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Journal Articles

Comprehensive exposure assessments from the viewpoint of health in a unique high natural background radiation area, Mamuju, Indonesia

Nugraha, E. D.*; Hosoda, Masahiro*; Kusdiana*; Untara*; Mellawati, J.*; Nurokhim*; Tamakuma, Yuki*; Ikram, A.*; Syaifudin, M.*; Yamada, Ryohei; et al.

Scientific Reports (Internet), 11(1), p.14578_1 - 14578_16, 2021/07

 Times Cited Count:1 Percentile:76.35(Multidisciplinary Sciences)

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 public and the environment. A cross-sectional study method was used with cluster sampling areas by measuring all parameters that contribute to external and internal radiation exposures. It was determined that Mamuju was a unique HNBRA with the annual effective dose between 17 and 115 mSv, with an average of 32 mSv. The lifetime cumulative dose calculation suggested that Mamuju residents could receive as much as 2.2 Sv on average which is much higher than the average dose of atomic bomb survivors for which risks of cancer and non-cancer diseases are demonstrated. The study results are new scientific data allowing better understanding of health effects related to chronic low-dose-rate radiation exposure and they can be used as the main input in a future epidemiology study.

Journal Articles

Morphological reproductive characteristics of testes and fertilization capacity of cryopreserved sperm after the Fukushima accident in raccoon (${it Procyon lotor}$)

Komatsu, Kazuki*; Iwasaki, Tsugumi*; Murata, Kosuke*; Yamashiro, Hideaki*; Goh, V. S. T.*; Nakayama, Ryo*; Fujishima, Yohei*; Ono, Takumi*; Kino, Yasushi*; Shimizu, Yoshinaka*; et al.

Reproduction in Domestic Animals, 56(3), p.484 - 497, 2021/03

We have established an archive system of livestock and wild animals from the surrounding ex-evacuation zone. Wildlife within the alert zone have been exposed to low-dose-rate (LDR) radiation for a long and continuous time. In this study, we analysed the morphological characteristics of the testes and in vitro fertilization (IVF) capacity of cryopreserved sperm of raccoons from the ex-evacuation zone of the FDNPP accident. This study revealed that the chronic and LDR radiation exposure associated with the FDNPP accident had no adverse effect on the reproductive characteristics and functions of male raccoons.

Journal Articles

A Unique high natural background radiation area; Dose assessment and perspectives

Hosoda, Masahiro*; Nugraha, E. D.*; Akata, Naofumi*; Yamada, Ryohei; Tamakuma, Yuki*; Sasaki, Michiya*; Kelleher, K.*; Yoshinaga, Shinji*; Suzuki, Takahito*; Rattanapongs, C. P.*; et al.

Science of the Total Environment, 750, p.142346_1 - 142346_11, 2021/01

 Times Cited Count:5 Percentile:96.3(Environmental Sciences)

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 radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h$$^{-1}$$ and 1109 nGy h$$^{-1}$$. Indoor radon concentrations ranged from 124 Bq m$$^{-3}$$ to 1015 Bq m$$^{-3}$$. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m$$^{-3}$$ recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure.

Oral presentation

External dose estimation of Japanese macaque and Procyon lotor using electron spin resonance spectroscopy

Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Ono, Takumi*; Tamaki, Hiroaki*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; et al.

no journal, , 

Releases of the radioactive materials from the Fukushima Daiichi Nuclear Power Plant accident result in an ionization exposure to people and animals, the precise dosimetry is required. To estimate the external dose due to the accident, we utilize electron spin resonance (ESR) spectroscopy which is a powerful tool for the dosimetry of external dose. The detection limit of this technique was 146 mGy, so that we have to improve the detection limit for the precise dosimetry. In this work, we developed a novel enamel-dentine separation technique and improved the detection limit down to 43 mGy, and estimated the external dose for Japanese macaque and Procyon lotor collected in Fukushima prefecture.

Oral presentation

Sample preparation procedure for the estimation of external exposure dose of wild animals using elecron spin resonance spectroscopy

Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Mitsuyasu, Yusuke*; Ono, Takumi*; Tamaki, Hiroaki*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

no journal, , 

Release of the radioactive materials from Fukushima Daiichi Nuclear Power Plant accident results in a long-term low dose rate ionization exposure to wild animals. The biological effects of the wild animal do not show a clear correlation with the external dose, which is estimated from the external dose rate of the captured point of the animal, a precise external dose estimation using ESR and tooth enamel is required instead of using the external dose rate. In this work, we attempted to estimate the external dose of wild Japanese macaque and Procyon lotor captured in the high dose rate area.

