Well, for starters you might consider what the biological mechanism is for causing so many people to drop dead in Boise within a very short time of being exposed to levels of radiation that are roughly similar to normal levels in Aspen Colorado.
The answer is that there is no such mechanism.
NB: The natural annual background radiation level at sea level is about 25 millirems. It is about 50 millirems in Denver. Ask yourself, do the Beautiful People who live in Malibu keel over shortly after reaching their ski lodges in Aspen, Vail, or Park City?
Probably. But not from radiation :)