The influence of geological factors on indoor radon concentrations in Norway.

Indoor radon levels in 1618 Norwegian dwellings located in different geological settings are compared with geological information. The results show a significant correlation between indoor radon levels and geological factors. Radium content and permeability of the building ground have been found to be useful indicators of indoor radon concentrations. Based on easily accessible geological data, an assessment of the radon potential of an area can be given. Areas of high radon risk in Norway include: (a) exposed bedrock with elevated levels of radium; and (b) highly permeable unconsolidated sediments derived from all rock types and moderately permeable sediments derived from rock types rich in radium. A comparison of indoor radon with house construction characteristics and ventilation habits suggests that radon concentrations in Norwegian dwellings are also influenced by ventilation system, aeration habits and floor level of the room where the measurements were carried out. The significant correlation between indoor radon levels and geological factors observed in the present investigation indicates that it is possible to outline areas of high radon risk in Norway based on geological information.