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Background Epidemiologic studies of radiation-exposed populations form the basis for human safety standards. They also help shape public health policy and evidence-based health practices by identifying and quantifying health risks of exposure in defined populations. For more than a century, epidemiologists have studied the consequences of radiation exposures, yet the health effects of low levels delivered at a low-dose rate remain equivocal. Materials and methods The Million Person Study (MPS) of U.S. Radiation Workers and Veterans was designed to examine health effects following chronic exposures in contrast with brief exposures as experienced by the Japanese atomic bomb survivors. Radiation associations for rare cancers, intakes of radionuclides, and differences between men and women are being evaluated, as well as noncancers such as cardiovascular disease and conditions such as dementia and cognitive function. The first international symposium, held November 6, 2020, provided a broad overview of the MPS. Representatives from four U.S. government agencies addressed the importance of this research for their respective missions: U.S. Department of Energy (DOE), the Centers for Disease Control and Prevention (CDC), the U.S. Department of Defense (DOD), and the National Aeronautical Space Agency (NASA). The major components of the MPS were discussed and recent findings summarized. The importance of radiation dosimetry, an essential feature of each MPS investigation, was emphasized. Results The seven components of the MPS are DOE workers, nuclear weapons test participants, nuclear power plant workers, industrial radiographers, medical radiation workers, nuclear submariners, other U.S. Navy personnel, and radium dial painters. The MPS cohorts include tens of thousands of workers with elevated intakes of alpha particle emitters for which organ-specific doses are determined. Findings to date for chronic radiation exposure suggest that leukemia risk is lower than after acute exposure; lung cancer risk is much lower and there is little difference in risks between men and women; an increase in ischemic heart disease is yet to be seen; esophageal cancer is frequently elevated but not myelodysplastic syndrome; and Parkinson's disease may be associated with radiation exposure. Conclusions The MPS has provided provocative insights into the possible range of health effects following low-level chronic radiation exposure. When the 34 MPS cohorts are completed and combined, a powerful evaluation of radiation-effects will be possible. This final article in the MPS special issue summarizes the findings to date and the possibilities for the future. A National Center for Radiation Epidemiology and Biology is envisioned.

Introduction. The use of ionizing radiation as a production factor in the late 1940s - early 1950s. began in the absence of a clear understanding of the permissible radiation doses for workers, as well as knowledge of diagnostic criteria and developed therapeutic measures for developing chronic radiation sickness (CRS). Since then, a great deal of experience has been accumulated in the diagnosis and treatment of CRS. Currently, there are no conditions at the workplace for chronic exposure of workers in doses exceeding the permissible ones. However, taking into account the constant expansion of the scope of using sources of ionizing radiation, it is necessary to remember about the possibility of CRS development due to prolonged exposure in case of violation of their storage or their loss. The study aimed to explore the formation of radiation bone marrow syndrome (RBS) due to chronic exposure in doses that exceed the maximum permissible, accumulated with different dose rates of radiation. Material and methods. We selected the medical records of 27 people (24 men and 3 women) who had RBS as a result of chronic professional gamma radiation exposure. The selection criteria were the diagnosis of grade II-III chronic radiation syndrome (CRS) in the presence of agranulocytosis or anemic syndrome in the period of the disease formation and, especially, in the development of myelodysplastic syndrome (MDS) or aplastic anemia in the period of the CRS consequences. Identified clinical and dosimetric CRS features of 27 patients exposed to chronic irradiation with a dose rate of 0.0002-0,009 Gy/h and the summary dose of 1.7 and 9.6 Gy, accumulated over a period of 6 to 96 months were compared the characteristics of 84 patients CRS exposed a lower dose rates (less than 0,0003 Gy/h) and 26 patients with acute radiation syndrome moderate (II) severity as a result of irradiation the dose rates of 0.14-3,7 Gy/h, total dose of 2 to 4 Gy. Results. The criteria of atypical subacute CRS course are identified: the rate of chronic radiation exposure - not less than 0.001-0.009 Gy/h with a summary dose of 1.7-9.6 Gy accumulated over a period of 6-96 months, the presence of agranulocytosis in the period of CRS formation and anemic syndrome in the periods of CRS formation and outcomes. These signs predict the development MDS in 60% of the patients in the period of the CRS consequences. Conclusion. Retrospective study determined that long-term human exposure to a dose rate of 0.001-0,009 Gy/h (0,005-0,05 Gy/day) and more in the accumulation of a summary dose of 1.7 and 9.6 Gy and duration of contact 6-96 months in 60% of cases can be expected development CRS with a subacute clinical course RBS. The main factor determining this feature of the course of RBS is the dose rate exceeding 0.001 Gy / h (2 Gy/year). In the subacute course of CRS, the early outcome in MDS is essentially deterministic. The development of agranulocytosis and anemic syndrome are typical signs of the subacute course of CRS.

The purpose of the study is to compare the excess relative risk (ERR per 1 Sv) of solid cancer mortality in acute - catastrophic or emergency, and occupational - fractionated or chronic exposure. Materials and research methods. A maintained database (database of sources) on nuclear workers from about 40 countries, on the basis of it a combined data analysis was carried out to determine the integral ERR value per 1 Gy for cancer mortality for comparison with parameters of cohorts exposed to catastrophic and emergency exposure: the LSS cohort victims of the atomic bombings in Japan, residents of the Techa River (radioactive contamination due to emissions from the Mayak plant) and Russian liquidators of the Chernobyl accident. Results. Comparison of the ERR per 1 Sv for cancer mortality for workers in the global nuclear industry (combining analysis of data from 37 studies) with the parameters of the LSS cohort, residents on the Techa River and liquidators of the Chernobyl accident showed the absence of logical and principial differences, and the risks for the last two cohorts were the highest. Although the data obtained partly confirm the approach of recent years by the United Nations Scientific Committee on the Effects of Atomic Radiation, according to which the carcinogenic effects of acute, accidental, and fractionated or chronic radiation exposure do not depend on the dose rate factor (DDREF), nevertheless, taking into account biological mechanisms and data radiobiological experiments, this issue cannot be considered unambiguously resolved. Conclusion. Based on the ERR per 1 Sv, the average external dose, and the annual background cancer mortality in Russia and the United States, the expected increase in cancer mortality for 100,000 nuclear workers will average 32-69 people over 10 years (0.032-0.069% of the group). Such risks, due to the many carcinogenic non-radiation factors of life and work, as well as fluctuations in the background value, cannot be taken into account in the practice of medicine and health care.

Objectives: To determine the influence of prolonged exposure to radiation based on dosimeter readings on hematological parameters among radiologic technologists (RTs) in Saudi Arabia. Methods: The study was specifically conducted on selected RTs with experience of more than 10 years and the highest thermoluminescent dosimeter (TLD) readings among all RTs in the Radiological Department, Sabya General Hospital, Ministry of Health, Saudi Arabia from August to October 2020. The RTs group was compared with a control group of non-irradiated participants. Blood samples were collected for hematological and coagulation profile evaluation. Results: The acquired radiation dose analysis revealed that the average accumulated dose in 10 years is 7.6 mSv. The medians of prothrombin time (PT) and activated partial thromboplastin time (APTT) of the RTs group were significantly lower when compared to the control group. In addition, RTs group exhibited a significant reduction in neutrophil count and an elevation in lymphocyte count. Conclusion: Chronic exposure to radiation revealed a significant change in blood tests and may reflect an effect on RTs tissues, leading to serious health problems. However, further investigation in a large cohort to study the association between alteration in hematological parameters and chronic radiation exposure is required.

