This article presents results of internal radiation dose assessments for the population based on radiation and hygienic surveys of settlements in the Bryansk region bordering the Republic of Belarus in 2019–2022.

   The objective of the study was to perform dose assessments with various models and to determine model parameters to updating. Materials and

   Methods: Calculations were performed for different age groups of the population of the surveyed settlements in the Bryansk region, as well as for critical groups, in accordance with current methodological documents. The results of comprehensive radiation and hygienic survey of settlements and radiation monitoring data were used for dose assessments.

   Results and Discussion: The greatest deviations from the model for ¹³⁷Cs intake with food products (covering the majority of local food products and their consumption by the population) were obtained for the model which parameters are the coefficients of radionuclide transfer from soil to food products (milk and mushrooms) for the adult population living in areas with high levels of soil contamination (more than 555 kBq/m² by ¹³⁷Cs). At the same time, for the population of other areas (the majority of the surveyed settlements), the convergence of the dose assessment results is satisfactory.

   Conclusion: The average annual effective doses of internal exposure to the population of the surveyed settlements do not exceed 1 mSv, and the internal doses to the critical groups do not exceed 5 mSv. Food products of wild origin make a greater contribution to the internal radiation dose than local agricultural food products. The methodology for dose assessment to the population of the Chernobyl territories has proven its stability in basic approaches. Modification of several model parameters has allowed to improve calculation results.

   Although several radioprotectors have been developed, their clinical use remains limited due to toxicity, a narrow therapeutic window, and reduced efficacy when administered post irradiation. Consequently, there is a pressing need to develop novel radioprotective agents with improved safety and effectiveness.

   The aim of this study was to evaluate the radioprotective efficacy of water-soluble sodium salt n-acetylcysteine (NAC).

   Materials and Methods: The study was conducted on 252 male Wistar rats to determine the radioprotective dose of sodium n-acetylcysteine, assess the effectiveness of its prophylactic administration prior to gamma irradiation, and analyze the dynamics of hematological parameters in peripheral blood. The drug was administered intraperitoneally 1 or 3 hours before irradiation, or 1 hour after exposure. Irradiation was performed using an IGUR-1 device at a dose of 7.0 Gy (LD 95–100/30 ). The working solution of sodium n-acetylcysteine (300 mg/mL, pH 7.5) was prepared ex tempore by dissolving 3 g of the dry substance in 3 mL of distilled water, followed by the addition of 3.5 mL of 5N NaOH and titration to the required pH.

   Results and Discussion: Intraperitoneal administration of sodium n-acetylcysteine at a dose of 2500 mg/kg contributed to partial preservation of hematopoiesis in animals exposed to 7.0 Gy (LD 95–100/30 ), promoted maintenance of the hematopoietic cell pool, and accelerated the recovery process. Evaluation of the specific radioprotective activity showed that administration at a dose of 2000 mg/kg provided 42 % survival in animals exposed to a lethal radiation dose.

   Conclusion: The findings in rats demonstrate the rationale for further investigation of the pharmacodynamic properties of sodium n-acetylcysteine, highlighting its significant potential as a radioprotective agent.

   Chronic radiation exposure can induce persistent epigenetic changes that affect the mechanisms of cell death and the development of long-term biological effects. The role of methylation of redox system genes in the regulation of apoptosis and necrosis of lymphocytes in chronically exposed individuals remains insufficiently studied.

   The aim of the study is to assess the association of promoter region methylation and transcriptional activity of redox system genes with the intensity of apoptosis and necrosis of peripheral blood lymphocytes in chronically exposed individuals.

   Materials and Methods: The study included 171 individuals: 99 persons exposed to chronic low-intensity radiation and 72 individuals from the comparison group who lived under similar social and living conditions. Apoptosis and necrosis of peripheral blood lymphocytes were assessed by flow cytometry. Molecular analysis included assessment of CpG dinucleotide methylation in the promoter regions of redox system genes and determination of their transcriptional activity.

   Results and Discussion: The level of lymphocyte necrosis was statistically significantly higher in the group of chronically exposed individuals compared with the comparison group (p = 0.033). Necrosis positively correlated with radiation doses to red bone marrow (ρ = 0.24; p = 0.001), thymus and peripheral lymphoid organs (ρ = 0.19; p = 0.013). Analysis of apoptosis revealed statistically significant positive correlations with methylation levels of SOD2 (ρ = 0.18; p = 0.017), GPX1 (ρ = 0.26; p = 0.001), GSTP1 (ρ = 0.22; p = 0.004), MPO (ρ = 0.41; p < 0.0001), and CAT (ρ = 0.21; p = 0.006). According to multiple regression analysis, apoptosis was associated with GSTP1 and MPO methylation.

