Shinji Tokonami

Hirosaki University · Institute of Radiation Emergency Medicine

At present, much emphasis is placed on the health risks associated with radioactivity present in the environment, especially since the accident at the Fukushima Daiichi Nuclear Power Plant. In this study, a walking survey was conducted in Hirosaki City using a NaI(Tl) scintillation spectrometer to estimate and map the distribution of the ambient do...

Radon (²²²Rn), a radioactive and gaseous progeny of Uranium (²³⁸U) decay series, accounts for almost 50% of the total background radiation in our dwelling environment. Inhalation and ingestion of radon in excessive amounts pose serious health effects to humans. The first-ever measurement of radon concentration in commercial bottled water available...

In thoron (220Rn)-prone areas, the contribution from thoron (including progenies) can be equal to or exceed that from radon (222Rn) during radiation exposure. The dose estimation is practically performed using the thoron concentration and thoron equilibrium factor. In the present study, thoron equilibrium factors were determined from direct measure...

This study was the first to determine the effectiveness of radon concentration measurement in water using the degassing method as a screening method based on the liquid scintillation counter method. The degassing method used two radon monitors (AlphaGUARD and RAD7) and two monitor-attached degassing devices (AquaKIT and RAD H 2 O). These were effec...

The recently discovered high-level natural background radiation area (HBRA) of Mamuju in Indonesia provides a unique opportunity to study the biological effects of chronic low-dose radiation exposure on a human population. The mean total effective dose in the HBRA was approximately 69.6 mSv y−1 (range: 47.1 to 115.2 mSv y−1), based on a re-evaluati...

Radon is well known as a radioactive gas, and the inhalation of radon and its progeny could lead to health risks, especially inducing carcinogenesis that potentially generates lung cancer. Therefore, it is essential to monitor concentrations of radon and its decay products to estimate the radiological hazards and risks to human health. In this pape...

The neutron- and X-ray-shielding, morphological, physical, mechanical, and self-healing properties were investigated for natural rubber (NR) composites containing varying gadolinium oxide (Gd2O3) contents (0, 25, 50, 75, and 100 parts per hundred parts of rubber; phr) to investigate their potential uses as self-healing and flexible neutron- and X-r...

To understand the behavior of atmospheric 129I that originated from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, activity concentrations of 129I in samples of atmospheric particulate matter (PM), comprising coarse (>1.1 μm) and fine (<1.1 μm) fractions (separated using a single stage impactor), were measured on a nearly monthly basi...

Researchers have used various methods to obtain the exhalation rates of radon and thoron from soil and building materials. One of the typical methods for radon exhalation rate is the circulation method using an accumulation container, an external or internal sampling pump and a continuous radon monitor. However, it is necessary to consider sampling...

Background: The objective of the study is to re-evaluate natural radiation exposure and to assess the related lung cancer risk to the public in the gold mining areas of Betare-Oya and vicinity. Materials and Methods: For this purpose, the car-borne survey, in-situ and laboratory measurements using a 3-in × 3-in NaI (Tl) scintillation spectrometer c...

This work experimentally determined the X-ray shielding and morphological, density, and tensile properties of sulfur-vulcanized natural rubber latex (SVNRL) nanocomposites containing varying content of nano-Bi2O3 or nano-BaSO4 from 0 to 200 phr in 100 phr increments, with modified procedures in sample preparation to overcome the insufficient streng...

The details of the dose-dependent response of serum proteins exposed to ionizing radiation, especially the oxidative modification response in amino acid sequences of albumin, the most abundant protein, are unknown. Thus, a proteomic analysis of the serum components from mice exposed to total body X-irradiation (TBI) ranging from 0.5 Gy to 3.0 Gy wa...

This article reports the radon tracing using a low-cost, locally manufactured smart electronic device with comparison to a reference radon measuring device. Developed for radiation protection and nuclear security, the proposed device consists of a ZP 1200 Geiger-Müller (GM) tube detector, low-cost components namely the Arduino microcontroller board...

A passive integrating discriminative radon-thoron monitor (Raduet) and a radon-thoron progeny monitor with a solid-state nuclear tracking detector were used for estimating indoor radon, thoron and their progeny concentrations in residential areas around the old mines of southern Thailand. Exposure to high background radiation levels from natural 23...

This paper presents the first measurement of the investigation of the health impacts of indoor radon exposure and external dose from terrestrial radiation in Chiang Mai province during the dry season burning between 2018 and 2020. Indoor radon activity concentrations were carried out using a total of 220 RADUET detectors in 45 dwellings of Chiang M...