BACKGROUND Radiation exposure is known to increase the risk of chronic inflammatory diseases, such as atherosclerosis, by modulating inflammation. METHODS To investigate the infiltration of leukocytes in radiation-aggravated atherosclerosis, we examined low-density lipoprotein receptor-deficient (Ldlr-/-) mice and C57BL/6j mice after exposure to 0.5 or 1 Gy radiation over 16 weeks. RESULTS We found that radiation exposure induced atherosclerosis development in Ldlr-/- mice, as demonstrated by increased lipid-laden plaque size, reactive oxygen species levels, and levels of the pro-inflammatory cytokines, IL-1β and TNF-α, in the aortas and spleens. Total plasma cholesterol, triglyceride, and LDL cholesterol levels were also increased by radiation exposure, along with cardiovascular risk. We also showed dose-dependent increases in neutrophils and monocytes that coincided with a reduction in lymphocytes in the spleens of Ldlr-/- mice. The correlation between the infiltration of leukocytes and cytokine production was also confirmed in the hearts and spleens of these mice. CONCLUSIONS We concluded that chronic radiation exposure increased the production of pro-inflammatory mediators, which was associated with the migration of neutrophils and inflammatory monocytes into sites of atherosclerosis. Thus, our data suggest that the accumulation of neutrophils and inflammatory monocytes, together with the reduction of lymphocytes, contribute to aggravated atherosclerosis in Ldlr-/- mice under prolonged exposure to radiation.

Persons exposed to ionizing radiation in utero and in early childhood constitute a risk group for the development of long-term stochastic consequences of irradiation. The imbalance of cytokines at the long terms after irradiation could be considered a carcinogenic triggering factor in subjects previously irradiated in utero and in early childhood, thus determining relevance of the study. The aim of the present study was to assess the levels of serum cytokines in native residents of coastal villages at the Techa River, whose chronic irradiation had been begun antenatally and to study probable interrelatirons between the detected changes, radiation and non-radiation factors at long terms after the exposure was begun. The main group included 61 persons from the Techa River Cohort who were born in 1950-1960, whose irradiation was begun in utero, being continued over the early postnatal period. For patients from the main group, the mean dose of antenatal radiation was calculated 74.7 mGy for red bone marrow as of, the mean dose of postnatal irradiation was calculated for red bone marrow as 537.5 mGy, and the median age of patients was 64.0 years. The comparison group (90 nonirradiated persons) was comparable to the main group in terms of age, gender, ethnicity and socio-economic status. The median levels for IL-2 in the main group were 1.37 pg/ml; in the comparison group, 2.70 pg/ml, p = 0.020; for IL-10, 4.53 pg/ml versus 7.58 pg/ml, p = 0.030 respectively; for GM-CSF, 0.39 pg/ml in the subjects who were irradiated in utero and in the early postnatal period versus 0.86 pg/ml in non-irradiated persons, p = 0.040. The median serum concentrations of IL-1β, IL-1α, IL-1(ra), IL-4, IL-6, IL-8, G-CSF, TNFα, IFNα, IFNγ in the study group did not show differences from the values in a group of non-irradiated persons. The decrease of the serum IL-2, IL-10 and GM-CSF levels in the persons of the main group did not depend on the dose of antenatal irradiation to red bone marrow, and on the radiation dose to red bone marrow received during the postnatal period of ontogenesis. In the main group, there was a moderate inverse relationship between the serum IL-10 level and age at the time of examination (SR = -0.53, p 0.001). Serum concentrations of IL-2 and IL-10 in the people from comparison group showed a moderate positive correlation with their present age (SR = 0.47, p 0.001 and SR = 0.42, p 0.001 respectively).

After the accident at the Fukushima Daiichi Nuclear Power Plant, an increased frequency of cancellation of the apical dominance has been revealed in young pine trees. The detected morphoses are most likely to result from radiation damage to the apical meristems of the conifers and also from changes in their phytohormonal status. To test this hypothesis, we have checked Japanese red pine populations from areas contaminated with radionuclides after the Fukushima accident for the frequency of morphoses related to cancellation of the apical dominance and estimated the content of main phytohormone classes: indoleacetic acid (IAA), indolylbutyric acid (IBA), zeatin, gibberellic acid (GA), and abscisic acid (ABA). The concentrations of phytohormones in the needles of young trees (5–8 years) were determined by high performance liquid chromatography. It has been shown for the first time that chronic radiation exposure changes the ratio of the main phytohormone classes in the needles of Japanese red pine: the concentrations of IAA, zeatin, and ABA increase, while the concentrations of GA decreases. The results have allowed us to explain the phenomenon of the increased frequency of cancellation of the apical dominance in the populations of young conifer trees from the zone of the Fukushima accident.

Objectives: Radiologic technologists (RTs) are typically exposed to low doses of radiations for longer periods, which have a health risk over many organs and tissues. Resistant tissues like nerves have shown neuropathic changes due to acute high-dose radiation exposure in the form of radiation therapy but the effect of low-dose chronic radiation exposure over peripheral nerves in RTs has been studied scantily. Materials and Methods: Nerve conduction parameters were recorded from 30 RTs and 30 age- and sex-matched healthy individuals who were not exposed to radiation. Motor nerve conduction study (NCS) of bilateral median, ulnar, radial, common peroneal and tibial nerves and sensory NCS of bilateral median, ulnar and radial nerves were recorded and compared. Results: Significant changes were observed in the form of reduction in motor and sensory nerve conduction velocity (P < 0.05) in all the examined nerves. Sensory nerve action potential (SNAP) amplitudes were reduced and latencies were prolonged significantly (P < 0.05) in all the examined sensory nerves. We also found reduced compound muscle action potential amplitude (significant in ulnar, radial, common peroneal and tibial nerves) along with prolonged motor distal latencies (significant in median, ulnar and tibial nerves) among RTs compared to healthy individuals. Conclusion: Chronic low-dose exposure of ionising radiation causes sub-clinical neuropathies affecting both sensory and motor nerves.

Background: The continued absorption of occupational radiation encounter by radiologic technologists and the potential resulting adverse effects have been a concern to the field for decades. This study investigates the risk factors of developing liver dysfunction among a selected group of radiologic technologists (RTs) to evaluates the correlation between cumulative radiation doses and liver injury. Methods: Only RTs who have been working in the radiology department for more than 10 years were selected for the study. The RTs and control groups were chosen based on several factors: adults, nonalcoholic, non-smoker, and have no history of hypertension or diabetes. A retrospective analysis was performed on the effective cumulative radiation dose for a selected RTs from 2009 to 2019. Fully automated biochemical analyzer was used to evaluate liver function tests. Alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), total bilirubin (BiL), direct BiL, indirect BiL, albumin (ALB), total protein (TP), cholesterol (CHOL), triglyceride (TG), high-density lipoprotein (HDL), and glucose (GLUH) were measured. Results: The result showed that the difference in the medians of liver biomarker GGT between control and RTs groups was statistically significant. The median of GGT in RTs group was higher than that of the control group. Conclusions: GGT test is a hallmark of liver function and alteration in GGT level may indicate a hepatic defect. Thus, further investigation in a large cohort to study the association between GGT elevation and chronic radiation exposure is required.

