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Journal Articles

Measurement and analysis of long-term variation of atmospheric $$^{7}$$Be activity concentrations in Dazaifu (western Japan)

Narazaki, Yukinori*; Sakoda, Akihiro; Akata, Naofumi*; Ito, Hisanori*; Momoshima, Noriyuki*

Journal of Environmental Radioactivity, 284, p.107612_1 - 107612_7, 2025/04

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

Atmospheric $$^{7}$$Be activity concentration was continuously measured in Dazaifu, western Japan, from 1999 to 2020, and its variation was analyzed. Daily $$^{7}$$Be data analysis, encompassing an analysis for 22 years, revealed a concentration range of not detected - 18 mBq/m$$^{3}$$, characterized by substantial monthly variation and smoothed annual variation. An average daily $$^{7}$$Be activity concentration of 5.0 $$pm$$ 2.6 mBq/m$$^{3}$$ was considered to be representative at the ground-surface-level in 30-40$$^{circ}$$N. Results from a two-way Analysis of variance (ANOVA) indicated statistical significance in monthly and annual $$^{7}$$Be variabilities. The monthly variability of $$^{7}$$Be activity concentration was approximately four times greater than the annual variability. Frequency analysis revealed that the monthly variability comprised major 12-month and minor 6-month periodicities. The substantial decrease in $$^{7}$$Be activity concentration during summer, a primary driver of monthly variation, was also observed at other locations in Japan, attributed to a stable high-pressure system in the Pacific Ocean that stalled over Japan's southern seas, followed by the inflow of air masses containing low $$^{7}$$Be activity concentrations. The annual variation was primarily influenced by the 11-year solar activity cycle, which affects the intensity of cosmic rays that produce $$^{7}$$Be.

Journal Articles

Recent research trends on indications for radon spa therapy and their mechanisms

Kataoka, Takahiro*; Sakoda, Akihiro; Kanzaki, Norie; Mitsunobu, Fumihiro*; Yamaoka, Kiyonori*

Nihon Onsen Kiko Butsuri Igakukai Zasshi, 16 Pages, 2024/11

Spa therapy in Misasa (Tottori Prefecture, Japan) is renowned worldwide for its radon therapy (particularly high-concentration radon hot-air bath therapy) along with mine therapy in Bad Gastein (Austria) and Montana (USA). Radon therapy is indicated for diseases related to the respiratory system, pain, digestive disorders, chronic degeneration, and aging caused by reactive oxygen species; however, most of these indications are based on empirical prescriptions. To address this, the authors have been conducting basic research to experimentally and mathematically identify significant radon and its progeny exposure pathways and their related behaviors in the body. The aim is to quantitatively evaluate the relationship between the biological reactions caused by radon inhalation and the absorbed doses in tissues and organs, and to elucidate new mechanisms related to these indications. Therefore, the mechanisms are being elucidated in terms of a series of moderate physiological stimuli caused by small amounts of oxidative stress induced by radon inhalation. Specifically, radon inhalation enhances antioxidant, immune regulation, and damage-repair functions; promotes anti-inflammation, hormone secretion, and circulatory metabolism; and induces apoptosis and heat shock proteins. New indications have been suggested, including inflammatory and neuropathic pain, inflammatory edema, gastric mucosal damage, ulcerative colitis, hyperuricemia, type 1 diabetes, liver and kidney damage, transient cerebral ischemia, and depression. Furthermore, combining radon therapy with antioxidants and therapeutic agents has been suggested to synergistically enhance the disease-suppressing effects of the therapy. Further clinical verification of the combined effects of radon therapy and conventional treatments is required to reduce the dosage of drugs that cause severe side effects.

