Mayak PA Research Articles

Преконцептивное облучение матерей: Риск фетоинфантильных потерь

Safety of female personnel exposed to occupational radiation is still a topical issue of radiation epidemiology. Mayak Production Association is the first Russian atomic enterprise and women made a quarter of its personnel. Fetal and infant losses (FILs) that include stillbirths and infant mortality could be used as an important criterion for assessing the effects of maternal preconception (prior to conception) exposure. The aim of this study was to assess FILs risk among the offspring of female Mayak PA workers exposed to occupational preconception external gamma-radiation. A retrospective analysis was performed among 15307 children born in 1949–1973; mothers of 4880 of them were Mayak PA workers. FILs were analyzed taking into account sex of the offspring, period of their birth, nosologies, parental age, and dose categories of preconception exposure. Methods of non-parametrical statistics were used and calculation of relative risk was performed with 95 % confidence interval. In general, fetal and infant losses demonstrated no statistical differences, 44.5 for 103 in the main group, 38.7 for 103 in the reference group, χ2 =2.79, p = 0.95. A statistically significant increase of FILs, stillbirths and infantile mortality was detected among the offspring with only their mothers working at Mayak PA. Dynamics analysis established the period from 1949 to 1953, in which FILs, stillbirths and infantile mortality were higher among the offspring of exposed mothers. Statistically significant differences in the FILs structure were obtained for fetal death that was more often registered in the main group, 3.48 vs 1.34 for 103, χ2 = 7.54, p = 0.006. FILs risk among mothers working at Mayak PA aged under 20 was statistically significantly higher for girls, 2.42 (1.25–4.67), and for both sexes, 2.16 (1.37–3.4). FILs were associated with the dose range of preconception external gamma-radiation of mothers from 0.16 mGy to 3006 mGy. The study also established certain categories of preconception exposure of the ovaries with significantly higher stillbirth risk in the main group as opposed to the reference one.

Preconception maternal exposure: Risk of fetal and infant losses

Safety of female personnel exposed to occupational radiation is still a topical issue of radiation epidemiology. Mayak Production Association is the first Russian atomic enterprise and women made a quarter of its personnel. Fetal and infant losses (FILs) that include stillbirths and infant mortality could be used as an important criterion for assessing the effects of maternal preconception (prior to conception) exposure. The aim of this study was to assess FILs risk among the offspring of female Mayak PA workers exposed to occupational preconception external gamma-radiation. A retrospective analysis was performed among 15307 children born in 1949–1973; mothers of 4880 of them were Mayak PA workers. FILs were analyzed taking into account sex of the offspring, period of their birth, nosologies, parental age, and dose categories of preconception exposure. Methods of non-parametrical statistics were used and calculation of relative risk was performed with 95 % confidence interval. In general, fetal and infant losses demonstrated no statistical differences, 44.5 for 103 in the main group, 38.7 for 103 in the reference group, χ2 =2.79, p = 0.95. A statistically significant increase of FILs, stillbirths and infantile mortality was detected among the offspring with only their mothers working at Mayak PA. Dynamics analysis established the period from 1949 to 1953, in which FILs, stillbirths and infantile mortality were higher among the offspring of exposed mothers. Statistically significant differences in the FILs structure were obtained for fetal death that was more often registered in the main group, 3.48 vs 1.34 for 103, χ2 = 7.54, p = 0.006. FILs risk among mothers working at Mayak PA aged under 20 was statistically significantly higher for girls, 2.42 (1.25–4.67), and for both sexes, 2.16 (1.37–3.4). FILs were associated with the dose range of preconception external gamma-radiation of mothers from 0.16 mGy to 3006 mGy. The study also established certain categories of preconception exposure of the ovaries with significantly higher stillbirth risk in the main group as opposed to the reference one.

Incidence risk of hepatobiliary malignant neoplasms in the cohort of workers chronically exposed to ionizing radiation

