Radon in an alum shale rich Norwegian area

Alum shale is known to contain enhanced levels of radium, and may thus be a source of enhanced radon concentrations. The Hedemarken area in the south-eastern part of Norway has, due to its high geological occurrence of alum shale, been the subject of an extensive study on indoor radon. Measurements of the activity concentration of soil and shale, radon exhalation from the ground and from geological samples, are reported, together with measurements of indoor radon concentrations in about 200 houses. In about 70 of the houses, the radon concentration exceeded 400 Bq.m-3, and the highest concentration (mean value for a house) was 5300 Bq.m-3. Radon exhalation measurements from the ground suggest that the alum shale areas generally should be classified as high radon risk areas. (author)