   Conclusion: Thus, in chronically exposed individuals in the long-term period after exposure, necrotic lymphocyte death is predominantly associated with radiation dose, whereas apoptosis is associated with hypermethylation of promoter regions of redox system genes.

   The gold standard for early diagnosis of malignant breast neoplasms is mammography (X-ray examination of the breast) performed using digital and analogue X-ray units. This procedure is routinely conducted for all women aged 40 to 75 years on a regular basis (once every one or two years); mammography of both breasts is performed in two projections (four X-ray images). Doses from mammography, in accordance with the Norms of the Radiation Safety NRB 99/2009, shall not exceed 1 mSv per year. Hence, reliable assessment of patient doses for this procedure is important.

   The aim of this study was to evaluate the patient doses from mammographic procedures in medical facilities in St. Petersburg and the Leningrad Region.

   Materials and Methods: Data collection was performed at 99 medical facilities in St. Petersburg and the Leningrad Region for 141 digital mammography units during the period 2023–2025. For each mammography unit, mean glandular dose and effective dose was assessed for various compressed breast thicknesses (2, 4, 6, 8, and 10 cm) and projections (craniocaudal and mediolateral oblique), in accordance with the methodological guidelines MU 2.6.1.2944-11.

   Results and Discussion: The mean effective doses per single mammographic image in either the craniocaudal or mediolateral oblique projection varied from 0.05 to 0.07 mSv; effective doses per complete mammographic examination (two craniocaudal and two mediolateral oblique images) varied from 0.2 to 0.3 mSv. At the same time, substantial differences in patient dose ranges were observed: the ratio between the minimum and maximum mean glandular dose and effective dose reached up by the factor of 60, respectively. The primary factors determining patient exposure doses were the exposure and the X-ray tube output. No significant correlation was found between patient doses and tube voltage, focal-image distance, or the anode/filter combination. Compressed breast thickness also did not significantly influence the effective dose.

   Conclusion: Although the mean patient exposure levels during digital mammography are acceptable and comparable with international practice, patient doses for several mammography units are anomalously high. For such units, the implementation of patient radiation protection optimization measures is a priority.

   Cancer is one of the major late effects of exposure to ionizing radiation. Low dose effect has been still remains one of the most challenging issues.

   The objective of the study is to analyze the dose dependence of the risk of upper gastrointestinal cancer mortality in members of the Southern Urals Population Exposed to Radiation Cohort over the period from 1950 to 2020.

   Materials and Methods: Southern Urals Population Exposed to Radiation Cohort includes people aggrieved as a result of two radiation accidents in the Southern Urals. Follow up period is 71 years, cohort size at the end of the follow up is 62,259 individuals, number of person-years at risk – 1964,136. In total 1,587 upper gastrointestinal cancers have been revealed, 844 of them were found in men, and 743 – in women. Dose to the stomach was used as the reference one. Maximum dose over the whole follow up period made up 1.13 Gy, mean dose – 0.04 Gy. Statistical analysis has been performed with the Epicure software package using the Poisson regression with simple parametric model of the excess relative risk. Maximum likelihood method with 95 % probability was applied to evaluate the statistical significance of the results.

   Results and Discussion: The analysis of the mortality risk of all the upper gastrointestinal cancers revealed linear dose relationship which started to be observed already with 2-year minimum latency period: ERR 0.76/Gy, р = 0.03. Dose dependence of the mortality from oral cavity cancer was also linear with 2-year minimum latency period, ERR/Gy was 4.95, p = 0.01. The risk of the development of upper gastrointestinal cancers did not exhibit statistically significant dependence on dose to the stomach. The effect of modifying factors per unit of radiogenic risk has also been evaluated.

   Conclusion: Based on the results of the study, a statistically significant excess relative mortality risk of all cancers of the upper gastrointestinal and oral cavity has been obtained.

   The relevance of the study is driven by the active development of the shipbuilding industry in Russia, including enterprises of atomic shipbuilding and ship repair, where radioactive waste is generated.

   The increase in work volumes with radioactive waste raises the risk of increased radiation doses to personnel, necessitating a comprehensive assessment of the radiation environment and improvement of the radiation control system.

   The aim of this work is to assess the radiation environment at personnel workplaces during radioactive waste handling and to identify priority directions for improving the radiation control system.

   Materials and Methods: The assessment of the radiation environment was performed based on the enterprise's production control materials and field study data. Parameter measurements were conducted using certified measurement methodologies. All measuring instruments underwent timely metrological verification.

