A national conservation group lists Colorado's Mesa Verde National Park as one of 10 national parks most threatened by existing and proposed coal fired power plants.

The National Parks Conservation Commission says coal-fired plants in New Mexico and Arizona are the largest sources of pollutants -- such as sulfur dioxide and nitrogen oxides -- in Mesa Verde. It says the pollutants harm the park's ancient Pueblo structures.

The commission says a new coal plant is under development about 45 miles from the park and three others are proposed within 190 miles of the park.