uncontrolled differences in radon-modifying property metrics between the urban and rural built environment , and / or findings that could not connect individual exposures to lung cancer risk 37 , 52 , 53 , 54 , 55 , 56 , 57 . To address these knowledge gaps in a systematic manner , we surveyed indoor air radon levels in residential properties across a broad geographic region with a highly diverse urban to rural paradigm , controlling for differences in regional building metrics that influence radon , and deriving radon exposure outcomes , radiation doses , and increased cancer risks based on the activity patterns of people living in these diverse communities .