Radon-prone areas in the Lombard plain.

This paper reports the results of indoor radon measurements carried out in the Lombard plain. The aim of this study, which is based on the geological context, was to identify radon high-risk areas. The underlying geology has been established by means of the available stratigraphies giving a schematic representation of the sites in which either occurrence of gravel or silt and clay predominate with depths ranging from 0 to 50 m. Radon measurements were performed in a sample of 411 one-family houses in seven villages located in the southern area of Bergamo and Brescia. The findings indicate that when the substrate is dominated by clay, radon concentration for dwellings on the ground floor are low, whereas a strong predominance of underlying gravel mixed up in sand gives in winter months high radon flux from underground.