Radon Concentrations in Schools and Kindergartens in Croatia - Implications on Design and Implementation of National Radon Action Plan

In the new European BSS (EU COUNCIL DIRECTIVE 2013/59/EUROATOM), radon has been treated in just three articles (54, 74, 103) and one Annex (XVIII) but it brings a different perspective on radon issue equalizing maximum radon reference values in homes and workplaces, for example. It is required, that every Member State shall establish a national radon action plan (NRAP). This document will address long-term risks from radon and its short-lived progeny exposure in dwellings, building with public access (such as schools, kindergartens, hospitals, etc.) and workplaces at national level. Furthermore, every Member State has to adopt their legal framework to ensure that appropriate measures for preventing radon ingress into new buildings are undertaken. But the most intriguing thing is the identification of areas where annual average radon concentration in a significant number of buildings is expected to exceed national reference level defined in NRAP. The definition of 'significant number of building' is a subject of various interpretations and it is expected that many Member States will approach to this definition in different ways. In this paper, various approaches to the definition and identification of radon-prone areas based on different parameters (indoor radon in homes and buildings with public access, soil gas radon, geogenic radon potential) and their values (arithmetic or geometric means, median, percentage of objects where selected value exceed reference value, probability that radon concentration in some object is higher than reference value) are discussed. Furthermore, differences between definitions of radon-prone areas based on administrative borders, grid-cells or geological polygons are commented. (author).