The paper presents results of a comprehensive radiation survey conducted in 2019 in six districts of the eastern part of the Orenburg region in 37 settlements with previously found elevated levels of activity concentration of natural radionuclides in tap water from groundwater sources of drinking water supply. The survey included measurements of indoor radon concentrations and EEC in residential and public buildings, as well as measurements of ambient dose equivalent rate of gamma radiation indoors and outdoors. The survey revealed that annual average indoor radon EEC in many residential buildings in 23 settlements and public buildings in 25 settlements exceeded the hygienic norm (action level) of 200 Bq/m3 adopted in Russia for existing buildings. The highest values of annual average indoor radon EEC were obtained in residential buildings in Novovinnitskoe (1242 Bq/m3), Bratslavka (987 Bq/m3) and Anikhovka (942 Bq/m3) in Adamovsky district, and in public buildings in Kvarkeno (2291 Bq/m3) in Kvarkensky district, Karabutak (1114 Bq/m3) and Novovinnitskoe (923 Bq/m3) in Adamovsky district. The established hygienic norms in terms of ambient dose equivalent rate indoors and outdoors were not exceeded in the surveyed settlements. Results of the survey showed that the main reason for high indoor radon concentrations in residential and public buildings in the settlements of the eastern part of the Orenburg region is not related to the usage of tap water from groundwater sources of drinking water supply with elevated levels of activity concentration of natural radionuclides.

The objective of the study is to obtain direct risk estimates of solid cancer mortality for members of the Southern Urals Populations Exposed to Radiation Cohort. Materials and methods: the cohort was first created in 2018 and combines all the residents of the Southern Urals exposed to radiation in the territory of the Techa River and East Urals Radioactive Trace. Combining individuals exposed in the two radiation accidents increased the number of cohort members to 62.5 thousand people, the number of solid cancer cases included in the analysis to 4,511 and the number of person-years at risk to 1.956 million with the maximum follow-up period up to 70 years. The analysis was conducted with the use of regression analysis and a simple parametric model for excess relative risk. Maximum likelihood method was used to calculate 95% confidence intervals. Stomach dose was taken as an analogue of the dose to soft tissues accumulated over the entire follow-up period, and calculated using the updated Dosimetry System-2016 in the Urals Research Center for Radiation Medicine. Results: the analysis revealed a statistically significant linear dependence of solid cancer mortality rates on the dose, which confirms and clarifies the conclusions of previous studies. Solid cancer mortality ERR was 0.078/100 mGy. The increase of the statistical power of the analysis due to the increase of the cohort size and extension of the follow-up period enabled to obtain statistically significant ERR values for certain population groups by sex, ethnicity and other parameters. It refines the previously obtained values, reduces uncertainty and allows using the data to refine the radiation safety standards for the population exposed to radiation in various situations.

In the modern world, such a situation has developed that the development of nuclear energy and the use of sources of ionizing radiation in various fields of activity have created a potential threat of radiation hazard to humans. In this connection, the actual direction is the study of ways to increase the radioresistance of human cells and tissues to the action of ionizing radiation. In addition, radioprotective compounds are also important in radiotherapy, since normal tissues of patients must be protected from radiation damage when using high doses of radiation in the treatment of malignant neoplasms. However, the radioprotectors currently used have some disadvantages. The aim of this work is to study the radioprotective properties of fumaric acid and 3-hydroxypyridine fumarate under the action of gamma radiation and radiation of 12C ions on tumor (SK-N-BE neuroblastoma) and normal (hTERT fibroblasts) human cells. The effect of radiation was evaluated according to the criteria of cell survival in culture, doubling time and clonogenic activity. It has been shown that the use of fumaric acid and 3-hydroxypyridine fumarate has a radioprotective effect on normal and tumor cells when they are irradiated with gamma radiation at doses of 1, 4, 6 and 10 Gy. The use of fumaric acid and 3-hydroxypyridine fumarate does not have a radioprotective effect on tumor cells when they are irradiated with 12C ions. A comparative analysis of the results of the action of the preparations with gamma rays and 12C ions showed a significant dependence of the manifestation of modifying properties on the quality of radiation. The study of cell doubling time showed that the presence of drugs in the control did not increase this indicator. On the contrary, under the action of gamma radiation at a dose of 10 Gy, the preparations reduced the doubling time of fibroblasts by more than two times and the doubling time of neuroblastoma cells by almost 1.5 times. The data obtained indicate that the antioxidant properties of the studied preparations open up new possibilities for modifying the action of ionizing radiation in the treatment of oncological diseases. The use of fumaric acid and 3-hydroxypyridine fumarate will reduce the radiation load on healthy cells, including reducing the effect of secondary products on healthy cells beyond the Bragg peak under the action of carbon ion therapy.