The increased risk of liver malignancies was found in workers of the first Russian nuclear production facility, Mayak Production Association, who had been chronically exposed to gamma rays externally and to alpha particles internally due to plutonium inhalation. In the present study, we updated the radiogenic risk estimates of the hepatobiliary malignancies using the extended follow-up period (1948–2018) of the Mayak worker cohort and the improved «Mayak worker dosimetry system–2013». The cohort comprised 22,377 workers hired at the Mayak PA between 1948 and 1982. The analysis considered 62 liver malignancies (32 hepatocellular carcinomas, 13 intrahepatic cholangiocarcinomas, 16 angiosarcomas, and 1 anaplastic cancer) and 33 gallbladder adenocarcinomas. The analysis proved the positive significant association of the liver malignancy risk (the total of histological types, hepatocellular carcinoma) with the liver absorbed alpha dose from internal exposure. The excess relative risk per Gy (95% confidence interval) of alpha dose (the linear model) was 7.56 (3.44; 17.63) for the total of histological types and 3.85 (0.95; 13.30) for hepatocellular carcinoma. Indications of non-linearity were observed in the dose–response for internal exposure to alpha radiation. No impact of external gamma-ray exposure on the liver malignancy incidence was found. In the study cohort, the number of angiosarcomas among various types of liver malignancies was very high (25.8%), and most of these tumors (73.3%) were registered in individuals internally exposed to alpha radiation at doses ranging between 6.0 and 21.0 Gy. No association with chronic occupational radiation exposure was observed for the incidence of gallbladder malignancies.

Assessing the applicability of a special model of plutonium behavior in presence of chelates in cases of wound intake of industrial compounds of plutonium in the FSUE Mayak PA workers

In cases of intake of higher levels of plutonium, a chelate diethylenetriaminepentaacetic acid is used to enhance the elimination and reduce deposition rate in the organs of major deposit in the form of calcium compound Ca-DTPA (pentacinum). To interpret the results of the nuclide measurements in excreta while estimating the doses of internal exposure to plutonium, the biokinetic and dosimetry models recommended by ICRP are applied; and in case of the actinide intake through damaged skin it is recommended to use the models of NCRP of the USA. Since the application of chelates significantly changes the picture of plutonium urinary excretion, special models of complex Pu-DTPA behavior are developed to describe the plutonium biokinetics in presence of chelates. The purpose of this work is to assess the suitability of a special model of plutonium behavior in presence of chelates elaborated by K. Konzen to describe the plutonium biokinetics in the body by the cases of wound intake of industrial plutonium compounds in the FSUE Mayak PA workers. This study used the measurements of plutonium activity in daily amount of urine for three cases with the actinide intake through damaged skin and Ca-DTPA treatment, the duration of pentacinum application and observation periods for workers depending on the levels of intake. For each case, the most likely type of an entered compound was selected using Akaike information criterion, then the daily urinary activity of plutonium was calculated by the model (estimated value) on the same days when it was determined actually (actual values). The analysis of the compliance of calculated data with actual data was conducted using the statistic tests of Foster-Stewart,Breusch-Godfrey, Mann-Whitney, Shapiro-Wilk, and the determination coefficient. It was found that for all cases considered, the adjusted determination coefficient and Foster-Stewart test indicated the compliance of actual data with calculated ones. The statistical analysis of the compliance of calculated data with actual measurements of plutonium urinary activity showed that the special model of plutonium behavior proposed by K. Konzen was able to predict the urinary activity of plutonium during both the radionuclide decorporation measures and the period of pentacinum aftereffect.

ИССЛЕДОВАНИЕ МИКРОРАСПРЕДЕЛЕНИЯ PU-239 В ПЕЧЕНИ РАБОТНИКОВ ПО «МАЯК» С ИСПОЛЬЗОВАНИЕМ НЕЙТРОННО-ИНДУЦИРОВАННОГО МЕТОДА ИЗМЕРЕНИЯ

Purpose: Conducted research was aimed at studying of microdistribution of 239Pu particles in liver tissues of former MAYAK PA workers. Current research is a continuation of studies of microdistribution of 239Pu particles in lung tissues of former MAYAK PA workers that were conducted earlier and published. Material and methods: Neutron-induced track method was utilized for studying the distribution of sizes of 239Pu nanoparticles. At Southern Urals Biophysics Institute this method was improved, optimized and adapted for studying of plutonium microdistribution in biological tissues. Liver samples studying started in 2020. Samples were chosen from Radiobiology Human Tissue Repository SUBI. Liver samples from Voronezh regional pathology and anatomical bureau and Tobolsk regional hospital #3 were obtained within the search of contemporary liver tissues. Application of liver samples on track detectors and their assembling into plastic box for following irradiation in nuclear reactor at Joint stock company “Institute of Nuclear Materials” was provided similarly to lung samples. Standart pathohistological techniqes were applied. The thickness of liver slides was 5 micrometers. Basic track count was conducted on the results of 36-minute etching. Single tracks and stars were counted. Stars with high density of tracks that exceeded counting abilities were counted on the results of 9-minute etching either directly (if all tracks were distinct) or in accordance with patent for invention RU 2733491 C2 that enables to calculate the number of tracks in a star by distinct peripheral tracks. Results: This study quantitatively compares 239Pu microdistribution in liver of three deceased former Mayak PA workers who were exposed to 239Pu by inhalation and three deceased subjects who had been never employed at Mayak PA (from Ozyorsk, Voronezh, Tobolsk). The comparison is made utilizing neutron-activation method of measurement. The results are compared to the results of less-sensitive autoradiographic method. The study demonstrated that the most of 239Pu activity in liver is concentrated in liver lobules. 239PuO2 nanoparticles found didn’t exceed the size of 20 nm. Track density for three liver samples of subjects who had been never employed at Mayak PA differed for less than two times.

