Radon is a radioactive inert gas that is produced naturally from the decay of uranium to radium. As it is formed, it is released into air or water-containing pores between soil and rock particles. From soil and rock natural forces move it into the earth and it dissolves in groundwater. This is of great medical concern as environmental radon is one of the major causes of dangerous health problems such as lung cancer. Measurements of radon content in water was carried out in the northeastern part of India namely Aizawl district and Kolasib district of Mizoram using SMART RnDuo. About 30 sources of water were examined in each district during the winter of 2017. Water samples were collected from stream water, spring water, pump water, open well, pond and Government supplied water. Radon content in water from Aizawl district ranges between 0.309 Bq/L to 32.53 Bq/L, and those from Kolasib district the range is 1.11 Bq/L to 22.18 Bq/ L. The overall average content of radon in water was found to be 6.88 Bq/L. The radon content measured for most of the sources were found to be well within the range which is considered safe (EPA 1998) except for few samples analysed.

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.

Radon is a highly radioactive, colourless, chemically unreactive and is produced from the natural decay of uranium. As it is being synthesized, it can be released into air or water-containing pores between soil and rock particles. Environmental radon is of great medical concern as it causes dangerous health problems such as lung cancer, and is classified as Group A carcinogen. Measurement of radon mass exhalation rate was performed on soil samples collected from 33 different sites within different fault regions of Aizawl district, Mizoram, India, using Smart RnDuo. The sampling sites are located within the region 23°22'39.5"N to 24°0 9'30.16"N latitude and 92°39'49.03"E to 92°56'49.35"E longitude. Soil samples were collected from three different points in each selected fault with a minimum of 200 m from each other. The type of soil collected from these regions was identified using mechanical sieve shaker and the result obtained was found to be mostly sandy type of soil for all the soil samples. The radon mass exhalation rate in soil was found to be in the range of 11.2 mBq/kg/hr to 72.2 mBq/kg/hr, with an average of 39.92 mBq/kg/hr. It was observed that radon mass exhalation rate is higher in fault regions of Aizawl district as compared to other regions of India such as northern Rajasthan,

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.

Measurement of natural radioactivity in soil samples collected from Aizawl district, Mizoram, was carried out using gamma spectrometer 5"X 4" NaI (Tl) detector. Soil samples were collected from 15 different sites located in various parts of Aizawl district. The activity concentrations were measured for three specific radionuclides, viz. 238 U, 232 Th and 40 K. The activity concentration of 238 U nuclides was found to be in the range of 20.13 Bq/kg to 60.4 Bq/kg, with an average value of 34.03 Bq/kg. For 232 Th nuclides, the activity concentration ranges between 53.68 Bq/kg to 161.03 Bq/kg, with an average value of 90.71 Bq/kg. For 40 K nuclides, it ranges from 279.58 Bq/kg to 964.62 Bq/kg, with an average value of 765.35 Bq/kg. To assess the uniformity of natural radioactivity in soil with respect to exposure, the radium equivalent activity was calculated and was found to be in the range of 135.62 Bq/kg to 350 Bq/kg, with an average value of 217.32 Bq/kg. Except for 238 U nuclides, the overall average activity concentrations of 232 Th and 40 K nuclides in collected soil samples were found to be higher than world average, but lower than the critical value set by IAEA. The radium equivalent activity value in all the samples was found to be lower than the critical value of 370 Bq/kg. Hence, no radiological hazards were observed within the specified study area.