Assessment of mouse rodents’ dose from the CHNPP contaminated territories

The main feature of the nearest 5-km zone of the Chernobyl nuclear power plant is the maximum concentration of fuel fallouts due to the accident in 1986. It is a unique testing ground for radiobiological research in the natural habitat of animals. At present, the background radiation level in the 5-km zone of the Chernobyl nuclear power plant fluctuates from 0.1 to 20 μSv/h. Besides, electrons from the decay of 90Sr and 137Cs add a significant contribution to the radiation background. Even though a large amount of experimental data on dose loads on the fauna of affected areas has been accumulated to date, the results obtained do not give an unambiguous idea of the dose dependences of radiobiological effects in natural ecosystems. In this work, we studied the total dose of irradiation of two murine rodents species: the bank vole (Clethrionomys glareolus) and the yellow-necked mouse (Apodemus flavicollis), living in territories of different levels of pollution near the destroyed power unit 4 of the Chernobyl nuclear power plant. We have assessed the density of radioactive contamination of the territory and study the isotopic composition of the fallout. Soil samples were taken to a depth of 30 cm, considering the depth of burrowing of mouse-like burrows is 10-15 cm. The 90Sr, 90Y, and 137Cs concentrations were measured using β- and γ-spectrometric methods for the selected soil samples. The 90Sr, 90Y, and 137Cs βactivity spectra were measured using a developed scintillation beta-spectrometer with a thin entrance window. Soil samples' gamma spectrometric studies were carried out using an anti-Compton device with an HPGe detector. The method for processing complex Xray and gamma-spectra in the energy range of 10-100 keV is developed. It takes into account the complexity of describing X-ray lines and providing a processing error of ≤1%. We calculated the murine rodents' radiation doses using the obtained data on the concentration of 90Sr, 90Y, and 137Cs activities in soil samples and animal bodies. The doses were calculated due to external irradiation with γ-quanta and electrons and internal irradiation with 137Cs and 90Sr electrons. For the first time, we obtained data on external electrons' contribution to the total dose of irradiation of murine rodents living in the contaminated territories of the 5-km zone of the Chernobyl nuclear power plant. Doses of internal irradiation and external γ-quanta are in good agreement with the data obtained for these territories earlier. It was found that the radiation dose is formed mainly due to external electrons for most rodents. Since many studies, including genetic and biochemical ones, are tied to the radiation dose, the correct account of the contribution of electrons to the radiation dose is, in many cases, critical.

Assessment of the dose burden and health status of the uranium processing workers of the Republic of Kazakhstan

The main objective of current study is to assess the dose burden and health status of workers at the uranium processing hydrometallurgical plant in order to develop measures aimed at reducing their incidence. This article presents the results of radiation monitoring and data on the health status of workers at the hydrometallurgical plant of the Stepnogorsk Mining and Chemical Combine (SMCC). The data of the accumulated effective dose for the entire length of service, as well as data on the incidence rate for the period 2013-2019, obtained from the base of the Industrial Radiation and Epidemiological Register, have been analyzed. Based on the results of measurements of the uranium content in urine, the expected effective dose of internal irradiation of the enterprise personnel was calculated. The assessment of the health status of workers was carried out based on the materials of outpatient and hospital visits, as well as the results of mandatory periodic medical examinations over the past 5 years. Based on the results, an excess of the expected effective dose of internal irradiation was revealed based on the analysis of a urine sample by 3 times. The most typical for the studied contingent of the main group turned out to be diseases of the eye and its adnexa (23%).

Internal doses in experimental mice and rats following exposure to neutron-activated 56MnO2 powder: results of an international, multicenter study

