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Francisco Kjolseth | The Salt Lake Tribune Clean air, public health and national park advocates march in support of the Environmen Courtesy | Colorado State University These photos show a hazy day and a clear day in Bryce Canyon National Park. The photos, ta photo courtesy National Park Service Haze fills the Grand Canyon in this photo from 1994. Courtesy | Colorado State University These photos show a hazy day and a clear day in Bryce Canyon National Park. The photos, ta