Evaluation of public exposure in high background natural radiation areas (HBNRAs) of Ramsar

Some areas in Ramsar, a northern city of IRAN, have the most natural radiation level in the world which is due to high concentration of 226Ra and its daughter products specially 222Rn and therefore these regions have been interested for radiation related investigations. The aim of this study also has been to evaluate public exposure in such areas in Ramsar, in order to obtain up to date information of the region. In this regard, 24 houses in the Ramsar HBNRAs were selected and indoor annual effective dose for some of the inhabitants (24 persons) were measured by passive methods using thermoluminescence dosimeters (TLDs) and radon diffusion chamber. Gamma dose rates were determined using survey meter, RDS-110. The measured annual effective dose due to 226Ra and 222Rn were in the range of: 2.11 up to greater than 68 mSv and indoor Rn concentrations varied between50 to greater than 2280 Bq.m-3.  The total annual effective dose due to indoor gamma radiation (due to 226Ra and its daughter products, 214Pb and 214Bi) and also 222Rn was measured in the range of 2.11 to greater than 68 mSv.