The Minnesota Pollution Control Agency is working on rules aimed at reducing haze in Voyageurs National Park, the Boundary Waters Canoe Area, and Isle Royale.
Federal law requires high-priority natural areas to be free from human-induced haze by 2064. In Minnesota, coal-fired power plants and taconite plants are key contributors.
The MPCA's Catherine Neuschler said electric plants will be required to reduce their emissions.
She said the agency also wants taconite plants to show how they can meet limits for emissions of nitrogen oxide and sulfur dioxide.
"Because they're prime contributors to the haze problem, it certainly should have a beneficial impact on regional haze," Neuschler said.
Critics say the plan doesn't actually require any reductions at taconite plants.
The MPCA citizens board is scheduled to decide on the state plan in March.
Meanwhile, the federal government's guidance for states is under court challenge.