Higher amounts of granite in the soil make it worse. Depending on the area, it can be a severe health hazard to the point no one puts in basements - others, kinda meh.

Here is a map! [https://www.epa.gov/sites/default/files/2018-12/documents/ra...]

I would think you want basements (and ventilate them), since otherwise the radon comes directly into the living space.