Assessment of Radioecologically Relevant Radionuclides 14C, 99Tc, and 129I in Vitrified High-Level Nuclear Wastes from Spent Fuel Reprocessing

A method is proposed for quantifying the specific activities of radioecologically significant radionuclides, including 14C, 99Tc, and 129I, in vitrified high-level wastes. The conditions for the separation and purification of these radionuclides from potential interfering components are optimized and the yield coefficients and purification factors are determined. The quantification of 14C entails a three-fold distillation in CO2 followed by the measurement of the 14C counting rate in the purified solution by liquid scintillation spectrometry. 129I was determined by dissolving a sample in HNO3, five-fold extraction, and the subsequent measurement of the 129I counting rate in the purified solution using liquid scintillation spectrometry. The determination of 99Тс included dissolving a sample in the presence of ClO–, double extraction-chromatographic separation of 99Тс with an adsorbent impregnated with methyltrioctylammonium nitrate, followed by the determination of its activity by inductively coupled plasma–mass spectrometry. We have applied this approach to a simulator of vitrified high-level waste, labeled with radionuclides, and achieved satisfactory results. This approach will be instrumental in the analysis of the accumulated vitrified high-level wastes at the “Mayak” Production Association (Mayak PA). The results will be important for modeling the engineering safety barriers of a deep disposal site for radioactive wastes.

Risk of perinatal mortality among the offspring of workers employed at production with radiation hazards

Studies that address risks of perinatal mortality among the offspring of people exposed to ionizing radiation in the workplace are significant for developing hygienic standards at production facilities with radiation hazards. The purpose was to analyze perinatal mortality (stillbirths and early neonatal deaths) among the offspring of workers employed by Mayak Production Association (Mayak PA), the first atomic production facility in Russia. A retrospective analysis was performed among 25,007 children born in 1949–1973; parents of 14,580 of these children were exposed to long-term occupational radiation at Mayak PA. The study provides frequency and dynamics of perinatal mortality and comparative analysis of perinatal mortality by sex, year of birth, parental age at childbirth, and dose categories of radiation exposure. Research data were analyzed by methods of non-parametric statistics. We calculated a relative risk (RR) of perinatal mortality among the offspring of exposed and unexposed parents with 95 % CI. The rate of perinatal mortality was generally the same in both groups, 19.9 for 103 in the test group and 17.9 for 103 in the control, p > 0.05. Stillbirths among male offspring were statistically significantly more often observed in the test group due to contribution of the children with only mothers exposed to occupational radiation exposure at Mayak PA prior to conception and offspring exposed in utero. Intrauterine fetal death was observed statistically significantly more often among boys of the test group compared to controls: 2.9 against 0.9 for 103. Rates of stillbirths and perinatal mortality in the main group statistically significantly exceeded the values in the comparison group in 1949–1953: RR = 2.69 (CI: 1.46–4.95) and 2.12 (1.38–3.28) respectively. Significant statistical differences in the perinatal mortality risk were established in certain categories of preconception and intrauterine gamma-exposure. The identified peculiarities of unfavorable outcomes in the perinatal period that were detected among the offspring of Mayak PA workers could be eligible for further epidemiological monitoring. Polyetiology character of perinatal mortality requires further follow up of the cohort of the offspring born to atomic production workers.

