Purpose: To assess the radiation risk of mortality from circulatory system diseases (CSD) in the cohort of liquidators of the consequences of the Chernobyl accident, considering the impact of other diseases detected in them during the observation period. Material and methods: Radiation risks of mortality from CSD were studied in the cohort of liquidators of the consequences of the Chernobyl accident observed in the National Radiation and Epidemiological Register (NRER) system from 1986 to 2022. The studied deaths are included in the codes I00–I99 of the International Statistical Classification of Diseases of the 10th Revision (ICD-10). Among the 89,594 members of the studied cohort, 16,780 deaths from CSD were identified. Mean age at the beginning of exposure was 34 years, the average absorbed dose of external gamma exposure of the whole body was 0.133 Gy, the maximum dose was 1.5 Gy, the average duration of exposure was 2.6 months. To analyze the dependence of the radiation risk of mortality from CSD on the presence of other diseases in them, regression models of excess relative risk (ERR) and nonparametric relative risk (RR) estimates in dose groups were used. Results: The average estimate of the excess relative risk ratio ERR/Gy=0.53 for the entire cohort, which is quantitatively comparable to the previously obtained estimate of ERR/Gy=0.74 for mortality from solid malignancies in the same cohort. The assessment of the radiation risk of mortality from CSD in the cohort of liquidators of the consequences of the Chernobyl accident depends on the presence of diseases from other categories identified in them during the observation period. Diseases of respiratory (J00-J99) and digestive organs (K00–K93) are radiation-competing risk factors for death from CSD. The risk group for radiation-related mortality from CSD with an estimate of ERR/Gy=1.22 consists of relatively healthy liquidators without respiratory and digestive diseases. Nonparametric estimates of relative radiation risk (RR) confirm the correctness of the linear non-threshold model of radiation risk of mortality of liquidators from CSD, regardless of the degree of multimorbidity of their health status. Conclusions: The practical dose thresholds for mortality of liquidators from CSD depend on their health status and are in the range of 0.01–0.21 Gy, which is significantly less than the currently accepted ICRP level of 0.5 Gy. The determination of such thresholds does not mean that there is no effect of radiation at doses below the threshold doses. Further accumulation of radiation and epidemiological data in the NRER system will allow for the analysis of radiation risks considering multimorbidity, more detailed by diagnosis.

The statistical relationships between radiation doses and blood diseases with the account of the multimorbidity factor in the Russian cohort of workers involved in mitigation of the consequences of the accident at the Chernobyl NPP have been investigated. For analysis observation data accumulated from 1986 over 2022 kept in the National Radiation Epidemiological Register were used. The size of the liquidators cohort was 89,578 men. During the follow-up period 6,013 blood disorders (D50-D89 ICD-10) were detected for the first time. The average radiation dose in the cohort was 0.13 Gy, and the average age at the first exposure was 33.6 years. Common approaches to data mining (Data Mining) were used to identify statistical relationships between blood diseases and other diseases; for radiation risk assessment, logistic regression models were used to link disease probability to radiation dose. The effect of low-dose radiation (less than 0.3 Gy) on blood diseases is statistically significant and is characterized by a multiplicative linear no-threshold model, the dose-response model with ERR/Gy=0.59 at 95% CI (0.23; 0.99). When considering multimorbidity in patients, the blood diseases radiation risk change was not statistically significant. Radiation risks several times higher than risks of malignant neoplasms, were found in three groups of diseases: 1) blood and haemopoietic organs other than anaemia and hemorrhages (D70-D77), with ERR/Gy=2.25; 2) immunodeficiency states (D80-D89), with ERR/Gr=2.01; 3) aplastic anemias (D60-D61), with ERR/Gy=5.56. The inclusion of aplastic anaemia in the officially approved list of diseases caused by exposure to ionizing radiation in Russia should be considered as scientifically justified document. The list may need to be supplemented by diseases of blood and haemorrhagic organs other than anaemia and hemorrhage, as well as immunodeficiency conditions. The radiation risk coefficients (ERR/Gy) for the main groups of blood diseases estimated for the first time will make it possible to establish radiation dependence in exposed people with the use of a dose and radiation-epidemiological approach, estimating the attributive fraction of radiation in the etiology of each specific disease case.

