Radiation accidents, fortunately, are rare events. However, the potential consequences can be very serious and radiation accident medical management is of great importance. In terms of clinical treatment decisions, it is crucial to rapidly obtain an estimate of the exposure scenario to predict the expected severity of radiation-induced injuries and to manage medical treatment. Accident scenarios involving dispersion of radioactive materials or nuclear power plants can mount up to large-scale events, like the accidents at Chernobyl and Fukushima. Thus, preparatory planning of the medical management of radiation accident victims is very important. Different types of radiation exposure, sometimes combined with injuries are possible and the diagnostic and therapeutic measure as well as the outcomes will accordingly differ. The absorption of significant doses of ionizing radiation will lead to acute radiation syndrome (ARS) whose clinical course depends on the absorbed radiation dose and its distribution. Besides the hematopoietic system being the most vulnerable organ system to radiation exposure, the skin plays an important role in diagnostics and treatment of radiation accident victims. Multi-organinvolvement and multi-organ-failure also need to be taken into account. Basics and principles of radiation accident medical management and the most important therapeutic approaches will be addressed.

Large scale radiological emergencies pose a particular problem for emergency preparedness because of potentially large numbers of worried well and the necessity to carry out triage in a timely manner. Here, an indispensable tool is biological dosimetry. Although a number of biodosimetric tools exist, not many have been tested and adapted for a large scale emergency scenario. In the framework of an EU-funded project MULTIBIODOSE we tested a variety of biodosimetric tools and adapted them to different mass casualty scenarios. The assays were chosen because they complement each other with respect to sensitivity, specificity to radiation and the exposure scenario, as well as speed of performance. The project was completed in April 2013. Its major conclusions are presented.

This paper describes performance experiments of a humidity control system in a thoron ²²⁰Rn chamber which adjusts and controls the humidity inside the chamber. The easily constructed and used humidity control system has a perfluorosulfonic membrane (commercially known as Nafion^®) tube as the air humidity conditioner. The tube includes tube moisture exchangers that allow the transfer of water vapor between a flowing sample gas stream and a flowing purge gas stream over the exterior surface of the tube. Thus the tube has an advantage of being able to adjust the sample air flow to the desired humidity conditions. We investigated the optimal operation of the air humidity conditioner, including such items as response time to humidity, ability to control the humidity in the air and the losses of ²²⁰Rn gas in passing through the air humidity conditioner. Our first experiment showed that the performance of the air humidity conditioner depended on the flow rate conditions of sample and purge air flows. Only small losses due to decay of ²²⁰Rn and adsorption of ²²⁰Rn gas onto the tube surfaces were also evident. In the second experiment with the ²²⁰Rn chamber, we were able to adjust and control the humidity in the chamber using the humidity control system with the air humidity conditioner.

This article describes our participation in a civil protection training exercise with a dirty bomb scenario that was held jointly by the Japanese government (Cabinet Secretariat), Aomori Prefecture and Hirosaki City on November 7, 2013. Our missions took place mainly in an evacuation area (safe shelter) and included a surface contamination survey, decontamination, risk communication, and interviews on participants‘ symptom and history. In total, 40 members of our faculty played important roles in this exercise in cooperation with staff from other organizations. About 240 evacuees were transported to an evacuation area for surface contamination surveys, interviews, group risk communication and filling out registration forms. Decontamination or personal consultation was also performed if necessary. Despite some confusion caused by multiple staffs from different organizations working together and many casualties coming in one after another, we believe that most of our tasks were successfully implemented as a result of our faculty’s experience with the project for radiation emergency medicine (REM) professions. Although nuclear disaster is considered rare, its effects are serious, and we must prepare a system to enable an effective response Our project which involves developing human resources for REM is considered essential for this purpose.

