Preliminary Population Exposure to Indoor Radon and Thoron in Dhaka City, Bangladesh

Radon, an element of natural radiation, is considered one of the leading causes of lung cancer worldwide. In Bangladesh, radon has been clarified as a foremost source of radiation exposure. Potential natural-radiation-induced elevated cancer risks were estimated in Bangladesh previously for the population. In this survey, as a very preliminary study in the country, comparative indoor radon (Rn-222, Rn) and thoron (Rn-220, Tn) concentration/population exposure was determined for the multistoried dwellings of south-western areas of Dhaka city. RADUET was used to assess annual Rn and Tn concentrations in determining the primary inhalation dose for the population. The annual effective dose of Rn and Tn was evaluated in this study for dwellings at 0.3 mSvy(-1), constituting a Tn dose contribution of an average of 40% with a dwelling-based wide range of 10-96%. Thus, Tn should not be neglected for Bangladesh while estimating radiological inhalation dose from the indoor environment. Again, the equilibrium factors, F of Rn and Tn, were determined by short-term measurement at averages of 0.6 and 0.02, respectively. Furthermore, using questionnaire estimation by principal component analysis, PCA following the dwelling characteristics, human lifestyles, and estimated long-term indoor Rn and Tn concentrations, this paper discussed indoor atmospheric/Rn factors for the investigated multistoried dwellings in Dhaka city.