Radiation Emergency Medicine Vol.4, No.2
- Publisher : Hirosaki University Press
- Language : English
- ISSN : 2186-8026 (PRINT)
- Release : August 2015
- Issue : Hirosaki University Press
- pp. 1-85
- Methods and Their Application to Epidemiology on Cancer and Radiation (4)
Natural Radiation in the Geological Anomaly of Pocos de Caldas Plateau, Minas Gerais, Brazil
The Pocos de Caldas anomaly has been subject to attention of geologists for many years. It is an about circular shaped structure of about 30 km diameter, elevated a few 100 m above the surrounding region, formed by an alkaline intrusion including volcanic activity. Within this geological unit there are geochemical anomalies, such as a uranium deposit which has been exploited by a U mine (now under remediation), and the notable Th and RE anomaly Morro de Ferro where ambient dose rate up to several 10 μSv/h is encountered. Several small cities are located in the otherwise rural region with population together about 200,000.
We give an overview on the geological setting and present data of radiometric surveys, which have been performed over the years. In the last years, they have been intensified and include detailed surveys of ambient dose rate, indoor Rn, and since recently, Rn in soil. In a few cases, largely increased indoor Rn concentrations up to above 1000 Bq/m3 were found. In addition, epidemiological data of cancer mortality are available which however require very considerate and restrained interpretation.
Mapping the Geogenic Radon Potential and Estimation of Radon Prone Areas in Germany
The geogenic Rn potential (RP) is conceptualized to quantify what “Earth delivers” in terms of Rn. The RP indicates the potential risk at a location or as mean over an area, which can arise due to indoor Rn in a building, originating from geogenic Rn, and depending on its physical characteristic regarding Rn infiltration. In geogenic Rn prone areas (RPA) which are ones with RP elevated after given criteria, the probability of encountering elevated indoor Rn concentrations is also elevated, again depending on house characteristics.
In Germany, the RP is estimated from Rn concentration in soil air and soil permeability, with geology as auxiliary categorical predictor. The hazard level is “calibrated” by relating the RP to indoor Rn concentrations in standardized types of dwellings, which by applying “hazard thresholds” leads to delineations of RPAs. The purposes of identifying RPAs are more efficient allocation of resources to intensified surveying, remediation and possibly implementation of building codes. It is also part of the national “Rn action plan” required by the new EU Basic Safety Standards.
We present an outline of methodology and show how RP and RPA maps can be generated. As examples, RP and RPA maps of Germany are shown.
Survey of Radioactive Contamination along Mt. Fuji's Climbing Routes Following TEPCO's Fukushima Daiichi Nuclear Power Plant Accident
TEPCO’s Fukushima Daiichi Nuclear Power Plant (FDNPP) accident occurred in March 2011,and the resulting release of radioactive nuclides contaminated Mt. Fuji’s ground surface. It was of great concern that climbers would be at a risk of being exposed to elevated radiation levels at Mt. Fuji. In this study, dose rates in air (absorbed dose rates in air) were continuously measured while climbing along two popular climbing routes: the Yosida (Kawaguchiko) and Subashiri routes. The dose rates ranged from 15 to 24 nGy/h, which are less than the background level for terrestrial gamma rays in Japan (51 nGy/h). This study suggests that the deposition of artificial radioactive nuclides over the Mt. Fuji and its climbing routes has little effect on the increase of the dose rates in air.
Transmission of Light through Recoiled Proton Tracks in Polycarbonate
Effect of light transmission through particle tracks due to scattering may be useful for softening the light to prevent glare in room lighting and in photography. This research aimed to investigate the effect of track density and track size of recoiled proton tracks registered in polycarbonate (PC) sheet on transmission of light. Locally-available PC plastic sheets for sunshade were irradiated with neutrons to produce latent recoiled proton tracks from (n,p) reaction. The latent tracks were then etched in a PEW solution which composed of 15% KOH, 40% ethanol and 45% water. The recoiled proton tracks were observed under an optical microscope and characterized by using the ImageJ program to obtain the average track density and size. Light and infrared transmission were finally tested using an energy transmission meter-SD 2400. In this study, four proton track-etch PC plastic sheets were prepared at 3 and 7 day irradiation times and different etching times from 15 to 60 minutes. The results showed that the prepared track-etch PC sheets could reduce intensity of visible light and infrared by approximately 4.7-15% and 1-12% in comparison with the untreated polycarbonate,respectively. The degree of reduction increased with increasing of track density. It could be concluded that the recoiled proton track-etched in PC sheets with different track densities lead to variation of transmission of visible light and IR by scattering with proton tracks.
A Comparison Study of Commercially Available Survey Meters for Measurement of Gamma-rays
In this study, we investigated the response of six models of commercially available survey meters for measurement of radiation dose rate of the background on the Bunkyo-cho campus of Hirosaki University. The 1 cm equivalent dose rate at nine places on the campus for the low to high dose rates ranged from 20 to 110 nSv/h. Even for the same measurement location, the readings differed greatly among the survey meters. For four of the models, the arithmetic mean of the relative standard deviation of the 1cm equivalent dose rate exceeded 10%. From the relationship between the absorbed dose rate in air obtained by the NaI(Tl) scintillation spectrometer and the 1cm equivalent dose rate of each survey meter, it was judged that the scintillation type survey meter showed good linearity and had only a small variation in the readings for natural radiation level. These results suggested that it is important to confirm beforehand both the variation and the response sensitivity of the readings of the survey meter even within the natural radiation dose rate of the background.
mRNA Expression Profiles in Human Lymphoid Progenitor Cell are Modified by High-dose Ionizing Radiation
The treatment of lymphocytopenia induced by high-dose ionizing radiation (IR), a component of acute radiation syndrome (ARS), is an important issue in radiation emergency medicine.