Journal Articles

Effect of radon inhalation on murine brain proteins; Investigation using proteomic and multivariate analyses

Naoe, Shota*; Tanaka, Ayumi*; Kanzaki, Norie; Takenaka, Reiju*; Sakoda, Akihiro; Miyaji, Takaaki*; Yamaoka, Kiyonori*; Kataoka, Takahiro*

Acta Medica Okayama (Internet), 78(5), p.387 - 399, 2024/10

Journal Articles

Evaluation of indoor radon risk for discussion on national action in Japan

Sakoda, Akihiro; Ishimori, Yuu

Hoken Butsuri (Internet), 59(3), p.109 - 117, 2024/09

International organizations such as WHO and ICRP recommended reference levels with the range of 100$$sim$$300 Bq/m$$^{3}$$ against residential radon exposure. In Japan, indoor radon activity concentration is generally low, and a national plan and reference level have not been set so far. This study aimed to evaluate the risks of indoor radon among Japanese populations and to discuss the effectiveness of an assumed reference level in terms of reduction in the number of lung cancer deaths. The US EPA model was used to calculate lifetime risks and population attributable fractions for ever smokers and never smokers using the recent Japanese-specific information such as demographic data and smoking prevalence. The result indicated that the number of lung cancer deaths was very low (i.e., less than 10 in 2020) among the population exposed to more than 100 Bq/m$$^{3}$$. This means that even if a reference level of 100 Bq/m$$^{3}$$ is set, the statistically significant reduction in lung cancer deaths could not be observed. Given the risk evaluation, we believe that expected national actions in Japan are to support individuals who consider taking measures for the own risk perception and control of lifetime risk, rather than to introduce regulations. Comprehensive argument and judgement would also be desired for better public health, based on information on not only radon but also other common modifiable risk factors.

Journal Articles

Seasonal variations in radon and thoron exhalation rates from solid concrete interior walls observed using in situ measurements

Sakoda, Akihiro; Ishimori, Yuu; Hasan, Md. M.*; Jin, Q.*; Iimoto, Takeshi*

Atmosphere (Internet), 15(6), p.701_1 - 701_12, 2024/06

 Times Cited Count:2 Percentile:41.97(Environmental Sciences)

Building materials such as brick and concrete are known indoor radon ($$^{222}$$Rn) and thoron ($$^{220}$$Rn) sources. Most radon and thoron exhalation studies are based on the laboratory testing of pieces and blocks of such materials. To discuss if laboratory findings can be applied to a real-world environment, we conducted intensive in-situ exhalation tests on two solid concrete interior walls of an apartment in Japan for over a year. Exhalation rates of radon ($$J_{rm Rn}$$) and thoron ($$J_{rm Tn}$$) were measured by a measurement system, mainly consisting of an accumulation chamber and dedicated monitors. The indoor air temperature ($$T$$) and absolute humidity ($$AH_{rm in}$$) were measured in parallel, and the wall-surface temperature and water content were occasionally measured. All data obtained here were investigated to reveal environmental and material-associated factors affecting exhalation from the concrete walls. There were weak correlations between $$J_{rm Rn}$$ or $$J_{rm Tn}$$ and T or $$AH_{rm in}$$ at one tested wall, and moderate correlations of $$J_{rm Rn}$$ and strong correlations of $$J_{rm Tn}$$ with $$T$$ or $$AH_{rm in}$$ at the other wall. Our findings on $$J_{rm Rn}$$ were consistent with those in a previous laboratory work where a concrete sample was subject to various temperatures, although a corresponding laboratory study of $$J_{rm Tn}$$ could not be collected. Additionally, moderate or strong correlation between $$J_{rm Rn}$$ and $$J_{rm Tn}$$ was observed for both tested walls. The comparison of the measured data and theoretical calculations revealed a new issue on how much impact each process of the emanation and migration within concrete pore spaces has on radon and thoron exhalation. This study provides an insight into parameterizing radon and thoron source inputs in modeling the spatiotemporal dynamics of indoor radon and thoron.

