Indoor radon/thoron concentration has been measured in Aizawl district, Mizoram, India, which has the highest lung cancer incidence rates among males and females in India. Simultaneously, radon flux emanated from the surrounding soil of the dwellings was observed in selected places. The annual average value of concentration of radon(thoron) of Aizawl district is 48.8(22.65) Bq m with a geometric standard deviation of 1.25(1.58). Measured radon flux from the soil has an average value of 22.6 mBq m s These results were found to be much below the harmful effect or action level as indicated by the World Health Organisation. On the other hand, food habit and high-level consumption of tobacco and its products in the district have been found to increase the risk of lung cancer incidence in the district.

Indoor radon and thoron concentrations have been measured in the year 2015-2016 using the newly developed pin-hole based radon/thoron discriminating dosimeters with single entry. The measurements have been carried out in fifty dwellings of eight different villages/town situated in Saiha and Lawngtlai District, Mizoram. Dwellings were selected from the building type along with an idea of different ventilation conditions which affects the indoor concentration. Reinforce Cement Concrete (RCC) type of buildings are found to have the highest concentration of indoor radon (100.34 ± 7 Bq/m3) and thoron (41.41 ± 18 Bq/m3) and grounded house are found to have higher concentration compared to that of house with crawl space. However, the concentrations obtained in this work lies in the range covered by nationwide survey result as well as the ICRP regulations.

Humans are constantly exposed to radiations, of which majority (87%) is from natural sources and a fraction (13%) is from man-made. Construction materials can contribute to natural background radiation in two ways, namely emission of gamma radiation, from primordial radionuclides like uranium, thorium and potassium and their decay products (external dose); and exhalation of radon (internal dose). The nature of soil largely determines the degree of gamma radiation. Measurement of natural radioactivity in soil and building materials from Siaha and Lawngtlai districts in Mizoram was carried out using 5"X 4" NaI (Tl) detector. Soil samples were collected from 25 different sites and five different commonly used building materials in the study area are also analysed. The activity concentrations were measured for three principal primordial radionuclides namely, 238 U, 232 Th and 40 K. The average activity concentration of soil samples was found to be 33.47 Bq/kg for 238 U, 67.00 Bq/kg for 232 Th nuclides and 942.25 Bq/kg for 40 K nuclides. The average activity concentration of 238 U & 232 Th are found to be highest in Glazed tiles and that of 40 K is found to be highest in bamboo.

Indoor radon and thoron concentrations have been measured using solid state nuclear track detector (LR-115 type-ІІ) based twin cup dosimeter with single and double entry deployed side by side. The measurements have been carried out in 50 dwellings of 8 different villages/towns situated in Saiha and Lawngtlai districts, Mizoram. Dwellings were selected primarily from the gamma level measured using Micro-R survey meter and the construction type of the building. The average concentrations of radon and thoron were found to be 75.76 Bq/m3 and 96.50 Bq/m3 for single entry dosimeter and 63.47 Bq/m3 and 19.79 Bq/m3 for double entry dosimeter. The single entry dosimeter was found to give more reliable observations than that of double entry in terms of trends of seasonal data and also on the theory behind the manufacturing qualities.