IMPORTANT: radon concentrations are highly variable within a county, and in a given county some homes will have concentrations more than 5 times as high as the medians shown here! You might be more interested in the odds that your particular home has an elevated radon concentration. For that, a map of the fraction of homes over 4 pCi/L (the EPA's recommended action level) might be more helpful.
Colors may be hard to distinguish, particularly among the greens. But this map isn't intended to give really detailed predictions anyway---remember, these are predictions, so there is some uncertainty in each county's actual median!
If you're interested in the statistical methods and data used to make
these maps, visit our research area.