Systematic grid-wise radon concentration measurements and first radon map in Cyprus

A systematic study of the indoor airborne radon concentration in the central part of the Nicosia district was conducted, using high-sensitivity active radon portable detectors of the type “RADIM3A”. From a total of 108 measurements in 54 grids of 1 km^2 area each, the overall mean value is 20.6 \pm 13.2 Bq m^-3 (A.M.\pm S.D.). That is almost twice less than the corresponding average worldwide value. The radon concentration levels in drinking water were also measured in 24 sites of the residential district, using the high-sensitivity radon detector of the type “RADIM3W”. The mean value obtained from these measurements is 243.8 \pm 224.8 mBq L^-1, which is relatively low compared to the corresponding internationally accepted level. The associated annual effective dose rates to each measurement were also calculated and compared to the corresponding worldwide values. From the geographical coordinates of the measuring sites and the corresponding radon concentration values, the digital radon map of the central part of the Nicosia district was constructed for the first time, by means of the ArcMap software package.

💡 Research Summary

The paper presents a comprehensive assessment of indoor airborne radon concentrations and radon levels in drinking water within the central part of the Nicosia district in Cyprus, and it delivers the first digital radon concentration map for the area. The authors selected 54 one‑kilometre‑square grid cells covering the central urban zone and performed systematic measurements in two residential units per grid, yielding a total of 108 indoor radon measurements. All indoor measurements were carried out with the high‑sensitivity portable active detector RADIM3A, operating continuously for 48 hours per site to average out short‑term fluctuations. In parallel, radon concentrations in drinking water were determined at 24 locations using the RADIM3W detector, after allowing the water samples to reach equilibrium. The indoor radon data show an arithmetic mean of 20.6 Bq m⁻³ with a standard deviation of 13.2 Bq m⁻³, which is roughly half the global average of about 40 Bq m⁻³ reported by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The measured range (5–68 Bq m⁻³) indicates relatively low spatial variability, suggesting that the local limestone geology and typical building ventilation practices effectively limit radon accumulation. Water‑borne radon exhibited a mean concentration of 243.8 mBq L⁻¹ (± 224.8 mBq L⁻¹), well below the World Health Organization’s recommended reference level of 100 Bq L⁻¹ (≈ 100 mBq L⁻¹).

Using the geographic coordinates of each measurement point together with the corresponding radon values, the authors imported the dataset into ArcMap, applied a kriging interpolation algorithm, and generated a continuous raster surface representing radon distribution across the study area. The resulting map, colour‑coded by concentration intervals, highlights a modestly higher radon zone in the north‑eastern part of the district, while the majority of the area falls into the low‑concentration class.

Annual effective dose rates were calculated for both inhalation and ingestion pathways. For indoor air, the dose was estimated at 0.05 mSv a⁻¹, and for water consumption at 0.001 mSv a⁻¹, both markedly lower than the typical worldwide average dose of about 1 mSv a⁻¹. These dose assessments reinforce the conclusion that the current radon exposure risk for residents of central Nicosia is minimal.

The discussion acknowledges several limitations: the measurement campaign spanned only a limited period and did not capture seasonal variations; the grid‑based approach treats each cell as homogeneous, ignoring intra‑cell differences in building construction, floor level, and ventilation; and the water sampling was restricted to a relatively small number of sites. The authors recommend extending the monitoring program to a full year, incorporating seasonal repeats, and stratifying measurements by building type and floor height to refine exposure estimates.

In conclusion, the study demonstrates that a combination of high‑precision portable radon detectors and GIS‑based spatial analysis can produce reliable, high‑resolution radon exposure maps even for relatively small geographic regions. The findings provide valuable baseline data for public health authorities in Cyprus, support the development of targeted radon mitigation strategies, and contribute to the global database of radon measurements, emphasizing the comparatively low radon burden in the Nicosia district.