A comparative study of phytoplankton communities inhabiting six reservoirs in the Southern Urals with different levels of radioactive contamination is presented. Along with increasing the level of radioactive contamination, the diversity of the phytoplankton species is decreases, however the abundance of surviving species and their biomass did not depend on the level of radiation contamination in the studied reservoirs. There were found no signs of ecological regression of phytoplankton communities caused by radioactive contamination up to 6.5 kBq l-1 in the reservoirs of the Techa river Reservoir Cascade R-11, R-10, R-4 and R-3. Ecological regression of the phytoplankton community was observed in reservoirs R-17 and R-9, with a total activity of β-emitting radionuclides 470 kBq l-1 and higher, a total activity of α-emitting radionuclides 220 kBq l-1 and higher. Ecological regression of communities was registered as a decrease in species diversity, fluctuations in the number of algae in the high ranges, and the predominant development of one species. Reduction of species diversity in adverse conditions and violations of interspecies relationships in the community often leads to sharp fluctuations in the biomass and abundance. Moreover, the highest biomass of the algal communities can result from either excessive species gain or species loss. In the most contaminated R-9 (Karachai Lake) species diversity is dramatically decreased to monoculture of a single cyanobacteria species, dominant species could vary in different years of the study.

Background. The study of the long-term effects of chronic radiation exposure on plants and animals, which are still the subject of scientific discussion, is necessary to understand the consequences of radiation accidents. After the Fukushima nuclear power plant accident, some of the young pines and spruces showed an increased frequency of apical dominance cancelling. The most probable cause of the observed morphoses is associated with damage to the apical meristem of coniferous plants by radiation in the first year of the accident, when they received the highest absorbed doses. If this hypothesis is true, then even 8 years after the accident it will be possible with high degree of probability to detect an increased level of cytogenetic abnormalities in the intercalary meristem of needles of plants from these populations. The aim of this work was to verify this hypothesis. Materials and methods. Five populations of Japanese red pine from territories contaminated with radionuclides as a result of the accident at the Fukushima nuclear power plant were investigated. The frequency and spectrum of cytogenetic abnormalities in the intercalary meristem of needles were determined by the ana-telophase analysis. Results. The frequency of aberrant cells in the needles intercalary meristem of Japanese red pine from the contaminated with radionuclides territory statistically significantly exceeds the control level in all impact sites and increases along with the dose rate. Although there is no correlation between the frequency of cytogenetic abnormalities in needles and the presence of cancellation of apical dominance in plants, all pine populations from radioactively contaminated territories are characterized by an increased frequency of both cytogenetic abnormalities and morphoses associated with the cancellation of apical dominance. Conclusion. Radiation damage to the apical meristems of conifers in the first year of the accident, when they received the highest absorbed doses, is the most likely cause of the increased frequency of cancellation of apical dominance in the studied populations of Japanese red pine from the zone affected by the accident at the Fukushima nuclear power plant.

Long after chronic radiation exposure mainly of red bone marrow (mean exposure dose was 0.98 ± 0.05 Gy, individual dose range was 0.08–2.14 Gy), changes in the T-cell immunity such as a decrease in the relative number of CD3+ lymphocytes and a decreased absolute number of CD4+ cells, which did not depend on the maximum dose rate and the absorbed dose on red bone marrow and soft tissues, were observed in peripheral blood lymphocytes of individuals with increased levels of chromosomal aberrations (mainly dicentrics and translocations). The concomitant increase in the relative number of CD19+ lymphocytes, which was mainly determined by the dose rate and absorbed dose on soft tissues, indicated a shift in the immunological balance in the direction of the humoral immune response.

Purpose: Study the apoptotic death of peripheral blood lymphocytes in long-term period in persons exposed to chronic radiation exposure, and analysis of association of the polymorphic regions rs4645878, rs2279115, rs28362491, rs664677, rs1042522, rs1801270, rs2279744 of the BAX, BCL2, NFkB, ATM, TP53, CDKN1A, MDM2 genes with apoptotic lymphocytes frequency in residents of the coastal villages of the Techa River. Material and methods: The study of apoptosis and genotyping was conducted in 390 persons exposed to chronic radiation exposure as a result of Mayak PA radioactive waste releases into the Techa–Iset–Tobol river system. The early stage of apoptosis was assessed on a flow cytometer by the presence of phosphatidylserine on the surface of the cell membranes using the Annexin V Apoptosis Detection Kit I and the late stage of apoptosis using the TUNEL method. Real-time PCR genotyping was performed of allelic variations of rs4645878, rs2279115, rs28362491, rs664677, rs1042522, rs1801270, rs2279744 of BAX, BCL2, NFkB, ATM, TP53, CDKN1A, MDM2 genes in a group of irradiated individuals. Results: The number of cells at the early stage of apoptosis is statistically significantly increased in individuals whose irradiation began during the period of intrauterine development and continued in the postnatal period compared to individuals exposed only in the postnatal period. At the same time, the number of lymphocytes at the stage of DNA fragmentation in the group irradiated in utero is lower than in the group irradiated postnatally and non-irradiated individuals. Also, a weak negative correlation between intrauterine doses of RBM irradiation and the doses of thymus and peripheral lymphoid organs with the number of cells in the late stage of apoptosis in individuals irradiated in utero. The influence of allelic variation rs4645878 of the BAX gene was established on the number of lymphocytes at the early stage of apoptosis in residents of coastal villages of the Techa River. A statistically significant decrease in the number of cells at an early stage of apoptosis is observed in C/C genotype carriers according to the allelic variation rs4645878 of the BAX gene compared with carriers of the T/T and T/C genotypes. Conclusion: Residents of coastal villages of the Techa River exposed to radiation during the period of prenatal development, there are differences in the frequency of apoptotic death of peripheral blood lymphocytes compared with non-irradiated persons and persons who were irradiated in the postnatal period. SNPs of apoptosis-regulating genes can modify the response of blood lymphocytes to radiation in a wide range of doses RBM.

Purpose: Assessment of major parameters of the system immunity in 376 Techa riverside residents affected by external γ- and internal (mainly due to 90Sr) irradiation 60–68 years after the onset of exposure. Material and methods: The study involved 376 residents of the settlements located in the basin of the Techa River which was contaminated due to releases of liquid radioactive waste of Mayak Production Association. Red bone marrow received the largest doses that reached 4457.1 mGy, mean dose value was 1080.8 ± 38.4 mGy. Doses to the thymus and peripheral organs of the immune system in the exposed individuals were much lower; mean dose value was 65.3 ± 4.9 mGy. The study of the systemic immunity included the analysis of the parameters that characterize functional status of adaptive and innate immunity, as well as of the cytokine system. Results: Pro-inflammatory changes of the cytokines spectrum (decrease of IL-4 in blood serum, increase of TNFα and IFNγ) were observed in exposed people with a background of involution changes. Conclusion: Persistent reduction in the number of neutrophils in blood against normal levels of granulocyte colony-stimulating and granulocyte-macrophage colony-stimulating factors in blood serum could be indicative of certain inefficiency of hematopoietic stem cell pool. The most distinct features of immunity in exposed persons concerned the cytokine spectrum which were inflammatory in nature and on the one hand could be involved in the mechanisms of development of long-term effects of radiation and on the other could have a protective effect on the protection of the body from cells carrying sublethal abnormalities.

