Dose assessment from the exposure to attached and unattached progeny of radon and thoron in indoor environment

The radiation dose from the exposure to radon (222Rn) and thoron (220Rn) is mainly contributed by their progeny, not by the gases themselves. This study aims to investigate the health risk associated with the internal exposure to attached and unattached progeny of 222Rn and220Rn in the indoor environment of Garhwal Himalaya, India. For this purpose, the passive measurements of attached and unattached progeny levels of 222Rn and 220Rn were performed in Garhwal Himalaya, India using nuclear track detector based recently developed progeny sensors. The measured values of unattached and total progeny concentrations were used to estimate the unattached fractions and annual effective doses. The annual mean unattached fractions of 222Rn and 220Rn progeny were found to be 0.15 ± 0.04 and 0.17 ± 0.05, respectively. The estimated values of the annual effective doses were found to be 3.4 ± 1.9 mSv/y and 0.7 ± 0.4 mSv/y due to the progeny of 222Rn and 220Rn, respectively. The methodology and results obtained are discussed in details.