This study focuses on the measurement of the concentrations of radon (222Rn) indoors and in the soil as well as their ambient dose equivalent rate in the cobalt-nickel bearing area of Lomié in the Eastern Region of Cameroon. A total of 98 radon track detectors (commercially RADTRAK2®, Radonova Laboratories AB, Uppsala, Sweden) were used for indoor...

Nkamouna-Kongo is a cobalt-nickel deposit located in Lomié, Eastern Cameroon. Mining cre-ates radiation exposure pathways that must be considered in risk management scenarios. RESRAD-ONSITE and RESRAD-BIOTA developed by the US DOE assess contaminated sites by deriving cleanup criteria and estimate the radiation dose and risk associated with residua...

Radiation exposure due to radon contributes most of the ionizing radiation exposure to people among natural radiation sources. This research measured the ²²²Rn, ²²⁰Rn by the RADUET and their progeny concentrations by the improved deposition based ²²²Rn and ²²⁰Rn progeny monitor, and the contribution of outdoor PM2.5 concentrations to indoors by a m...

It has been considered difficult to detect the biological effects of low-dose radiation exposure below approximately 100 mSv in humans. Serum proteomic analysis and oxidative modification profiling were conducted with blood samples collected from residents of a newly discovered high-level natural background radiation area (annual effective dose app...

A Town in Fukushima Prefecture evacuated its residents after a nuclear power accident 2011. We investigate a series of radiation risk communication round table discussions among the residents and researchers/experts over three years, beginning five years after the said evacuation order and ending one year after its partial lifting. By analyzing the...

Radon exposure is the second leading cause of lung cancer, after smoking. In upper northern Thailand (UNT), lung cancer incidence was frequently reported by Thailand National Cancer Institute. Besides smoking, radon exposure may also influence the high lung cancer incidence in this region. Indoor radon concentrations were measured in 192 houses in...

The present work reports measurements of activity concentrations of radon (222Rn) and thoron (220Rn) in dwellings followed by inhalation dose assessment to the public and the development of regulation and national radon action plan in Cameroon. Radon, thoron and thoron progeny measurements were carried out from 2014 to 2017 using radon-thoron discr...

In the long-lasting decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), the dismantling of nuclear fuel debris (NFD) remaining in the damaged reactors is an unavoidable but significant issue with many technical difficulties. The dismantling is presumed to involve mechanical and/or thermal processing of the NFD, generating significa...

222Rn and 226Ra concentrations of less than a few to several thousands of Bq L−1 have been observed in several underground bodies of water around the world. Although regulations for these concentrations in water have been implemented internationally, there are currently no regulations in place in Japan. However, concentrations that exceed these int...

Resuspension of 137Cs from the contaminated ground surface to the atmosphere is essential for understanding the environmental behaviors of 137Cs and estimating external and inhalation exposure of residents. Kajino et al. (2016) assessed the 137Cs resuspension flux from bare soil and forest ecosystems in eastern Japan in 2013 using a numerical simul...

Mamuju, Indonesia, is an area with high natural background radiation. This study assesses heavy metal content in soil samples from this area to determine the level of public and environmental hazard it presents. This study analyzes natural radionuclide elements using high purity germanium (HPGe) gamma spectrometry and performs heavy metals analysis...

The areas around Homa and Ruri hills in Homa Bay County in Kenya are associated with high background radiation levels. The activity concentration of the natural radionuclides (²²⁶Ra, ²³²Th, and ⁴⁰K) in earthen building materials used in the areas of Homa and Ruri hills has been measured using a NaI (Tl) detector in this work. The measured values of...

The International Commission on Radiological Protection (ICRP) issued its Publication 137, Occupational Intakes of Radionuclides: Part 3 in which the radon equilibrium factor is fixed as 0.4 for tourist caves; however, several studies have reported a different value for the factor and its seasonal variation has also been observed. In this study, th...

Although the epidemiological studies provide evidence for an increased risk of lung cancer risk associated with residential radon, an issue of radon-thoron discrimination remains to be solved. In this study, an updated evaluation of lung cancer risk among the residents in Gansu, China was performed where one of the major epidemiological studies on...

Radon is a major cause of lung cancer (LC) deaths among non-smokers worldwide. However, no serum biomarker for screening of LC risk in high residential radon (HRR) areas is available. Therefore, the aim of this study was to determine diagnostic values of serum carcinoembryonic antigen (CEA), cytokeratin 19 fragment (Cyfra21-1), human epididymis pro...

