Abstract
• Doses estimation for 96 persons residing near a uranium mining enterprise. • Dose rates in tooth enamel samples were estimated by dividing doses by donors age. • The annual EPR doses are consistent with external dose rates in places of residence. • For two persons high EPR dose were obtained in comparison with other citizens. To assess the impact of natural and technogenic radioactivity in uranium mining enterprises on the population, an investigation by the tooth enamel EPR (Electron Paramagnetic Resonance) dosimetry method was conducted for a group of the population living in the Stepnogorsk city (North Kazakhstan) placed near a uranium mining plant. Accumulated radiation EPR doses in enamel were assessed for 96 teeth samples. From the measured values of EPR doses and the age of tooth enamel since its formation, the individual annual EPR dose rates (DR) were determined with average value of 1.75 ± 0.46 mGy/year corresponding to the hourly DR of 0.20 ± 0.05 µGy/hour (here and below after ± sign the error of the mean is shown). Data on the individual DR were analyzed for samples collected for population of different parts of Stepnogorsk (microdistricts). These data were compared with ambient dose equivalent rate (ADER) of gamma radiation measured by the conventional instrumental dosimetry. No significant differences in DR and ADER between microdistricts were found. The average ADER through the microdistricts of Stepnogorsk was 0.23 ± 0.01 µGy/hour (corresponding to 2.0 ± 0.1 mGy/year), which is consistent with the average DR measured by EPR. For some tooth donors significantly higher individual EPR doses and DR, exceeding up to several times the bulk level for the investigated group of population were obtained. These high values may be result of local increased radiation level caused by the wastes of uranium mining enterprises.