Livrables
The project mainly addressed the biological and environmental assessment in the settlement of Dolon, just outside the Semipalatinsk test site (STS), known to be heavily affected by the nuclear weapons testing. Base on critically reviewed literature identified during this project and corroborated by field surveys and laboratory analyses, Dolon inhabitants were exposed to elevated doses (up to 850 mSv) primarily due to the first test in 1949, whereas tests carried out until the 1960's added to the radiation burden to a much lesser extent. The mid- and long-term impact on the environment is dominated by the heterogeneous deposition of Pu and Sr. Importantly, the population of Kurchatov and Semipalatinsk were also affected several times by the fallout from nuclear tests. However, since the resulting doses were several orders of magnitude lower, it is justifiable to use either as control population for comparative radiological studies.
Two field missions took place in September 1996 and October 1998 to collect environmental and biological samples for analysis in Europe. dose-rate was found to be remarkably constant at various locations of the settlement at levels similar to those found in Western Europe (less than 100nSv/h). The radiuonuclide content has been measured in more than 200 environmental samples, giving particular emphasis to Pu, Sr and Cs contamination. Included are vegetation samples, soil samples collected at different depths, samples representative of the major types of foodstuff and drinking water supply used by the local population, samples of air outdoors for the determination of the dose contribution due to resuspension of dust. An extensive survey on the dose rate (outdoor and indoor) in the dwellings inhabited by the Dolon residents, measurements of indoor Rn concentration, and in situ spectrometry were also carried out. Quality assurance/Quality Control tests have been carried out for environmental dose rate measurements, Pu and Sr concentration in environmental samples, showing a satisfactory level of agreement.
The present radiological situation can be summarised as follows:
(a) The total dose in dominated by the contribution from the inhalation of the natural radioactive Rn and its decay products;
(b) The role of Pu-inhalation is not of significance in the area id the settlement itself. However, this component should not be considered negligible in the area of the plume-axis from the fallout deposited after the first test in 1949;
(c) The most probable total annual effective dose is estimated to be 4.0 mSv.
The biological assessment was carried out on 100 blood samples from individuals living in the Beskaragaisky district aged more than 49 years and 100 samples from a matched control group living in an uncontaminated area. Metaphases from peripheral blood lymphocytes were analysed by chromosome painting, a molecular cytogenetic technique able to detect stable chromosome aberrations (reciprocal translocations), and by conventional cytogenetic techniques for the detection of unstable chromosome aberrations. Not all samples have been analysed because of problems encountered in sample transportation and processing. However, from the samples that have been scored, the preliminary results provide borderline differences between the exposed and the control groups. Somatic mutations at the glycophorin A gene were also measured by a two-colour fluorescence flow cytometric technique on peripheral blood erythrocytes. This test represents an additional, independent, and long-term biodosimeter of past radiation exposure. All samples from MN heterozygotes were successfully analysed. Again, no difference between the exposed and the control groups was detected. Moreover, the number of variant erythrocytes remained at levels considered absolutely normal for aged individuals. These results could be indicative of an altered cytogenetic picture due to a residual low contamination and further studies are needed to investigate radiation induced genetic damage in populations living around the STS.
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