Purpose: To give a general idea of the most common combinations of diseases in the male population of the Russian Federation and to identify the combinations of diseases, the development of which could be influenced by ionising radiation. Material and methods: Cohort study of the influence of external gamma irradiation on multimorbidity of the Chernobyl accident liquidation participants according to the data of the National Radiation Epidemiological Registry. Multimorbidity was defined as the presence in one participant of the cohort of two or more diseases from the list consisting of ten groups of diagnoses: diseases of lower respiratory tract, diseases of musculoskeletal system, diseases of endocrine system, mental disorders, oncology, neurology, diseases of digestive organs, diseases of cardiovascular system, diseases of genitourinary system, diseases of sense organs. The cohort consisted of men born between 1919 and 1969 who worked in the accident zone from 1986 to 1987 and had a documented whole-body external gamma dose. Cohort follow-up period: 1992–2021. The cohort size at the beginning of the follow-up was 59 290 people. The study participants were divided into two groups according to external gamma dose: up to 150 mGy – 34602 individuals, 150 mGy and more – 24 688 individuals. For all possible combinations of diagnoses, relative radiation risk was calculated as a measure of the association of exposure with diseases. The relative radiation risk was considered statistically significant if the left border of the one-sided 95 % confidence interval was greater than 1. Statistical analyses were performed using the R programming language for statistical computing and the R arules package. Results: During 30 years of follow-up, multimorbidity was noted in 62 % of individuals. The most common combinations of chronic diseases were combinations of cardiovascular diseases with digestive diseases (23 % of the original cohort), with lower respiratory diseases (22 %) and with musculoskeletal diseases (18 %). A combination of all four diagnosis groups was identified in 5 % of individuals. Nineteen multimorbid combinations with statistically significant relative radiation risk in the range (1.07–1.23) were identified. Conclusions: No effect of radiation exposure on the number of individuals with multimorbidity was found, but in the studied cohort there are individuals with cardiovascular diseases, endocrine diseases, oncology and combinations of these groups of diagnoses with diseases of other body systems may be caused by radiation exposure. The statistically significant relative radiation risk for combinations of diagnoses is, in general, greater than for the individual diseases that make up these combinations.

In the past decade the lawful use of radiation risks of non-cancer diseases estimates to solve ra-diation safety problems has become more significant. The highest statistical power of low dose (less than 0.2 Gy) radiation risks research is possible in the cohort of the Chernobyl clean-up workers (liquidators) registered and been under medical monitoring in the system of the National Radiation Epidemiological Register (NRER) since 1986. The liquidators total number exceeds 130 thousand people. Because of the large-scale annual collection of health data, carried out in the NRER system, verification of the diseases diagnoses and medically certified causes of death, a natural question of radiation risk estimates compatibility with consideration to probable errors in a disease diagnosis and cause-of-death reporting on death certificates arises. The work is aimed at estimating the radiation risk of mortality from diseases of the circulatory system and diseases of the digestive organs in the Russian cohort of liquidators, with account of possible errors in the disease diagnosis and certified causes of death. The size of the cohort considered for mortality analysis was 91,013 people, the average age at the Chernobyl zone entry was 33.6 years, average radiation dose was 0.133 Gy. In this study, the method of maximizing the partial likelihood function was used to assess radiation risks, with consideration of individual radiation doses to liquidators and the assessment of background mortality using the Breslow method. The specificity of the diagnosis of the primary causes of death in the NRER system significantly exceeds the level of 0.99. Considering the specificity index of 0.99, the estimates of radiation risk coefficients ERR/Gy for mortality from diseases of the circulatory system and diseases of the digestive system in the cohort of Russian liquidators do not differ from the estimates obtained in the assumption that there are no first kind errors (false positive diagnosis) in the diagnoses of the primary causes of death in the NRER database. The results obtained confirm the high stability and validity of the assessments of radiation risks of mortality from diseases of the circulatory system and diseases of the digestive system, obtained earlier from the data on liquidators registered in the NRER.