   Results and Discussion: Results showed that the main radiation factors affecting personnel working conditions are external gamma radiation and radioactive contamination of work surfaces by beta-emitting radionuclides (both fixed and removable). An uneven distribution of dose load on the body was identified during different stages of radioactive waste handling. At the workplaces involved in processing liquid and solid radioactive waste, gamma radiation levels exceed those at other workplaces. However, the average individual radiation doses of personnel do not exceed dose limits and tend to decrease both within specific personnel categories and across the enterprise as a whole.

   Conclusion: The conclusion confirms the effectiveness of current radiation safety measures and identifies priority directions for improving the radiation control system at the enterprise.

   Despite international recommendations, some medical organizations continue the practice of using protective aprons, including for children. Existing calculation methods do not allow for the assessment of absorbed doses when using an apron, which makes direct dosimetric research relevant.

   Materials and Methods: The study was performed using a phantom of a 5-year-old child with thermoluminescent detectors. Chest scanning was conducted on a Somatom Force tomograph (Siemens, Germany, manufactured in 2022) with three apron use options: without an apron; with an apron wrapped around the phantom; and with an apron used as a blanket. Two scanning parameter sets were used: 1) fixed voltage of 70 kV with tube current modulation; 2) fully automatic mode.

   Results and Discussion: Wrapping the apron resulted in both dose reduction in some radiosensitive organs and dose increase in others by a factor of 3–8. Using the apron as a blanket led to a substantial dose increase for the majority of radiosensitive organs and tissues, including organs fully or partially covered by the apron (3–15 times). In organs partially covered by the apron, dose changes depending on the PPE use case were most pronounced: in automatic scanning modes, when using the apron wrapped around the phantom, doses in these organs increased by a factor of 1.1–4.2 compared to doses in the same organs without protective apron; when using the apron as a blanket, doses in organs partially covered by the apron increased by a factor of 4.5–8.5.

   Conclusion: The use of an apron during computed tomography reduces doses in some organs but is accompanied by a significant (up to 15 times or more) increase in doses in others, especially in automatic modes.

   Osteogenic and hematopoietic stem cells can be exposed to radiation during cancer radiotherapy with radiopharmaceuticals due to adsorption of radionuclides into bones. Calculation of doses to normal radiosensitive cells is important for assessing the benefit/harm ratio. Therefore, the creation of a dosimetric model of bone and bone marrow, which takes into account the microdistribution of radionuclides and target cells, is an important task.

   Objective: an analytical review of the current state of knowledge about the
histomorphometric characteristics of the trabecular bone and adjacent areas of the bone marrow in order to create an anatomical and morphological basis for constructing a microdosimetric model for calculating doses to hematopoietic stem cells and osteoblasts.

   Materials and Methods: A search was conducted for published data on the structure and mineralization of bone tissue in the trabecular bone, the cellular composition of the bone marrow, the morphology and location of cells in its volume relative to the bone surface.

   Results and Discussion: Currently, the morphophysiological features of bone mineralization and the size of the corresponding structures are well studied. The surface of the trabeculae is covered with a layer of unmineralized bone matrix 1-5 microns thick, which is capable of rapidly adsorbing radionuclides. An adjacent layer of osteoblasts is about 1 micrometer thick. Data on the distribution of stem cells in the bone marrow volume is very limited. It is known that most of the stem cells are located within 200 micrometers from the surface of the trabeculae. The cell size is about 6-7 micrometers.

   Conclusion: Based on the existing knowledge about the structure of bone and the distribution of osteogenic and hematopoietic stem cells in the bone marrow, it is planned to create a model consisting of the number of layers, including a source layer and target layers, describing osteogenic cells and hematopoietic stem cells at different distances from the bone.

   People and the environment must be protected from radiation risks now and in the future.

   In this regard, the aim of this work was to summarize the existing data on the tailings of the uranium industry in Tajikistan and to develop scientifically grounded radiation-hygienic approaches to the management of low-level radioactive waste.

   The objective of the research was to analyze the formation of radioactive tailings in the territory of Tajikistan.

   Materials and Methods: The information base of the research was the results of previously conducted scientific works. The main characteristics of tailings storage facilities, as well as their radiation impact on the environment, have been examined.

   Particular attention is given to the issues of categorization and passportization of radioactive waste.

   Radiation monitoring was carried out using modern measuring instruments and equipment manufactured in the Russian Federation (“Doza”), the Republic of Belarus (“Atomtech”), the USA (“Canberra”), and Germany (“Thermo”).

