Mayak Research Articles

Heritable effects in offspring associated with harmful exposure to parents (Literature review)

A review of literature data regarding the heritable effects in offspring due to parents’ contact with mutagenic risk factors is presented. Studies on various factors of adverse effects on the hereditary apparatus, including chemical, infectious, physical and biological, are considered. The influence of smoking and parents’ age on the occurrence of de novo mutations is shown. Particular attention is paid to the review of publications on the role of the radiation factor in the genesis of hereditary disorders in offspring. Development stages of radiation genetics, the evolution of conception about radiation harm are described. The results of experimental, cytogenetic, molecular genetic, epidemiological studies analyzing the contribution of parental exposure to inherited pathology in progeny are presented. Special attention is paid to the “untargeted” effects of radiation and studies which prove the possibility of transgenerative transmission of genome instability are presented. The special contribution of studies on the cohort of atomic bomb victims offspring in Hiroshima and Nagasaki, which is considered as the main scientific platform for radiation risk assessment, is noted. There are articles about the offspring of persons who underwent therapeutic exposure, who had professional contact with ionizing radiation, who were exposed to radiation as a result of the Chernobyl accident, nuclear weapons tests at the Semipalatinsk test site, chronic radiation in the radioactively contaminated territory of the Techa river, areas with naturally increased radioactivity. As a result, it was noted that, despite numerous confirmations of radiation-induced effects in offspring obtained within experimental and molecular genetic studies, the results of epidemiological studies remain controversial. Possible reasons for these discrepancies are considered. An idea of views evolution regarding heritable effects in the international system of radiation safety is given. A new approach of the International Commission on Radiological Protection to heritable effects is described; the dynamics of tissue weighting factors for gonads in the assessment of effective radiation dose is shown. Methods for evaluating heritable effects are presented: the direct method and the doubling dose method. Attention is focused on the uncertainties that remain in the modern assessment of radiation genetic damage. The necessity of further study of radiation-induced heritable effects is shown. The perspective directions of studying the heritable effects are considered. The possibility of the analysis of heritable effects is described using the example of a cohort of the Mayak Production Association workers’ offspring – the country’s first nuclear industry enterprise.

Glaucoma incidence risk in a cohort of Mayak PA workers occupationally exposed to ionizing radiation

Glaucoma is a major cause of visual impairment, and secondary glaucoma manifested as neovascular glaucoma has long been known to occur following high-dose fractionated radiation therapy. In contrast, little is known as to whether ionizing radiation exposure causes primary glaucoma, except that a single study in Japanese atomic bomb survivors has reported a significantly increase risk. Therefore, the effect of lower dose and lower dose rate remains unclear. Here we report that in Russian Mayak Production Association workers occupationally exposed to chronic radiation for prolonged periods, incidence of total primary glaucoma and primary open-angle glaucoma is significantly associated with various non-radiation factors (sex, attained age, and cataract diagnosed prior to glaucoma), but neither with cumulative dose from external γ-rays nor with cumulative neutron dose nor with the unweighted sum of cumulative γ and neutron doses. The present results suggest for the first time that chronic radiation exposure does not cause primary glaucoma, although the analyses need to be made in other cohorts exposed at various dose and dose rate.

Registry for chronic radiation syndrome in a worker cohort of the Russian nuclear enterprise, Mayak Production Association

A registry for chronic radiation syndrome (CRS), a deterministic effect of chronic exposure to external and/or internal radiation at doses and dose rates exceeding thresholds for tissue reactions, was established within a medical and dosimetry database known as ‘Clinics’, of the Southern Urals Biophysics Institute at the Federal Medical and Biological Agency of Russia. It includes 2068 CRS cases: 1517 (73.4%) in males and 551 (26.6%) in females. The majority of workers (97.9%) diagnosed with CRS at one of the main facilities of the first Russian nuclear enterprise, Mayak Production Association, were hired in the period 1948–1954. On the date of CRS diagnosis, the mean cumulative red bone marrow (RBM) absorbed doses from external gamma rays were 1.1 ± 0.66 Gy in males and 1.0 ± 0.58 Gy (±standard deviation) in females, with mean annual doses of 0.46 ± 0.33 Gy and 0.38 ± 0.22 Gy, respectively, and maximum annual doses of 0.67 ± 0.46 Gy and 0.55 ± 0.34 Gy, respectively. The frequency of CRS cases significantly increased with the increasing cumulative and mean annual RBM absorbed doses from external gamma rays. The paper presents the structure and descriptive characteristics of the CRS registry as well as prospects for its use.

