Measurement of Indoor Radon-Thoron Concentration in Dwellings of Bali Island, Indonesia

The indoor radon, thoron and their decay products are the main contributors of total inhalation dose in the
living environment. Measurement of their levels in dwellings is an important aspect to assess the inhalation dose rate to humans. The exposure of population to radon and thoron gases has become an important issue in terms of radiological protection. The data on the radon and thoron gases in dwellings of Bali island, Indonesia is not available. The main objective of this study is to assess the health hazard due to the indoor radon-thoron in dwellings belonging to residential areas of Bali island. The measurements of radon and thoron concentrations in dwellings of Bali island were carried out using passive dosimeters with the CR-39 alpha track detector. The dosimeters were installed in living room and bedroom of each house. The radon and thoron concentrations in the dwellings varied from 9 to 48 Bq/m3 and not detected to 66 Bq/m3 respectively. The total annual effective dose due to the exposure of indoor radon, and thoron in study area have been found to vary from 0.38 mSv/y to 2.4 mSv/y with an mean value of 1.08 mSv/y. The mean annual estimated effective dose received by the residents of the studied area was found to be less than the action level recommended. The annual effective dose due to the exposure to radon and thoron concentrations in the dwellings of Bali island are within the permissible limits.