Notes: US CDC’s Environmental Public Health Tracking Network has radon testing data at the state and county level for most of the continental United States. Users can explore the number of buildings tested, number and percent of pre-mitigation tests by radon level, number and percent of post-mitigation tests by radon level, median pre-mitigation test levels of radon, and maximum pre-mitigation levels of radon. Radon testing data on the Tracking Network come from some Tracking Program-funded states and several national radon testing laboratories.  