Abstract
We assessed individual doses of inhabitants living in high-level natural radiation areas (HLNRAs) in Ramsar. Each of 15 inhabitants in HLNRAs and 10 inhabitants in a control area carried about an electronic personal dosimeter (EPD) for one day, twice in 2005. In addition, their individual doses were estimated from ambient radiation dose rates determined with a NaI(Tl) survey meter and occupancy factors. Results of personal dosimetry carried out twice were essentially similar, and a good correlation existed between the dose rate values obtained through estimation and personal dosimetry. Each of the dosimetric subjects carried about also an optically stimulated luminescence dosimeter (OSLD) for about one month, but a few values obtained by these measurements deviated widely from those obtained by one-day measurements with EPDs and those estimated by the above method. This deviation would be ascribed to the fact that these OSLDs were left behind somewhere in houses, since it was too troublesome for a few inhabitants to always wear dosimeters for a month. As a result, observed dose values depended heavily on the place where dosimeters had been left, because of the non-uniform distribution of Ra-226 contained in materials of their houses built in the HLNRAs. For this reason, one-day measurements with sensitive dosimeters would produce more reliable results than a-few-month measurements, if the former measurements are repeated every season and the results are confirmed by comparison with those estimated from ambient radiation dose rates.