Journal Articles

Improved data analysis techniques for calculating more accurate radon and thoron exhalation rates from building interior solid walls

Sakoda, Akihiro; Ishimori, Yuu; Jin, Q.*; Iimoto, Takeshi*

Applied Radiation and Isotopes, 207, p.111180_1 - 111180_8, 2024/05

 Times Cited Count:2 Percentile:57.00(Chemistry, Inorganic & Nuclear)

The impacts of mathematical models and associated parameters on radon ($$^{222}$$Rn) and thoron ($$^{220}$$Rn) exhalation rates based on in-situ testing at building interior solid walls were demonstrated to improve data analysis techniques. The results showed that the heterogeneity of their activity concentrations within the measurement system was more significant for thoron than radon. The diurnal variation in indoor radon should be considered for better data quality. In conclusion, a model should be appropriately made and selected under the purposes and accuracy requirements of the exhalation test.

Journal Articles

The Report on "study meetings about the ICRP Internal Dosimetry"

Nakajima, Junya; Hirota, Seiko*; Tsuji, Tomoya; Watanabe, Yuki; Sakoda, Akihiro; Kobayashi, Noriko*

Hoken Butsuri (Internet), 58(1), p.13 - 20, 2023/04

no abstracts in English

Journal Articles

Testing mosses exposed in bags as biointerceptors of airborne radiocaesium after the Fukushima Dai-ichi Nuclear Power Station accident

Di Palma, A.; Adamo, P.*; Dohi, Terumi; Fujiwara, Kenso; Hagiwara, Hiroki; Kitamura, Akihiro; Sakoda, Akihiro; Sato, Kazuhiko; Iijima, Kazuki

Chemosphere, 308, Part 1, p.136179_1 - 136179_13, 2022/12

 Times Cited Count:2 Percentile:12.53(Environmental Sciences)

The present study shows the use of mosses transplanted in bags, called as moss bags, as biosensors of airborne radioactive dusts in the environment of the evacuated zone of Fukushima. A standardized protocol was applied and three moss species were used. Background sites of Okayama Prefecture were used for comparison. In the Fukushima area, the moss bags were able to accumulate radiocaesium in all exposure sites and periods, with Sphagnum palustre moss acting as the most performant moss. The radiocaesium activity concentrations dectected in mosses were in strong agreement with the Cs deposition levels and decontamination status of each exposure site. The accumulation of soil-derived radiocaesium by moss bags was supported by autoradiography and electron microscopy analyses. The linear dependency of Cs accumulation with the exposure time allowed a radiocaesium quantitative assessment.

Journal Articles

Changes in sulfur metabolism in mouse brains following radon inhalation

Kanzaki, Norie; Sakoda, Akihiro; Kataoka, Takahiro*; Sun, L.*; Tanaka, Hiroshi; Otsu, Iwao*; Yamaoka, Kiyonori*

International Journal of Environmental Research and Public Health, 19(17), p.10750_1 - 10750_14, 2022/09

 Times Cited Count:1 Percentile:12.16(Environmental Sciences)

Reactive sulfur species (RSS) involve oxidative stress deeply and contribute anti-inflammatory effect, but no studied have focused on RSS changes after irradiation. In this study, we comprehensively analyzed the metabolites, focusing on RSS in mouse brain following radon inhalation. The ratio of oxidized glutathione to reduced glutathione and proportion of RSS in GSH or cysteine increased by radon inhalation. The sulfur ion might bind to GSH or cysteine chemically under conditions of oxidative stress, even at very low-dose exposure. We performed the overall assessment of high-dimensional data by applying machine learning and showed the specific characteristics of the effects by the exposure conditions. Our results suggested that RSS could produce a biological defense against oxidative stress following radon inhalation.

