Public exposure from inhalation of radon and thoron around the tin mine and smelter areas in Bangka, Indonesia

Radon (222Rn) and thoron (220Rn) were reported as the highest contributors to natural radiation received by humans. Furthermore, radon has been stated as the second-highest cause of lung cancer. The concentrations of 238U and 232Th (the parent nuclide of radon and thoron, respectively) in nature vary with geological conditions and can be enhanced by human activities. Bangka Island in Indonesia is one such case with tin mining, where the environment contains a high amount of 232Th due to the island's granite bedrock. This study assesses the public's exposure to radon and thoron inhalation on Bangka Island by conducting measurements using a continuous radon-thoron monitor and a time-integrated monitor for radon, thoron, and thoron progeny concentrations. From those measurements, their diurnal and seasonal variation in the dwellings on Bangka Island were analyzed. From 135 dwellings on Bangka Island, the estimated annual effective dose derived from the inhalation of radon, thoron, and their progenies reaches 4.3 mSv at the highest and a mean of 1.7 +/- 0.8 mSv in which thoron contributes more than two times higher than radon. Note that the public exposure to radon and thoron inhalation in Bangka was within the reference level for the existing exposure situation.