A new report from the American Lung Association shows some improvements in air quality in Minnesota's urban areas, but Ramsey County had poor grades for fine particle pollution for the third year in a row.
The annual "State of the Air" report released Wednesday focuses on two forms of air pollution: ozone and fine particle pollution. Ozone, a leading component of smog, forms when vehicle exhaust and solvents combine with heat and sunlight. Fine particle pollution comes from burning things like coal and wood and can cause haze. Both pollutants can cause respiratory problems.
The Twin Cities metro area was ranked the 42nd most polluted in a list of 235 metro areas nationwide. Last year the metro ranked 36th most polluted. Ramsey County's poor grades in fine particle pollution have been contributing to the metro area's overall ranking. In the category of fine particle pollution days, Ramsey County improved from an F grade last year to a D grade in the category of fine particle pollution.
Minnesota cities in report:
Twin Cities region: ranked 42nd among 235 most polluted metro areas nationwide
Duluth: ranked 16th cleanest for annual fine particle pollution and was among 50 cleanest metro areas for ozone
Rochester: ranked among 50 cleanest metro areas for ozone
Fargo, N.D.: ranked among 50 cleanest metro areas for ozone
The grade has little to do with efforts in Ramsey County to reduce emissions through increased use of mass transit and installing electric vehicle charging stations, 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."
The report uses a three-year average to get a more accurate reading of a city's air pollution.
The report shows Duluth is among the cleanest cities in the country. Moffitt said Duluth's climate has a lot to do with its good grades for ozone.
"Generally temperature and sunlight have to be at a certain level. That's why ozone is such a big problem in southern California. But when you're up at Duluth with the cooling effect that they get off of the lake, it's very rare to reach those type of temperatures, so that's going to help cut down on the risk of ozone," he said.
Duluth was the 16th-cleanest city for annual particle pollution, according to the report.
The U.S. Environmental Protection Agency recently announced stricter standards for fine particle pollution and is enforcing ozone standards set in 2008. The Minnesota Pollution Control Agency's 2013 air quality report shows the state currently meets federal air pollution standards.
The MPCA said future concerns include more air pollution coming from sources whose air emissions are not regulated, such as cars and trucks, construction equipment and residential wood burning.
MAKING THE GRADE:
The American Lung Association assigns letter grades to the country's most populous counties, including 18 in Minnesota. A, B and C grades meant a county had six or fewer unhealthy air days. D grades were given to counties that had 7 to 9 days over the standard (if 9 days they all had to be rated "unhealthy for sensitive groups" or lower). F grades were given to counties that had 9 or more days over the standard (if 9 days at least one of the days had to be rated "unhealthy to all") Data for both ozone and particle pollution are not available for every county, and air monitoring locations sometimes change, limiting availability of the data.
MAP: Minnesota counties' grades: