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

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