РИСК ПЕРИНАТАЛЬНЫХ ПОТЕРЬ СРЕДИ ПОТОМКОВ ПЕРСОНАЛА РАДИАЦИОННО ОПАСНОГО ПРОИЗВОДСТВА

A retrospective analysis was performed among 25,007 children born in 1949–1973; parents of 14,580 of these children were exposed to long-term occupational radiation at Mayak PA. The study provides frequency and dynamics of perinatal mortality and comparative analysis of perinatal mortality by sex, year of birth, parental age at childbirth, and dose categories of radiation exposure. Research data were analyzed by methods of non-parametric statistics. We calculated a relative risk (RR) of perinatal mortality among the offspring of exposed and unexposed parents with 95 % CI. The rate of perinatal mortality was generally the same in both groups, 19.9 for 103 in the test group and 17.9 for 103 in the control, p > 0.05. Stillbirths among male offspring were statistically significantly more often observed in the test group due to contribution of the children with only mothers exposed to occupational radiation exposure at Mayak PA prior to conception and offspring exposed in utero. Intrauterine fetal death was observed statistically significantly more often among boys of the test group compared to controls: 2.9 against 0.9 for 103. Rates of stillbirths and perinatal mortality in the main group statistically significantly exceeded the values in the comparison group in 1949–1953: RR = 2.69 (CI: 1.46–4.95) and 2.12 (1.38–3.28) respectively. Significant statistical differences in the perinatal mortality risk were established in certain categories of preconception and intrauterine gamma-exposure. The identified peculiarities of unfavorable outcomes in the perinatal period that were detected among the offspring of Mayak PA workers could be eligible for further epidemiological monitoring. Poly-etiology character of perinatal mortality requires further follow up of the cohort of the offspring born to atomic production workers.

Разработка и верификация метода разложения b-спектра смеси радионуклидов на основе кусочно-комбинированных функций с полиномиальной или кусочно- линейной аппроксимацией их параметров

Development and verification of own method of b-spectrum processing of ultra-low background radiometer-spectrometer Quantulus-1220 with minimal or no sample preparation, with H-3, K-40 and Sr-90+Y-90 presence in liquid sample at various ratio by activity considering quenching. Development of software Aspect-SUBI which implements the method.
 Materials and Methods. The method is based on deconvolution of the measured b-spectrum in the form of a superposition of model spectra of several radionuclides. b-spectra, obtained from standard radioactive solutions H-3, K-40 and Sr-90+Y-90 mixed with liquid scintillator Optiphase Hisafe 3 in volume ratio 8 ml : 12 ml were used. Methyl orange was used as a quencher. A sum of piecewisecombined functions was used for radionuclide libraries building. The lest squares method was used to determine radionuclide activities in the sample. Computer software Microsoft Excel, Sigma Plot 2000 and R version 4.0.2 was used for statistical processing of findings, their visualization as well as verification of the developed method.
 Results. Libraries of model b-spectra were built as a sum of piecewise-combined functions with polynomial approximation (library «P») or approximation by piecewise linear functions of their parameters (library «L») depending on quench parameter SQP(E). Verification of interpretation method on paired samples proved its capacity for simultaneous measurement of activity: 1) H-3 (library «P», with relative error ±9%) and K-40 (library «L», with relative error ±20%); 2) H-3 (library «P», with relative error ±11%) and Sr-90+Y-90 (library «L», with relative error ±21%) with limitations due to the levels of activities ratio and strong quenching. At simultaneous measurement of activity K-40 (library «L») and Sr-90+Y-90 (library «L») only correct measurement of activity Sr-90+Y-90 is possible with the error level ±10% taken quench parameter SQP(E) is in the range from 600 to 706. 
 Conclusion. The developed method can be used for simultaneous measurement of volume activity of H-3 and K-40 in urine samples of Ozyorsk population and Mayak PA workers, as well as volume activity of H-3 and Sr-90+Y-90 in samples from Lake Kyzyltash located in the Mayak PA affected area. The developed software Aspect-SUBI can be used not only with Quantulus-1220 but also with any other liquid scintillation spectrometer with logarithmic type of intensification and automatic quench detection.

Gas ebullition associated with biological processes in radioactively contaminated reservoirs could lead to airborne radioactive contamination

BackgroundStorage reservoirs of radioactive waste could be the source of atmospheric pollution due to the efflux of aqueous aerosol from their water areas. The main mechanism of formation of aqueous aerosols is the collapse of gas bubbles at the water surface. In this paper, we discuss the potential influence of biological factors on gas ebullition in the water areas of the radioactively contaminated industrial reservoirs R-9 (Lake Karachay) and R-4 (Metlinsky pond) of the Mayak PA. The emission of the released non-dissolved gases captured with gas traps in reservoir R-9 was (88–290) ml/m2 per day (2015) and in reservoir R-4 (270–460) ml/m2 per day (2016). The analysis of gas composition in reservoir R-4 (60% methane, 35% nitrogen, 2.4% oxygen, 1.5% carbon dioxide) confirms their biological origin. It is associated with the processes of organic matter destruction in bottom sediments. The major source of organic matter in bottom sediments is the dying phytoplankton developing in these reservoirs. ConclusionThe obtained results form the basis to set a task to quantify the relationship between the phytoplankton development, gases ebullition and radioactive atmosphere contamination.