Purpose: To assess the radiation risk of cataracts among the Chernobyl clean-up workers (liquidators), considering the impact of concomitant diseases on this risk and to determine the dose threshold for the development of cataracts. Material and methods: Radiation risks of cataract incidence were studied in the cohort of liquidators of the consequences of the accident at the Chernobyl nuclear power plant, observed in the system of the National Radiation and Epidemiological Register (NRER) from 1986 to 2021. Among the 62,828 male liquidators, 9,461 new cases of cataracts were detected. The average age of the liquidators at the beginning of exposure was 34 years, the average absorbed dose of external gamma exposure of the whole body was 0.132 Gy, the maximum dose was 1.5 Gy, and the average duration of exposure was 2.5 months. To analyze the relationships of cataract incidence with other diseases and with the dose, a statistical method of link analysis, free from the type of distribution, as well as logistic regression models, were used. Results: The radiation risk of cataracts in the cohort of liquidators who did not have diagnoses of diabetes mellitus, hypoparathyroidism, malnutrition and myotonic disorders depends on the presence of concomitant diseases in the patient: glaucoma (ICD-10 H40–H42), hyperopia (H52.0), myopia (H52.1) or presbyopia (H52.4). For liquidators with comorbidities, radiation risk is statistically significant only 15 years after exposure, with an excess relative risk of ERR/Gy=0.46 with 90 % CI (0.06; 0.90). For liquidators without comorbidities, ERR/Gy decrease over time: from 4.42 with 90 % CI (0.72; 13.41) in the first 5 years, to zero risk 15 years after exposure. Nonparametric estimates of the relative risk (RR) of cataracts for the dose groups of liquidators are consistent with the estimates of ERR/Gy in the linear non-threshold (LNT) model. The determination of the dose threshold for cataracts according to the LNT model, in accordance with the recommendations of the ICRP, leads to estimates from 1.2 Gy to 13.3 Gy, depending on the presence or absence of cataract concomitant diseases in the liquidators. Conclusions: At present, there are no epidemiological evidence for reducing the equivalent dose limit for the lens of the eye for occupational exposure in planned exposure situations at the level of 150 mSv per year, previously established by the recommendations of the ICRP in 2007 and the current Russian radiation safety standards NRB-99/2009.

The paper provides research on statistical relationship between endocrine diseases registered in the Chernobyl liquidators and radiation dose they received. Data of clinical and epidemiological observations accumulated at the National Radiation Epidemiological Register (NRER) for the period from 1986 to 2020 were used for analysis. The cohort contained 41,979 liquidators with 107,713 established diagnoses included in the ICD-10 Е00-E90 blocks. Statistical relationship between radiation doses and endocrine diseases was investigated with the use of statistical methods. Statistical Data Mining methods free of apriori guesses for probable doses and diagnoses distribution, models of dose-effect (disease) relationship were used for analysis of statistical relationship between radiation dose and the diagnoses structure. Statistically significant relationship between radiation doses and diagnoses were found in the blocks E01 (iodine deficiency), E04 (goiter), E06 (thyroiditis), E11 (type II diabetes mellitus). Relationships between radiation dose and diagnosis were also found in the E01.2 block (endemic goiter, caused due to iodine deficiency) and in E04.0 block (non-toxic diffuse goiter). Existence of identified statistical relationship is supported with the estimates of excess relative risk (ERR) and the relative risk (RR). The threshold relationship between RR and radiation dose with threshold of 0.3 Gy shows that radiation effect on human endocrine system is a deterministic effect (tissue reactions). Quantitative risks estimates for endocrine diseases in the liquidators are stable in relation to the diagnostic specificity index up to 90%. The general statistic Data Mining method to search relationship between a disease diagnosis and radiation dose is useful for the diseases identification in order to estimate radiation risk with conventual radiation epidemiology approaches.

A bias in radiation risk estimates may be caused by diagnostic errors. In this paper radiation risk estimates are examined with the use of the contingency table 2х2 of irradiated cancer cases with account of sensitivity and specificity indicators of diagnostic methods accuracy were examined. Radiation risk is estimated by metrics of the odds ratio (OR) and relative risk ratio (RR). It is shown that the estimation of radiation risk in the RR metric did not depend on the diagnostic sensitivity indicator, and therefore is preferable, compared to the OR metric. When the specificity of the diagno-sis is reduced, the RR value increases, compared to the risk estimated with the use of observed number of cancer cases regardless of the specificity. As a numerical example, data on trachea, bronchus and lung cancers in a cohort of the Chernobyl cleanup workers of Russia formed by using data monitored within frames of the National Radiation Epidemiological Register (NRER) from 1992 to 2020. During this period, 2,222 cancer cases were reported in the cohort of 67,587 people. The cohort members were divided into two groups, those who were unexposed to radiation (radia-tion doses less than 0.1 Gy) and other, exposed to radiation. If the specificity indicator is taken to be 100%, then the RR=1.07 at 95% CI (1.02; 1.13). The estimates of radiation risks of malignant neoplasms obtained directly from the observed number of cancer cases in exposed and unexposed groups of people, excluding the specificity and sensitivity indicators of diagnosis accuracy, are the lower estimates of radiation risk. As the probability of diagnostic errors increases (as the specificity and sensitivity of diagnostic tests decrease), and when these errors are taken into account, the es-timates of radiation risks increase. If the specificity is reduced to 98.7% CI radiation risk estimates for trachea, bronchus and lung cancer among cleanup workers of the Chernobyl accident increase to RR=1.13, but it is within 95% CI of the RR estimate if specificity is 100%. The radiation risk as-sessment approach used in the study, based on the comparison of exposed and unexposed groups of cleanup workers in OR or RR metrics, imposes high requirements to the specificity indicator of the complex of diagnostic methods in trachea, bronchus and lung (Sp>98.7%) in order to obtain unbiased estimates of radiation risks of cancer in the cleanup workers received dose below 1 Sv. These requirements are not supported by current screening methods, they can be fulfilled as a result of longterm medical monitoring within the system of the NRER.

