The measurement of 222Rn and 220Rn concentrations in air was carried out in 50 dwellings belonging to 20 locations in and around Mandya city, Karnataka. Annual mean values of 222Rn and 220Rn concentrations were found to be 22.4 ± 1.5 and 24.1 ± 1.8 Bq m−3, respectively. The total annual effective dose received by the general public due to radon and thoron was found to be 1.36 ± 0.08 mSv y−1. The doses to different organs and tissues were calculated using the International Commission on Radiological Protection (ICRP) model of the respiratory tract and inter-comparison was made. The flooring, roofing type and age of the buildings were noted and the radon levels with respect to these parameters were analysed and discussed. An attempt was made to predict the indoor radon levels in dwellings using the existing model which was based on the mass balance equation and the results were compared with measured values.

Measurement of dissolved radon concentrations in the water samples collected from selected borewells (depth ~300 ft), wells (depth ~25 ft) and overhead tanks (height ~30 ft) of Mandya city, Karnataka, India, has been carried out by using Emanometry method. The radon concentrations in the waters of borewell, well and overhead tank ranges from 1.5 ± 0.1 to 102.8 ± 5.1, 1.3 ± 0.1 to 3.8 ± 0.4 and 2.5 ± 0.2 to 9.7 ± 1.1 Bq l−1 with the mean values of 16.8, 2.5 and 6.2 Bq l−1, respectively. Majority of borewell water samples showed higher concentrations of dissolved 222Rn compared to waters of well and overhead tank. The overall mean value of dissolved radon concentration of 12.2 Bq l−1 is found to be close to the maximum contaminant level of 11 Bq l−1 suggested by US Environment Protection Agency. The physicochemical parameters like pH, TDS and conductivity were also measured, and dependence of dissolved 222Rn on these parameters has been studied. Using the mean value of dissolved radon concentration, a new attempt has been made to compute the doses imparted to different organs and tissues of the human body. Dosimetric calculations showed that stomach and small intestine receive greater doses due to dissolved radon compared to other organs.