The experiment was performed in support of a Japanese initiative to investigate the biological effects of irradiation from residual neutron-activated radioactivity that resulted from the A-bombing. Radionuclide 56Mn (T1/2 = 2.58 h) is one of the main neutron-activated emitters during the first hours after neutron activation of soil dust particles. In our previous studies (2016–2017) related to irradiation of male Wistar rats after dispersion of 56MnO2 powder, the internal doses in rats were found to be very inhomogeneous: distribution of doses among different organs ranged from 1.3 Gy in small intestine to less than 0.0015 Gy in some of the other organs. Internal doses in the lungs ranged from 0.03 to 0.1 Gy. The essential pathological changes were found in lung tissue of rats despite a low level of irradiation. In the present study, the dosimetry investigations were extended: internal doses in experimental mice and rats were estimated for various activity levels of dispersed neutron-activated 56MnO2 powder. The following findings were noted: (a) internal radiation doses in mice were several times higher in comparison with rats under similar conditions of exposure to 56MnO2 powder. (b) When 2.74 × 108 Bq of 56MnO2 powder was dispersed over mice, doses of internal irradiation ranged from 0.81 to 4.5 Gy in the gastrointestinal tract (small intestine, stomach, large intestine), from 0.096 to 0.14 Gy in lungs, and doses in skin and eyes ranged from 0.29 to 0.42 Gy and from 0.12 to 0.16 Gy, respectively. Internal radiation doses in other organs of mice were much lower. (c) Internal radiation doses were significantly lower in organs of rats with the same activity of exposure to 56MnO2 powder (2.74 × 108 Bq): 0.09, 0.17, 0.29, and 0.025 Gy in stomach, small intestine, large intestine, and lungs, respectively. (d) Doses of internal irradiation in organs of rats and mice were two to four times higher when they were exposed to 8.0 × 108 Bq of 56MnO2 (in comparison with exposure to 2.74 × 108 Bq of 56MnO2). (e) Internal radiation doses in organs of mice were 7–14 times lower with the lowest 56MnO2 amount (8.0 × 107 Bq) in comparison with the highest amount, 8.0 × 108 Bq, of dispersed 56MnO2 powder. The data obtained will be used for interpretation of biological effects in experimental mice and rats that result from dispersion of various levels of neutron-activated 56MnO2 powder, which is the subject of separate studies.

Quantitative γ-H2AX immunofluorescence method for DNA double-strand break analysis in testis and liver after intravenous administration of 111InCl3

Background It is well known that a severe cell injury after exposure to ionizing radiation is the induction of DNA double-strand breaks (DSBs). After exposure, an early response to DSBs is the phosphorylation of the histone H2AX molecule regions adjacent to the DSBs, referred to as γ-H2AX foci. The γ-H2AX assay after external exposure is a good tool for investigating the link between the absorbed dose and biological effect. However, less is known about DNA DSBs and γ-H2AX foci within the tissue microarchitecture after internal irradiation from radiopharmaceuticals. Therefore, in this study, we aimed to develop and validate a quantitative ex vivo model using γ-H2AX immunofluorescence staining and confocal laser scanning microscopy (CLSM) to investigate its applicability in nuclear medicine dosimetry research. Liver and testis were selected as the organs to study after intravenous administration of 111InCl3. Results In this study, we developed and validated a method that combines ex vivo γ-H2AX foci labeling of tissue sections with in vivo systemically irradiated mouse testis and liver tissues. The method includes CLSM imaging for intracellular cell-specific γ-H2AX foci detection and quantification and absorbed dose calculations. After exposure to ionizing radiation from 111InCl3, both hepatocytes and non-hepatocytes within the liver showed an absorbed dose-dependent elevation of γ-H2AX foci, whereas no such correlation was seen for the testis tissue. Conclusion It is possible to detect and quantify the radiation-induced γ-H2AX foci within the tissues of organs at risk after internal irradiation. We conclude that our method developed is an appropriate tool to study dose–response relationships in animal organs and human tissue biopsies after internal exposure to radiation.

Organ-on-a-chip: the next generation platform for risk assessment of radiobiology

Organ-on-a-chip technology has great potential for the next generation risk estimation of low dose internal irradiation, due to its success in mimicking human organs/tissues, which possibly can significantly improve on current animal models.

EXPOSURE OF THE BIOGAS STATION OPERATORS WORKING WITH CONTAMINATED BIOMASS

The article deals with evaluation of irradiation of an operator of a 1 MW biogas station (BGS), processing silage plant biomass contaminated by 137Cs and 134Cs. External irradiation and internal irradiation by the means of aerosol particles inhalation were considered. For calculation of the external irradiation, a BGS model was created in the MCNP. The calculated total committed effective doses received by the operator during annual handling of biomass contaminated by 1 kBq per kg of 137Cs or 134Cs were 34 or 69 μSv, respectively. Three scenarios of contamination were evaluated: freshly contaminated silage after model accident, silage right after the Chernobyl accident and at the current radiation situation in the Czech Republic.