After an air monitor detected hazardous pollutants in north Minneapolis, Mayor Jacob Frey and Council Members Jeremiah Ellison and Phillipe Cunningham are urging the state to reduce air pollution in the riverfront industrial zone.

The three leaders sent a letter on Tuesday to John Linc Stine, commissioner of the Minnesota Pollution Control Agency, urging him to "take enforcement steps as long as air pollution exceeds federal and state standards."

The letter went out a few days after the agency released data showing, for the second time this year, high levels of a dangerous air pollutant called PM10 near the Northern Metal Recycling shredder.

The agency said it couldn't pinpoint what's causing the recent pollution spike other than that warmer weather might play a role. Last year, Northern Metals agreed to shut down its shredder in the area and relocate in 2019 after years of air-pollution problems and pressure from neighbors.

"Northern Metals has a long history of exceeding the air-pollution standards to the detriment of those who work and live in the Hawthorne neighborhood and surrounding community," the three officials said in the letter. "It is of the highest importance that every effort be made to protect Minnesotans from exposure to PM10, which can result in asthma aggravation, respiratory distress, exacerbation of lung and heart maladies, and heart attacks."

The letter writers acknowledged the relocation settlement with Northern Metals, "but until that relocation occurs it is imperative that authorities do everything possible to address violations."