Journal Articles

Potential inhibitory effects of low-dose thoron inhalation and ascorbic acid administration on alcohol-induced hepatopathy in mice

Kataoka, Takahiro*; Ishida, Tsuyoshi*; Naoe, Shota*; Kanzaki, Norie; Sakoda, Akihiro; Tanaka, Hiroshi; Mitsunobu, Fumihiro*; Yamaoka, Kiyonori*

Journal of Radiation Research (Internet), 63(5), p.719 - 729, 2022/09

 Times Cited Count:3 Percentile:35.92(Biology)

Journal Articles

The Young generation in radiation protection (IRPA YGN) in social media and online learning; "Brave New World" or "Online Nightmare"?

Andresz, S.*; Papp, C.*; Clarijs, T.*; Sakoda, Akihiro; S$'a$ez-Mu$~n$oz, M.*; Qiu, R.*

Journal of Radiological Protection, 42(3), p.031516_1 - 031516_10, 2022/09

 Times Cited Count:0 Percentile:0.00(Environmental Sciences)

While online working seems to become more common since the start of the Covid-19 pandemic, social media has the potential to offer greater interactivity and networking capacities. It seems therefore relevant for the IRPA Young Generation Network to investigate the usage of social media by the young generation in radiation protection trough a survey disseminated online. It was also the opportunity to investigate the early feedbacks about on-line learning. The survey collected 89 answers from 15 countries. The most commonly used social media platforms are first Facebook, then LinkedIn and Twitter, but other social media where reported too. The respondents have a multi-objectives approach on social media, using it for different purposes (chiefly for sharing of news and RP related information/education material) and different audiences (ex. public, professional audience), and are not frenetic users based on the frequencies of publication and consultation and the challenges they see within social media. The survey collected the view of the young generation about their practical experience about learning in virtual setting and its advantages and disadvantages vs. in-person. Most participants expressed mixed-feeling about on-line learning. These results show that the young generation can play a role in supporting the extra and intra-communication of the RP community.

Journal Articles

Analysis of factors contributing to the increase in $$^{7}$$Be activity concentrations in the atmosphere

Narazaki, Yukinori*; Sakoda, Akihiro; Akata, Naofumi*; Ito, Hisanori*; Momoshima, Noriyuki*

International Journal of Environmental Research and Public Health, 19(16), p.10128_1 - 10128_9, 2022/08

 Times Cited Count:4 Percentile:45.94(Environmental Sciences)

In March 2013, increased $$^{7}$$Be activity concentrations in the atmosphere were observed for successive days in Dazaifu, western Japan. The daily $$^{7}$$Be activity concentration averages ranged from 0.93 to 14 mBq/m$$^{3}$$, with a monthly average of 8.3 mBq/m$$^{3}$$. This average was the highest among the monthly averages observed between 1999 and 2015 and higher than the monthly average over this period (4.7 mBq/m$$^{3}$$) plus twice the standard deviation (1.7 $$times$$ 2 mBq/m$$^{3}$$ = 8.1 mBq/m$$^{3}$$). Also, this exceeded the monthly average (6.0 mBq/m$$^{3}$$) only for March 1999-2015, excluding 2013, where the cosmic-ray intensity, a component producing $$^{7}$$Be, decreased. Based on the backward trajectory analysis results, the inflow of air from the stratosphere and upper troposphere at high latitudes that frequently occurred in March 2013 was considered the reason for the $$^{7}$$Be activity concentration increase.

Journal Articles

Radon solubility and diffusion in the skin surface layer

Sakoda, Akihiro; Ishida, Tsuyoshi*; Kanzaki, Norie; Tanaka, Hiroshi; Kataoka, Takahiro*; Mitsunobu, Fumihiro*; Yamaoka, Kiyonori*

International Journal of Environmental Research and Public Health, 19(13), p.7761_1 - 7761_12, 2022/07

 Times Cited Count:1 Percentile:12.16(Environmental Sciences)

In specific situations such as bathing in a radon spa, where the radon activity concentration in thermal water is far higher than that in air, it has been revealed that radon uptake via skin can occur and should be considered for more precise dose evaluation. The primary aim of the present study was to numerically demonstrate the distribution as well as the degree of diffusion of radon in the skin, with a focus on its surface layers (i.e., stratum corneum). We made a biokinetic model that included diffusion theory at the stratum corneum, and measured radon solubility in the stratum corneum to get a crucial parameter. The implementation of the model suggested that the diffusion coefficient in the stratum corneum was as low as general radon-proof sheets. The depth profile of radon in the skin was found to be that after a 20-minute immersion in water, the radon activity concentration at the top surface skin layer was approximately 1000 times higher than that at the viable skin layer. The information on the position of radon as a radiation source would contribute to special dose evaluation where specific target cell layers are assumed for the skin.

