PHILADELPHIA (WPVI) -- The Philadelphia area earned mixed grades on the American Lung Association's yearly pollution report card.
The area scored the fewest days ever of high particle pollution. That's from sources such as coal fires or power plants, even wild fires.
The particles are dangerous because they settle deep into the lungs, and are linked to heart disease, stroke, and lung cancer.
Despite fewer days, Philadelphia is still among the worst cities in the country for this.
And the city got an "F" on ozone smog, which got worse for a second year in a row.
Both forms of pollution are harmful.
Ozone especially hurts children, older adults, and people with asthma and other lung diseases
Lung Association: Philadelphia area gets "F" on ozone smog
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