Abstract: Background: Many different methods are applied for radon mapping depending on the purpose of the map
and the data that are available. In addition, the definitions of radon priority areas (RPA) in EU Member
States, as requested in the new European EURATOM BSS (1), are diverse.
Objective: 1) Comparison of methods for mapping geogenic and indoor radon, 2) the possible transferability
of a mapping method developed in one region to other regions and 3) the evaluation of the impact of different
mapping methods on the delineation of RPAs.
Design: Different mapping methods and several RPA definitions were applied to the same data sets from six
municipalities in Austria and Cantabria, Spain.
Results: Some mapping methods revealed a satisfying degree of agreement, but relevant differences were also
observed. The chosen threshold for RPA classification has a major impact, depending on the level of radon
concentration in the area. The resulting maps were compared regarding the spatial estimates and the delineation
Conclusions: Not every mapping method is suitable for every available data set. Data robustness and harmonisation
are the main requirements, especially if the used data set is not designed for a specific technique.
Different mapping methods often deliver similar results in RPA classification. The definition of thresholds for
the classification and delineation of RPAs is a guidance factor in the mapping process and is as relevant as
harmonising mapping methods depending on the radon levels in the area.