The results of 40 years research of the radiobiological effects in plants and animals inhabiting areas contaminated by radionuclides as a result of the Chernobyl NPP accident have been summarized. Long-term radioecological studies under conditions of widespread and uneven radioactive contamination resulting from the largest accident in the history of nuclear power have yielded unique information about the responses of living nature at various levels of biological organization–from the molecular and cellular to the ecosystemic. Unique ecosystems, developed under chronic radiation exposure, are developing in areas contaminated by radionuclides in the absence of humans. The 30-km zone of the Chernobyl NPP has become a unique testing ground for studying, under natural conditions, the long-term ecological and biological consequences of abrupt changes in a complex of environmental factors, as well as the direction and intensity of selection.
Four decades after the Chernobyl accident, more than 1,500 settlements remain radioactively contaminated (with Cs-137 levels exceeding 37 kBq/m2), 72 of which have average annual exposures doses exceeding 1 mSv. This article examines the current challenges of returning settlements with elevated radiation levels to normal living conditions and explores possible solutions. It is shown that all settlements with average annual exposure doses exceeding 1 mSv (the city of Novozybkov and 71 rural settlements with a total population of 63,900) are located in five southwestern districts of the Bryansk region. The most critical dose-forming areas (population 26,000) are rural settlements, where up to 80% of local milk, beef, and wild mushroom samples currently fail to meet SanPiN requirements for Cs-137 content. In these settlements, the contribution of 137Cs-contaminated milk from the private sector to the internal exposure dose of residents averages approximately 60%, mushrooms 20%, and potatoes and meat 10% each. The deterioration of the demographic situation and age structure of the population in recent decades, as well as changes in the diet of rural residents in the southwestern Bryansk region, must be taken into account when assessing internal exposure doses and their relationship with external radiation exposure. To reduce the exposure doses of residents of 71 rural settlements to below 1 mSv/year, a targeted rehabilitation strategy has been justified, incorporating the most effective technologies for reducing internal and external exposure of the population. An assessment of the radiological effectiveness of rehabilitation was conducted using GIS to support decision-making based on the costs of implementing technologies and stakeholder attitudes toward them. In addition to the radiation factor, the need to improve the demographic situation and develop the social infrastructure of populated areas to restore them to normal living conditions was noted.
When protecting and managing populations exposed to ionizing radiation, special attention is paid to the problem of proving hereditary risks of radiation-induced morbidity in humans. The study of the morbidity of the descendants of the first generation of participants in the consequences of the Chernobyl accident was carried out using data accumulated in the National Radiological and Epidemiological Registry over 38 years of observation of a cohort consisting of 15,450 descendants. The previous analysis of data on the health status of participants in the offspring cohort was conducted five years ago. Parametric modeling of morbidity did not reveal an association between the radiation dose of fathers and the prevalence of congenital diseases of their offspring. The age of the father at the time of conception was a statistically significant factor – the congenital morbidity was higher in offspring whose fathers were over 30 years old. The age of the father, his exposure, and the time elapsed from the father's exposure to the birth of the child did not affect the cancer incidence of the offspring. For most classes of non-cancerous diseases, no statistically significant dependence on the dose of the father's radiation was found, but a relationship with age and time elapsed after irradiation was revealed. At the end of the study, the cohort members were under 40 years old. Continued monitoring of their health status may lead to stable estimates of radiation risk for individual diseases.
In accordance with the provisions of Federal Law No. 329-FZ dated December 30, 2012, one of the main tasks of the National Radiation and Epidemiological Registry (NRER) state information system is to predict the medical radiological consequences of the Chernobyl accident, including long-term consequences. The purpose of this study is to assess the degree of conservativeness of the radiation risk models identified in the NRER studies for the Russian cohort of liquidators, compared with the models recommended by the ICRP, the UNSCEAR and the American-Japanese Radiation Effects Research Foundation (RERF) for solving radiation protection problems at the global level. A comparative analysis of the projected mortality radiation risks calculated using the NRER models and reputable international organizations has shown that conservative (highest) estimates of lifetime mortality radiation risks from solid malignant neoplasms, diseases of the circulatory system and respiratory diseases are provided by NRER models, and for mortality radiation risks from leukemia (excluding cases of chronic lymphocytic leukemia) – UNSCEAR models. The conservative estimate of the lifetime radiation risk of mortality from solid malignant neoplasms in the cohort of liquidators (according to the NRER model) is 1.7 times higher than the estimate obtained for the same cohort using the nominal radiation risk of mortality of the ICRP. For mortality from leukemia, the conservative estimate of lifetime radiation risk (according to the UNSCEAR model) is 1.4 times higher than the estimate obtained using the corresponding nominal risk coefficient of the ICRP. Further research from the point of view of application to the tasks of radiation protection in emergency situations requires a lifetime radiation risk of mortality from non-oncological diseases, which is 2.3 times higher than the corresponding risk for malignant neoplasms. Thus, for the Russian cohort of liquidators, the nominal coefficients of radiation mortality risks of the ICRP, laid down in the foundations of radiation safety standards, significantly underestimate the severity of the long-term radiological consequences of the Chernobyl accident.
As a result of the accident at the Chernobyl nuclear power plant on April 26, 1986, part of the territory of the Russian Federation was contaminated with radionuclides. In the first months after the accident, iodine radioisotopes generated doses of internal radiation to the thyroid of the population, which averaged about 0.1 Gy, but reached 4.5 Gy among children under 5 years of age. The total body radiation doses accumulated by residents of areas contaminated with cesium radioisotopes averaged 0.03 Sv, and for 98% of the population did not exceed 0.2 Sv. The assessment of radiation risks of the population of contaminated territories is of high scientific relevance due to the significant share of internal exposure in the formation of radiation doses and great practical importance due to the large number of this population. This work is an update of the radiation risk assessments of the population of the four most contaminated regions of Russia (Bryansk, Kaluga, Orel and Tula oblasts), conducted by the National Radiation Epidemiological Registry until 2019. Among the 311 thousand residents the average thyroid dose in children and adolescents was 0.171 Gy and 0.038 Gy in adults. During the follow-up period from 1991 to 2024, 1,790 cases of thyroid cancer were detected in the cohort: 542 cases among children and adolescents under the age of 18 at the date of the accident and 1,248 among adults. For the age of 20, the statistically significant coefficient of excess relative risk is ERR/Gr=4.49 and decreases with increasing age. As of the date of the accident, 43.4% of cases of thyroid cancer were radiation-induced among children and adolescents, and 59% of cases of thyroid cancer were radiation-induced for children under 5 years of age. The screening rate during the registration of thyroid cancer diseases was 5.8 for children and adolescents and 3.0 for adults. Statistically significant radiation risks for solid malignant neoplasms, including breast cancer in women, as well as for leukemia among the adult population of the most radionuclide-contaminated areas have not yet been identified. Further observations of a cohort of people living or who have lived in radionuclide-contaminated territories of the Russian Federation will increase the statistical power of radiation and epidemiological studies and clarify estimates of human radiation risks with prolonged exposure in low doses.
