Indoor radon exposure in Serbia - A critical review

The aim of this study was to provide the first comprehensive assessment of indoor radon levels in Serbia based on long-term monitoring data and available studies, including a critical review of methodological limitations. The analysis, conducted using activated charcoal canisters, includes 875 buildings (2011-2024) across seven cities in Serbia, with radon concentrations ranging from 5 to 1609 Bq/m³, an arithmetic mean value of 119 ± 149 Bq/m³, and a geometric mean value of 76 ± 3 Bq/m³. About 38% of buildings exceed 100 Bq/m³, while 7% exceed 300 Bq/m³. Comparison with other national studies shows a much wider range (1-13,400 Bq/m³ in residential and commercial buildings and 10-1130 Bq/m³ in schools and kindergartens), depending on building type, geology, and measurement methodology. Higher values were observed in southern Serbia and in Kosovo and Metohija, with a log-normal distribution and pronounced local variability. Effective dose estimates indicate moderate average exposure, but also localized areas of elevated risk (average < 4 mSv/y, maximum up to 40 mSv/y). The critical analysis highlights key limitations, including data heterogeneity, dominance of short-term measurements within monitoring campaigns, inconsistent national criteria compared with WHO guidelines, and insufficient spatial coverage. In particular, there is a lack of epidemiological studies and insufficient integration of radon data with geological and building material sources. The conclusion is that Serbia exhibits moderate average indoor radon levels, but with pronounced local radiation risks. Standardization of measurement methods, long-term monitoring aimed at developing a more comprehensive radon map compared to the current one, expansion of the monitoring network, and development of epidemiological studies are necessary to improve public health protection.