ST. PAUL, Minn. (AP) -- The citizens board of the Minnesota Pollution Control Agency has approved rules aimed at reducing haze over Voyageurs National Park and the Boundary Waters Canoe Area.

The board voted unanimously Tuesday to send the rules to the federal Environmental Protection Agency for approval.

The EPA is seeking to improve visibility in national parks and wilderness areas. The haze over Voyageurs and the BWCA comes mostly from Minnesota's coal-fired power plants and taconite plants on the Iron Range.

The rules approved Tuesday were looser than MPCA staff originally proposed. They were eased after Cliffs Natural Resources said its Hibbing Taconite and United Taconite plants would have trouble complying with the nitrogen oxide limits.

Environmental groups say the revisions don't make enough progress toward the goals of cleaner air and better health.