Dosimetry of thoron and its progeny in the environment

It is an establish fact that exposure of high radon 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 the dose due to exposure to 220Rn and its progeny can equal or several times exceed that of 222Rn and its progeny. The results of thoron and its progeny measurements in the houses of normal and high background radiation areas (HBRA) of India using both active and passive techniques in different types of houses are presented here. 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)