Human exposure to the natural radiation environment and the consequent radiation doses can serve as a benchmark against which different artificial radiation exposures can usefully be compared. In radiation risk communications with the public such comparisons can help the public to have an informed perspective of radiation exposures and risks. A short overview is given here of the main components of natural radiation to which humans are exposed both externally and internally. The average annual global effective dose from radiation has been estimated by UNSCEAR to be about 3.0 mSv of which approximately 80% (2.4 mSv) is due to natural radiation. At the level of the individual, however, a wide variability of doses from natural radiation exists. This is true in particular of the doses received in the indoor environment from the inhalation of airborne progeny of radon and thoron gases. This account of some aspects of natural radiation in the environment is based on the 1st IRSCC (International Radiation Science Collaboration Centre) Seminar of the Institute of Radiation Emergency Medicine, Hirosaki University, Japan which was given by the author of this paper in February 2021.
Research has been conducted to speed up and simplify the 90Sr analysis method in water samples based on the importance of 90Sr measurement for environmental monitoring in the event of a radiological incident. To optimize the measurement with ICP-MS, which enables rapid analysis, we examined the pre-treatment conditions when cation exchange resin chromatography and Sr Resin solid-phase extraction were used. Sr was quantitatively recovered by cation exchange resin from 1 L synthetic water samples, and anionic components such as Ge and Se were efficiently removed. In addition, under the elution condition using 3 M HNO3, it is possible to suppress the elution of Zr with a small volume of eluent. The eluate from cation exchange chromatography can be used for successive solid-phase extraction of Sr-Resin directly, which provides further Sr purification and concentration sufficient for 90Sr determination by ICP-MS. Verification was performed on real samples including high hardness bottled water. We confirmed that the results of the synthetic sample analysis were reproduced, and that Sr was quantitatively recovered (96-100%) and coexisting elements were removed sufficiently so as not to interfere with the measurement of 90Sr. 90Sr was concentrated by a factor of 100 during chemical separation procedure without any evaporation step. Processing time for more than 10 samples was 3 hours, which is fast enough for emergency response in the case of radiological incident.
In Yomitan-son, a village of Okinawa prefecture located in the subtropical region of Japan, the highest annual average of indoor radon (222Rn) concentration, 220 Bq m-3, has been observed in a private residence by a nationwide survey. In this study, to estimate the distribution and origin of the high concentration, measurements for atmospheric radon were conducted on eight dwellings intermittently from 2005 to 2013. And in situ measurements of gamma radiation energy spectrum on the outdoor ground were performed at 26 points in 2018 to estimate the origin of the high indoor radon concentration. As the result, the highest indoor radon concentration, 289 Bq m-3, was observed in a dwelling. For the seasonal variation, indoor radon concentration in winter is obviously higher than that in summer was observed in several dwellings. From the results for the analyses of gamma radiation data, useful information about the origin of the high indoor radon concentration was not provided in this study.
The impact of COVID-19 has hampered participative training over the last few years at the Advanced Radiation Emergency Medical Support Center and Nuclear Emergency Core Hospital. Therefore, the Advanced Radiation Emergency Medical Support Center at the Hirosaki University has introduced e-learning since 2020. Monthly notifications of e-learning opportunities were sent to each department. According to a survey regarding internal training completion rate in radiation emergency medicine since the start of the training program, as of March 2021, 89.3% of all Hirosaki University Hospital employees have already completed training. Thus, human resource development in the hospital had progressed steadily; including training in 2020, when e-learning was introduced. This indicates that e-learning effectively promotes participation. In addition, detailed notifications about events were provided to each department, which was effective in raising awareness among staff and improving attendance. In this paper, we report the details of our training program through e-learning.
Dose assessment is very important to triage exposed patients and to carry out efficient medical care and treatment in radiation emergency medicine. In cytogenetic biodosimetry, peripheral blood collected from exposed patients must be cultured to induce chromosome-analyzable metaphases in peripheral lymphocytes. Medical institutions that accept exposed patients must understand the time of blood sampling, choice of anticoagulant, temperature conditions for blood storage according to the type of anticoagulant and the method of blood transportation to the laboratory for biodosimetry. However, as medical institutions tend to have insufficient understanding on blood collection and shipment required for biodosimetry, this information must be provided to aid in reliable dose estimation. In addition, dose assessment requires some basic information from patients such as age, gender, smoking history, alcohol intake, underlying medical conditions and previous radiation exposures including occupational and medical exposure. The medical institution should also be prepared to provide such information to the biodosimetry laboratory. This article provides a summary of essential information from blood collection to blood transportation carried out by medical institutions for cytogenetic biodosimetry.
In a biodosimetry laboratory, blood collected from exposed patients is cultured and the exposure dose is estimated based on the frequency of chromosome aberrations. Blood is defined as an infectious specimen because it may contain hepatitis virus and human immunodeficiency virus (HIV) and must be handled in a biosafety level (BSL) 2 facility. Due to the recent coronavirus pandemic with SARS-CoV-2, further strengthening of infection control measures is required. This article outlines the requirements for setting up a BSL2 laboratory, personal protective equipment for infection control, treatment of infectious biological waste and emergency response measures. Furthermore, it is essential to safely manage hazardous chemicals used in biodosimetry. Biodosimetry laboratories should conduct risk assessments of blood handling and chemical use and consider risk mitigation measures. In addition, laboratory personnel must educate workers on infection control and chemical safety.