—The eight-year dynamics of the quality of motherwort (Leonurus quinquelobatus Gilib.) seed progeny growing for more than 60 years under chronic radiation in the East-Ural Radioactive Trace (EURT) zone, in comparison with background cenopopulations, has been studied. The absorbed dose rates of the parent plants in the EURT area exceed the background level by 1–3 orders of magnitude. The unique dependence between the radiation dose of mother plants and the seed progeny quality was not found. A key role in the formation of Leonurus quinquelobatus seeds belongs to weather factors, as well as the combined effect of weather conditions and chronic irradiation. All the studied characteristics of Leonurus quinquelobatus seed progeny quality from the EURT zone positively correlated with the effective temperature sum in April, i.e., with thermal conditions at the beginning of plant vegetation. The main meteorological factors that affected the physiological response (viability, mutability, and radiosensitivity) of Leonurus quinquelobatus of the background and impact zones were Selyaninov’s index in April of the current season and the amount of precipitation in November of last year. The viability of seed progeny had a negative correlation with Selyaninov’s index, whether the mutability of seed progeny had a positive correlation with Selyaninov’s index for background and impact samples. The physiological response to weather conditions, assessed by the seed radioresistance, was positive in the background samples and negative in the impact samples. The dependencies between the total precipitation in November of last year and the quality of seeds in the background samples were positive, and these dependences were negative in the impact samples.

The potential mechanisms of radioprotective effect of radiomodulators as agents of “biological” protection against oxidative stress in conditions of acute and chronic irradiation at high- and low-dose-rate ionizing radiation are considered. Radiomodulators, as natural antioxidants, prevent lipid peroxidation of cell membranes and reduce radiation toxemia. The radioprotective and radiomitigative properties of natural antioxidants are limited in terms of a dose reduction factor of 1.15–1.2. The dose–effect interrelation of antioxidants has a dome-shaped character; they can be prooxidants under certain conditions. With this mechanism they are also able to reduce acute toxicity of medicines and poisons. Long, low-intensive radiation at more than 100 mSv/year causes the development of oxidative stress with activation of the mechanisms of antioxidant defense upon its further exhaustion with a decrease in the ascorbic acid content in tissues and endogenous reduced thiols. In this case, the use of natural antioxidants allows a reduction in manifestations of oxidative stress via substrate therapy, thereby compensating for vitamin deficiency under the conditions of their intense consumption. At the same time, the delivery of exogenous purine nucleoside favors the synthesis of DNA and RNA in the course of their postradiation repair. In the condition of oxidative stress, the basis of adaptation shifts in the antioxidant system eventually consists of activation of the nuclear factor Nrf2 and NAD-dependent histone deacetylases sirtuins. Via hormesis, plant polyphenols, coumarins, purine nucleosides, and melatonin can modulate the Nrf2 nuclear factor and sirtuin activity and reduce the remote consequences of chronic radiation exposure, such as a reduction of the human lifespan, by a delay of the development of atherosclerosis, cardiovascular, and neurodegenerative diseases, metabolic syndrome, diabetes mellitus, and the risk of carcinogenesis.

Radiation-induced changes in the immune system develop quite early after the onset of radiation exposure and persist over a long time after it's removal. In case of chronic radiation exposure at dose rate lower than 0.1 Gy/year, the threshold of annual dose to suppress red bone marrow hemato- and immunopoiesis reaches 0.3-0.5 Gy. It was shown that adaptation mechanisms are triggered under the chronic impact of ionizing radiation in the hematopoietic system. In our study we quantitatively and qualitatively analyzed relationships between individual arms of the immune system which is important for understanding features of homeostasis and the adaptation capacity of immune system in chronically irradiated subjects at later time points. The main group included 376 persons exposed to chronic irradiation due to 1949-1960 industrial pollution with radioactive waste residing in Techa River basin. Average radiation dose for the red bone marrow in this group was 1.08±0.04 (0.08-4.46) Gy. The comparison group included 162 unexposed persons. The mean age of people in the main and comparison group was 70.3±0.3 (58-88) and 69.3±0.5 (58-90) years, respectively. The Kendall correlation analysis identified 82 statistically significant correlations (correlation coefficient higher than 0.3, p 0.05) between individual immune parameters versus 65 similar correlations found in the comparison group. The majority of identified correlation links in both groups ranged from 0.3 to 0.5 (main group – 57 correlations, comparison group – 41 correlations). There were found 16 and 14 correlations in the main and comparison group, respectively, with a coefficient ranged from 0.5 to 0.7. The correlation coefficient value higher than 0.7 was noted for 9 correlations in the main group and for 10 – in the comparison group. The χ-square analysis revealed no significant differences between total number of correlations and number of correlations of varying strength both in the main and comparison groups. The obtained data are consistent with previous studies and confirm that delayed changes in the immune system of subjects exposed to chronic low-rate irradiation were mild and evidenced about developed feedforward and feedback compensatory mechanisms.

PURPOSE: The environmental impact of the Fukushima Daiichi nuclear power plant accident is a source of ongoing concern as there is uncertainty regarding the effects of chronic radiation exposure on local plant and animal life from Fukushima-derived radionuclides. In the current study, changes in proteomic biomarker expression due to chronic environmentally derived radiation exposures was examined in wild field mice. METHODS: Serum from 10 wild field mice (Apodemus speciosus) native to the Fukushima difficult to return zone and from 8 wild field mice native to the Soma area (control) were collected. External dose estimations were completed using measurements of ambient radiation levels and calculating (137)Cs concentrations in soil. Internal dose was estimated by counting whole mice using an HPGe detector. Age of the mice was estimated using molar wear. Serum was screened using the aptamer-based SOMAscan proteomic assay technology, for changes in expression of 1,310 protein analytes. A subset panel of protein biomarkers which demonstrated significant changes in expression between control and exposed mice was determined and analyzed using Ingenuity Pathway Analysis (IPA). RESULTS: Control animals had a calculated lifetime dose range from 0.001 to 0.007 Gy and exposed animals had a calculated lifetime dose range from 0.01 to 0.64 Gy. No discernable effect of dose rate was seen as relative dose rate correlated with dose for all samples. Detectable values were obtained for all 1,310 proteins included in the SOMAscan assay. Subset panels of proteins demonstrating significant p < 0.05 changes in expression with either an upregulated or downregulated 1.5 fold change over control were identified for both the sample cohort inclusive of all exposed samples and the sample cohort restricted to samples from animals receiving “low” dose exposures. These panels of proteins from exposed animals were analyzed using IPA which highlighted changes in key biological pathways related to injury, respiratory, renal, urological and gastrointestinal disease and cancer. CONCLUSION: Significant changes in expression of proteomic biomarkers were seen in the serum of wild field mice who received environmental exposures to Fukushima-derived radionuclides. Our findings demonstrate novel biomarkers of radiation exposure in wildlife within the Fukushima difficult to return zone.

During space missions, astronauts experience acute and chronic low-dose-rate radiation exposures. Given the clear gap of knowledge regarding such exposures, we assessed the effects acute and chronic exposure to a mixed field of neutrons and photons and single or fractionated simulated galactic cosmic ray exposure (GCRsim) on behavioral and cognitive performance in mice. In addition, we assessed the effects of an aspirin-containing diet in the presence and absence of chronic exposure to a mixed field of neutrons and photons. In C3H male mice, there were effects of acute radiation exposure on activity levels in the open field containing objects. In addition, there were radiation-aspirin interactions for effects of chronic radiation exposure on activity levels and measures of anxiety in the open field, and on activity levels in the open field containing objects. There were also detrimental effects of aspirin and chronic radiation exposure on the ability of mice to distinguish the familiar and novel object. Finally, there were effects of acute GCRsim on activity levels in the open field containing objects. Activity levels were lower in GCRsim than sham-irradiated mice. Thus, acute and chronic irradiation to a mixture of neutrons and photons and acute and fractionated GCRsim have differential effects on behavioral and cognitive performance of C3H mice. Within the limitations of our study design, aspirin does not appear to be a suitable countermeasure for effects of chronic exposure to space radiation on cognitive performance.

