The European map of the geogenic radon potential.

As part of its projected European Atlas of Natural Radiation (EANR), the Joint Research Centre (JRC) of the European Commission, in cooperation with research institutions and radioprotection authorities all over Europe, is currently developing a map of the geogenic radon potential. In an accompanying report the state of knowledge, mapping approaches and problems are discussed. We explain the rationale and the legal situation in Europe and present an overview on the main problems stemming from the heterogeneity of input datasets between participating countries and from the definition of input variables and their differently implemented sampling procedures or protocols. Further topics are definition of the target variable which quantifies the geogenic radon potential and its estimation from heterogeneous input and proxy variables, as well as problems specific to mapping, such as choice of mapping support and resolution. The geogenic map was preceded by a European map of indoor radon concentrations, which is still growing as ever more countries decide to participate, and which served as training for harmonisation problems occurring in the European data realm. We shall also briefly discuss its main results and implications for the geogenic map.