222Rn and 220Rn surface exhalation rates from earthen building materials used in high background radiation areas of Homa and Ruri, Kenya have been measured using an accumulation chamber coupled with RAD7 detector. Activity concentrations of 226Ra and 232Th in the building materials were determined by γ-ray spectroscopy. In Homa the average 222Rn su...

Resuspension of 137Cs from the contaminated ground surface to the atmosphere is essential for understanding the environmental behaviors of 137Cs and estimating external and inhalation exposure of residents. Kajino et al. (2016) assessed the 137Cs resuspension flux from bare soil and forest ecosystems in East Japan in 2013 using a numerical simulati...

A total of 223 sand samples collected from seven provinces in Northeastern Thailand were analyzed for their gamma radioactivity from naturally occurring radioactive materials (NORMs), and the data were used to calculate the concentrations of Ra-226, Th-232, and K-40. Radiological safety indicators such as the indoor external dose rates (Din), the a...

Recently, some commercially available active-type radon–thoron monitors were developed; however, their performance has not been characterized. This article presents the characteristics of three commercially available active-type radon–thoron monitors (RAD7, Radon Mapper, and AlphaGUARD) at different sampling flow rates. The thoron concentration mea...

Some areas around the world have anomalies with high natural radiation that may affect public health due to chronic-low-dose radiation exposure. In the paper, we summarized several studies that find Mamuju, Indonesia, a unique high natural radiation area. The majority of the relevant papers are about monitoring, main sources, and influential factor...

Mamuju is one of the regions in Indonesia which retains natural conditions but has relatively high exposure to natural radiation. The goals of the present study were to characterize exposure of the entire Mamuju region as a high natural background radiation area (HNBRA) and to assess the existing exposure as a means for radiation protection of the...

This paper does not necessarily reflect the views of the International Commission on Radiological Protection. Several radiation monitoring research projects are underway on dose assessment, biological analysis, and risk communication under an agreement with Namie Town. Indoor radon and thoron progeny concentrations have been measured using passive-...

This special issue of JRP includes a selection of research papers and review articles presented at the IRPA15 congress as chosen by the scientific committee. All invited journal contributions are suitably expanded beyond the initial conference presentations to meet the criteria for a full journal article and include (1) presentation within a compre...

In this study, a portable cascade impactor was developed to more efficiently determine the activity size distribution of attached radon and thoron progeny in a natural environment. The developed impactor consisted of four stages with a backup filter stage for collection of the aerosol samples. The aerosol cut points were set for 10, 2.5, 1, and 0.5...

Emergency medical responders (EMRs) who treat victims during a radiation emergency are at risk of radiation exposure. In this study, the exposure dose to EMRs treating hypothetically contaminated patients was estimated using a Monte Carlo simulation, and the findings may be useful for educating EMRs and reducing their anxiety. The Monte Carlo simul...

This study aimed at understanding the atmospheric concentrations of 210Pb and major ions in aerosols in Qingdao, China, including their seasonal variations and relationships with weather data and to identify the sources of atmospheric sulfur as a part of the Japan-China joint project, “Aeolian Dust Experiment on Climate Impact (ADEC)”. The sampling...

A long-term measurement technique of radon exhalation rate was previously developed using a passive type radon and thoron discriminative monitor and a ventilated type accumulation chamber. In the present study, this technique was applied to evaluate the thoron exhalation rate as well, and long-term measurements of radon and thoron exhalation rates...

Radiation exposure due to 222Rn is recognized as a matter of international concern for its health risk to humans. Portable devices for 222Rn concentration measurements, which are user-friendly, can be easily installed and provides a direct readout of values of 222Rn concentration on the built-in LCD (liquid-crystal display) and internal storage. Ho...

Ten years have elapsed since the accident at the Fukushima Daiichi Nuclear Power Plant in 2011, and the relative contribution of natural radiation is increasing in Fukushima Prefecture due to the reduced dose of artificial radiation. In order to accurately determine the effective dose of exposure to artificial radiation, it is necessary to evaluate...

The world community has long used natural hot springs for tourist and medicinal purposes. In Indonesia, the province of West Java, which is naturally surrounded by volcanoes, is the main destination for hot spring tourism. This paper is the first report on radon measurements in tourism natural hot spring water in Indonesia as part of radiation prot...

The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiat...

Emergency medical responders (EMRs), who save victims in a radiation emergency, are at risk of radiation exposure. In this study, the exposure dose to EMRs assisting contaminated patients was estimated using a Monte Carlo simulation, and will produce data that contributes to EMR education and anxiety reduction. Using the Monte Carlo simulation, we...