Analysis of genetic diversity represents a fundamental component of ecological risk assessments in contaminated environments. Many studies have assessed the genetic implications of chronic radiation exposure at Chernobyl, generally recording an elevated genetic diversity and mutation rate in rodents, plants, and birds inhabiting contaminated areas. Only limited studies have considered genetic diversity in aquatic biota at Chernobyl, despite the large number of freshwater systems where elevated dose rates will persist for many years. Consequently, the present study aimed to assess the effects of chronic radiation exposure on genetic diversity in the freshwater crustacean, Asellus aquaticus, using a genome‐wide SNP approach (Genotyping‐by‐sequencing). It was hypothesized that genetic diversity in A. aquaticus would be positively correlated with dose rate. A. aquaticus was collected from six lakes in Belarus and the Ukraine ranging in dose rate from 0.064 to 27.1 µGy/hr. Genotyping‐by‐sequencing analysis was performed on 74 individuals. A significant relationship between geographical distance and genetic differentiation confirmed the Isolation‐by‐Distance model. Conversely, no significant relationship between dose rate and genetic differentiation suggested no effect of the contamination gradient on genetic differentiation between populations. No significant relationship between five measures of genetic diversity and dose rate was recorded, suggesting that radiation exposure has not significantly influenced genetic diversity in A. aquaticus at Chernobyl. This is the first study to adopt a genome‐wide SNP approach to assess the impacts of environmental radiation exposure on biota. These findings are fundamental to understanding the long‐term success of aquatic populations in contaminated environments at Chernobyl and Fukushima., This study utilized a genotyping by sequencing method to provide a novel assessment of the impacts of chronic radiation exposure at Chernobyl on a freshwater crustacean. No significant impact of over 30 years of radiation exposure on genetic variation was recorded. These findings are fundamental to understanding the long‐term success of aquatic populations in contaminated environments at Chernobyl and Fukushima.

Glaucoma is a major cause of visual impairment, and secondary glaucoma manifested as neovascular glaucoma has long been known to occur following high-dose fractionated radiation therapy. In contrast, little is known as to whether ionizing radiation exposure causes primary glaucoma, except that a single study in Japanese atomic bomb survivors has reported a significantly increase risk. Therefore, the effect of lower dose and lower dose rate remains unclear. Here we report that in Russian Mayak Production Association workers occupationally exposed to chronic radiation for prolonged periods, incidence of total primary glaucoma and primary open-angle glaucoma is significantly associated with various non-radiation factors (sex, attained age, and cataract diagnosed prior to glaucoma), but neither with cumulative dose from external γ-rays nor with cumulative neutron dose nor with the unweighted sum of cumulative γ and neutron doses. The present results suggest for the first time that chronic radiation exposure does not cause primary glaucoma, although the analyses need to be made in other cohorts exposed at various dose and dose rate.

In this paper the main results of long-term (2003-2016) observations on Scots pine populations inhabiting sites affected by the Chernobyl accident are presented. Populations growing for many years under chronic radiation exposure are characterized by the enhanced mutation rates, increased genetic diversity, changes in the gene expression and in the level of genome-wide methylation, alterations in the temporal dynamics of cytogenetic abnormalities and genetic structure of populations. However, significant changes at the genetic level had no effects on enzymatic activity, morphological abnormalities, and reproductive ability of pine trees. The results presented increase our understanding of the long-term effects of chronic radiation exposure on plant populations in the wild nature and provide important information for the management and monitoring of radioactively contaminated territories.

Up to now there is no clear understanding of health risk and type of dose dependence for the population chronically exposed within a range of low and average dose levels (to 1Gy). In this respect studies performed in cohorts with a sufficient number of persons can have a significant potential in providing necessary information. Objective: to study peculiarities of lens opacity in exposed persons at later time after chronic radiation exposure with due account for dose impact and nonradiation factors. The study includes patients from the URCRM registry of exposed population examined by an ophthalmologist in the period 2016-2018 (total 1,377 persons). The same technique of medical examination with photofixation of lens opacity was applied to all examined individuals. A case-control technique was used to conduct the study. Individual exposure doses to lens were calculated on the basis of TRDS-2016 for the first time within the framework of the present study. As a result of the performed study among persons exposed to long-term ionizing low-dose radiation we have determined an exposure dose impact on risk growth of opacity in the posterior capsule and lens nucleus. No reliable statistical dependence of lens change with an increasing exposure dose in anterior capsule and cortical layers as well as colour change of the lens nucleus was obtained. Belonging to different ethnical groups showed no impact on priority opacification development in any lens layers.

Background: Exposure to radiation alters the equilibrium of the protection mechanism by producing of free radicals, resulting in an imbalance in prooxidant, antioxidant status inside the cells. Oxidative stress has been shown to affect our nervous system. Natural dietary supplements have been shown to have antioxidant properties which can protect our bodies against free radicals. For example, Aphanizomenon flos-aquae (AFA) is a specific dietary supplement that has clinically proven health-promoting effects especially on the nervous system. Objectives: to study the radio-protective impact of AFA as a natural antioxidant on the cerebellar neuronal cells of adult albino rats against the gamma radiation damaging effects. Material and Methods: The research was performed on 24 adult male albino rats weighed 120±3 g and equally divided into Group 1, Group 2: rats were exposed to daily oral intake of AFA extract for one month. Group 3: rats were exposed to irradiation via exposing them to 6 Gy. Group 4: rats were exposed to a combination of irradiation (in the same way like group 3) plus oral intake of AFA extract for one month. For histologic, histochemical, immunohistochemical and morphometric tests, paraffin sections were prepared from the cerebellum. Results: Sections studied demonstrated significant cellular damage in group 3 relative to the control groups. Group 4 demonstrated obvious reduction in pathological changes occurring in comparison with group 2. Conclusion: These findings indicate that AFA has a radio-protective function as it decreases pathological cellular injuries in the cerebellar neuronal cells caused by chronic radiation exposure doses.

The 2011 Tohoku earthquake-tsunami and the subsequent nuclear accident at the Fukushima Dai-ichi Nuclear Power Station (FDNPS) led to large-scale radionuclide contamination of the marine and freshwater environment. Monitoring studies of marine food products in the Fukushima region have generally demonstrated a declining trend in radiocaesium concentrations. However, the accumulation and elimination of radiocaesium and potential biological effects remain poorly understood for freshwater biota inhabiting highly contaminated areas at Fukushima. Consequently, the present study aimed to assess radiocaesium accumulation and developmental effects on the commercially important catadromous Japanese mitten crab, Eriocheir japonica. E. japonica were collected from four sites along a gradient of radionuclide contamination 4–44 km in distance from the FDNPS in 2017. To determine potential developmental effects, fluctuating asymmetry (FA) was used as a measure of developmental stability. Combined 134Cs and 137Cs values for whole E. japonica from highly contaminated sites 4 and 16 km in distance from the FDNPS were 3040 ± 521 and 2250 ± 908 Bq kg−1 wet weight respectively, 30 and 22 times greater than the Japanese standard limit of 100 Bq kg−1. Estimated total dose rates based on radiocaesium concentrations in whole crabs and sediment ranged from 0.016 to 37.7 μGy h−1. No significant relationship between radiocaesium accumulation and FA was recorded, suggesting that chronic radiation exposure at Fukushima is not inducing developmental effects in E. japonica as measured using fluctuating asymmetry. Furthermore, estimated dose rates were below proposed regulatory limits where significant deleterious effects are expected. The present study will aid in the understanding of the long-term consequences of radiation exposure for non-human biota and the management of radioactively contaminated environments.