   Results and Discussion: Existing radioecological risks in the areas where unsealed tailings pond is located have been identified. The radiation and hygiene requirements for ensuring the radiation safety of industrial waste have been considered. It is noted that the reclamation work carried out at the facilities in the of Istiklol city has significant practical importance, as it ensured the reduction of the radiation background to the normative level (0.3 µSv/h), decreased the anthropogenic load on the environment, and increased the ecological safety of the population.

   Conclusion: Promising directions include the continuation of reclamation of problematic areas, including the tailings pond of shop No. 3 of the former hydrometallurgical plant, the implementation of the Digmay tailings restoration project with the dismantling of contaminated infrastructure, the adoption of measures to ensure the safety of the Adrasman tailings pond, as well as the introduction of a state program for the safe management of uranium legacy with a long-term radioecological monitoring system. The comprehensive implementation of the aforementioned measures will ensure further reduction of radiation and environmental risks, create a foundation for the safe and sustainable development of the area, and also enable its safe future use.

   In recent years, several methodological documents have been approved and a number of scientific articles have been published concerning the assessment of radiation risks associated with medical exposure. Risk assessment is performed using various quantitative and qualitative risk indicators; however, the issue of their correct application, taking into account the specifics of a particular exposure scenario for solving applied problems in risk management, often remains unresolved.

   The aim of this study is to develop a framework and to substantiate a method for selecting and applying radiation risk indicators associated with diagnostic medical X-ray and radiological procedures, depending on the purpose of risk assessment, the type and parameters of the procedure, patient sex and age, and other factors.

   Materials and Methods: An analysis of radiation risk indicators was carried out based on a literature review, comparative analysis of definitions, and calculation methods.

   Results and Discussion: The main radiation risk indicators and their scope of application were analyzed; a list of indicators recommended for solving applied problems in medical diagnostic exposure was substantiated; a qualitative risk level scale and a scheme for selecting indicators are proposed.

   Conclusion: The developed approach allows for the alignment of the choice of risk indicator with the assessment purpose, target audience, dose burden, and availability of initial data.

   The problem of insufficient awareness among healthcare workers about the effects of ionizing radiation and radiation protection methods remains relevant worldwide, as knowledge deficits may lead to unjustified referrals for procedures, increased radiation risks for patients, and heightened anxiety.

   The aim of this study was a comparative analysis of the level of awareness among medical students and practicing physicians regarding the effects of ionizing radiation on human health and the principles of radiation protection, based on data from national and international publications.

   Materials and Methods: A systematic review and qualitative analysis of data from sociological surveys and scientific articles published between 2009 and 2024 in Russia, Poland, Norway, India, Pakistan, Ireland, Romania, Japan, Australia, and New Zealand was conducted; a total of 33 sources were analyzed.

   Results and Ddiscussion: Medical students and physicians in most countries demonstrate fragmented knowledge of dosimetry, biological effects of radiation, and protection methods, while targeted additional training significantly improves the level of awareness and reduces anxiety, whereas length of service alone does not constitute a factor in improving knowledge.

   Conclusion: The practical significance of the work lies in substantiating the need to introduce specialized courses into the core educational programs of medical universities and to organize systematic postgraduate training on radiation safety; a promising direction is the development of differentiated educational approaches for various categories of medical personnel.

   A special role among natural radionuclides is occupied by radon and its short-lived daughter decay products, which form from 50 to 90 % of the total radiation dose of the population. A danger to a person is represented by closed poorly ventilated rooms in which radon can accumulate in excess of the established hygienic standard. One of the factors for the accumulation of radon in buildings and structures is its emanation from rocks and subsoil. The method of measuring the radon flux density from the subsoil surface is used to assess the potential radon hazard of the land plot intended for the construction of buildings and structures.

   The purpose of the study is radiation and environmental assessment of the potential radon hazard of the territory of Tyumen and its surroundings.

   Materials and Methods: The studies were carried out from May to August 2025; the area covered was 697 km². The measurement of the radon flux density from the soil surface was performed using the AlphaRad Plus-R radiometer (Russia) at 513 control points. At the same time, meteorological parameters (air temperature and humidity, atmospheric pressure) were measured at the measurement sites; the physical properties of the soil (temperature, density, and field moisture) were also measured. The mapping data was created using the QGIS geoinformation system.

   Results and Discussion: The radon flux density from the soil surface ranges from 20 to 730 mBq/(s·m²). An increase in temperature and a decrease in air humidity intensify the natural erosion of the upper layers, causing cracks and changes in density, resulting in higher radon flux densities from the soil surface in these areas.

