"We see very noticeable haze on some days from a number of sources, and these two coal-fired power plants are the source of some of that pollution," said Danny Giovale, owner of Flagstaff, Ariz.-based Kahtoola, a manufacturer of outdoors equipment. "It does have an impact on the recreational value of northern Arizona … when you stand on the south rim of the Grand Canyon and look out on these hazy days  people have traveled from all over the world to see this natural wonder, and it's being obstructed by some pretty heavy pollution."