[Source: Proceedings of the National Academy of Sciences of the United States of America, full page: (LINK). Abstract, edited.]


Radiation dose rates now and in the future for residents neighboring restricted areas of the Fukushima Daiichi Nuclear Power Plant

Kouji H. Harada<SUP>a</SUP>, Tamon Niisoe<SUP>b</SUP>, Mie Imanaka<SUP>c</SUP>, Tomoyuki Takahashi<SUP>d</SUP>, Katsumi Amako<SUP>e</SUP>, Yukiko Fujii<SUP>a</SUP>, Masatoshi Kanameishi<SUP>a</SUP>, Kenji Ohse<SUP>f</SUP>, Yasumichi Nakai<SUP>f</SUP>, Tamami Nishikawa<SUP>f</SUP>, Yuuichi Saito<SUP>f</SUP>, Hiroko Sakamoto<SUP>g</SUP>, Keiko Ueyama<SUP>h</SUP>, Kumiko Hisaki<SUP>i</SUP>, Eiji Ohara<SUP>i</SUP>, Tokiko Inoue<SUP>j</SUP>, Kanako Yamamoto<SUP>k</SUP>, Yukiyo Matsuoka<SUP>l</SUP>, Hitomi Ohata<SUP>e</SUP>, Kazue Toshima<SUP>m</SUP>, Ayumi Okada<SUP>n</SUP>, Hitomi Sato<SUP>o</SUP>, Toyomi Kuwamori<SUP>p</SUP>, Hiroko Tani<SUP>p</SUP>, Reiko Suzuki<SUP>q</SUP>, Mai Kashikura<SUP>q</SUP>, Michiko Nezu<SUP>r</SUP>, Yoko Miyachi<SUP>s</SUP>, Fusako Arai<SUP>t</SUP>, Masanori Kuwamori<SUP>u</SUP>, Sumiko Harada<SUP>v</SUP>, Akira Ohmori<SUP>v</SUP>, Hirohiko Ishikawa<SUP>b</SUP>, and Akio Koizumi<SUP>a</SUP>,<SUP>1</SUP>
<SUP></SUP>
Author Affiliations: <SUP>a</SUP>Department of Health and Environmental Sciences and <SUP>c</SUP>Department of Preventive Medicine, Kyoto University Graduate School of Medicine, Kyoto 6068501, Japan; <SUP>b</SUP>Research Division of Atmospheric and Hydrospheric Disasters, Disaster Prevention Research Institute, Kyoto University, Uji 6110011, Japan; <SUP>d</SUP>Department of Nuclear Science and Engineering, Kyoto University Research Reactor Institute, Kumatori 5900494, Japan; <SUP>e</SUP>Faculty of Nutrition, Kobe Gakuin University, Kobe 6512180, Japan; <SUP>f</SUP>Fukushima Future Center for Regional Revitalization, Fukushima University, Fukushima 9601296, Japan; <SUP>g</SUP>Department of Food Nutrition, Kyoto Bunkyo Junior College, Uji 6110041 Japan; <SUP>h</SUP>Faculty of Human Life Sciences, Senri Kinran University, Suita, 5650873 Japan; <SUP>i</SUP>Department of Life Design, Osaka International College, Moriguchi 5708555, Japan; <SUP>j</SUP>Kyoto First Red Cross Hospital, Kyoto 6050981, Japan; <SUP>k</SUP>Aiseikai Yamashina Hospital, Kyoto 6078086, Japan; <SUP>l</SUP>National Hospital Organization Kyoto Medical Center, Kyoto 6120861, Japan; <SUP>m</SUP>Ekiya Rehabilitation Sakura, Fukuyama 7201131, Japan; <SUP>n</SUP>Best Life Promotion Ltd., Kawasaki 2118588, Japan; <SUP>o</SUP>Syojyukai Social Welfare Service Corporation Ikoinosato, Hirakata 5731161, Japan; <SUP>p</SUP>Faculty of Human Life Studies, Jin-ai University, Echizen 9150015, Japan; <SUP>q</SUP>Department of Food and Nutrition, Fukushima Gakuin Junior College, Fukushima 9600181, Japan; <SUP>r</SUP>Department of Food and Nutrition, Yamanashi Gakuin Junior College, Kofu 4008575, Japan; <SUP>s</SUP>Department of Health and Nutrition, Yonezawa Women's Junior College of Yamagata Prefecture, Yonezawa 9920025, Japan; <SUP>t</SUP>Faculty of Human Life Studies, University of Niigata Prefecture, Niigata 9508680, Japan; <SUP>u</SUP>Department of Nutrition, Mimasaka Junior College, Tsuyama 7088511, Japan; and <SUP>v</SUP>Department of Food and Nutrition, Toyama College, Toyama 9300175, Japan