Methodological approach to development of dosimetric models of the human skeleton for beta-emitting radionuclides

Objective of the study : to develop a skeleton model for assessing red bone marrow dose from osteotropic beta-emitting radionuclides. This article describes the modeling methodology which takes into account the individual variability of the macro- and microstructure of bone tissue. Materials and methods: it is proposed to model bone sites with active hematopoiesis by dividing them into small segments described by simple geometric shapes. Spongiosa, which fills the segments, is modeled as an isotropic three-dimensional grid (carcass) of rod-like trabeculae that “run through” the bone marrow. In the process of randomization, multiple carcass deformations are simulated by changing the positions of the grid nodes and the thickness of the rods. Model grid parameters are selected in accordance with the parameters of spongiosa microstructures taken from the published papers. Stochastic modeling of radiation transport in heterogeneous environments simulating distribution of bone tissue and marrow in each of the segments is performed by Monte Carlo method. The model output for the lumbar vertebra is given as an example. The generated vertebral model allowed us to obtain the dosimetric characteristics of bone marrow irradiation, which are comparable to the results obtained with ICRP model developed based on the data of micro-images of bone structures. For the first time ever confidence intervals of dosimetric characteristics associated with individual variability of bone structure were evaluated. The developed methodology for the calculation of doses absorbed in the bone marrow from osteotropic radionuclides does not require additional studies of autopsy material. The obtained results will be used to calculate individual doses in a cohort of Techa riverside residents who were exposed due to Techa River contamination as a result of liquid radioactive waste discharges by the Mayak Production Association.

Hypertension Incidence Risk in a Cohort of Russian Workers Exposed to Radiation at the Mayak Production Association Over Prolonged Periods.

The study was aimed to assess hypertension incidence risk in a cohort of workers occupationally exposed to ionizing radiation. The cohort included workers of Russian Mayak nuclear enterprise who were employed in 1948 to 1982 and followed up until December 31, 2013 (22 377 workers). All workers were occupationally exposed to external γ-rays and some (76.03%) also to α-particles from internally deposited plutonium. Mean cumulative absorbed liver doses from external γ-rays (mean±SD) were 0.45±0.65 Gy in male and 0.37±0.56 Gy in female, whereas doses from internal α-particles were 0.23±0.65 and 0.44±1.93 Gy in males and females, respectively. An excess relative risk per unit dose was calculated based on Poisson regression analysis and was described as linear and nonlinear trends with radiation dose including adjustments for nonradiation factors via stratifications. As of the end of the follow-up period, 8425 hypertension cases (38% of workers) were verified in the cohort (5745 cases in males [36%] and 2680 cases in females [49%]). Hypertension incidence was found to be significantly linearly associated with cumulative liver absorbed dose from external γ-rays: excess relative risk/Gy=0.14 (95% CI, 0.09-0.20). No significant association of hypertension incidence with cumulative liver absorbed dose from internal α-particles was found: excess relative risk/Gy=-0.01 (95% CI, non-available-0.05). Hypertension incidence risk in the study cohort was higher than that in the Japanese cohort of atomic bomb survivors (AHS [Adult Health Study]) but lower than a corresponding estimate for Chernobyl clean-up workers.