   Conclusion: The identified boundaries of anomalies with high values of radon flux density from the soil surface can be used: 1) in urban planning during the construction, repair, and reconstruction of buildings and structures in order to ensure radiation safety of the population; 2) in the field of engineering surveys and environmental monitoring by executive authorities and private firms.

   The paper presents some methodological approaches to the organization of radiation survey and radiation control at oil and gas industry enterprises in order to ensure the radiation safety of workers exposed to natural sources of ionizing radiation.

   Summary. The paper highlights the issue of the lack of guidelines defining the procedure for organizing and conducting radiation survey and radiation control at enterprises in non-nuclear industries where exposure of workers to natural sources of ionizing radiation in industrial conditions is possible. The analysis of radiation sources affecting workers during the extraction, transportation and processing of oil and gas has shown that the main reason for increased levels of exposure in this industry is the generation of industrial waste with elevated concentration of natural radionuclides. It is noted that the mechanisms of waste generation in the oil industry and the gas industry are of a different nature. Based on practical experience, an approach to setting action levels in terms of removable radioactive alpha and beta contamination of technological equipment, ensuring that the established dose limit of 5 mSv/year is not exceeded given single-factor exposure situation, have been proposed for the first time. Several types of measurements are recommended to assess the doses of exposure to workers in the oil industry (gamma dose rate in the workplaces, radon concentration during certain types of operations, activity concentration of natural radionuclides in dust in the presence of dusting processes) and the gas industry (level of removable radioactive contamination with alpha and beta emitting natural radionuclides of the dismantled equipment, gross beta activity concentration in the air of the working area during equipment cleaning from accumulated sediment).

   Conclusion. The recommendations presented in the paper will be taken into account when developing guidelines for the organization and conduct of radiation survey and radiation control at enterprises in non-nuclear industries where workers are exposed to natural sources of ionizing radiation in industrial conditions. The applying of the guidelines in practice should become the practical basis for implementation of the requirements for ensuring the radiation safety of workers in the oil and gas industry of the Russian Federation.

   The contribution of medical exposure to the collective effective dose is increasing both in the Russian Federation and in the Rostov Region, as confirmed by the results of the annual radiation-hygienic passportization.

   The objective of this study is to analyze the structure of X-ray procedures and the collective dose from medical exposure in the Rostov Region in 2019-2024 period. Materials and

   Methods: The radiation-hygienic passports of medical facilities for the period 2019–2024 have been analyzed, along with the forms of federal state statistical reporting No. 3-DOZ and No. 30.

   Results and Discussion: The analysis indicated that there were 621 medical facilities with medical sources of ionizing radiation in the Rostov Region, with private medical clinics accounting for 71 %. In 2024 there were 1,904 X-ray units, representing an increase of 23.32 % relative to the 2019 level (1,544 X-ray units). Radiographic and fluorographic procedures constituted the primary contribution to the structure of X-ray diagnostics: 63 % and 27 %, respectively. The contribution of computed tomography to the structure of X-ray diagnostics increased from 4.38 % in 2019 to 9.91 % in 2024. Over the same period, the collective dose from medical exposure doubled, rising from 2,067.22 man - Sv to 4,296.05 man -Sv, predominantly due to computed tomography its contribution changed from 55.91 % in 2019 to 63.11 % in 2024. The maximum contribution of computed tomography to the collective dose structure (70 %) was observed in 2020, during the COVID-19 pandemic.

   Conclusion: The increasing number of X-ray procedures and the use of modern high-dose imaging modalities will undoubtedly influence the dynamics of change in the contribution of diagnostic medical exposure to the collective dose from all major sources of ionizing radiation.

   The prolonged discharge of tritium-containing water from the Fukushima Daiichi Nuclear Power Plant into the Pacific Ocean leads to the gradual transport of tritium into Russian fishing zones and its accumulation in marine products. Tritium is incorporated into organic compounds, including seafood. Upon consumption of these seafood products, dose coefficients for organically bound tritium forms exceed those for tritiated water forms. Monitoring of organically bound tritium constitutes a critical component of radiological surveillance and the assessment of internal exposure doses.

   The purpose of this communication is to summarize current approaches to determining organically bound tritium in environmental media and biological tissues.

   Based on an analysis of scientific publications, this communication provides brief information on established and currently used methods for preparing counting samples to measure the content of organic tritium compounds in environmental media and biological tissues.

   Conclusion: Modern methods for determining organically bound tritium provide reliable data but are complex and require standardization. Promising directions for determining organically bound tritium content include improving sample preparation, enhancing the efficiency of converting organically bound tritium into a measurable form, implementing more sensitive analytical methods, and developing a metrological assurance system.