title: An evaluation of early countermeasures to reduce the risk of internal radiation exposure after the Fukushima nuclear incident in Japan.
abstract: After a radiation-release incident, intake of radionuclides in the initial stage immediately following the incident may be the major contributor to total internal radiation exposure for individuals in affected areas. However, evaluation of early internal contamination risk is greatly lacking. This study assessed the relationship between initial stage evacuation/indoor sheltering and internal radiation contamination levels 4 months after the 2011 Fukushima nuclear incident in Japan and estimated potential pathways of the contamination. The study population comprised 525 participants in the internal radiation screening program at Minamisoma Municipal General Hospital, 23 km north of the Fukushima nuclear plant. The analysed dataset included the results of a screening performed in July 2011, 4 months after the incident, and of a questionnaire on early-incident response behaviours, such as sheltering indoors and evacuations, completed by participants. Association between such early countermeasures and internal contamination levels of cesium-134 were assessed using Tobit multiple regression analyses. Our study shows that individuals who evacuated to areas outside Fukushima Prefecture had similar contamination levels of cesium-134 to individuals who stayed in Fukushima (relative risk: 0.86; 95% confidence interval: 0.74-0.99). Time spent outdoors had no significant relationship with contamination levels. The effects of inhalation from radiological plumes released from the nuclear plant on total internal radiation contamination might be so low as to be undetectable by the whole-body counting unit used to examine participants. Given the apparent limited effectiveness of evacuation and indoor sheltering on internal contamination, the decision to implement such early responses to a radiation-release incident should be made by carefully balancing their potential benefits and health risks.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, Norfolk Place, London W2 1PG, UK, minamisoma-kyukyu@bz04.plala.or.jp.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Nomura
authors.affiliation: Department of Radiation Protection, Minamisoma Municipal General Hospital, 54-6 Takami-cho, Haramachi-ku, Minamisoma, Fukushima 975-0033, Japan, Department of Radiation Protection, Soma Central Hospital, 3-5-18 Okinouchi, Soma, Fukushima 976-0016, Japan, Division of Social Communication System for Advanced Clinical Research, the Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan and.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Tsubokura
authors.affiliation: Department of Global Health Policy, Graduate School of Medicine and.
authors.forename: Stuart
authors.initials: S
authors.lastname: Gilmour
authors.affiliation: Department of Physics, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Ryugo S
authors.initials: RS
authors.lastname: Hayano
authors.affiliation: Department of Physics, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Yuni N
authors.initials: YN
authors.lastname: Watanabe
authors.affiliation: Division of Social Communication System for Advanced Clinical Research, the Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan and.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kami
authors.affiliation: Department of Radiation Protection, Minamisoma Municipal General Hospital, 54-6 Takami-cho, Haramachi-ku, Minamisoma, Fukushima 975-0033, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Kanazawa
authors.affiliation: Department of Radiation Protection, Minamisoma Municipal General Hospital, 54-6 Takami-cho, Haramachi-ku, Minamisoma, Fukushima 975-0033, Japan, minamisoma-kyukyu@bz04.plala.or.jp.
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Oikawa
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D062406:Fukushima Nuclear Accident; D006801:Humans; D019570:Inhalation Exposure / Q000517:prevention & control / Q000706:statistics & numerical data; D007564:Japan; D008297:Male; D008875:Middle Aged; D000069079:Radiation Exposure / Q000517:prevention & control* / Q000706:statistics & numerical data; D012307:Risk Factors; D055815:Young Adult
keywords: Evacuation; Fukushima nuclear incident; indoor sheltering; inhalation; internal radiation exposure