Exposure to radon occurs not only by inhaling radon but also by drinking water. When using the direct method, the radon concentration in water is measured with a conventional liquid scintillation counter (LSC), which can measure samples contained in vials up to 20 ml. The purpose of our research is to develop effective measures for lowering the minimum detectable radon concentration. For the present study, the radon concentration in water was determined using a high efficiency LSC, which can measure larger than usual samples and hence detect lower minimum radon concentrations. In this case, it is a problem that only a few institutes are equipped with the high efficiency LSC. Moreover, the samples are not designated as articles prohibited for mailing by the Japanese Postal Law if they have been prepared. But, by using a mineral oil scintillator with an ignition point higher than 30℃, the samples can be transported to measuring institute without being designated as articles prohibited for mailing by the Japanese Postal Law. We examined the conditions for that. The results suggest that radon leakage from samples contained in Teflon LSC 100 ml vials is negligible for 6 days after sampling. When samples can be mailed to an institute equipped with a counting system capable of measuring the 100 ml vials, results of the samples can be obtained at lower minimum detectable radon concentrations.

The radioactivity released from the Fukushima Daiichi Nuclear Power Plant (F1NPP) into the environment after an accident clearly decreased. The decrease in radiocesium on the surface of the ground directly results in a decrease in the ambient dose rate. The term “terrestrial halflife” was used to describe the decrease of a radionuclide only from the surface of the ground due to weathering. Terrestrial half-lives of cesium on artificial pavement was determined to be 1.1—2.6 y using official monitoring dose-rate data measured in several areas of the Fukushima region.

The aim of this study was to measure two parameters concerning the severity of acute radiodermatitis and to investigate the clinical relevance of the measurement, considering the implication of preventive and protective skin-care for the radiodermatitis. The subjects were five patients with breast cancer who underwent postoperative radiotherapy after breast-conserving surgery. Skin surface temperature (SST) and erythema intensity (EI) within the irradiated fields were measured twice, during radiotherapy and one month after. The measurement during radiotherapy was performed in the last week of radiotherapy, and the irradiated dose ranged from 44 to 48 Gy. For the contralateral breast, measurement was also performed as a control. The SST during radiotherapy was 1.1±0.7 (average±standard deviation), and that after radiotherapy 1.0±0.3. The EI during radiotherapy was 101±44, and that after radiotherapy 85±55. No significant difference in the values during and after radiotherapy was observed for each of the parameters. Inflammation of the irradiated skin tissues appeared to continue even one month after radiotherapy. Therefore it was suggested that skin-care is needed for a certain period following radiotherapy as well as during the therapy in order to prevent the condition of irradiated skin becoming worse.

Introduction

Anthropogenic radionuclides of plutonium (Pu) have been released into the environment because of atmospheric nuclear weapons testing. In addition, Pu can be used as fuel after reprocessing the spent nuclear fuel. Therefore, Japan plans to reprocess nuclear fuel; hence, it is important to investigate the behavior of Pu in the environment. The purpose of this study was to review the existing literature related to the fate of Pu in the environment and to estimate the internal exposure dose of residents living near the Sellafield reprocessing plant. In particular, the study focused on internal radiation exposure based on the consumption of seafood.

Sources of Pu in the environment

The principal source of Pu in the environment is the fallout caused by atmospheric nuclear weapons testing. Pu can be released from other sources including nuclear fuel reprocessing plants, falling satellites, accidents during nuclear weapon transportation, and during nuclear facilities accidents. Pu has been distributed throughout the world because of atmospheric nuclear testing. Other sources have a more localized affect and can be distinguished according to the differences of ²⁴⁰Pu/²³⁹Pu atom ratios.

Estimating internal radiation dose from the Sellafield reprocessing plant

The Sellafield site consists of various nuclear facilities that have discharged radioactive materials into the Irish Sea since the 1950s. Discharge of Pu from reprocessing plant operations and the total discharge amounts of ^{239, 240}Pu and ²³⁸Pu were 587 TBq and 144 TBq, respectively. The environmental monitoring of radionuclide levels around the Sellafield reprocessing plant was performed by a U.K. government agency. The present study estimates the internal exposure dose of residents by determining Pu concentrations in seafood and the average yearly seafood consumption of residents. Figure 1 shows that the internal radiation dose from Pu was up to 10 mSv in the late 1970s, which was approximately 1/10 lower than the internal radiation dose from ¹³⁷Cs. Moreover, the global average dose was 290 mSv. Thus, the internal radiation dose from Pu near the Sellafield reprocessing plant was considerably lower than that from other sources such as ¹³⁷Cs and the global average.