Oral presentation

Study on transport of radionuclides in watershed environment

Nakanishi, Takahiro; Tsuruta, Tadahiko; Funaki, Hironori; Sakuma, Kazuyuki; Miura, Tomisato*; Yoshida, Mitsuaki*

no journal, , 

To elucidate the mechanism of transport of dissolved radiocesium to masu trout, a feeding experiment was conducted in a culture pond introduced with mountain stream water (dissolved $$^{137}$$Cs concentration: 0.1 - 0.2 Bq/L) using a non-contaminated bait. The $$^{137}$$Cs concentration in the muscle of the adult masu trout (n = 10) was relatively high, showing individual differences (30 - 200 Bq/kg-wet). Pond bottom gravel was found in their stomach, suggesting a source of $$^{137}$$Cs other than bait and stream water. As a result of dietary analysis using stable isotope ratios, the contribution of aquatic organisms was higher in masu trout with higher $$^{137}$$Cs concentration in the muscle. This suggests that the $$^{137}$$Cs concentration in masu trout does not exceed the Japanese limit of 100 Bq/kg for general foodstuffs by transport only from the dissolved $$^{137}$$Cs.

Oral presentation

Sample preparation procedure for ESR dosimetry using teeth of wild animal

Oka, Toshitaka; Mitsuyasu, Yusuke*; Takahashi, Atsushi*; Koarai, Kazuma; Kino, Yasushi*; Sekine, Tsutomu*; Okutsu, Kenichi*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

no journal, , 

Releases of the radioactive materials from the Fukushima Daiichi Nuclear Power Plant accident result in a low dose exposure to wild animals. The external dose of wild animals is commonly estimated by the external dose rate of the captured point, but the estimated exposure dose has huge uncertainties because the size of the habitat and/or the movement of the wild animals are not included in the estimation. To estimate the external dose precisely, we utilize electron spin resonance (ESR) dosimetry. In this work, we investigated the sample preparation procedure of wild animals. The ESR spectrum of enamel of racoon captured in Namie-town, Fukushima has a broad ESR signal due to metal components. The linear relationship between the Co$$_{2}$$ intensity and the absorbed dose that we can apply ESR dosimetry for racoon teeth. Using this relationship, the external exposure dose was estimated.

Oral presentation

Elucidation of migration routes of radiocesium to freshwater fish using the model water area

Miura, Tomisato*; Nakanishi, Takahiro; Sakuma, Kazuyuki

no journal, , 

From the analysis of yamame trout and aquatic insects inhabiting the Ukedo River system, it is speculated that the main migration route to yamame trout is via non-carnivorous aquatic insects. And, analysis of the yamame trout pond revealed a negative correlation between yamame trout body weight and radiocesium concentration, suggesting that individuals unable to receive non-contaminated food prey on benthos inhabiting the bottom of the pond. In this study, we analyze the concentration and stable isotope composition of radiocesium in yamame trout, aquatic insects, and benthos, and analyze the migration route of radiocesium to yamame trout.

Oral presentation

Assessment of chromosome translocation in wild Japanese macaques in Fukushima

Fujishima, Yohei*; Suzuki, Masatoshi*; Goh, V. S. T.*; Ariyoshi, Kentaro*; Kasai, Kosuke*; Nakata, Akifumi*; Kino, Yasushi*; Oka, Toshitaka; Shinoda, Hisashi*; Shimizu, Yoshinaka*; et al.

no journal, , 

After the Fukushima Daiichi Nuclear Power Plant accident, the surrounding environment was contaminated with radionuclides. Although the ambient dose rates are decreasing, prolonged effects of chronic low-dose exposure on animals are expected to be seen in the coming years. It is necessary to assess the effects of radioactivity on the wild animals in this area to better understand about the risk of low dose radiation. The chromosome translocation frequency of Japanese macaques were significantly higher in Fukushima groups comparing from control groups in Miyagi. Furthermore, chromosome translocation frequencies tended to correlate between external doses or internal dose-rates. However, chromosome translocation frequency was decreasing year by year, which may reflect restoration of environments such as decreasing of ambient dose-rates and decontamination efforts.

Oral presentation

External exposure dose estimation using ESR dosimetry technique

Oka, Toshitaka; Takahashi, Atsushi*; Mitsuyasu, Yusuke*; Koarai, Kazuma; Kino, Yasushi*; Okutsu, Kenichi*; Yamashita, Takuma*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

no journal, , 

Electron spin resonance (ESR) dosimetry technique is a powerful tool that has been used in the study of external exposure dose assessment of human by measuring CO$$_{2}$$ radicals of teeth. In this work, we applied this technique for wild monkey and wild racoon captured in Fukushima prefecture, and estimated the external exposure dose.

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