After the Chernobyl accident, a certain proportion of agricultural land was withdrawn from normal use due to significant radioactive contamination. Forestry is one of the options currently under consideration to return the abandoned agricultural land to economic circulation in Russia. When using former agricultural land for forestry in radioactively contaminated areas, it is important to have an assessment of the potential radiation doses for forestry workers and the public. The aim of this study was to assess the radiological situation in a young pine forest planted and grown after the Chernobyl accident in the resettlement zone on a former arable field. A nearby old pine forest, which had grown before the Chernobyl accident, was taken for comparison. The study of the radiological situation was performed in the period 1998–2022. In the young forest, ¹³⁷Cs was fairly evenly distributed in the upper 20 cm soil layer; further with depth, the activity concentration of ¹³⁷Cs sharply decreased. In the old forest, the maximum activity concentration of ¹³⁷Cs in the soil was in the top 0–2 cm layer. The activity concentration of ¹³⁷Cs decreased with depth. In 1998, the average value of the absorbed dose rate in the air from ¹³⁷Cs+134Cs was lower by a factor of 3 in the young forest compared to the old forest. The difference was associated with differences in the vertical distributions of ¹³⁷Cs in the soil. Over time, the absorbed dose rate in air from ¹³⁷Cs+134Cs decreased at both sites with the same effective halftime period of 21.7 year. The activity concentration of ¹³⁷Cs in the biota (pine trees, edible mushrooms) in the young forest was lower by a factor of 4–30 compared to the old forest. The “forest” component of the external effective dose to adults from the ¹³⁷Cs source in the young forest was lower by a factor of 3 compared to the old forest. The “forest” component of the internal effective dose from ¹³⁷Cs was lower by a factor of 10 when eating edible mushrooms from the young forest compared to the old one. In general, the performed study shows that the use of radioactively contaminated abandoned arable land for forestry can be expedient and justified from a radiological point of view.

The Russian Law “On Radiation Safety of the Population” defines the effective dose as “the amount of exposure to ionizing radiation used as a measure of the risk of long-term consequences of human’s body exposure…” In turn, the Russian “Radiation Safety Standards” (RSS 99/2009) establish a procedure for assessing the health risk, associated with exposure to low doses, for two types of harmful effects (oncological diseases and hereditary effects) and two age and sex groups (“whole population” and “adults”) by multiplying corresponding linear risk coefficients per effective dose. At the same time, these documents do not impose restrictions on the risk assessment procedure, without excluding the use of any other risk indicators or risk assessment for other sex and age groups of the population. The value of radiation detriment to health, calculated by the method described in RSS 99/2009 to characterize the risk, as a unit of measurement, uses the fatal oncological disease caused by exposure to ionizing radiation, weighted by the number of years of life lost, or weighted by the severity of non-fatal cancer. Currently, mortality-based health measures are considered insufficiently informative characteristics of the impact of external factors on population health. Such indicators are poorly suited for a comparative analysis of risks, especially taking into account the different distribution of negative consequences over time. The paper presents an applied approach to expand the application of the radiation risk assessment methodology, without making significant changes to the established practice of radiation protection. The possibility of using the DALY value (disability-adjusted life years) as an measure of radiation risk is being considered; the expediency of changing approaches to calculating the effective dose (by using different values of weighting factors for tissues and organs during effective dose calculation for different age and sex groups of the population) and the possible scope of the proposed approaches to risk assessment in practice are discussed; an approach is proposed for calculating the DALY value using the effective dose and the corresponding risk factors (DALY×Sv-1).

