An annual report card from the American Lung Association shows some improvements in air quality in Minnesota's urban areas. But it also gives Ramsey County poor grades for fine particle pollution for the third year in a row.
The "State of the Air" report focuses on ozone and fine particles. Ozone is a leading component of smog and comes from vehicle exhaust and solvents. Fine particle pollution comes from burning things like coal and wood and can cause haze.
Minnesota Public Radio reports the Twin Cities were ranked the 42nd most polluted out of 235 metro areas nationwide, an improvement of six places from last year. Ramsey County improved from an F last year to a D for fine particles.
The report also ranks Duluth among the country's cleanest cities.