Is radon worse in Iowa or Minnesota?

Iowa has the worse radon problem, and it is not close: Iowa has the highest average indoor radon concentration of any state in the country, with the Iowa DNR estimating roughly five in ten Iowa homes test above the EPA action level of 4.0 picocuries per liter. Minnesota is also a serious radon state, with about two in five homes above the action level and nearly the entire state classified as EPA Zone 1, the highest-risk designation. So the honest answer is that both states demand testing, but Iowa leads the nation. The reason is geology: the glacial deposits that blanket both states are rich in uranium-bearing material, and as that uranium decays it releases radon gas that seeps into basements through sump pits, floor cracks, and foundation joints. Because radon is invisible and odorless, the only way to know your home's level, in Ankeny or in Anoka, is a measurement. We perform radon testing across both Minnesota and Iowa, typically as an add-on to a home inspection, using monitors placed for a minimum 48-hour test. If you are buying in either state, test. If you are choosing between the two states based on radon, know that mitigation works equally well in both, and a mitigated Iowa home is safer than an untested Minnesota one.