10. San Diego-Carlsbad, CA
Out of 288 metropolitan areas, San Diego-Carlsbad is ranked 7th on our list of the most polluted cities in the US in 2017 based on the high ozone days. On the other hand, it is ranked 34th for 24-hour particle pollution out of 186 metropolitan areas and 47th for annual particle pollution out of 184 metropolitan areas. Also, 1,432 people are fighting lung cancer.
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