Распределение индивидуальных доз в когорте людей в результате радиоактивного загрязнения реки Течи

Purpose: Descriptive analysis of the distributions of organ/tissue doses for individuals exposed to radiation as a result of liquid waste releases into the Techa River by the Mayak Production Association (PA) in 1949–1956. 
 Material and methods: The dosimetry system TRDS-2016D has been used to compute individual doses of external and internal exposures. TRDS-2016D databases include information on radionuclide intakes and dose rates in air for settlements located in the contaminated areas of the Techa River and the East Ural Radioactive Trace (EURT). Combining these village-average data with the residence history and age of a particular person, the system produces an individual scenario of external exposure and individual radionuclide intakes and then calculates corresponding external and internal doses from the Techa River and EURT. Available 90Sr-body-burden measurements and available information on individual household locations relative to the contaminated river have been used for refinement of individual dose estimates. 
 Results: Individual doses have been calculated for 29,647 persons included in the Techa River Cohort (TRC). According to residence history data, 5,280 members of the TRC were additionally exposed due to residency in the EURT villages. The cohort-average dose for the majority of extra-skeletal tissues does not exceed 100 mGy, while for the red bone marrow (RBM) it is equal to 350 mGy. In addition to the doses from the Techa River and EURT, individual thyroid doses for TRC members exposed to the Mayak PA atmospheric 131I releases have been calculated in a separate computer program. The cohort–average thyroid dose is 210 mGy. Maximum doses (about 1 Gy to the majority of extra-skeletal tissues and over 7 Gy to the thyroid and RBM) are observed for the persons who lived in their childhood and adolescence in the upper Techa region at close distance to the Mayak PA.
 Conclusion: The TRC members were exposed to chronic radiation over a wide range of doses, but at low-to-moderate-dose rates. Estimates of absorbed doses can be used to analyze the dose dependences of the incidence of solid cancers and leukemias. This can make it possible to verify risk coefficients of low-dose-rate effects of ionizing radiation which can be used for radiation protection purposes.

Risk of cataract removal surgery in Mayak PA workers occupationally exposed to ionizing radiation over prolonged periods.

In this study, the risk of cataract removal surgery was assessed in a cohort of workers occupationally exposed to ionizing radiation over a prolonged period. The study cohort includes 22,377 workers of the Mayak Production Association (about 25% of whom are females) first employed at one of the main facilities in 1948-1982, who were followed up to the end of 2008. Dose estimates used in the study are provided by the Mayak Worker Dosimetry System 2008. The mean cumulative dose from external γ-rays [personal dose equivalent Hp(10)] is 0.54 ± 0.76Sv for males and 0.44 ± 0.65Sv for females. The mean cumulative doses from neutrons (personal dose equivalent Hp(10)n) were 0.034 ± 0.080Sv for males and 0.033 ± 0.092Sv for females. Relative risks and excess relative risks per unit dose were calculated based on maximum likelihood. Among 4,177 workers diagnosed with a verified diagnosis of senile cataract, 701 lens removal surgeries (16.7%) were performed by the end of the follow-up period. The risk of cataract removal surgery was shown to be significantly associated with non-radiation factors such as sex, attained age, smoking, an ocular comorbidity (e.g., glaucoma), and a somatic comorbidity (e.g., diabetes mellitus). There was no significant association of cataract removal surgery with external γ-dose regardless of inclusion of the neutron dose adjustment with either linear or non-linear models. It is concluded that cataract removal surgery rate may not be a highly sensitive and specific indicator that could serve as a surrogate for radiation-related cataracts.

