Nationwide indoor 222Rn and 220Rn map for India: a review

Considering the role of radon in epidemiology, an attempt was made to make a nation-wide map of indoor 222Rn and 220Rn for India. More than 5000 measurements have been carried out in 1500 dwellings across the country comprising urban and nonurban locations. The solid state nuclear track detectors based twin cup 222Rn/220Rn discrimination dosimeters were deployed for the measurement of indoor 222Rn, 220Rn and their progeny levels. The geometric means of estimated annual inhalation dose rate due to indoor 222Rn, 220Rn and their progeny in the dwellings was 0.94 mSvy−1 (geometric standard deviation 2.5). It was observed that the major contribution to the indoor inhalation dose was due to indoor 222Rn and its progeny. However, the contribution due to indoor 220Rn and its progeny was not trivial as it was found to be about 20% of the total indoor inhalation dose rates. The indoor 222Rn levels in dwellings was significantly different depending on the nature of walls and floorings.

► A countrywide survey on 222Rn and 220Rn levels for India was carried out in dwellings. ► The regional values are obtained from the data on a few houses in that area. ► Calibration factors for the measurements were derived experimentally as well as theoretically. ► The 222Rn and 220Rn levels are represented on the maps.