Currently, the system of standards and rules of radiation protection considers the need to con-straint the absorbed radiation doses in order to prevent the development of deterministic effects of ionizing radiation on humans. Deterministic effects in terms of mortality include bone marrow syndrome with a dose threshold of 1 Gy, gastrointestinal syndrome and pneumonitis with dose thresholds of 6 Gy. For inclusion in international radiation safety standards, a threshold of 0.5 Gy for cardiovascular and cerebrovascular diseases is being discussed. The wide experience of ra-diation-epidemiological studies shows that the deterministic effects of mortality are not limited to those effects that are currently considered in the system of standards and rules of radiation pro-tection. This paper presents estimates of radiation risks of mortality from diseases of the circula-tory system (CSD) and the digestive system, as well as dose thresholds corresponding to these effects, in the Russian cohort of liquidators of the Chernobyl accident registered in the National Radiation and Epidemiological Register (NRER), who have registered doses from external whole-body exposure to gamma radiation within 1 Gy. The risks were estimated over the follow-up peri-od 1986-2020. The stability of estimated radiation risks of mortality from CSD and from the di-gestive system diseases in relation to the uncertainty of personal doses received by liquidators has been studied. The absorbed doses received by 11% of the liquidators were estimated from the data of personal dosimeters, the maximum error was about 50%. For the remaining 89% of liquidators, group and route doses were registered, and the maximum uncertainty of individual doses was about 500%. For CSD mortality, the excess relative rates per 1 Gy (ERR/Gy) were 0.361 and 0.349, excluding and considering dose uncertainties, respectively. For mortality from diseases of the digestive system, ERR/Gy=0,791 excluding dose uncertainty and ERR/Gy=0,726 with considering dose uncertainty. Uncertainties in individual dose estimates result in 5% and 8% reductions in ERR/Gy estimates (for CSD mortality and digestive disease, respectively). This re-duction in risk estimates is not related to a bias in the dose estimates. It is caused by the statistical properties of radiation risk models in conventional radiation epidemiology. If the excessive mor-tality from the studied causes is attributed to deterministic effects, then the estimates of the corre-sponding dose thresholds, considering the uncertainty of individual doses, also increase quite slightly: for CSD – from 0,028 Gy to 0,029 Gy, and for diseases of the digestive system – from 0,013 Gy to 0,014 Gy. The obtained results confirm the high stability and validity of radiation risk assessments of non-oncological diseases obtained earlier from the doses of Russian partici-pants in the liquidation of the consequences of the Chernobyl accident registered in the unified federal database of the NRER.

Thirty five years ago, the All-Union Distributed Registry of Persons Exposed to Radiation as a re-sult of the accident at the Chernobyl Nuclear power plant (Chernobyl Registry) was created. The Computing Center of the Research Institute of Medical Radiology of the USSR Academy of Sci-ences (Obninsk) became the core of the Chernobyl Registry. Their contribution to the creation of the registry was made by all former Soviet republics. Currently, the registry is called the National Radiation and Epidemiological Register (NRER), which is a state information system for personal data of Russian citizens exposed to radiation as a result of radiation accidents and incidents. The NRER is a multi-level system consisting of 85 regional segments in subjects of Russian Federa-tion and 4 departmental sub-registries. Currently, the NRER stores information about 811 thou-sand people, of which 751 thousand people represent the so-called “Chernobyl contingent”. The article presents the description of regulatory framework, organizational structure and technologi-cal approaches to the management of NRER. The article also describes the specific elements and subsystems of the registry that ensure the effective functioning of the NRER system for many years. The final part of the article presents the main results of research on the assessment of the radiological consequences of the Chernobyl disaster, obtained on the basis of the analysis of da-ta accumulated in the NRER for the period 1986-2020.