SKIN MELANOMA INCIDENCE IN WORKERS OCUPATIONALLY EXPOSED TO IONIZING RADIATION OVER A PROLONGED PERIOD

Purpose of the study. The study is aimed to investigate skin melanoma incidence in workers occupationally exposed to radiation over a prolonged period. Materials and methods. Skin melanoma incidence was studied in a cohort of workers first employed at nuclear facility Mayak Production Association (PA) between 1948 and 1982 who had been followed up till 31.12.2013 (22,377 individuals). Mean cumulative doses from external gamma-rays over the whole follow-up period were 0.54±0.001 Sv in males and 0.44±0.002 Sv in females. Incident rates for skin melanoma were analyzed by sex, attained age, calendar period of diagnostics and radiation dose using worldwide standard and the direct standardization technique. Results. 60 skin melanoma cases (37 in males and 23 in females) were registered in the study cohort over the whole follow-up period. The standardized skin melanoma incident rate was 8.51±1.46 in males and 8.78±2.27 in females per 100000 workers revealing statistically higher rates compared to corresponding rates for general populations of the Russian Federation, Urals Federal District and Chelyabinsk region. Skin melanoma incidence was significantly increased in the period of 1994 - 2013 as compared to the period of 1974 - 1993. Skin melanoma incidence excess in females was greater than that for males. Skin melanoma incidence increment in females was mostly driven by modifications of disease occurrence risk while in males it was driven by a combined effect of age pattern modifications in the study cohort and increase of disease risk. Conclusions. Skin melanoma incidence rates in the cohort of workers occupationally exposed to ionizing radiation over a prolonged period were associated with sex and attained age workers and the calendar period of diagnostics. No significant association of skin melanoma incidence with dose from external gamma-rays was observed. A significantly increasing trend was observed for skin melanoma incidence by the end of the follow-up in both males and females.

The radiation exposure of fish in the period of the Techa river peak contamination

Waterborne radioactive releases into the Techa River from the Mayak Production Association in Russia during 1949–1956 resulted in downstream contamination of the river ecosystem. The discharged liquid waste contained both short-lived isotopes (95Zr, 95Nb, 103,106Ru, 141,144Ce, 91Y, 89Sr and 140Ba with half-life from 3 days to 1.02 years) and the long-lived 90Sr and 137Cs (half-life - 28.79 y and 30.07 y, respectively). Even now, when two half-lives of 90Sr and 137Cs have passed, the contamination in the upper river region (about 70 km from the source of releases) is still relatively high. Current anthropogenic dose rates calculated for the fish of the Techa River depend on the distance along the stream and decrease from 150 to 3 μGy day−1. Radiation exposure of fish is expected to have been much higher at the time of the releases. The aim of the study was to evaluate the dose rates for the most common fish species of the river, viz., roach (Rutilus rutilus), perch (Perca fluviatilis) and pike (Esox lucius), in the period of peak contamination of the upper reaches of the Techa River from 1950 to 1951. To achieve this objective, calculation of both internal and external dose rates was performed. For dose rate calculation, the contamination of the river compartments was modeled, body-size dependent dose coefficients were evaluated, morphometric data were analyzed. Maximum dose rates were obtained for roach; minimum – for pike, it depends on fish lifestyle (time spent at the bottom). In the period before September 1950, fish of the upper reaches are assessed to have been exposed to dose rates exceeding the screening level equal to 240 μGy day−1. From September 1950 up to the end of 1952 the fish dose rates along the Techa River were found to be close to the UNSCEAR threshold equal to 9.6 × 103 μGy day−1 or even much more higher (up to 1.9 × 105 μGy day−1). Extremely high historical dose rates did not lead to the difference in fish size and fish growth rate currently observed in the Techa River and in the comparison waterbody (the Miass River). Discussion includes the description of radiation effects observed currently in the river fish. Today the effects observed in hematopoietic system may be the consequence of radiation exposure of fish over several generations. For example, long term dwelling of fish in the radioactively contaminated environment leads to their adaptation to chronic radiation exposure. At the same time, an increase their sensitivity and decrease their adaptive capacity to respond to other stress factors can be observed.

Заболеваемость раком предстательной железы при пролонгированном профессиональном облучении работников Производственного объединения «Маяк»

Заболеваемость раком предстательной железы при пролонгированном профессиональном облучении работников Производственного объединения «Маяк»

Risk of various types of cataracts in a cohort of Mayak workers following chronic occupational exposure to ionizing radiation.

