Indoor 222Rn in Tennessee Valley Houses: Seasonal,Building, and Geological Factors

A two-season survey of indoor ²²²Rn concentrations was conducted in 226 occupied houses in Roane County, TN, during 1985 and 1986. A similar survey of 86 houses in Madison County, AL, was conducted in 1988 and 1989. Alpha track detectors were placed in each of the houses for three or more months during the winter heating season. Detectors were placed at the same sampling sites during the following cooling season. In this study, comparisons were made between winter and summer sampling times and between building types. For the data from Madison County, additional comparisons were made among regions of the county that differed in geological characteristics, especially the thickness of overburden above the Chattanooga Shale layer a geological stratum that has high concentrations of ²²⁶Ra and is widely found in the southeastern United States. The geometric means of summer and winter measurements in Roane County were 33 and 54 Bq m^?3, respectively. For Madison County, the summer and winter geometric means were 121 and 88 Bq m^?3, respectively. The winter ²²²Rn concentrations for houses in Roane Coutuy exceeded summer ²²²Rn concentrations, as is generally the case for houses in the US. For houses in Madison County, we found the opposite and atypical situation of higher ²²²Rn concentrations in the summertime. ²²²Rn concentrations differed significantly among groups of houses in distinguishable regions of Madison County. Substructure and other building factors had no observable effect on indoor ²²²Rn concentrations found in this study.