Radiation exposure due to radon, thoron and their progeny in different types of dwellings in two districts of Meghalaya, India

A survey on indoor radon, thoron and their progeny activity concentration has been carried out in two districts of Meghalaya, India, using the recently developed pin-hole dosimeter and DRPS/DTPS progeny sensors. Significant variation in these radionuclides has been observed amongst different house types and seasons of the year; responsible factors are discussed in detail. The mean observed concentration level of radon, thoron and their progeny are 63.7 ± 6, 65.1 ± 8, 24.8 ± 2 and 1.3 ± 0.1 Bq m^-3, respectively. These values are higher than the global average but lie within the prescribed limit. The estimated total annual effective dose is 2.07 mSv, which is within the permissible limit (3-10 mSv) as recommended by the International Commission on Radiological Protection (ICRP). Calculated values of radon and thoron equilibrium factors are, at par, with global findings. Positive but weak correlations between radon, thoron and their progeny concentrations have been observed.