Variability of radon and thoron concentration with type of dwellings in a hilly area

Abstract

Indoor radon, thoron and progenies are major contributors to the indoor radiation dose which have been measured by our study for different types of dwellings during four seasons of a year. The indoor radon, thoron and progeny levels observed in the present study found to vary with seasons of a year. The average highest radon, thoron and progeny were observed during winter and the corresponding lowest values were observed during summer. The highest 222Rn, 220Rn and progenies concentrations were observed in mud houses and the lowest values were recorded in wooden houses. A good correlation with a correlation coefficient of 0.85 was observed between indoor 222Rn and concentration of its grandparent 238U in underlying soil. A moderate correlation was found between 220Rn and 232Th concentration in underlying soil. The effective dose received by the general public in the present study due to radon and thoron was estimated as 1.43 and 1.13 mSv y−1, respectively. The 222Rn and 220Rn progenies contribute 0.79 and 0.25 mSv y−1, respectively to the annual effective dose received. The inhalation dose received by the general public of the study area due to these airborne isotopes 3.69 mSv y−1 is less than the action limit of International Commission of Radiological Protection (ICRP) (2009).