Low-temperature treatments (i.e., hypothermia) may be one way of regulating environmental radiation damage in living systems. With this in mind, hibernation under hypothermic conditions has been proposed as a useful approach for long-term human space flight. However, the underlying mechanisms of hypothermia-induced radioresistance are as yet undetermined, and the conventional risk assessment of radiation exposure during hibernation remains insufficient for estimating the effects of chronic exposure to galactic cosmic rays (GCRs). To promote scientific discussions on the application of hibernation in space travel, this literature review provides an overview of the progress to date in the interdisciplinary research field of radiation biology and hypothermia and addresses possible issues related to hypothermic treatments as countermeasures against GCRs. At present, there are concerns about the potential effects of chronic radiation exposure on neurological disorders, carcinogenesis, ischemia heat failures, and infertility in astronauts; these require further study. These concerns may be resolved by comparing and integrating data gleaned from experimental and epidemiological studies.

The Chernobyl and Fukushima nuclear power plant (NPP) accidents that occurred in 1986 and 2011 respectively have led to many years of chronic radiation exposure of wildlife. However, controversies remain on the dose threshold above which an impact on animal health occurs. Fish have been highly exposed immediately after both accidents in freshwater systems around Chernobyl and in freshwater and marine systems around Fukushima. The dose levels decreased during the years after the accidents, however, little is known about the effects of environmental low doses of radiation on fish health. The present laboratory study assesses the effects of an environmentally relevant dose range of radiation (0.1, 1 and 10 mGy/day) on early life stages of the 3-spined stickleback, Gasterosteus aculeatus. The cardiac physiology and developmental features (head width, diameter, area) of high exposed embryos (10 mGy/day) showed no significant change when compared to controls. Embryos exposed to the medium and high dose were slower to hatch than the controls (between 166 and 195 h post-fertilization). After 10 days of exposure (at 240 h post-fertilization), larvae exposed to the high dose displayed comparable growth to controls. High-throughput sequence analysis of transcriptional changes at this time point revealed no significant changes in gene regulation compared to controls regardless of exposure conditions. Our results suggest that exposure of fish embryos to environmental radiation elicits subtle delays in hatching times, but does not impair the overall growth and physiology, nor the gene expression patterns in the recently hatched larvae.

In order to understand the effect of chronic exposure to low-dose-rate radiation on female fertilities and the risk of heritable genetic effects on domestic animals after the Fukushima Daiichi Nuclear Power Plant (FNPP) accident, we assessed the developmental ability of oocytes, and examined the histological characters and structure of ovaries. We showed that potentially viable oocytes could be collected from the ovary of abandoned cattle in the ex-evacuation zone set within a 20-km radius from FNPP, resulting in production of the morphologically normal calves following in vitro culture and embryo transfer. The proliferation of cattle ovarian granulosa cells was confirmed by expression of Ki-67. Apoptosis of oocytes and granulosa cells was few determined by the TUNEL assay. In addition, porcine and inobuta oocytes had the abilities of in vitro maturation. These results suggest that chronic radiation exposure associated with the FNPP accident may have little effect, if any, on the female fertilities of domestic animals.

This study aimed to identify immunological biomarkers for prolonged occupational radiation exposure and thus studied a random sample of the Mayak Production Association worker cohort (91 individuals). The control group included 43 local individuals never employed at the Mayak Production Association. To identify biomarkers, two groups of workers were formed: the first one included workers chronically exposed to external gamma rays at cumulative doses of 0.5-3.0 Gy (14 individuals); the second one included workers exposed to combined radiation-external gamma rays at doses ranging from 0.7 to 5.1 Gy and internal alpha radiation from incorporated plutonium with 0.3-16.4 kBq body burden (77 individuals). The age range of the study individuals was 66-91 y. Peripheral blood serum protein concentrations of cytokines, immunoglobulins, and matrix metalloproteinase-9 were analyzed using enzyme-linked immunoassay following the manufacturer's protocol. Flow cytometry was used to analyze levels of various lymphocyte subpopulations. The findings of the current study demonstrate that some immunological characteristics may be considered as biomarkers of prolonged chronic radiation exposure for any radiation type (in the delayed period after the exposure) based on fold differences from controls: M immunoglobulin fold differences were 1.75 ± 0.27 (p = 0.0001) for external gamma-ray exposure and 1.50 ± 0.27 (p = 0.0003) for combined radiation exposure; matrix metalloproteinase-9 fold differences were 1.5 ± 0.22 (p = 0.008) for external gamma-ray exposure and 1.69 ± 0.24 (p = 0.00007) for combined radiation exposure; A immunoglobulin fold differences were 1.61 ± 0.27 (p = 0.002) for external gamma-ray exposure and 1.56 ± 0.27 (p = 0.00002) for combined radiation exposure; relative concentration of natural killer cell fold differences were 1.53 ± 0.23 (p = 0.01) for external gamma-ray exposure and 1.35 ± 0.22 (p = 0.001) for combined radiation exposure; and relative concentration of T-lymphocytes fold differences were 0.89 ± 0.04 (p = 0.01) for external gamma-ray exposure and 0.95 ± 0.05 (p = 0.003) for combined radiation exposure. Based on fold differences from controls, interferon-gamma (3.50 ± 0.65, p = 0.031), transforming growth factor-beta (2.91 ± 0.389, p = 0.026), and relative blood serum levels of T-helper cells (0.90 ± 0.065, p = 0.02) may be used as immunological markers of chronic external gamma-ray exposure. Moreover, there was a significant inverse linear association of relative concentration of T-helper cells with dose from external gamma rays accumulated over an extended period.

Data about the long-term effects of the chronic radiation exposure of forests to the radioactive trail of the Chernobyl disaster are insufficient. The method of vertical electrophoresis in PAAG is used to estimate the polymorphism of enzymes in Scots pine populations growing on the territory of Bryansk oblast, which was contaminated with radionuclides. The activity of enzymes in Scots pine seeds is estimated by spectrophotometry. The overall frequency of mutations in the isozyme loci increases with the dose rate of chronic irradiation (7–130 mGy/year), as well as some characteristics of the genetic structure of the populations. The activity of enzymes does not depend on the level of the dose absorbed by the generative organs of pine. The impact of radiation contributes to changes in the genetic structure of Scots pine populations.