Acute radiation sickness due to critical accidents at a nuclear production facility

Introduction. Nuclear accidents are rare, however, today they cannot be entirely excluded. Thereupon the wealth of global experience is of particular value for prediction of outcomes that potentially follow short-term exposures to ionizing radiation at high dose rates.The objective is to describe clinical simptoms and signs in workers exposed to acute gamma-neutron radiation.Methodology. This paper considers healths effects after radiation exposure due to a critical accident that happened on January, 2 1958 during operations with an experimental flask containing uranium nitrate solution at the Mayak PA. During accident four workers were exposed to short-term gamma-neutron radiation and subsequently suffered from acute radiation syndrome of different severity degree.Results and discussion. Symptoms of the initial response, development of disorders in various organs and systems and the course of the acute radiation syndrome in exposed individuals are described.Conclusion. Multiple organs or tissues are involved in severe acute radiation syndrome at an early period after acute exposure, at that cardiovascular collapse is the most critical physiological state. Multiple organs or tissues failure in the longtrem period after acute exposure is a secondary manifestation both of the primary nonspecific response to radiation and specific radiation-induced direct damage of highly sensitive cells

ПОКАЗАТЕЛИ ЗАБОЛЕВАЕМОСТИ ЗЛОКАЧЕСТВЕННЫМИ НОВООБРАЗОВАНИЯМИ ЖЕНСКИХ ПОЛОВЫХ ОРГАНОВ В КОГОРТЕ ЖЕНЩИН, ПОДВЕРГШИХСЯ ПРОФЕССИОНАЛЬНОМУ ОБЛУЧЕНИЮ

Purpose: To assess the association of incidence rates of malignant neoplasms of female genital organs (MNs of FGO) in women who were chronically occupationally exposed to ionizing radiation (IR) with radiation and non-radiation factors. Material and methods: To perform the study, the cohort of females employed at the Mayak PA during 1948–1982 and followed up until 31 December 2018 was considered. All members of the considered cohort were chronically exposed to IR. Results: 83.6 % of females were first diagnosed with a MN of FGO at age after 50 years. More than 50 % of MNs of FGO were reported during 1991–2010. Standardized rates of MNs FGO varied with the calendar period with the highest rates observed during 1996–2005. The analysis of the variation of the standardized rates with time demonstrated a significant tendency to increase by the end of the follow-up (R²=0.67, p=0.03). The incidence rates of MNs of FGO on average increased annually by 1.0 % (95 % CI 0.3–1.6). The standardized rates of MNs of FGO were significantly higher in females who had been diagnosed with endometriosis prior to MNs of FGO. The standardized rates of MNs of FGO were significantly higher in females externally exposed to gamma-rays at uterus absorbed dose of 0.2–0.5 Gy and above 0.5 Gy compared to females who had been exposed at lower doses. MNs of the uterine body were the most common among total MNs of FGO. More than 90 % of MNs of the uterine body were registered during menopause. The standardized rate of MNs of the uterine body in females of the study cohort was 0.37 ± 0.05. The decrease in the standardized rate of the MNs of the uterine body was observed in 1986–1995 calendar period. The spline regression analysis of the variation of the standardized rate of MNs of the uterine body demonstrated the annual increment by 0.9 % (95 % CI 0.7–2.5) on average. The analysis demonstrated a tendency of the standardized rate of MNs of the uterine body to increase in the study cohort of females (R²=0.46, p=0.16). The standardized rates of MNs of the uterine body were significantly higher in females who had been diagnosed with endometriosis prior to MNs of the uterine body. Standardized rates of MNs of the uterine body were significantly higher in females externally exposed to gamma rays at the cumulative uterus absorbed dose above 0.5 Gy compared to females exposed at lower doses. Conclusion: MNs of FGO were associated with both known non-radiation factors (age, calendar period, endometriosis) and the cumulative uterus absorbed dose from chronic occupational exposure to ionizing radiation.