Edited by Kirk R. Smith, University of California, Berkeley, CA, and approved January 22, 2014 (received for review August 21, 2013)


Significance

There is a potential risk of human exposure to radiation owing to the March 2011 Fukushima Daiichi Nuclear Power Plant accident. In this study, we evaluated radiation dose rates from deposited radiocesium in three areas neighboring the restricted and evacuation areas in Fukushima. The mean annual radiation dose rate in 2012 associated with the accident was 0.89–2.51 mSv/y. The mean dose rate estimates in 2022 are comparable with variations of the average 2 mSv/y background radiation exposure from natural radionuclides in Japan. Furthermore, the extra lifetime integrated dose after 2012 is estimated to elevate lifetime risk of cancer incidence by a factor of 1.03 to 1.05 at most, which is unlikely to be epidemiologically detectable.


Abstract

Radiation dose rates were evaluated in three areas neighboring a restricted area within a 20- to 50-km radius of the Fukushima Daiichi Nuclear Power Plant in August–September 2012 and projected to 2022 and 2062. Study participants wore personal dosimeters measuring external dose equivalents, almost entirely from deposited radionuclides (groundshine). External dose rate equivalents owing to the accident averaged 1.03, 2.75, and 1.66 mSv/y in the village of Kawauchi, the Tamano area of Soma, and the Haramachi area of Minamisoma, respectively. Internal dose rates estimated from dietary intake of radiocesium averaged 0.0058, 0.019, and 0.0088 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. Dose rates from inhalation of resuspended radiocesium were lower than 0.001 mSv/y. In 2012, the average annual doses from radiocesium were close to the average background radiation exposure (2 mSv/y) in Japan. Accounting only for the physical decay of radiocesium, mean annual dose rates in 2022 were estimated as 0.31, 0.87, and 0.53 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. The simple and conservative estimates are comparable with variations in the background dose, and unlikely to exceed the ordinary permissible dose rate (1 mSv/y) for the majority of the Fukushima population. Health risk assessment indicates that post-2012 doses will increase lifetime solid cancer, leukemia, and breast cancer incidences by 1.06%, 0.03% and 0.28% respectively, in Tamano. This assessment was derived from short-term observation with uncertainties and did not evaluate the first-year dose and radioiodine exposure. Nevertheless, this estimate provides perspective on the long-term radiation exposure levels in the three regions.

Fukushima nuclear disaster - exposure assessment - Strontium-90 - forest contamination - food duplicate


Footnotes

<SUP>1</SUP>To whom correspondence should be addressed. E-mail: koizumi.akio.5v@kyoto-u.ac.jp.

Author contributions: K.H.H. and A.K. designed research; K.H.H., T. Niisoe, M.I., K.A., Y.F., M. Kanameishi, K.O., Y.N., T. Nishikawa, Y.S., H. Sakamoto, K.U., K.H., E.O., T.I., K.Y., Y. Matsuoka, H.O., K.T., A. Okada, H. Sato, T.K., H.T., R.S., M. Kashikura, M.N., Y. Miyachi, F.A., M. Kuwamori, S.H., A. Ohmori, and A.K. performed research; K.H.H., T. Niisoe, Y.F., M. Kanameishi, and A.K. analyzed data; and K.H.H., T. Niisoe, M.I., T.T., K.A., H.I., and A.K. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1315684111/-/DCSupplemental.

Freely available online through the PNAS open access option.


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