We have studied the morphometric indices of needles in Scots pine populations that grow in Bryansk oblast in sites with radioactive contamination long after the Chernobyl accident. The variability in needle weight and length, as well as the fluctuating asymmetry indices and occurrence of necroses and morphoses, were studied in four contaminated and two reference populations of Scots pine in 2011, 2013, and 2014. The exposure of needles in radioactively contaminated sites varied from 7 to 130 mGy/yr. We found brachyblasts with three needles in contaminated Scots pine populations; this morphosis was absent in the reference populations. A dependence of the occurrence of needles damaged by necrosis on the levels of radiation exposure in 2011 was found. However, it was statistically insignificant in other years. The length and weight of needles in contaminated populations differed from the control values; however, the dependence of these indices on the level of radiation exposure was not revealed in the studied range of doses. In 2011 and 2013, the index of fluctuating asymmetry in needle length exceeded the control levels in sites where the absorbed doses were 90 and 130 mGy; this index also tended to grow (statistically significantly in 2011) with an increase in the characteristics of radioactive contamination of the studied plots: the exposure dose rate and the specific activity of 90Sr and 137Cs in cones and of 137Cs in the soil. Therefore, one can observe the consequences of chronic radiation exposure at the organismic level in populations of Scots pine (one of the most radiosensitive plant species) even 25 years after the accident. The data that we obtained in natural habitats confirm the international estimates, according to which the annual chronic radiation exposure of 100 mGy can be considered the limit of safe radiation exposure of natural populations according to morphological and ontogenetic parameters.

The purpose of this paper is to review basic radiation biology and associated terminology to impart a better understanding of the importance of basic concepts of ionizing radiation interactions with living tissue. As health care workers in a field that utilizes ionizing radiation, nuclear medicine technologists are concerned about the possible acute and chronic effects of occupational radiation exposure. Technologists should have a clear understanding of what they are exposed to and how their safety could be affected. Furthermore, technologists should be knowledgeable about radiation effects so that they can adequately assuage possible patient fears about undergoing a nuclear medicine procedure. After reading this article, the nuclear medicine technologist will be familiar with basic radiation biology concepts; types of interactions of radiation with living tissue, and possible effects from that exposure; theoretic dose-response curves and how they are used in radiation biology; stochastic versus nonstochastic effects of radiation exposure, and what these terms mean in relation to both high- and low-dose radiation exposure; and possible acute and chronic radiation exposure effects.

Knowledge regarding complex radiation responses in biological systems can be enhanced using genetically amenable model organisms. In this manuscript, we reviewed the use of the nematode, Caenorhabditis elegans (C. elegans), as a model organism to investigate radiation’s biological effects. Diverse types of experiments were conducted on C. elegans, using acute and chronic exposure to different ionizing radiation types, and to assess various biological responses. These responses differed based on the type and dose of radiation and the chemical substances in which the worms were grown or maintained. A few studies compared responses to various radiation types and doses as well as other environmental exposures. Therefore, this paper focused on the effect of irradiation on C. elegans, based on the intensity of the radiation dose and the length of exposure and ways to decrease the effects of ionizing radiation. Moreover, we discussed several studies showing that dietary components such as vitamin A, polyunsaturated fatty acids, and polyphenol-rich food source may promote the resistance of C. elegans to ionizing radiation and increase their life span after irradiation.

Five herbaceous plant species (Aquilegia vulgaris L., Capsella bursa-pastoris L., Dactylis glomerata L., Taraxacum officinale Wigg., and Trifolium repens L.) were sampled at twelve plots in the radioactively contaminated Chernobyl exclusion zone. These plots comprise dose rates from 0.27 to 12.5 μGy/h. The sensitivity of each plant species to chronic multigenerational radiation exposure was estimated using a broad range of parameters, including transcriptional, biochemical, physiological, morphological, and reproductive end-points. We suggest that chronic radiation exposure may influence the state of antioxidant system of chronically irradiated plants in a species-specific way, possibly leading to changes in photosynthetic capacity. ATP and ABA contents were not influenced by chronic irradiation at the plots. For most of the species studied, chlorophyll a fluorescence measurements may be a more appropriate way to assess the stress response to chronic irradiation, while biochemical parameters had significantly higher natural heterogeneity. High-throughput sequencing of the transcriptome of C. bursa-pastoris leaves from radioactively contaminated plots revealed significant stress response to chronic irradiation and supported a predicted important role of histones and chaperons in adaptation to chronic radiation exposure in field conditions. Overall, the results suggest that a prediction of herbaceous species sensitivity to chronic radiation might be initially derived from data on sensitivity to acute radiation exposure.

Introduction: Chronic radiation exposure, particularly among technicians using medical imaging instruments, may contribute to chronic disease, including renal dysfunction. Investigating the potential association of this exposure with biochemical changes may assist disease detection and prevention. Objectives: The study explores the risk of renal dysfunction among radiologic technologists (RTs) with ten years or more of diagnostic imaging experience to evaluate the association of accumulated radiation doses and possible renal injury. Patients and Methods: A retrospective analysis was performed on the effective accumulative radiation dose from 2009 to 2019 among RTs of radiological department at a general hospital in southern Saudi Arabia. Blood samples were collected, and key biomarkers analyzed using a fully automated biochemical analyzer. Serum levels of the following were measured; sodium, gamma-glutamyl transferase (GGT), chloride, creatine kinase (CK), calcium, albumin, urea, creatinine, lactate dehydrogenase, total protein and potassium. In statistical analysis, PResults: Even with exposure to only low-level radiation sources, RTs were statistically predisposed to variation in biochemical profiles. RTs exhibited GGT and CK levels higher than that of controls, while serum chloride was significantly low. Conclusion: The current study found a significant change in renal biochemical profiles among RTs who had worked in a radiological department for more than ten years. The association between GGT, CK with Kidney diseases was reported in several reports. Chronic exposure to radiation may contribute to a rise in GGT and CK levels and reduction of chloride and thus could develop the risk of renal diseases.

After the Fukushima Daiichi accident, there have been long controversial discussions on “how safe is safe?” between the authorities and the residents in the affected area. This controversy was partly attributable to the way the authorities made a judgement based on the annual effective dose rate, meanwhile, many of the local residents have serious concerns about future consequences for their health caused by chronic radiation exposure, particularly of small children. To settle this controversy, the author presents an approach based on long-term cancer risk projections of female infants, i.e., the most radiosensitive group, following land contamination by radiocesium deposition into ground with different surface conditions, the land was classified into three categories on the basis of decaying patterns of radiation dose rate: “Fast”, “Middle”, and “Slow”. From the results of analyses with an initial dose rate of 20 mGy per year, it was predicted that the integrated lifetime attributable risk (LAR) of cancer mortality of a female person ranged by a factor of 2 from 1.8% (for the Fast area) to 3.6% (for the Slow area) that were clearly higher than the nominal risk values derived from effective dose estimates with median values of environmental model parameters. These findings suggest that accurate site-specific information on the behavioral characteristics of radionuclides in the terrestrial environment are critically important for adequate decision making for protecting people when there is an event accompanied by large-scale radioactive contamination.

Neuroblastoma accounts for >15% of cancer-associated mortalities of children in the USA. Despite aggressive treatment regimens, the long-term survival for these children remains

Summary: Background. The vast forest areas were affected by radioactive fallout of the Chernobyl accident. Data about the long-term effects of chronic radiation exposure are insufficient, as well as knowledge about its influence on the genetic structure of populations. Study of isozyme polymorphism allows us to identify how chronic low-dose radiation exposure affects the genetic structure of plant populations and to develop new methods for assessing the biological effects of anthropogenic impact on terrestrial ecosystems. Materials and methods. The study was conducted in six sites in the Bryansk region (4 radioactively contaminated and 2 reference ones). The method of vertical electrophoresis in PAAG was used for estimation of polymorphism of three enzymes involved in metabolic pathways. Activity of enzymes in seeds of Scots pine was assessed by spectrophotometry. Results. The frequency of mutations in isozymes loci increased along the level of radiation exposure (7-130 mGy/year), as well as some characteristics of the genetic structure of populations. Biochemical activity of studied enzymes does not depend on the level of dose absorbed in the generative organs of pine. Conclusions. It was found that the frequency of mutational events in loci of catabolic/anabolic enzymes and in the loci of previously studied antioxidant enzymes increases along the level of radiation exposure. The degree of the biological effect of chronic exposure was different in groups of catabolic/anabolic enzymes and antioxidant enzymes. Radiation exposure contributes to changes in the genetic structure of Scots pine populations.

