Prediction of the radon priority areas in the Slovak Republic and its experimental verification

Background: The identification of the areas with increased indoor radon levels, generally referred to as “radon priority areas”, is an internationally recognized issue. Many scientific studies propose methods for locating such areas using measured soil characteristics. Objective: To utilize a modified Neznal radon potential classification for mapping radon potential across the Slovak Republic and experimentally verifying the predictions of radon priority areas. Methods: The study applied a modified version of the Neznal radon potential classification, using measurements of soil air radon concentration and soil gas permeability, to develop a radon potential map for the Slovak Republic. Municipalities with high radon potential were primarily selected for the experimental verification of radon priority area predictions. The verification process involved comparing measured indoor radon activity concentrations against predicted values, which were derived from a previous study correlating averaged indoor radon activity concentrations with averaged Neznal radon potential for selected municipalities. Results: The investigation revealed an approximately linear relationship between the measured indoor radon activity concentrations and their predicted values, with a correlation coefficient R2 = 0.43. Notably, in one municipality predicted to have medium-high radon potential, indoor radon concentrations exceeded the reference level of 300 Bq.m-3 even in buildings constructed after 2008, highlighting the significant influence of soil radon content on indoor levels despite stricter building material standards. The analysis of radon priority areas in relation to bronchial and lung cancer mortality data across various districts in Slovakia did not show statistically significant results. Conclusion: The proposed method of predicting radon risk areas is important for radiation protection of the population against high effective doses of radon and can contribute to the successful implementation of the National Radon Action Plan of the Slovak Republic.