Now that you mention it, I have heard about some Wyoming water problems:
Water can be a problem, as you might imagine. Thermopolis town water is pretty fair by Wyoming standards, and purified water is dispensed from machines at the town?s two grocery stores. Water found outside of town, however, is fit mostly for animals and crops. In most places, it takes very deep, very expensive drilling to get human-potable water. As a consequence, you often see pickup trucks with huge white tanks in their beds?ranchers hauling town water to their homesteads for drinking and washing. Some install reverse osmosis water systems.
http://www.backwoodshome.com/articles2/salinger85.html
Also someone I know near Medicine Bow has water hardly suitable for drinking or watering crops. These are problems with heavy minerals rather than with human-caused pollution.
So yeah, if growing crops is your thing, you will definitely need to get some idea about wells or water rights.
As to air quality, it doesn't get much better than Wyoming. Can actually see the stars at night. "Ground contamination"? Not much. This is a big state with few people.
Of course you might also look to yourself about some of this. It
is possible to get worked up over unimportant things, for example "second-hand smoke".
I'm not saying that's true in this case, just something to consider. Western life, especially that out in the boonies, is not really for the faint of heart. You're pretty much on your own, and have to be tough. So I've heard.