Ionizing radiation induces severe oxidative stress, resulting in individual death by acute radiation syndrome. The nuclear factor-erythroid-2-related factor 2 (Nrf2) plays an important role in the antioxidant response pathway. Recently, romiplostim (RP), an idiopathic thrombocytopenic purpura therapeutic drug, was reported to completely rescue mice...

The present paper outlines characteristics of thoron and its progeny in the indoor environment. Since the half-life of thoron (220Rn) is very short (55.6 s), its behavior is quite different from the isotope radon (222Rn, half-life 3.8 days) in the environment. Analyses of radon and lung cancer risk have revealed a clearly positive relationship in e...

An improved passive CR-39-based direct 222Rn/220Rn progeny detector with 3 detection channels was designed and tested in this study to measure and calculate equilibrium equivalent concentration (EEC) of both 222Rn and 220Rn without the equilibrium factor. A theoretical model was established to calculate the EEC with optimization. Subsequently, an e...

Radon is the leading source of lung cancer mortality after smoking in Chiang Mai, Thailand. Finding a source of carcinogens is one of the important measures for preventing the cancer risk for this region. Specific sites at Pa Miang, Doi Saket have the highest incidences of lung cancer and have a combination of factors that influence indoor radon co...

The aim of the study was to evaluate the risk and threshold doses of lens opacity among residents exposed to low-dose radiation. Residents aged ≥45 years were recruited from a high natural background radiation (HNBR) area in Yangjiang City and a control area selected from nearby Enping City. Lens opacities (LOPs) were classified according to the Le...

Mamuju is a region of Indonesia with relatively high exposure to natural radiation. Since 2012, Mamuju has been a uranium and thorium exploration area. Several mapping studies of the region have been carried out to depict NORM (naturally occurring radioactive material) areas and areas with uranium anomalies. This paper is the first study to use rad...

Mamuju is an area of Indonesia with high radiation exposure compared to the average across the country. It is included in the high background radiation area (HBRA) category. Radium-226 (226Ra) is one of the natural radionuclides that, if contained in drinking water, can be harmful to human health. Mamuju’s residents generally use well water for the...

The caesium retention characteristics of a potassium-nickel hexacyanoferrate resin in a polyacrylnitrile (KNiFC-PAN) matrix were tested in fresh water over the range of 2.5-400 mL min-1. The experimental setup used 2 mL resin and 4-L aliquots of freshwater samples. The results showed nearly 100% retention at speeds below 10 mL min-1, above 80% up t...

The International Commission on Radiological Protection (ICRP) recently recommended a new dose conversion factor for radon based on the latest epidemiological studies and dosimetric model. It is important to evaluate an inhalation dose from radon and its progeny. In the present study, a passive radon personal monitor was designed using a small cont...

Interest in radon (Rn) is not limited only to its impact on health and its dose to the public, but due to its properties, the techniques to analyse its behavior can be used in many fields such as radiotherapy, atmospheric physics, geophysics, geohazards, mineral exploration, and even planetary science. Nowadays machine learning methods provide extr...

Activity concentrations of 234U, 235U, 238U, 226Ra, 228Ra, 222Rn, 210Po, 210Pb, 40K, 3H, 14C, 134Cs and 137Cs were determined in 20 different Japanese bottled drinking water commercially available in Japan. The origins of the mineral water samples were geographically distributed across different regions of Japan. Activity concentrations above detec...

In Japan, the Nuclear Emergency Response Guidelines were announced in 2015 after the Fukushima Daiichi nuclear power plant accident, and each local government is currently formulating a plan for the evacuation of its residents and a subsequent radioactive contamination inspection. However, there are no reports about the state of preparation of the...

Radon (222Rn) and thoron (220Rn), sources of natural background radiation, have been the subjects of long-standing studies, including research into radon and thoron as major causes of lung cancer at domestic and international levels. In this regard, radon and thoron measurement studies have been widely conducted all over the world. Generally, the t...

The exposure from radon, thoron, and thoron progeny was measured for 45 dwellings in high background radiation area in Takandeang, Indonesia with ambient dose equivalent rate ranging from 0.34 μSv h−1 to 1.90 μSv h−1. The measurement was taken using passive radon and thoron discriminative detector and thoron progeny detector. This measurement was t...

The deposition-based direct indoor 222Rn and 220Rn progeny measurement techniques are mostly affected by the indoor environmental conditions, such as the ventilation, concentration of condensation nuclei, and reactions with the structure and its furnishings. In this study, a theoretical model of a direct 222Rn and 220Rn progeny monitor based on all...