A limited stockpile of cytokines (hematopoietic stimulation factors) is recommended by the International Atomic Energy Agency in case of radiation disasters leading to high numbers of ARS cases. We hypothesized the presence of a radiosensitive target molecule specifically in lymphoid cells (the most radiosensitive lineage of hematopoietic cells) could improve treatment of ARS through pharmacological intervention. To examine this, human lymphoid progenitor mRNA from IM-9 cell was isolated and analyzed using cDNA microarray. The mRNA profiles demonstrated a strong correlation between IR and up-regulation of p53 signaling and 10 other molecules that together constituted a complete signaling pathway (TNFRSF10B, FAS, PIK3CG, BBC3, TP53I3, CDKN1A, JUN, MDM2, RRM2B, and TP53INP1). Only one member of this pathway, RB1, was found to be down-regulated. The induction of apoptosis and accumulation of G2/M cell cycle phase were observed following IR. These results identified that behavior of lymphoid progenitor cell following IR regulates apoptosis-related signaling and cell cyclerelated signaling by eleven mRNAs. In our next study phase, we aim to verify whether the alternation of these gene expressions is similarly observed in each lymphoid lineage (from immature progenitors to mature cells) and other radiosensitive cell types following IR, and whether gene expression control is possible in lymphoid cells.
210Po, 210Pb, 226Ra, 232Th, 40K and 137Cs Concentration of Medicinal Herbs
The 210Po, 210Pb, 226Ra, 232Th, 40K and 137Cs activity concentrations were measured related to dry material of ten types of medicinal herbs factory packaged for making tea. For 210Po measurement alpha-spectrometry was applied, while the rest of the radionuclides were determined by gammaspectrometry method. In case of 210Po the highest activity concentration (10-19 Bq/kg) was measured in herbs consisting of only leaves, while the lowest activity concentration ( ≤ 2 Bq/kg) was measured in medicinal herbs consisting of solely flowers and for 210Pb similar trend was found. For the rest of the radionuclides of natural origin the relation was not so obvious. In case of 137Cs, the measured values were lower (0.4-1.6 Bq/kg) in cultivated medicinal herbs, than in case of wild grown samples (0.4-20 Bq/kg).
Comparison between Irradiation Side Sampling Flat-Panel Detector System and Computed Radiography System for Reduction of Radiation Exposure
As digital image equipment for X-ray, computed radiography (CR) systems and flat-panel detector (FPD) systems have become the mainstream. Additionally, newer FPD systems have been developed that offer high-resolution irradiation side sampling (ISS-FPD), and reduction of each patient incident skin dose is expected. Accordingly, we measured image qualities of an ISS-FPD system and a CR system and compared them for the purpose of reducing radiation exposure. In comparing a lying-position X-ray photographing table-integrated ISS-FPD and a CR system, pre-sampled modulation transfer functions (pre-sampled MTFs), normalized noise power spectrums (NNPSs), and detective quantum efficiencies (DQEs) were measured. Furthermore, visual evaluations by the use of image quality figures (IQFs) were carried out by photographing Burger phantoms. As a result, DQEs of the ISS-FPD were higher and suggested the reduction of radiation exposure by approximately 50%. Also, in the visual evaluation, IQFs of the ISS-FPD system were lower than those of the CR system, suggesting that radiation exposure can be reduced. Our results indicate that this method does not evaluate performance of an image receptor as a single unit but can compare reduction of radiation exposure by calculating the DQE even in image equipment with an integrated grid.
Radiation Exposure Problems of Tourist Cave Workers Originating from Radon in Relation to the New IAEA BSS and ICRP Recommendations
The regulation of radiation exposure originating from radon has become strict during the past years; in 2014 the reference level was given to be 300 Bq/m3 in case of dwellings and other buildings with high occupancy factor by International Basic Safety Standards (IAEA BSS) – released by IAEA) – or the maximum allowable value in non-radiation conditions (radiation workers)1). We had previously been surveying the changes of radon concentration in the tourist cave’s air for 8 years, and had measured the radiation exposure of those working there for 11 years. The 8-year average of radon concentration was 7430 Bq/m3. Before the renovation works at the end of 2011 (removing previous coal slag filling) it was 8630 Bq/m3, while during the years 2012-2014 it was 5430 Bq/m3, however, it still considerably exceeds the current reference level of 1000 Bq/m3 (and that planned for the future as 300 Bq/m3). The workers’ radiation exposure has been surveyed individually using track detectors during the past 11 years. The average number of workers was 12 per year and the average radiation exposure was 10.6 mSv/year which resulted in a committed effective dose of 18.55 mSv/year calculated using the new recommendation. During the 11 years the annual effective dose exceeded 20 mSv/year in 6 cases.
Applying the new dose conversion factor the actual radiation exposure exceeded the 20 mSv year value in 44 cases where the average radiation exposure was 28.9 (20.4-53.0) mSv/year.