This study is the first to report cataract type specific risks in a cohort of Russian Mayak Production Association workers following chronic occupational exposure to ionizing radiation. In this retrospective cohort study, 22,377 workers (females 25.4%) first employed in 1948-1982 were followed up till the end of 2008. All cataract subtypes were significantly dependent on sex, attained age, diabetes mellitus, myopia and glaucoma. For each of posterior subcapsular (PSC), cortical and nuclear cataracts, the risk of cataract incidence significantly linearly increased with increasing radiation dose. Excess relative risk per unit effective dose (ERR/Sv) from external γ-rays based on the linear model was 0.91 [95% confidence intervals (CIs) 0.67, 1.20] for PSC, 0.63 (95% CIs 0.49, 0.76) for cortical, and 0.47 (95% CIs 0.35, 0.60) for nuclear cataracts. For all three types of cataracts, exclusion of an adjustment for neutron dose as well as inclusion of additional adjustments for body mass index and smoking index decreased ERR/Sv of external γ-rays. Inclusion of an additional adjustment for glaucoma, however, modestly increased incidence risks for cortical and nuclear cataracts, but not PSC cataracts. Inclusion of an adjustment for diabetes mellitus decreased ERR/Sv of external γ-rays only for PSC incidence. Both males and females had increased risks for all three types of cataracts, but ERR/Sv was significantly higher in females than in males (p < 0.001), particularly for PSC cataracts. The results suggest that chronic occupational radiation exposure significantly increases risks of PSC, cortical and nuclear cataracts, and that such risks are higher in females than in males.

Risk of malignant skin neoplasms in a cohort of workers occupationally exposed to ionizing radiation at low dose rates.

Recently an increasing trend in skin cancer rates has been observed in various populations including those exposed to different radiation types. Risk and dose-response following prolonged radiation exposure remain unclear. The present study was aimed to assess skin melanoma (SM) and non-melanoma skin cancer (NMSC) incidence risks in a cohort of workers occupationally exposed to ionizing radiation at low dose rates over prolonged periods. The study cohort included workers of a Russian nuclear production facility, Mayak Production Association (PA), who were first employed in 1948–1982 and followed up till the end of 2013 (the total of 22,377 individuals with 25% of females). Using AMFIT module of EPICURE software, relative risk and excess relative risk per unit dose (RR and ERR/Sv) were calculated. 60 SM and 294 NMSC cases were registered in members of the study cohort. SM and NMSC incidence was dependent on sex, attained age, age at first employment at the enterprise, type of facility, education level and was not dependent on calendar period of first employment, calendar period of diagnosis, duration of employment, smoking and alcohol consumption statuses. The risk of NMSC incidence was found to be significantly increased in workers occupationally exposed to ionizing radiation at cumulative doses above 2.0 Sv (RR = 2.52; 95% CI: 1.60, 3.97) compared to a reference dose category (0–0.05 Sv). NMSC incidence was found to be significantly associated with cumulative external gamma-dose with ERR/Sv of 0.49 (95% CI: 0.22, 0.90) without an adjustment for neutron dose and 0.51 (95% CI: 0.22, 0.93) while adjusted for neutron dose. Results of the analysis did not reveal a significant association of SM incidence with cumulative dose from external gamma-rays with ERR/Sv of 0.22 (95% CI: -0.29, 1.46) not including a neutron dose adjustment and of 0.15 (95% CI: -0.41, 1.31) while adjusted for dose from neutron exposure.

