Norway has concentrations of radon gas in dwellings that are among the highest in the world.
It is estimated that as many as 9 % of all dwellings (175,000) have radon concentrations in indoor air above the recommended action limit of 200 Bq/m3.
Long term exposure to radon in indoor air is responsible for between 250 and 300 new cases of lung cancer each year in Norway. New radon awareness maps covering the region around Oslo and Oslofjord help identify the areas worst affected by radon.
The Geological Survey of Norway (NGU) and Norwegian Radiation Protection Authority (NRPA) launched the new map series in 2006. These maps provide local authorities with important information on the spatial distribution of potential radon hazards, and can be used when prioritizing radon measurements in existing dwellings and when evaluating the future development of new areas.
In constructing radon awareness maps, NGU measured uranium concentrations in the ground using instruments mounted in helicopters and airplanes.
The NRPA contributed measurements of indoor radon in 6326 dwellings within the study area. Comparison of these data sets, and incorporation of information on bedrock and drift geology, resulted in radon awareness maps covering some 10,000 square kilometres from Hadeland and Romerike in the North to Fredrikstad and Skien in the South. Almost two million people reside in this area.
The maps contain four important factors used in the evaluation of radon awareness:
- Existing measurements of radon concentrations in indoor air
- Measurements of uranium concentrations in the ground
- Distribution of uranium rich rock types. Rock types like alum shale and granite, and their weathering products, are often rich in uranium. These rock types are commonly associated with elevated levels of radon in indoor air
- Distribution of permeable drift deposits. Sand and gravel can permit the transport of radon from large ground volumes into dwellings. The presence of these kinds of deposits in the substrates of dwellings is generally regarded as a high radon hazard factor
The radon awareness maps are also made available to the public in the form of an interactive map (in Norwegian) here
Published: 11. January 2008