Inhalation dose and seasonal variability in indoor radon, thoron, and their progeny in the sub-mountainous Dhauladhar region of Himachal Pradesh, NW Indian Himalaya
摘要
The general public in the Himalayan region is exposed to considerable radiation from indoor radon, thoron, and their decay products. The estimation of natural radiation, source apportionment, and concentrations of its decay products is vital for population health risk assessment. In this study, the inhalation dose and seasonal variability of indoor radon, thoron, and their progeny were investigated in the sub-mountainous Dhauladhar region of the north-west (NW) Himalaya, India. A total of 51 dwellings from 17 villages, such as cemented (H1), slate + mud (H2), and cemented + tin roofs (H3), were randomly selected for indoor radon, thoron, and their progeny measurements. The annual indoor average radon and thoron concentrations measured in H1 houses were 74.8–53.0 Bq/m3, respectively. Whereas, in H2 and H3, it showed an average of 90.6, 67.8, 69.8 and 48.4 Bq/m3, respectively. The correlation between indoor radon and thoron was found to be 0.77. The inhalation dose in the H1 was found to be 0.69–0.35 mSv/y, respectively. Similarly, for the H2 and H3, the values found to be 0.80, 0.43,0.65 and 0.32 mSv/y, respectively. The result suggests that the high indoor radon, thoron, and their progeny were recorded during winter seasons and radon and thoron levels in H2 houses was found slightly higher compared to the H1 and H2 houses, mainly depending on the type of dwelling, ventilation rate and cold environmental conditions.