ANALYSIS OF THE RESULTS OF LONG-LIVED RADIONUCLIDE BODY BURDEN MONITORING IN RESIDENTS OF THE URALS REGION

Objective of the study: To conduct a comprehensive analysis and assessment of the dynamics of internal exposure levels in the territories contaminated due to the activities of the Mayak Production Association, based upon the results of long-term monitoring of the long-lived anthropogenic radionuclide body burden in residents of the Urals region. Materials and methods: The data of postmortem and in vivo examinations for three groups of population were analyzed: 1) residents of riverside villages of the upper and middle reaches of the Techa River, contaminated in 1949-1956 with liquid radioactive waste; 2) people who were exposed as a result of the 1957 accident on the territory of the East Urals Radioactive Trace; 3) residents of the Ozyorsk city, located at an 8 km distance from the enterprise. The following methods of the examinations were used: 1) radiochemical analysis of specimens of organs and tissues sampled at autopsy; 2) in vivo measurements with the use of the whole body counters. The results of measurements of cesium-137, strontium-90 and trans-uranium radionuclide body burden over the period 1950s – present are provided. Data analysis made it possible to distinguish two historically formed groups of population with the maximum levels of current strontium-90 and plutonium body burden. The first group included people who lived in the early 1950’s in the basin of the Techa River, for whom the levels of oral intake of 90Sr reached 1.4 MBq/year. The second group comprised residents of the Ozyorsk city, for whom the levels of inhalation intake of plutonium in the period 1951–1958 reached 8 Bq/year. Conclusion: Estimates of the committed effective doses due to the intake of long-lived radionuclides over the period from 1949 through 2012 for critical groups of residents of the Urals were: 300 mSv for former residents of the Muslyumovo settlement on the Techa River (90Sr contribution – 85%) and 13 mSv for residents of the Ozyorsk city (the contribution of trans-uranium radionuclides is 30%).

Extraction of Long-Lived Radionuclides from High-Level Alkaline Waste with p-Alkylcalix[8]arene

p-Alkylcalix[8]arene containing six tert-butyl and two isononyl groups on the upper rim of the macrocycle was suggested for extraction recovery of long-lived β- and α-emitting nuclides from high-level alkaline waste. The influence of the compositions of the organic and aqueous phases on the extraction efficiency was examined. After four contacts of the extractant solution with the real high-level alkaline solution, the activity of the major dose-producing radionuclide, 137Cs, decreases by two orders of magnitude, and that of α-emitting radionuclides, by a factor of 3.5–40 depending on the initial solution pretreatment. The degree of stripping of the radionuclides after the first contact of the loaded organic phase with the acid exceeds 99%. p-Alkylcalix[8]arenes show promise for treatment of high-level alkaline waste at the Mayak Production Association.

Immunological Markers of Chronic Occupational Radiation Exposure.

This study aimed to identify immunological biomarkers for prolonged occupational radiation exposure and thus studied a random sample of the Mayak Production Association worker cohort (91 individuals). The control group included 43 local individuals never employed at the Mayak Production Association. To identify biomarkers, two groups of workers were formed: the first one included workers chronically exposed to external gamma rays at cumulative doses of 0.5-3.0 Gy (14 individuals); the second one included workers exposed to combined radiation-external gamma rays at doses ranging from 0.7 to 5.1 Gy and internal alpha radiation from incorporated plutonium with 0.3-16.4 kBq body burden (77 individuals). The age range of the study individuals was 66-91 y. Peripheral blood serum protein concentrations of cytokines, immunoglobulins, and matrix metalloproteinase-9 were analyzed using enzyme-linked immunoassay following the manufacturer's protocol. Flow cytometry was used to analyze levels of various lymphocyte subpopulations. The findings of the current study demonstrate that some immunological characteristics may be considered as biomarkers of prolonged chronic radiation exposure for any radiation type (in the delayed period after the exposure) based on fold differences from controls: M immunoglobulin fold differences were 1.75 ± 0.27 (p = 0.0001) for external gamma-ray exposure and 1.50 ± 0.27 (p = 0.0003) for combined radiation exposure; matrix metalloproteinase-9 fold differences were 1.5 ± 0.22 (p = 0.008) for external gamma-ray exposure and 1.69 ± 0.24 (p = 0.00007) for combined radiation exposure; A immunoglobulin fold differences were 1.61 ± 0.27 (p = 0.002) for external gamma-ray exposure and 1.56 ± 0.27 (p = 0.00002) for combined radiation exposure; relative concentration of natural killer cell fold differences were 1.53 ± 0.23 (p = 0.01) for external gamma-ray exposure and 1.35 ± 0.22 (p = 0.001) for combined radiation exposure; and relative concentration of T-lymphocytes fold differences were 0.89 ± 0.04 (p = 0.01) for external gamma-ray exposure and 0.95 ± 0.05 (p = 0.003) for combined radiation exposure. Based on fold differences from controls, interferon-gamma (3.50 ± 0.65, p = 0.031), transforming growth factor-beta (2.91 ± 0.389, p = 0.026), and relative blood serum levels of T-helper cells (0.90 ± 0.065, p = 0.02) may be used as immunological markers of chronic external gamma-ray exposure. Moreover, there was a significant inverse linear association of relative concentration of T-helper cells with dose from external gamma rays accumulated over an extended period.