After the atomic bombings in 1945, the incidence of thyroid cancer increased among residents of Hiroshima and Nagasaki, Japan. Similarly, the incidence of thyroid cancer substantially increased among the exposed children or adolescents in Belarus, Ukraine, and the four other affected regions of the Russian Federation after the Chernobyl disaster. This trend has been maintained even 20 years after exposure, with 5127 cases (among those aged < 14 years in 1986) and 6848 cases (among those aged < 18 years in 1986) of thyroid cancer have been reported between 1991 and 2005 in Belarus, the Ukraine, and the affected regions in the Russian Federation.

The average thyroid radiation dose, mainly due to consumption of milk contaminated with I-131 during the first few weeks following the accident, was estimated be approximately 490 mGy. There is no doubt that this increased exposure to radioiodine due to the Chernobyl disaster has substantially contributed to the increase in the incidence of thyroid cancer. Therefore, the possible health risks in the evacuees of the Fukushima disaster is of concern, particularly those of infant thyroid cancer due to the release of radioactive iodine 131 _{I into the environment. Local health authorities measured thyroid activity of 1149 children} aged <15 years in Iwaki City, Kawamata Town, and Iitate Village, Japan, from March 24–30 in 2011. The maximum dose was considered to be equivalent to a thyroid dose of 35 mSv. 131 _{I activity measurements in the thyroids of residents and evacuees in Namie Town during} the period from April 12–16 were also conducted. The Tsushima District of Namie Town is located within a 30-km radius of the reactor. ¹³¹I activity in the thyroids of 46 out of the 62 residents and evacuees were measured. The median thyroid equivalent dose was estimated to be 4.2 mSv and 3.5 mSv in children and adults, respectively. The maximum thyroid doses for children and adults were 23 mSv and 33 mSv, respectively. Considering the relatively low levels the present estimated thyroid gland equivalent radiation dose, an increased in the incidence of thyroid cancer among Fukushima disaster survivors is less likely.

Radiation and radioactive materials are generally used in various medical fields for diagnostic imaging or blood inactivation for blood transfusion. Furthermore, they are useful in non-destructive tests, growth inhibition of agricultural products, and industrial sterilization. Despite their useful applications in specific fields, their influence on human health cannot be neglected. Although radiotherapy is one of the most typical therapeutic methods for cancer treatment, side effects generally follow each treatment in many clinical cases. Therefore, mitigation methods are required to alleviate the side effects of radiotherapy for achieving optimum therapeutic effects of cancer treatment. To this end, many studies have been performed to reduce the side effects of radiations and to protect human bodies from the radiations. There are several types of medicines known as typical radiation protective agents such as amifostine (WR-2721), which exhibits radioprotective effect by radical elimination or low oxygen action, and it can improve the production of hematopoietic cell growth factors such as G-CSF and GM-CSF. Other medicines include Prussian blue, a chelating agent, and stable iodine, which promote the excretion of radioactive materials induced by internal contamination. However, no radioprotective medicine for clinical usage has been approved in Japan so far. Therefore, the development of a new material for radioprotective medicine is in urgent need. In the development of radiation-protective agents, not only drug development processes but also the search for functional food materials has been performed. However, very little knowledge about the medical effects and toxicity of the food material with radiological protection function has been accumulated. In this review, medical data about radioprotective functional foods reported from 1990 to 2012 has been verified and medical verification about the validity of the data and the data-analysis method has been performed. A structured abstract of about 88 archived research reports extracted from PubMed is created. The analytical result suggested that most of the reports about radioprotective functional food material were at rudimentary medicine level. Furthermore, standardization of medical evidence data has not been performed to date; and it is difficult to compare the effect of each type of material objectively. Therefore, the development of standardized models consisting of safety assessment and further data verification models is needed. However, since some materials have been followed until the clinical trial stage, the application of radiation-protective agents that utilize functional natural food materials is expected.