Radon and geology in the United States

Regional geology and indoor radon concentrations appear to be related in the US. Using data from probability based samples, indoor radon frequency distributions have been developed in areas with similar regional geology. These frequency distributions can be used to define relative radon potential in the US. The geologic factors which determine regional radon potential are: (1) Lithologic: Rock types with known or potentially high uranium concentrations have a high probability of generating elevated indoor radon levels. Lithologies with US DOE National Uranium Resource Evaluation (NURE) equivalent uranium concentrations greater than 3 ppm may constitute high radon potential areas. (2) Soils: Soil permeability greatly influences radon potential. For example, evidence suggests that high permeabilities (> 0.01 cm.s-1) can cause elevated indoor radon levels even if radium concentrations are low. (author)