Thoron and its progeny measurements in high background radiation area

Exposure to radon, 222Rn, is supposed to be the most significant source of natural radiation to human beings. It is thought that radon and its progeny is one of the causative factors of human lung cancer. The presence of thoron, 220Rn, was often neglected because it was considered that the quantity of thoron in the environment is less than that of radon. However, recent studies have shown that high thoron concentration were found in some regions and the exposure to 220Rn and its progeny can equal or several time exceed that of 222Rn and its progeny. The results of thoron and its progeny measurements in the houses of high background radiation area (HBRA) of southeastern coast of Orissa, India are presented here. This area is one of the high background radiation areas in India consists monazite sand as the source of thoron. Both active and passive methods were employed for the measurement of thoron and its progeny in cemented, brick and mud houses of the area. Thoron concentration was measured using RAD7, Raduet and pinhole radon dosimeters. CR-39 track detector was employed for the measurement of environmental thoron progeny, both in active and passive modes. Thoron and its progeny concentrations were found comparatively high in the area. A comparison between the results obtained with various techniques is presented in this paper. The effectiveness of various thoron and progeny measurement techniques and their usefulness in estimating the dose to general public are discussed in details. (author)