What seems to be nothing more than a free business promotional effort, KGW attempts to put fear into your life for doing what is not only common sense but rational - weatherizing your home. [Weatherizing your home may increase radon]. A lot of government, i.e., taxpayer dollars, has gone into convincing anyone that might listen that weatherizing is good.
Not only do they not make an attempt to define radon, they make no attempt to describe how that gas might negatively affect anyone's health. It claims a "study "conducted by the U.S. Department of Energy found that reducing air leakage in a home by just 20 percent resulted in a 40-percent increase in indoor radon concentration." But not a citation. Nor could I find such a study doing a quick Google search.
A search on radon produces no definitive research on any ill effects except possibly in some particular situations. This article makes more sense - Radon: Truth vs. myth. A read of this EPA article suggests that weatherizing is first line of defense - A Citizen's Guide to Radon.