Some areas of the Russian Federation were contaminated with radionuclides released as a re-sult of the Chernobyl accident. The current paper clarifies some items of the previously published study based on NRER (National Radiation-Epidemiological Registry, the Registry) data. The pre-vious issue presented estimates of radiation risks of cancer incidence among the population of four the most contaminated regions of the Russian Federation: Bryansk, Kaluga, Oryol and Tula oblasts. Risks of thyroid cancer are estimated with account of screening effect. The cohort con-sisted of more than 327 thousand people resided in the contaminated areas. The average dose to the thyroid of children and adolescents was 0.174 Gy, the average dose to the thyroid of adults was 0.035 Gy. Thyroid cancer was diagnosed in 1549 members of the cohort during the follow-up period from 1991 over 2019, among them 423 cases were children and adolescents at the accident and 1126 cases were adults. Significant increase in thyroid cancer incidence was ob-served in adults exposed internally through the intake of iodine-131 at a young age. The statisti-cally significant radiation risk of thyroid cancer persists over 30 years after exposure. The risk de-creases with increasing the attained age. In people exposed to radiation before the age of 1 year and reaching the age of 20 years, the coefficient of excess relative risk of thyroid cancer (ERR/Gy) was 4.61. Radiation associated thyroid cancer is attributed to 20.6% of the cohort mem-bers exposed internally through the intake of radioiodine isotopes in their childhood and adoles-cence, and thyroid cancer from intake of radioiodine is attributed to 58% of cases exposed to ra-diation under 4 years of age. Marked screening effect (ES) was found during the disease diag-nosing, screening coefficient was 5.6 for children and 2.1 for adults. There were not attributed to radiation statistically significant risks of solid cancers, including radiation induced breast cancer in females, in the cohort of people resided in the areas contaminated with radionuclides. Radia-tion risk of leukemia was also not identified, although the average value of excess relative risk in men exceeded zero. Further observations of the cohort of persons resided in areas contaminated with radionuclides will increase the statistical power of radiation-epidemiological studies and clarify the assessment of radiation risks of human for chronic exposure at low doses.

In the absence of man-made sources of ionizing radiation health risks are related primarily to non-malignant diseases, particularly circulation diseases. However, risks of radiation-induced non-cancer diseases can make a notable contribution to the overall radiation-associated detri-mental effects to the human health. The impacts of harm caused by radiation induced non-cancer and cancer diseases are comparable. That is why the study of risks of non-cancer diseas-es for health of the Chernobyl cleanup workers is actual scientific problem, it is also essential for radiation protection. The aim of the study is to estimate radiation risks of incidence and mortality from non-cancer diseases identified in the Russian cohort of the Chernobyl liquidators during the follow-up period. All considered non-communicable diseases have proven diagnoses identified according to ICD-10 chapters and code sets. The data for the study are available in the system of the National Radiation Epidemiological Registry (NRER). For estimating risks of low radiation doses the linear non-threshold (LNT) model was used. For 9 of 19 disease diagnosis codes in-vestigated for statistical significance of associations between excess incidence of a disease and radiation dose received by liquidators can be considered as significant code sets. These are the following diseases: 1) Diseases of the blood and blood-forming organs and certain disorders in-volving the immune mechanism (D50-D89); 2) Diseases of the endocrine system, nutritional dis-orders and disorders of metabolism (E00-E90); 3) Mental and behavioural disorders (F00-F99); 4) Diseases of the nervous system (G00-G99); 5) Diseases of the circulatory system (I00-I99); 6) Diseases of the respiratory system (J00-J99); 7) Diseases of the digestive system (K00-K93); 8) Diseases of the musculoskeletal system and connective tissue (M00-M99); 9) Diseases of the genitourinary system (N00-N99). Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50-D89); diseases of the circulatory system (I00-I99); blood diseases (D50-D89) are characterized by the highest radiation risk coefficients (ERR/Gy). The estimates are ERR/Gy=0.55 and ERR/Gy=0.57, respectively. To date, epidemiolog-ical studies provide sufficient evidence for the existence of statistically significant radiation risks of the circulatory system diseases (I00-I99). For estimating contribution of non-cancer diseases to the overall radiation detriment further research is required.

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Эффект переноса моделей радиационного риска МКРЗ на популяцию РФГорский А.И., Чекин С

Радиационные риски российских участников ликвидации последствий аварии на Чернобыльской АЭС за период 1992-2017 гг.Часть I: заболеваемость солидными раками Иванов В.К