The Missoula valley can have some bad air but Salt Lake City has got a real problem. A thick fog over the Salt Lake City area is making some people sick. It's prompted more than 100 local doctors to tell authorities to immediately lower highway speed limits, curb industrial activity and make mass transit free for the rest of the winter. The EPA has singled out the greater Salt Lake region as having the nation's worst air for much of this month.The only time I've seen it this bad in Missoula was during some of the summer fires.