Journal Articles

Environmental monitoring of trace elements and evaluation of environmental impacts to organisms near a former uranium mining site in Nigyo-toge, Japan

Horai, Sawako*; Murakami, Shoichi*; Sakoda, Akihiro; Nakashita, Rumiko*; Kunisue, Tatsuya*; Ishimori, Yuu

Environmental Monitoring and Assessment, 194(6), p.415_1 - 415_25, 2022/06

 Times Cited Count:4 Percentile:27.80(Environmental Sciences)

This study conducted an investigation of trace element behavior at a former uranium (U) mining site and evaluated environmental impacts to biota. Concentrations of trace elements were determined in sediments, water, and three organism types (insects, frogs, and newts) from three zones in the former U mining site. Concentrations of As and U in the sediments and water samples were the highest at the mill tailings pond site, where post-U extraction remnants have been accumulated. Additionally, among the organisms analyzed the highest levels of these elements/isotopes were found in newts from MP. Considering data analyses of the whole-body element concentrations, bioaccumulation factors, and $$delta$$$$^{15}$$N values for the organisms, it was concluded that newts might be the most vulnerable species in this location. Further monitoring and more accurate evaluation of the ecological impacts are preferred for this former U mining site.

Journal Articles

Mechanisms of action of radon therapy on cytokine levels in normal mice and rheumatoid arthritis mouse model

Kataoka, Takahiro*; Naoe, Shota*; Murakami, Kaito*; Yukimine, Ryohei*; Fujimoto, Yuki*; Kanzaki, Norie; Sakoda, Akihiro; Mitsunobu, Fumihiro*; Yamaoka, Kiyonori*

Journal of Clinical Biochemistry and Nutrition, 70(2), p.154 - 159, 2022/03

 Times Cited Count:3 Percentile:21.50(Nutrition & Dietetics)

Journal Articles

Status of radon exposure in Bangladeshi locations and dwellings

Hasan, Md. M.*; Janik, M.*; Sakoda, Akihiro; Iimoto, Takeshi*

Environmental Monitoring and Assessment, 193(12), p.770_1 - 770_10, 2021/12

 Times Cited Count:2 Percentile:7.62(Environmental Sciences)

Potentially higher cancer risk due to exposure from natural background radiation was indicated for Bangladeshi population by estimations based on the countrywide study. Several regions with elevated natural background exhibited higher soil radium and thorium contents than the world average. Being the decay products of these radioactive elements, natural radon isotopes could constitute environmental risk factors for internal radiation exposure to the lungs of people living in these areas. Although lung cancer is one of most prevalent types of cancer in Bangladesh, its status and features are still unclear. To clarify the present status of one of the potential risk factors for lung cancer in the country, this review intends to ascertain the countrywide radon exposure, and its pathways by types of local dwelling and by regions; which would provide an indication of the internal exposures in areas of elevated natural background radiation and radionuclides of soil as well as an understanding of the preliminary contribution of environmental radon on the country's lung cancer prevalence. In this review, countrywide air radon exposures for Bangladeshi dwellings and workplaces are organized from peer-reviewed published papers. Radon has been identified as one of influential sources of radiation dose in Bangladesh with its higher radon exhalation and emanation rate from soil. A novel nationwide depiction of the overall indoor and soil radon levels for Bangladesh has been made through radiation maps. This would be helpful for designing future systematic radon/radiological surveys and research on the country's lung cancer prevalence.