Lifetime of Mayak workers after acute radiation syndrome of various severity levels

Assessment of the impact of radiation exposure on human lifetime is an actual problem in radiation medicine. The aim of the study was to assess lifetime in Mayak PA workers who had developed acute radiation syndrome following accidental acute high-dose external exposure and in those individuals who had taken part in nuclear accidents but had not developed the syndrome. Study analyses considered 58 deceased Mayak PA workers (50 males and 8 females) and were performed using STATISTICA 10 software. Five indicators of lifetime were studied: static – before and after acute exposure, total lifetime, as well as potential – potential years of life lost and the proportion of people who lived less than 35 years. The study demonstrated significant decrease in static indicators excluding lifetime before acute exposure and increase in potential indicators of lifetime in workers with severe and especially with extreme acute radiation syndrome compared to workers with moderate and modest acute radiation syndrome and to workers free of the syndrome. The reason for the decrease of lifetime in workers with extreme acute radiation syndrome was extremely severe course of the disease. Decrease of lifetime in cases with severe level of the syndrome was mainly due to early death from malignancies. A significant linear regression association with natural logarithm of acute radiation dose in Gy was observed for lifetime indicators. At 1 logarithm of the radiation dose, the lifetime after acute exposure was reduced by 8.3 years, total lifetime by 8.8 years, and potential years of life lost increased by 8.4 years. The relative risk of the increase of the proportion of workers with less than 35 years of life was considerably higher in workers with extreme and severe acute radiation syndrome and in workers with acute radiation doses above 10 Gy compared to other groups of workers: 26.8 and 18.8 (95% CI: 3.8–191.1 and 2.7–129.8; p<0.001), respectively. Thus, for the first time, a reduction in lifetime after acute radiation syndrome was found among Mayak PA workers.

Excess Relative Risk of Mortality from Diseases of the Circulation System after Irradiation. Report 1. Overview of Reviews and Meta-analysis Declared Effects of Low Doses

A review of two reports is devoted to the problem of the significance of excess relative risks (ERR) per 1 Gy/Sv for mortality from diseases of the circulatory system for various exposed groups from the standpoint of epidemiology and in terms of the effects of low doses of radiation. Report 1 provides an overview of reviews and meta-analyses, together with key studies, on this topic. In most sources, 2005–2021 (publications by M.P. Little with co-workers, and others) reveals an ideological bias towards the effects of low doses of radiation (noted in the titles or summaries of almost all papers), and often there was a lack of understanding about the upper limit of this range accepted by international organizations for low LET radiation (up to 0.1 Gy according to UNSCEAR, ICRP, BEIR, etc.). In selected M.P. Little and co-authors sources for reviews and meta-analyses observed both absurd ERR values per 1 Gy and incorrect recalculations of the risk estimated in the originals at 0.1 Gy. Examples of the incorrectness of such estimations are presented, since ERR per 1 Gy calculated for ranges of lower doses may differ from those for high dose ranges by many times, and this is a systemic phenomenon, despite all the declarations of a linear non-threshold concept. Selection of sources for meta-analyses used by M.P. Little and other authors (2010–2020) violates the principles of homogeneity (groups with radiotherapy (including children with tinea capitis) are combined with miners, liquidators of the Chernobyl accident, etc.), representing an illustration of a meme of critics of meta-analytical approaches (“combination of apples and oranges”). The values of ERR per 1 Gy obtained as a result of meta-analyses for diseases of the circulatory system in general and for their individual types according to epidemiological risk scales (R.R. Monson scale, 1980; 1990) are either insignificant (ERR = 0–0.2), or, rarely, located on the border of weak associations (ERR = 0.2–0.5). An analysis of data from reviews and meta-analyses on the topic did not reveal sources that investigated effects limited to low dose ranges. In almost all cases, with some exceptions (miners with radon exposure, cohorts with absurd risks, etc.), the upper limit of the range for groups in the samples was either medium (0.1–1 Gy) or high (1 Gy). ) doses. An analysis of almost all publications on the topic of Mayak employees (T.V. Azizova with co-workers; 2010–2018; 31 sources) showed a lack of risk studies for groups with low doses of external exposure (up to 0.1 Gy), with the exception of works from 2014 and 2018, in which either reverse or weak effects were established in the absence of dose dependence. Thus, no samples in reviews and meta-analyses, as well as data for Mayak PA, provide material on the correspon-ding effect of low doses, despite the prevailing general idea of its “proof”. It was concluded that one should adhere to the statement of international organizations (USCEAR, ICRP, NCRP, BEIR, etc.) that the threshold for increasing mortality from diseases of the circulatory system is not less than 0.5 Gy, and then raise the issue of their radiation attribution for low doses impractical.

