Worst in the country in the winter-
“Oh ye mountains high and the clear blue sky . . .” These are words from a Mormon hymn that isn’t sung in church much anymore. I don’t know the reason, but it is appropriate because northern Utah has slowly developed the dirtiest air the country in the winter. High emissions are one reason, but the biggest factor is the strong temperature inversions that form in the mountain valleys whenever high pressure builds. High pressure usually means good weather, but not in northern Utah.
Cache Valley is the best (or worst) example. In part, I grew up there. I still remember the dirty winter fogs and the cloud of black that hung over Logan, a large town, when I was in high school. The black is gone because coal isn’t burned any more for space heating, but the pollution is now more widespread and more toxic.
The population of Cache Valley has grown. This is in part because of its beauty 3 seasons of the year. This means more traffic. In the remaining agricultural parts of the valley, CAFOs have proliferated. The result is residents breathing sun-modified auto emissions and manure emissions throughout the winter.
Utah’s bad air. Opinion in the Salt Lake Tribune
http://www.airquality.utah.gov/aqp/ This URL gives real time pollution levels, and they are not bad in the springtime.