy particle days dropped by 86 percent, the organization noted. Cleaner vehicles that produce fewer tailpipe emissions were credited with the improvement.