Analysis of correspondence between the current individual monitoring system of internal exposure caused by plutonium intake and the relevant ICRP recommendations

Individual dosimetry monitoring of occupational internal exposure due to plutonium intake is performed by the bioassay method which measures the plutonium isotopes in daily urine samples. Then, to estimate normalized values (committed effective dose and intake), biokinetic and dosimetry models are used. The currently valid major instruments of radiation safety in the Russian Federation are based on the requirements and approaches outlined in Publications 68 and 78 of the International Commission on Radiobiological Protection. In implementing the requirements of Publication 130 there will be a need for updating the Russian guidance documents to the new requirements. The purpose of this study was the analysis of correspondence of the current system of individual monitoring of internal exposure caused by plutonium intake to the relevant recommendations of the International Commission on Radiobiological Protection outlined in Publication 130 by the example of the FSUE “Mayak PA” production conditions. As a result of the study, the values of annual limit of plutonium intake were determined based on new biokitetic and dosimetry models, and the measured values were calculated during the current dosimetry monitoring corresponding to the value of committed effective dose limit for Category A, B personnel and women under 45 years of age. It was found that following the introduction of new requirements of the International Commission on Radiobiological Protection for Type M compounds, an intake of more than 1/4 of annual limit of plutonium intake could be determined within a year after intake using the method of alpha spectrometry. To determine an intake of 1/20 of annual limit of intake at the recommended interval of 180 days between measurements, it is necessary to use inductively-coupled plasma mass spectrometry. For the personnel working with insoluble compounds of plutonium, an intake of one annual limit of intake and 1/4 of annual limit of intake can be determined using mass spectrometry, and 1/20 of annual limit of intake can be determined using only a more sensitive method.

Medical consequences of the Urals radiation accidents: Comparative analysis

• In 1957, liquid radioactive waste (LRW) was released into the Techa River and the explosion of the storage tank for LRW at the Mayak Production Association (Mayak PA) led to radioactive contamination and long-term public exposure of a part of the Urals region, Russia. • The countermeasures on the Techa River were insufficient and implemented with delay whereas those after the 1957 accident were immediate and more extensive. • 90 Sr-body burdens and exposure doses to red bone marrow in the residents of the Techa riverside settlements were significantly higher than those in the residents of the East Urals Radioactive Trace (EURT), and medical consequences were more severe despite the comparability of radioactivity emitted into environment. • Health damage of the Techa residents assessed by the criterion of collective effective dose was significantly higher than that of the EURT population, and it correlated with the registered early and late health effects. The paper provides comparative analysis of health effects after radioactive contamination of the Techa River and the 1957 radiation accident at the Mayak Production Association (Mayak PA) in terms of efficiency of performed protective measures. Both radiation accidents took place in the Urals Region, Russia, within a short period of time due to poor-quality of storage technology of liquid radioactive waste. Despite different pathways of radioactive contamination of the environment (air or water), similar long-term combined (external γ- and internal) exposure of the population took place. Countermeasures after the 1957 radiation accident included not only scheduled but also emergency evacuation of people. Scheduled activities on the Techa River were delayed and insufficient and resulted in exposure of local residents at doses greatly exceeding permissible levels. It also led to development of both early deterministic effects and increase in leukemia and solid cancer incidence, and mortality in the long-term period.

Risk factors of liver malignancies in workers chronically exposed to ionizing radiation

OBJECTIVE: To assess the impact of non-radiation factors and ionizing radiation on the incidence of liver malignant neoplasms in workers of a nuclear facility.
 METHODS: This was a retrospective study that considered a cohort of Mayak PA workers (22,377 individuals hired during 19481982 and followed up until 31.12.2018). The analysis included 60 malignant neoplasms of liver that were histologically confirmed. Hazard ratio (HR) and 95% confidence intervals (CI) were estimated in relation to factors under the study using Poissons regression.
 RESULTS: The risk of total liver malignancies increased with attained age and for individuals with chronic liver diseases HR=3,59 (95%CI 1,57; 7,21), chronic gallbladder and biliary tract diseases HR=1,83 (95%CI 1,07; 3,11), gallstone disease HR=2,45 (95%CI 1,15; 4,77). Viral hepatitis elevated the risk of hepatocellular carcinoma (HCC) HR=7,41 (95%CI 1,20; 24,63). Gallstone disease raised the risk of cholangiocarcinoma (CC) HR=14,69 (95%CI 3,05; 56,18). Risk of hemangiosarcoma (HAS) was increased in individuals with chronic liver diseases HR=7,52 (95%CI 1,68; 24,48), and with diseases of the gallbladder and biliary tract HR=6,01 (95%CI 1,86; 26,88). The risks of total liver malignancies and HAS were found to increase due to external exposure at gamma dose 0,5 Gy and internal exposure at alpha dose of plutonium 1,0 Gy. The risk of HCC increased with alpha dose 4,0 Gy and was not associated with external gamma-ray exposure. The risk of CC increased with gamma-ray exposure at doses 1,0 Gy and was not associated with alpha particle exposure. Among total liver malignancies, the number of HAS was high (26,7%) and among them 68,8% were observed at internal exposure alpha doses 4,0 Gy.
 CONCLUSIONS: Incidence of liver malignancies in Mayak PA workers was associated with ionizing radiation, chronic diseases of hepatobiliary tract and viral hepatitis (in case of HCC). To investigate the risk related to occupational radiation exposure, we need to perform a dose-response analysis that will consider non-radiation factors.

