title: Dose rate estimation of the Tohoku hynobiid salamander, Hynobius lichenatus, in Fukushima.
abstract: The radiological risks to the Tohoku hynobiid salamanders (class Amphibia), Hynobius lichenatus due to the Fukushima Dai-ichi Nuclear Power Plant accident were assessed in Fukushima Prefecture, including evacuation areas. Aquatic egg clutches (n = 1 for each sampling date and site; n = 4 in total), overwintering larvae (n = 1-5 for each sampling date and site; n = 17 in total), and terrestrial juveniles or adults (n = 1 or 3 for each sampling date and site; n = 12 in total) of H. lichenatus were collected from the end of April 2011 to April 2013. Environmental media such as litter (n = 1-5 for each sampling date and site; n = 30 in total), soil (n = 1-8 for each sampling date and site; n = 31 in total), water (n = 1 for each sampling date and site; n = 17 in total), and sediment (n = 1 for each sampling date and site; n = 17 in total) were also collected. Activity concentrations of (134)Cs + (137)Cs were 1.9-2800, 0.13-320, and 0.51-220 kBq (dry kg) (-1) in the litter, soil, and sediment samples, respectively, and were 0.31-220 and <0.29-40 kBq (wet kg)(-1) in the adult and larval salamanders, respectively. External and internal absorbed dose rates to H. lichenatus were calculated from these activity concentration data, using the ERICA Assessment Tool methodology. External dose rates were also measured in situ with glass dosimeters. There was agreement within a factor of 2 between the calculated and measured external dose rates. In the most severely contaminated habitat of this salamander, a northern part of Abukuma Mountains, the highest total dose rates were estimated to be 50 and 15 μGy h(-1) for the adults and overwintering larvae, respectively. Growth and survival of H. lichenatus was not affected at a dose rate of up to 490 μGy h(-1) in the previous laboratory chronic gamma-irradiation experiment, and thus growth and survival of this salamander would not be affected, even in the most severely contaminated habitat in Fukushima Prefecture. However, further studies of the adult salamanders may be required in order to examine whether the most severe radioactive contamination has any effects on sensitive endpoints, since the estimated highest dose rate to the adults exceeded some of the guidance dose rates proposed by various organisations and programmes for the protection of amphibians, which range from 4 to 400 μGy h(-1). Conversely, at one site in Nakadori, a moderately contaminated region in Fukushima Prefecture, the dose rate to the adult salamanders in spring of 2012 was estimated to be 0.2 μGy h(-1). Estimated dose rates to the overwintering larvae in spring of 2012 were 1 and 0.2 μGy h(-1) at one site in Nakadori, and in Aizu, a less contaminated region in Fukushima Prefecture, respectively. These results suggest that there is a low risk that H. lichenatus will be affected by radioactive contamination in these districts, though further studies on dose rate estimation are required for definitive risk characterisation.
authors.affiliation: Project for Environmental Dynamics and Radiation Effects, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan. Electronic address: fuma@nirs.go.jp.
authors.forename: Shoichi
authors.initials: S
authors.lastname: Fuma
authors.affiliation: Hokkaido University of Education Kushiro Campus, 1-15-55 Shiroyama, Kushiro, Hokkaido 085-8580, Japan.
authors.forename: Sadao
authors.initials: S
authors.lastname: Ihara
authors.affiliation: Project for Environmental Dynamics and Radiation Effects, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Kawaguchi
authors.affiliation: Department of Technical Support and Development, Research, Development and Support Centre, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishikawa
authors.affiliation: Project for Environmental Dynamics and Radiation Effects, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Watanabe
authors.affiliation: Project for Environmental Dynamics and Radiation Effects, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kubota
authors.affiliation: Fukushima Wildlife Workshop, Japan.
authors.forename: Youji
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Tokyo Nuclear Services Co., Ltd., Sorimachi Building, 1-3-5 Taito, Taito-ku, Tokyo 110-0016, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Project for Environmental Dynamics and Radiation Effects, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Aono
authors.affiliation: Office of Biospheric Assessment for Waste Disposal, Research Centre for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Ishii
authors.affiliation: Project for Environmental Dynamics and Radiation Effects, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Haruhi
authors.initials: H
authors.lastname: Soeda
authors.affiliation: Laboratory of Veterinary Physiology 1, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan.
authors.forename: Kumi
authors.initials: K
authors.lastname: Matsui
authors.affiliation: Laboratory of Veterinary Pathology, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Une
authors.affiliation: Graduate School of Environment and Information Science, Yokohama National University, Tokiwadai 79-7, Hodogaya, Yokohama, Kanagawa 240-8501, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Minamiya
authors.affiliation: Project for Environmental Dynamics and Radiation Effects, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yoshida
mesh_terms: D000818:Animals; D002588:Cesium Radioisotopes / Q000378:metabolism*; D062406:Fukushima Nuclear Accident; D007564:Japan; D007814:Larva / Q000378:metabolism; D008297:Male; D011829:Radiation Dosage; D011834:Radiation Monitoring; D018570:Risk Assessment; D012990:Soil Pollutants, Radioactive / Q000378:metabolism*; D014562:Caudata / Q000254:growth & development / Q000378:metabolism*
chemical_list: D002588:Cesium Radioisotopes; D012990:Soil Pollutants, Radioactive
keywords: Amphibian; ERICA; In situ measurement; Radiation; Radiocesium; Risk