ST. PAUL -- Environmental groups want to know how much the proposed PolyMet copper-nickel mine in northeastern Minnesota could affect climate change.

The groups are asking the federal government to do a more thorough analysis of PolyMet's potential climate change impacts.

Most of the debate has centered on potential water pollution from the mine. But new federal guidelines instruct agencies to account for a project's greenhouse gas emissions.

Advocacy director Aaron Klemz of Friends of the Boundary Waters Wilderness says PolyMet could have "the equivalent of putting over 150,000 new vehicles on Minnesota roads."

The Minnesota Department of Natural Resources already has approved PolyMet's final environmental impact statement. But the U.S. Forest Service and U.S. Army Corps of Engineers have yet to sign off on the document.