The Grand Portage Air Program monitors for PM 2.5, which is fine particulate matter present in the air. Sources of PM 2.5 are fires, power plants, and any combustion sources. You can monitor the air in Grand Portage and all of Minnesota by visiting the MPCA website. On the right side of their home page, they have "Today's Air" posted. You can also visit AIRnow to monitor the nation's air quality.
Image from AIRnow.gov.