FILE - This Jan. 4, 2013, file photo, shows the haze from an inversion hanging over downtown Salt Lake City. The geography that makes Utah one of the worldÃ¢€™s most beautiful places also brings the nationÃ¢€™s dirtiest air in winter, when an icy fog smothers mountain valleys for days or weeks at a time. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday demanding immediate action by elected officials. The group wants Gov. Gary Herbert and mayors of northern Utah cities to cut the pollution.