High radon areas in Norway

Abstract

Norway is considered to be one of the most radon-affected areas in Europe. Based on results of nationwide surveys, the mean radon concentration in Norwegian dwellings has been estimated to be 89 Bq/m 3, and 9% of houses have an annual mean radon concentration exceeding the recommended action level of 200 Bq/m 3. Very high radon concentrations (50,000 Bq/m 3) have been recorded in houses located on highly permeable sediments. In some of these areas, more than 2/3 of the housing stock exceeds the action level. In most of these areas, the external background level and the concentration of radium in geological samples near the surface are moderate or low (less than 100 Bq/kg) and the high levels are due to transport of radon from large volumes of permeable material surrounding the construction. High indoor radon concentrations (above 10,000 Bq/m 3) have also been recorded in areas of exposed bedrock with elevated levels of radium and in areas of moderately permeable sediments containing radium rich rock fragments such as alum shale and uranium-rich granites. The identification of high radon areas in Norway is based on extensive municipal surveys with measurements most sparsely populated areas. In a sample, where 2–20% of houses in municipalities were randomly selected, depending on their population density (2% in the most densely populated areas and 20 in the most sparsely populated areas). So far, nearly 200 out of 435 municipalities have carried out radon surveys in accordance with the mapping strategy recommended by NRPA. In this paper, results and characteristics of some of the high radon areas will be briefly discussed.