Phosphate-based glasses and glass ceramics for immobilization of lanthanides and actinides

Borosilicate glasses used to be a choice to vitrify nuclear wastes in most of the countries. However, Russian HLW vitrification plant at the Mayak Production Association (Chelyabinsk Region, Urals) uses phosphate-based glasses. Initially, Russian HLW glasses were based on sodium-aluminophosphate with the following approximate composition (mol.%): 40 Na2O, 20 Al2O3, 40 P2O5. Recently we have modified this composition by replacing of up to 50% Al2O3 with Fe2O3. Such replacement increases chemical durability and resistance to devitrification and radiation of the glasses. The phase composition and structure of these glasses containing ~ 10 wt% RE oxides and ~ 10, ~ 50, and ~ 100 wt% UO3 (over 100 wt%) were studied in details using XRD and FTIR. Glasses and glass-ceramics have high chemical durability. Thus, the glasses and glass ceramics on sodium-aluminum-iron-phosphate basis are good waste forms for lanthanide fraction of HLW generated at spent nuclear fuel pyroprocessing and minor actinides.

Показатели заболеваемости и смертности от цереброваскулярных заболеваний в когорте работников, подвергшихся профессиональному облучению

Purpose: Cerebrovascular disease (CVD) incidence and mortality rates were estimated in the cohort of nuclear workers occupationally exposed to radiation over a long period at the Mayak PA. Material and methods: Study cohort included 22377 workers (25 % females) of the Mayak Production Association employed during 1948–1982 and was based on “Clinic” medical dosimetry database and “Dosimetry system for Mayak workers 2008”. Statistica 6.0 software was used for statistical treatment and data analysis. Intensive (crude) and standardised incidence and mortality rates were calculated per 100 000 workers. Results: Number of cases and deaths from CVD were 8910 and 930 respectively. The greatest number of CVD cases (84 % of males and 87 % of females) was among workers of 50–69 years old, and the greatest number of CVD deaths (85 % of males and 94 % of females) was among workers of 60 years old and older. Conclusion: The present study showed that CVD incidence and mortality in the studied cohort of the Mayak nuclear workers occupationally exposed to radiation depended on the gender, age and calendar period. Statistically significant decreasing trends in CVD incidence and mortality over 1948–2013 period were not revealed.

MALIGNANT TUMORS OF THE CENTRAL NERVOUS SYSTEM IN THE CHILDREN OF THE NUCLEAR PRODUCTION WORKERS

The incidence of malignant neoplasms of the brain and the spinal medulla in children of Mayak Production Association workers who exposed preconceptive gamma irradiation was analyzed in the paper. The retrospective analysis was carried out within the cohort of children under the age of 15 born in 1948-2013 which includes 72316 people born and have been living in Ozersk, located near the nuclear plant. Overall 13 cases of malignant neoplasms of the central nervous system were registered among descendants of persons exposed in the workplace. The average value of the total dose of preconceptive gamma irradiation among mothers reached 251.95 mGy, among fathers - 211.42 mGy. The most frequent localization of malignant process was cerebellum, the most frequent morphological type of tumor was astrocytoma. Comparative analysis of morbidity was carried out by the method of indirect standardization, herewith regional and national age-sex incidence rates were applied. There was no significant excess of the incidence of malignant neoplasms of the central nervous system among children of nuclear workers. Standardized incidence ratio in comparison with the national statistics for children under 15 generally amounted in 1.04 in boys (95% confidence interval 0.5-1.87), in girls - 0.58 (0.18-1.35); in comparison with the regional statistics: in boys - 1.16 (0.56-2.09), in girls - 0.36 (0.11-0.85).

