An annual report card from the American Lung Association showed Minnesota's urban areas made some improvements in air quality.
An annual report card from the American Lung Association showed Minnesota's urban areas made some improvements in air quality. But it also gave Ramsey County poor grades for fine particle pollution for the third year in a row.
The "State of the Air" report released Wednesday focuses on ozone and fine particles. Ozone is a leading component of smog and forms when vehicle exhaust and solvents combine with heat and sunlight. Fine particle pollution comes from burning things such as coal and wood and can cause haze. Both pollutants can cause respiratory problems.
The Twin Cities metro area was ranked the 42nd most polluted out of 235 metro areas nationwide, Minnesota Public Radio reported. That's an improvement from being the 36th most polluted last year. Ramsey County, which includes St. Paul, improved from an F last year to a D for fine particles.
The report also ranks Duluth among the country's cleanest cities.
The low grades for Ramsey County, which is working to reduce emissions through increased use of mass transit and installing electric vehicle charging stations, may not be the county's fault, said Robert Moffitt, a spokesman for the American Lung Association in Minnesota.
"Air pollution is not a local problem, it's a regional problem," he said. "Sometimes it's just where your monitor is being placed, and sometimes it's where the wind is blowing. ... So many different factors come into play, it's hard to look at the letter grades and say for sure exactly we know what caused that."
Duluth was the 16th-cleanest city for particle pollution. Duluth, Rochester and Fargo-Moorhead also ranked among the 50 cleanest metro areas for ozone.