Radon, 222Rn, is the major contributor to natural radiation in human environment. The exposure of high radon is known as one of the causative factors of lung cancer. Though thoron, 220Rn, has been a matter of study in atmospheric science, but it was often neglected compared to radon. It was considered that the amount of thoron in the environment is less than that of radon. However, recent studies show that thoron and its progeny sometime contribute significantly to the radiation dose in residential buildings. A review of methodologies, measurement protocols and concepts used in various thoron measurement surveys performed in India is presented in this paper. The results of measurements of thoron and its progeny, carried out in the Himalayan region and in the high background radiation area of the south-eastern coast of Odisha, India are also presented. The results obtained using various thoron measurements techniques and the resulting doses to the general public are discussed in details.
Keywords: Dose conversion factor; HBRA; Monazite sand; Thoron.
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