RETROSPECTIVE ANALYSIS OF CANCER MORTALITY RATE IN THE POPULATION EXPOSED TO ACCIDENTS AT MAYAK PRODUCTION

Radioactive pollution of the territory of the Chelyabinsk district is significantly determined by accidents happened at the largest nuclear industry enterprise - Mayak Production Association related to the waste disposal of radioactive fluids into the Techa River due to the accident of 1957 and the spread of the dusty radioactive clay from the Karachay lake with the wind. We executed a selective retrospective epidemiologic study of the mortality rate in the population residing in five districts (Argayashsky, Kaslinsky, Krasnoarmeysky, Kunashaksky, Sosnovsky), and two cities - Kasli and Kyshtym (all of them are located in the Chelyabinsk region), exposed to atmospheric and liquid radioactive wastes. In the administrative districts, those were inhabited only in settlements located within the zone of the intensive radioactive pollution were studied. The source of information about the cases of death was the official death records provided by the Office of Vital Records of the Chelyabinsk region for the time period of 1947-1996. As a whole about 135 thousand death records were considered. The gain in the cancer mortality rate was noted for both males and females in cities of Kyshtym and Kasli. In 1950-60s the highest mortality rate indices were typical for the population of Kasli, and in 1960-70-s - for Kyshtym. A two-fold gain in the cancer mortality rate was noted in districts of Chelyabinsk region suffered from the accidents. Practically the permanent excess of estimated benchmarks was noted in Argayashsky and Kaslinski districts and during some periods in Krasnoarmeisky and Sosnovsky districts. In the city of Kasli, Kaslinsky, Argayashsky and Krasnoarmeisky districts the rise in the mortality rate was noted already from the beginning of 1950s and was twice or more as much. The increase in the cancer mortality rate among the population of both genders is sufficiently determined by the growth of age coefficients (in ages of 60-69 and 70 years and older). The coefficient of the cancer mortality rate decreases progressively to the distance from Mayak Production Association.

External dose reconstruction for the former village of Metlino (Techa River, Russia) based on environmental surveys, luminescence measurements, and radiation transport modelling.

In the first years of its operation, the Mayak Production Association, a facility part of the Soviet nuclear weapons program in the Southern Urals, Russia, discharged large amounts of radioactively contaminated effluent into the nearby Techa River, thus exposing the people living at this river to external and internal radiations. The Techa River Cohort is a cohort intensely studied in epidemiology to investigate the correlation between low-dose radiation and health effects on humans. For the individuals in the cohort, the Techa River Dosimetry System describes the accumulated dose in human organs and tissues. In particular, organ doses from external exposure are derived from estimates of dose rate in air on the Techa River banks which were estimated from measurements and Monte Carlo modelling. Individual doses are calculated in accordance with historical records of individuals' residence histories, observational data of typical lifestyles for different age groups, and age-dependent conversion factors from air kerma to organ dose. The work here describes an experimentally independent assessment of the key input parameter of the dosimetry system, the integral air kerma, for the former village of Metlino, upper Techa River region. The aim of this work was thus to validate the Techa River Dosimetry System for the location of Metlino in an independent approach. Dose reconstruction based on dose measurements in bricks from a church tower and Monte Carlo calculations was used to model the historic air kerma accumulated in the time from 1949 to 1956 at the shoreline of the Techa River in Metlino. Main issues are caused by a change in the landscape after the evacuation of the village in 1956. Based on measurements and published information and data, two separate models for the historic pre-evacuation geometry and for the current geometry of Metlino were created. Using both models, a value for the air kerma was reconstructed, which agrees with that obtained in the Techa River Dosimetry System within a factor of two.