ASSESSMENT OF THE COMMITTED EFFECTIVE DOSE EQUIVALENT AND ITS UNCERTAINTY FROM INCIDENTAL INTERNAL TRITIUM EXPOSURE.

The objective of the study was to estimate the committed effective dose equivalent from internal tritium exposure and its uncertainty in case of tritium incident at Mayak PA. According to worker's self-report, he had been exposed as a result of pouring "heavy" water over himself while performing technological operation in September 2019. Two-component exponential model of tritiated water (HTO) excretion including fast and slow phases was used to describe HTO content in the body. The individual's specific value of tritium biological half-life in the fast phase was 8.9days, which is close to the average value of 10days in the ICRP model. The slow-phase HTO excretion fraction is two orders of magnitude lower than the corresponding value in the ICRP model. The calculated committed effective dose equivalent (CEDE) due to tritium intake (7.4mSv) depended mostly on fast-phase excretion. The uncertainty factor calculated as ratio of the 97.5% quantile and the mean value was equal to 1.14. The contribution of the slow-phase excretion to the CEDE due to internal exposure was as low as from 0.1 to 0.2% of total CEDE. This demonstrates that after the case of a single intake of tritium, which we studied, the CEDE is determined mostly by the excretion in the fast phase. The metabolized organically bound tritium dose fraction was in the range from 0.3 to 2.0%. The use of all the results of the measurement of HTO activity concentration in urine made it possible to obtain a lower estimate of the uncertainty of the CEDE of internal exposure in comparison with the use of only the first measurement result.

Приборно-методическое обеспечение контроля радиоактивных выбросов на объектах ядерно-топливного цикла ФГУП «ПО «Маяк»

Data on instrumentation and methodological support of radioactive release monitoring are summarized. Flow charts of continuous and periodical (analytical) gas release monitoring are described. Methods used at the Mayak PA for monitoring of the air medium activity in process ducts, room active ventilation systems and gas release sources are summarized.

East Ural Radioactive Trace: cancer mortality over a 57-year period (1957-2014)

The objective of the current study was to assess the cancer mortality risk in the cohort of the exposed population on the territory of the East Urals Radioactive Trace over a 57-year follow-up period from 1957 to 2014 using individual doses. Materials and methods: At the end of September 1957 as a result of an accident in the cooling system of storage tanks with liquid radioactive waste, an explosion occurred on the territory of the Mayak PA which led to the formation of the East Urals Radioactive Trace. The population living in the contaminated settlements of the Chelyabinsk and Sverdlovsk regions has been affected by prolonged external and internal exposure. The cohort of individuals exposed in the territory of the East Urals Radioactive Trace numbers 21,384 people, of whom 2,055 persons had lived in Techa riverside settlements before the 1957 accident and received additional radiation exposure. The mean stomach dose for members of the East Urals Radioactive Trace cohort was 36 mGy, the maximum dose was 1130 mGy. The updated TRDS-2016 dosimetry system was used to assess individualized doses. Over the 57-year follow-up period of the cohort (1957-2014), 1294 deaths from cancer were registered in the catchment area. The number of person-years at risk was 511278. The analysis of the cancer mortality risk was carried out with the EPICURE statistical package using the Poisson regression method. Confidence intervals were calculated using the maximum likelihood method. Results: In the course of the cancer mortality analysis in the East Urals Radioactive Trace cohort over a 57-year period, a statistically significant excess relative risk of mortality per 100 mGy equal to 0.05 (95% CI: 0.002; 0.11, p = 0.04) was obtained in the entire East Urals Radioactive Trace cohort. If individuals who received additional exposure on the Techa River were excluded from the analysis, the value of the risk loses its statistical significance.