Radiation protection dosimetry最新文献

Ionizing radiation not only affects irradiated but also non-irradiated surrounding cells through intercellular communication, indicating that the former cells could affect the latter. The present study investigated the effect of X-irradiated normal human lung fibroblast WI-38 cells on the clonofenic potential of human lung cancer A549 cells by co-culturing them. Moreover, the relationship between the effects of co-culturing on the clonogenic potential of A549 cells and cellular senescence in WI-38 cells was investigated. The co-culture with 10-Gy-irradiated WI-38 cells and A549 cells enhanced the clonogenic potential of non- or X-irradiated A549 cells. Irradiated WI-38 cells exhibited high SA-β-gal activity, a cellular senescence hallmark. Importantly, treatment with senolytic drugs, which eliminate senescent cells, not only influenced high-SA-β-gal-activity cell percentages among the irradiated WI-38 cells but also the effect of irradiated WI-38 cells on the clonogenic potential of A549 cells. In conclusion, our results suggest that irradiated WI-38 cells promote A549 cell clonogenic potential and irradiated senescent WI-38 cells contribute to this effect.

Cancer risks attributable to low-dose and low-dose-rate radiation are a serious concern for public health. Radiation risk assessment is based on lifespan studies among Hiroshima-Nagasaki A-bomb survivors; however, there are statistical limitations due to a small sample size for low-dose radiation. Therefore, basic biological studies are helpful in understanding the mechanism of radiation carcinogenesis. The detrimental effects of ionising radiation (IR) are caused by reactive oxygen species (ROS)-mediated oxidative DNA damage. IR-induced delayed ROS are produced in the electron transport chain reaction of the mitochondrial complex. Thus, mitochondria are a source of ROS and a primary target for ROS attacks. Consequently, mitochondrial dysfunction is thought to be a key event in the metabolic changes of cancer cells and is important in radiation-induced carcinogenesis. In this paper, we present recent findings on radiation carcinogenesis effect assessment, focusing on mitochondrial function as stress sensors.

The radon (Rn) and thoron (Tn) concentrations and other environmental parameters were measured in the vicinity of active faults in two regions with different geology structure of Japan. The range of measured values was from 1.2 to 74 kBq m$^{-3}$, 1.1 to 38.9 kBq m$^{-3}$, 0% to 4.35%, and 2$times $10$^{-13}$ to 4$times $10$^{-11}$ m$^{2}$, for Rn, Tn, CO$_{2}$, and soil permeability, respectively. Significant differences in the measured parameters were observed, suggesting that Rn concentrations near faults are strongly influenced by geological structure and fault type. Based on statistical analysis, good correlations were found between Rn, Tn, and CO$_{2}$ (carried gas ) concentrations. It is planned to continue the study with measurements at a number of additional sites.

This study investigated the induction of DNA double-strand breaks (DSBs) in the hTERT-immortalized normal human diploid epithelial cells (RPE1-hTERT) continuously exposed to 6000 Bq/ml of tritiated water (HTO) and organically bound tritium (OBT). The relationship of the DSBs induction with the intracellular amount as well as the localization of tritium was also examined. Tritium-labeled thymidine (3H-Thy) and palmitic acid (3H-PA) were used as OBT. The average number of DSBs, which were indicated as co-localized foci of 53BP1 with phosphorylated H2AX, per cell was higher in the order of treatments with 3H-Thy, 3H-PA, and HTO. This order was consistent with that of tritium localization in the insoluble nuclear fraction but not with the intracellular amount of tritium. In addition to the intracellular amount of tritium, we showed that the subcellular localization of tritium is an important factor in cellular effects stimulated by DSBs.

Radiation disasters can lead to a myriad of direct and indirect health effects. The term 'disaster-related deaths' is commonly used in Japan; however, comprehensive studies in regions severely impacted by nuclear accidents are scarce. Our research primarily focuses on Minamisoma City, situated north of the Fukushima Daiichi Nuclear Power Plant (FDNPP), and aimed to study the risks associated with evacuation and disaster-related death. We introduce the following studies: (1) risks from evacuation in elderly care facilities after the FDNPP accident; (2) detailed case reports on hospital evacuation and (3) detailed reports on disaster-related deaths. A critical lesson from the FDNPP accident is the significant risk to life posed by evacuation actions taken to avoid radiation exposure. Despite evacuation being an effective measure to reduce exposure, our preparation and knowledge are insufficient for safe execution. This paper ensures that the lessons from Fukushima are leveraged in future radiation protection measures.

