title: An influential factor for external radiation dose estimation for residents after the Fukushima Daiichi Nuclear Power Plant accident-time spent outdoors for residents in Iitate Village.
abstract: Many studies have been conducted on radiation doses to residents after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Time spent outdoors is an influential factor for external dose estimation. Since little information was available on actual time spent outdoors for residents, different values of average time spent outdoors per day have been used in dose estimation studies on the FDNPP accident. The most conservative value of 24 h was sometimes used, while 2.4 h was adopted for indoor workers in the UNSCEAR 2013 report. Fukushima Medical University has been estimating individual external doses received by residents as a part of the Fukushima Health Management Survey by collecting information on the records of moves and activities (the Basic Survey) after the accident from each resident. In the present study, these records were analyzed to estimate an average time spent outdoors per day. As an example, in Iitate Village, its arithmetic mean was 2.08 h (95% CI: 1.64-2.51) for a total of 170 persons selected from respondents to the Basic Survey. This is a much smaller value than commonly assumed. When 2.08 h is used for the external dose estimation, the dose is about 25% (23-26% when using the above 95% CI) less compared with the dose estimated for the commonly used value of 8 h.
authors.affiliation: Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Hikarigaoka 1, Fukushima City, 960-1295, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Seiji
authors.initials: S
authors.lastname: Yasumura
authors.forename: Akira
authors.initials: A
authors.lastname: Ohtsuru
authors.forename: Akira
authors.initials: A
authors.lastname: Sakai
authors.forename: Keiichi
authors.initials: K
authors.lastname: Akahane
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Yonai
authors.forename: Ritsu
authors.initials: R
authors.lastname: Sakata
authors.forename: Kotaro
authors.initials: K
authors.lastname: Ozasa
authors.forename: Masayuki
authors.initials: M
authors.lastname: Hayashi
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ohira
authors.forename: Kenji
authors.initials: K
authors.lastname: Kamiya
authors.forename: Masafumi
authors.initials: M
authors.lastname: Abe
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D004781:Environmental Exposure / Q000032:analysis*; D005260:Female; D062406:Fukushima Nuclear Accident; D006801:Humans; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011834:Radiation Monitoring; D011795:Surveys and Questionnaires; D013997:Time Factors