Journal Articles

Review of engagement activities to promote awareness of radiation and its associated risk amongst the Japanese public before and after the Fukushima Daiichi Nuclear Power Plant accident

Sakoda, Akihiro; Nomura, Naoki*; Kuroda, Yujiro*; Kono, Takahiko; Naito, Wataru*; Yoshida, Hiroko*

Journal of Radiological Protection, 41(4), p.1258 - 1287, 2021/12

 Times Cited Count:1 Percentile:7.14(Environmental Sciences)

Following the Fukushima Daiichi Nuclear Power Plant accident, many radiation experts directly experienced a vast gap between ideal and real public understanding (PU) of radiation in risk communication. Therefore, this study collated and reviewed information about PU activities for radiation and its risk that six Japanese academic societies - which seemed to be socially neutral expert communities - related to radiation and radiation risk conducted before and after the accident. Activities these radiation-related societies provided to general public were discussed from the following perspectives: (1) difficulties in two-way communication due to resources, motivation, public interest and concerns; (2) balance between academic research and PU activities; (3) academic societies' building trust with the public whilst ensuring member experts' neutrality and independence; (4) discussions among academic societies to prepare for public engagement. We hope that this paper encourages experts and academic societies in radiation protection to hold more national and international discussions about their roles in public communication and outreach.

Journal Articles

Cosmogenic $$^{7}$$Be; Particle size distribution and chemical composition of $$^{7}$$Be-carrying aerosols in the atmosphere in Japan

Narazaki, Yukinori*; Sakoda, Akihiro; Takahashi, Shunta*; Momoshima, Noriyuki*

Journal of Environmental Radioactivity, 237, p.106690_1 - 106690_7, 2021/10

 Times Cited Count:7 Percentile:31.98(Environmental Sciences)

The particle size distributions of airborne aerosols with $$^{7}$$Be were measured using cascade impactors at Dazaifu, a city in western Japan, in 2018 to observe their seasonal variation. $$^{7}$$Be was found to be attached to aerosols with a particle size of less than 2.1 $$mu$$m; in general, particles sized 0.43-0.65 $$mu$$m had the highest $$^{7}$$Be activity concentrations. The activity median aerodynamic diameter (AMAD) of $$^{7}$$Be was in the range of 0.39-0.52 $$mu$$m, which is the size range of particles that can reach human alveoli, and had an annual mean of 0.43$$pm$$0.035 $$mu$$m. The activity concentrations of $$^{7}$$Be were significantly lower in summer, which affected its activity concentrations in the particle size distributions of $$^{7}$$Be. The particle size distribution of $$^{7}$$Be-carrying aerosols was also affected by that of the aerosol particles in the atmosphere. Finally, findings suggest that $$^{7}$$Be was mainly attached to sulfate aerosols (particularly ammonium sulfate aerosols).

Journal Articles

Panel session toward improved communication and engagement with the public after the Fukushima Daiichi Nuclear Power Plant Accident; Study reports and discussion with specialists from relevant fields

Yoshida, Hiroko*; Kuroda, Yujiro*; Kono, Takahiko; Naito, Wataru*; Sakoda, Akihiro

Journal of Radiation Protection and Research, 46(3), p.134 - 142, 2021/09

The Japan Health Physics Society established a task group on "Public Understanding after the Fukushima Daiichi Nuclear Power Plant Accident" in the 2018-2019 fiscal year. This task group collected and analyzed various activities that had been made for promotion of public understanding since the Fukushima accident, and then discussed some issues such as expert's roles. This paper outlines a panel session for this task group held at the 53rd Annual Meeting of the Japanese Health Physics Society (Online). This session consisted of (1) reporting what the task group achieved, (2) having comments by two designated experts in the fields of sociology and ethics, (3) making a panel discussion with three representatives from the task group and the two designated speakers, and (4) summarizing this session by a rapporteur.

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