AREAS OF THE UNITED-STATES WITH ELEVATED SCREENING LEVELS OF RN-222

As part of an Environmental Protection Agency/ State cooperative progr am, 38 of the 48 contiguous states have successfully conducted probabi lity-based surveys of indoor Rn-222. These surveys produced short-term screening measurements in similar or equal to 55,000 randomly selecte d houses. An objective common to all surveys was to identify geographi c regions within the state with elevated screening levels of Rn-222. T his paper examines the survey results as they relate to this objective . The 38 states were partitioned into 225 geographic regions and summa ry statistics of Rn-222 concentrations (e.g., arithmetic mean, geometr ic mean, percentage of houses exceeding a specified level) and associa ted 95% confidence intervals were calculated for each region. Twenty-f our of the 225 regions had arithmetic means exceeding 222 Po m(-3) (6 pCi L(-1)); these are analyzed in detail.