Radiation safety is an important counterpart in all facilities utilizing ionizing radiations. The concept of radiation safety has always been a hot topic, especially with the late reports pointing to increased hazards with chronic radiation exposure. Adopting a nationwide radiation safety program is considered one of the most urging topics, and is a conjoint responsibility of multiple disciplines within the health facility.

Molecular mechanisms of radiation dose-rate effects are not well understood. Among many possibilities, long-lasting sustained alterations in protein levels would provide critical information. To evaluate sustained effects after acute and chronic radiation exposure, we analyzed alterations in protein expression in the livers of mice. Acute exposure consisted of a lethal dose of 8 Gy and a sublethal dose of 4 Gy, with analysis conducted 6 days and 3 months after irradiation, respectively. Chronic irradiation consisted of a total dose of 8 Gy delivered over 400 days (20 mGy/day). Analyses following chronic irradiation were done immediately and at 3 months after the end of the exposure. Based on antibody arrays of protein expression following both acute lethal and sublethal dose exposures, common alterations in the expression of two proteins were detected. In the sublethal dose exposure, the expression of additional proteins was altered 3 months after irradiation. Immunohistochemical analysis showed that the increase in one of the two commonly altered proteins, MyD88, was observed around blood vessels in the liver. The alterations in protein expression after chronic radiation exposure were different from those caused by acute radiation exposures. Alterations in the expression of proteins related to inflammation and apoptosis, such as caspase 12, were observed even at 3 months after the end of the chronic radiation exposure. The alterations in protein expression depended on the dose, the dose rate, and the passage of time after irradiation. These changes could be involved in long-term effects of radiation in the liver.

The multiple stressors, in different combinations, may impact differently upon seed quality, and low-level doses of radiation may enhance synergistic or antagonistic effects.During 1991-2014 we investigated the quality of the dandelion (Taraxacum officinale s.l.) seed progeny growing under low-level radiation exposure at the East-Ural Radioactive Trace (EURT) area (result of the Kyshtym accident, Russia), and in plants from areas exposed to background radiation. The viability of the dandelion seed progeny was assessed according to chronic radiation exposure, accounting for the variability of weather conditions among years. Environmental factors (temperature, precipitation, and their ratio in different months) can modify the radiobiological effects. We found a wide range of possible responses to multiple stressors: inhibition, stimulation, and indifferent effects in different seasons.The intraspecific variability of the quality of dandelion seed progeny was greatly increased under conditions of low doses of chronic irradiation. Temperature was the most significant factor for seed progeny formation in the EURT zone, whereas the sums of precipitation and ratios of precipitation to temperature dominantly affected organisms from the background population.

Crustaceans have been designated as internationally important model organisms in the development of environmental radioprotection measures. Despite the known sensitivity of sperm to ionizing radiation, the impacts of chronic radiation exposure on male fertility in crustaceans have not been studied. For the first time, the present study aimed to assess the impacts of chronic radiation exposure on male fertility, sperm DNA damage and concomitant impacts on breeding in two amphipod crustaceans. Echinogammarus marinus and Gammarus pulex (male fertility only) were exposed to phosphorus-32 at dose rates of 0, 0.1, 1 and 10 mGy/d and sperm parameters, DNA damage and knock-on impacts on breeding were assessed. Sperm quality parameters and DNA damage were assessed using a fluorescent staining method and single cell gel electrophoresis respectively. Concomitant effects of male exposure to radiation on fecundity were determined by pairing phosphorus-32 exposed males to unexposed sexually mature females. In E. marinus, a statistically significant reduction of 9 and 11% in the quality of sperm was recorded at dose rates of 1 and 10 mGy/d respectively, with no significant effects recorded on sperm counts. Conversely in the freshwater G. pulex, no significant impact of radiation on sperm quantity or quality was recorded. For E. marinus, a statistically significant increase in DNA damage was recorded at doses of 10 mGy/d. Reduced fecundity and an increase in the frequency of abnormal embryos was recorded in female E. marinus breeding with males exposed to radiation. These findings suggest sperm quality may be a sensitive indicator of radiation exposure in invertebrates with potential impacts on the unexposed embryo, though unclear dose-response and differences between two closely related species necessitate further study before robust conclusions can be drawn.

Gut microbiota play an important role in host health. Yet, the drivers and patterns of microbiota imbalance (dysbiosis) in wild animals remain largely unexplored. One hypothesised outcome of stress on animal microbiomes is a destabilised microbial community that is characterised by an increase in inter-individual differences compared with microbiomes of healthy animals, which are expected to be (a) temporally stable and (b) relatively similar among individuals. This set of predictions for response of microbiomes to stressors is known as the Anna Karenina principle (AKP) for animal microbiomes. We examine the AKP in a wild mammal inhabiting disturbed environments by conducting a capture-mark-recapture survey of bank voles Myodes glareolus in areas that contrast in levels of radionuclide contamination (Chernobyl, Ukraine). Counter to key predictions of the AKP, bank voles that are not exposed to radionuclides harbour variable (increased inter-individual differences) and temporally dynamic gut microbiota communities, presumably tracking the natural spatio-temporal variation in resources. Conversely, bank voles exposed to radionuclides host more similar gut microbiota communities that are temporally stable, potentially due to a dysbiosis or selection (on host or bacteria) imposed by chronic radiation exposure. The implication of these data is that environmental stress (radiation exposure) can constrain the natural spatial and temporal variation of wild animal gut microbiota.

Chronic inflammation is a common denominator linking a wide range of health conditions, including tissue response to radiation exposure. This pilot study investigates whether inflammatory cytokines—interleukins IL-6, −8, −10, monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor α (TNFα)—can be used as early biomarkers of radiation-induced adverse health effects in occupationally exposed individuals. The study included 33 workers externally exposed to gamma radiation from the nuclear industry with cumulated doses from 0.11 to 190 mSv and 42 non-exposed controls of comparable age and socio-economic status. IL-6, IL-8, MCP-1, TNFα and IL-10 were analyzed by enzyme-linked assay (ELISA) in blood plasma samples. Total antioxidant status (TAS) of blood plasma was determined by a colorimetric assay. The radiation-exposed and control groups measured significantly different levels of MCP-1, TNFα and IL-10. Seventy-five percent of radiation workers had either high MCP-1 levels or low IL-10 levels and 30% had all three cytokines dysregulated. Approximately 50% of workers showed upregulated antioxidant status, which appeared to compensate the pro-inflammatory cytokine shift in these individuals. In contrast, only 2% of the control subjects were found to have three dysregulated cytokines, and all of them measured within the normal TAS range. The present study may represent an important step towards the establishment of a reliable set of biomarkers for health-risk estimation in population cohorts exposed to low radiation doses.