Evaluation of Natural Radioactivity Levels and Exhalation rate of 222Rn and 220Rn in the Soil Samples from the Kuthiran Hills, Kerala, India

Background: Exposure to radon and its decay products is one of the important contributors of radiation doses to human population. Radon exhalation study is important for understanding the contribution of the soil towards the total radioactivity concentration found inside the dwellings. Purpose: The aim of the present study is to investigate the radioactivity levels and radium and radon exhalation rates in soil samples collected from Kuthiran hills and nearby places in Thrissur district, Kerala state, India. On the basis of this data, radiological health hazard parameters are also evaluated. Methods: About 18 soil samples were collected from the study location. The radium, thorium and potassium activity concentrations were analyzed by HPGe gamma ray spectrometer. The “can technique” using LR-115 type II plastic track detectors have been used for the measurement of radon exhalation rate in soil samples. Results: The mean values of activity concentrations of 226Ra, 232Th and 40K were 64.60 Bqkg-1, 109.03 Bqkg-1and 972.67 Bqkg-1 respectively. The mean value of radon mass exhalation rate is 9.19 mBqkg-1h-1 and thoron surface exhalation rate is and 237.9 mBqm-2s-1. The radium equivalent activity concentration of all the soil samples was below the level of 370 Bqkg-1, recommended for building materials, by OECD 1979 (Organization for Economic Cooperation and Development). Conclusions: The results show that the study area is safe, as far as the health hazard effects of radium and radon exhalation rate are concerned. This data will be helpful in establishing new regulations and safety limits, related to the radiation dose and radon activity in Kuthiran hills.