High natural radiation exposure in radon spa areas: a detailed field investigation in Niška Banja (Balkan region)

The measurement campaigns have been done in the rural community of Niška Banja, a spa town located in southern Serbia, to evaluate population exposure to natural radioactivity. After a screening survey in 200 houses, annual radon and thoron concentrations were measured in 34 houses, and in 2004 a detailed investigation was carried out at six houses with elevated indoor radon concentrations. The paper presents the results of these detailed measurements. The complementary techniques were applied to determine radon and thoron concentrations in indoor air, in soil gas, radon exhalation from soil, soil permeability, and indoor and outdoor gamma doses. Soil and water samples were collected and analysed in the laboratory. Indoor radon and thoron concentrations were found to be more than 1 kBq m−3 and 200 Bq m−3, respectively. Extremely high concentrations of soil-gas radon (>2000 kBq m−3) and radon exhalation rates (1.5 mBq m−2 s−1) were observed. These results will be utilised to set up the methodology for a more systematic investigation.