Ground-truthing predicted indoor radon concentrations by using soil-gas radon measurements

Predicting indoor radon potential has gained in importance even asthe national radon programs began to wane. A cooperative study to produceradon potential maps was conducted by the Environmental Protection Agency(EPA), U.S. Geological Survey (USGS), Department of Energy (DOE), and LawrenceBerkeley Laboratory (LBL) with the latter taking the lead role. They developeda county-wide predictive model based dominantly on the National Uranium ResourceEvaluation (NURE) aerorad data and secondly on geology, both small-scale databases. However, that model breaks down in counties of complex geology anddoes not provide a means to evaluate the potential of an individual home orbuilding site. In this current study, soil-gas radon measurements on a largescale are shown to provide information for estimating radon potential at individualsites sort out the complex geology so that the small-scale prediction indexcan be validated. An example from Frederick County, Maryland indicates a positivecorrelation between indoor measurements and soil-gas data. The method doesnot rely on a single measurement, but a series that incorporate seasonal andmeteorological considerations.