Retrospective estimation of individual accumulated doses for population of Bryansk region irradiated as a result of Chernobyl accident using tooth enamel EPR-spectroscopy technique

The developed standardized procedure of individual accumulated dose estimation based on ESR-spectroscopy of tooth enamel samples was applied to large-scale dosimetric study. Measurements of over 2000 individual accumulated doses in residents of the southwest areas of Bryansk region with radio-contamination density between 5 and 30 Ci/km2 and in "clean" (control) territories were made. Teeth extracted according to medical prescription were collected in dentist outpatients. Dose values were estimated with the use of calibration relationships obtained after exposure of tooth enamel samples to the direct beam of gamma-radiation of a 137Cs source. Measured dose values were put into computer data bank and underwent statistical analysis. Dose value patterns for population of various areas were satisfactory described by log-normal functions. With accounting for the systematic correction value of the methodical approach used the average dose values for "clean" territories equal to 3-5 cGy. For residents of 137Cs contaminated areas the averaged dose values are in the range up to 12 cGy. Persons with accumulated doses essentially exceeding the above mentioned averaged values are included into groups of risk. They are subjected to compulsory medical examination and follow up as well as medical and dosimetric investigation. The clear correlation between the measured by ESR and averaged dose values and the level of ra-diocontamination of certain territories was found. The slope of the appropriate linear regression was 2 found equal to 0.24 ± 0.08 cGy/(Ci/km ). The dependence of individual doses on age of patients is described by linear regression with the slope of 0.14 ± 0.05 cGy/year. The mentioned relationships are in agreement with results obtained using calculations models of retrospective estimation of accumulated doses.