This study summarises the responses to information on thyroid cancer, which possibly provoked misunderstanding and unfounded rumour, described in a letter issued by five former Japanese Prime Ministers on 27 January, 2022. Fukushima Medical University (FMU) implemented countermeasures and follow-up in three phases in response to the letter. In Phase 1, FMU shared scientific facts on the relationship between radiation exposure and thyroid cancer, as well as the response of FMU towards those who read the letter and were concerned about the description. Furthermore, FMU organised lectures and workshops to facilitate peer support among medical and non-medical staff, which were publicised through a newspaper article. In Phase 2, the peer support programme targeting patients with thyroid cancer was launched. In Phase 3, FMU participated in a TV programme to explain the medical aspects of thyroid cancer and the importance of providing peer support to patients with cancer, featuring individuals with experiences as medical staff and survivors.

Long-term changes in particulate and dissolved 137Cs concentrations in rivers and dam reservoirs have been reconstructed using 137Cs depth distributions in bottom sediments near Chornobyl and Fukushima. However, few studies have applied this method to pond water. This study tested the applicability of this reconstruction method in ponds within the Fukushima evacuation zone. Bottom sediments in ponds were collected in November 2019. Our reconstruction of a shallow closed pond disagreed with our observations. Even in ponds where the reconstruction agreed well with observations, underestimations may have occurred because the time constant for the decrease in 137Cs concentration was lower than those previously reported. We conclude that the present reconstruction method may be applied to deeper Fukushima ponds with inflow and outflow, but underestimations of initial 137Cs concentrations in water may lead to uncertainties. For realistic reconstruction, attention should be paid to pond characteristics, catchment conditions, and sediment core selection.

Researchers have stressed that crops may absorb radioactive cesium (Cs) in the soil and translocate it to its edible parts. Therefore, a method was developed to suppress Cs absorption through high K fertilisation. However, this method is less effective for rice plants after ear emergence, thus demanding the application of a suppression method at this stage. In this study, we test whether immersion of ears in a Ca solution during its ripening period could suppress the translocation of Cs from roots to brown rice. The results show that the translocation of Cs absorbed from the hydroponic solution to brown rice is reduced based on the Ca concentration applied to the ears. In addition, differences in the inhibition of translocation were observed among the different Ca salts. In addition, the effect of immersion of ears in Ca solution on Cs translocation was effective at lower concentrations than that effective for K.

In applying fluorescent nuclear track detectors for heavy ion measurement, the fluorescence intensity directly influences linear energy transfer (LET) estimation. However, the conventional analysis highly depends on the analyzed depth and the reference frames from the optical readout. To improve the accuracy of measurements of heavy ions, the gradient of intensity and moving average fluorescence intensity were acquired and calculated to optimize the measurement conditions. The results indicate that the intensity gradient is an alternative quantity to discriminate ions with different LET, and the moving average fluorescence intensity is readily differentiated among individual ions without overlapping values in fluorescence intensity. The scanned range of 25-45 μm is suggested to be the most suitable depth for measurement. To exclude the impact of the variation in fluorescence intensity on evaluation, it is recommended to use the quantities calculated in moving averages with depth in the future.

Nuclear fuel reprocessing plant releases several kinds of radioactive nuclides, mainly 3H and 129I, into the oceans. Radio iodine causes thyroid dose. Iodine accumulates in several marine species such as wakame and abalone, which are food materials. Therefore, an analysis of iodine behavior in the marine environment is important to assess the impact of 129I. Iodine in seawater exists mainly in two chemical forms: iodide (I-) and iodate (IO3-). Their environmental behaviors are different. Thus, understanding these behaviors is important to assess the environmental behavior of total iodine. In this study, iodate and iodide transfer between seawater and abalone (Haliotis discus hannai) with 125I tracer was observed.