 Philadelphia County received an ozone grade of F and a 24-hour particle pollution rating of D in the American Lung Association's 2017 State of the Air report, which analyzed data from 2013–15.The city was ranked 22nd for ozone, 20th for short-term particle pollution, and 11th for year-round particle pollution.According to the same report, the city experienced a significant reduction in high ozone days since 2001—from nearly 50 days per year to fewer than 10—along with fewer days of high particle pollution since 2000—from about 19 days per year to about 3—and an approximate 30% reduction in annual levels of particle pollution since 2000.