In recent years, an increase in the collective dose from medical exposure has been recorded annually, which is associated with an increase in the availability of high-tech methods of medical care and an increase of their percentage in the structure of X-ray studies. However, any exposure to ionizing radiation on a patient is associated with an increased risk of stochastic effects. The justification principle is the most effective to ensure the radiation safety of patients. The article considers in detail the experiment on the application of the justification principle in medical organizations. The aim of the study was to evaluate the incidence of unjustified referrals to radiological examinations and their impact on the collective effective dose of patients in outpatient medical organizations. As a result, it was ound, that the collective dose from studies with unjustified referrals contributes 21% to the annual collective dose from X-ray studies in outpatient medical organizations. The result obtained confirms the need to ensure the availability of information on clinical recommendations, the accumulated effective dose and patient characteristics in medical information systems, and proves the importance of using this information when prescribing X-ray radiological studies.

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.

The objective of the study is to obtain direct estimates of the excess relative risk of the reproductive organ cancer in women from the cohort of the Southern Urals population exposed to radiation under chronic exposure in the dose range not exceeding 1 Gy. Materials and Methods: The analytical cohort of the Southern Urals population exposed to radiation of women included 26,076 individuals with a follow-up period of 65 years (1956 to 2019) and 749,053 person-years at risk. The cancer incidence catchment area is limited to five districts of the Chelyabinsk region, the city of Chelyabinsk and the city of Ozyorsk. Over a 65 year-period 601 cases of the reproductive organ cancers have been registered in the incidence catchment area. The average cumulative dose to the uterus for women in the analytical cohort was 42 mGy; the maximum dose was 988 mGy. A regression analysis with a simple parametric model of the excess relative risk was used in the study. The significance of the results was assessed by the maximum likelihood method with 95% probability. Calculations were performed with the statistical software package “Epicure”. Results: The risk analysis revealed a statistically significant linear dependence of the excess relative risk of the cervical cancer incidence and that of all reproductive organ cancers in total on the dose accumulated in the walls of the uterus. The paper assesses the influence of modifying factors available for analysis on the magnitude of the risk. No dependence of either uterine body cancer risk on the dose to the uterus or ovary cancer risk on the dose to the ovaries was revealed. The possibility of obtaining significant risk values of the development of site-specific cancers appeared with an increase in the size of the analyzed population as a result of combining people exposed in the Southern Urals in two radiation accidents into one cohort, which increased the statistical power of the study. Assessment of the excess relative risk of the reproductive organ cancer in this cohort was carried out for the first time. This cohort has a great potential for further research to obtain direct estimates of the radiation risk of cancer and non-cancer diseases due to chronic exposure in the dose range up to 1 Gy.

The paper continues the cycle of publications addressed to the study of regularities of 137Cs content changes in agricultural products after the Chernobyl accident. The aim of the studies was to analyze the information describing changes in the ¹³⁷Cs concentrations in agricultural animal forage: hay, haylage, silage and green fodder in the southwestern districts of the Bryansk region affected by the contamination after the ChNPP accident. The data on countermeasures in the fodder production are given and the system of radiological monitoring of fodder contamination is described. It is shown that the dynamics of changes in the ¹³⁷Cs concentrations in fodder was mainly determined by the dynamics of implementation of remedial measures. The effective halflives of ¹³⁷Cs concentration in forages during the first period after the accident (1987-1990) varied from 0.57 to 2.7 years. Subsequently (1991-2021) the decrease in feed contamination slowed down and the half-lives ranged from 8.0 to 50.0 years and longer depending on the scope of remediation and the characteristics of the plants used for the animal feed production.

Interventional procedures are accompanied with high levels of patient exposure and even with the possibility of radiation skin damage. That’s why any actions leading to reduction of patients’ exposure levels are of utmost importance. Implementation of diagnostic reference levels is considered to be one of the most successful actions to reduce patient exposure levels. However the basic concept of diagnostic reference levels cannot be used for interventional radiology due to fact that procedures are not standardized. The article studies the main difficulties in applying the standard concept of diagnostic reference levels for interventional radiology procedures and proposes a new concept, taking into account the specifics of these procedures; the domestic and international documents are analyzed. The list of interventional procedures for diagnostic reference levels establishment is suggested based on the statistical data on performed procedures in the Russian Federation. The results of this study were used for the new Russian guidelines “Optimization of radiation protection of patients undergoing medical radiation diagnostic examinations through the use of diagnostic reference levels”.