title: Estimated association between dwelling soil contamination and internal radiation contamination levels after the 2011 Fukushima Daiichi nuclear accident in Japan.
abstract: Measurement of soil contamination levels has been considered a feasible method for dose estimation of internal radiation exposure following the Chernobyl disaster by means of aggregate transfer factors; however, it is still unclear whether the estimation of internal contamination based on soil contamination levels is universally valid or incident specific.
  
  
  
  To address this issue, we evaluated relationships between in vivo and soil cesium-137 (Cs-137) contamination using data on internal contamination levels among Minamisoma (10-40 km north from the Fukushima Daiichi nuclear power plant), Fukushima residents 2-3 years following the disaster, and constructed three models for statistical analysis based on continuous and categorical (equal intervals and quantiles) soil contamination levels.
  
  
  
  A total of 7987 people with a mean age of 55.4 years underwent screening of in vivo Cs-137 whole-body counting. A statistically significant association was noted between internal and continuous Cs-137 soil contamination levels (model 1, p value <0.001), although the association was slight (relative risk (RR): 1.03 per 10 kBq/m(2) increase in soil contamination). Analysis of categorical soil contamination levels showed statistical (but not clinical) significance only in relatively higher soil contamination levels (model 2: Cs-137 levels above 100 kBq/m(2) compared to those <25 kBq/m(2), RR=1.75, p value <0.01; model 3: levels above 63 kBq/m(2) compared to those <11 kBq/m(2), RR=1.45, p value <0.05).
  
  
  
  Low levels of internal and soil contamination were not associated, and only loose/small associations were observed in areas with slightly higher levels of soil contamination in Fukushima, representing a clear difference from the strong associations found in post-disaster Chernobyl. These results indicate that soil contamination levels generally do not contribute to the internal contamination of residents in Fukushima; thus, individual measurements are essential for the precise evaluation of chronic internal radiation contamination.
authors.affiliation: Division of Social Communication System for Advanced Clinical Research, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan Department of Radiation Protection, Minamisoma Municipal General Hospital, Minamisoma, Fukushima, Japan Department of Radiation Protection, Soma Central Hospital, Soma, Fukushima, Japan.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Tsubokura
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, Norfolk Place, London, UK.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Nomura
authors.affiliation: Department of Radiation Protection, Minamisoma Municipal General Hospital, Minamisoma, Fukushima, Japan.
authors.forename: Kikugoro
authors.initials: K
authors.lastname: Sakaihara
authors.affiliation: Department of Radiation Protection, Soma Central Hospital, Soma, Fukushima, Japan.
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Kato
authors.affiliation: Department of Radiation Protection, Minamisoma Municipal General Hospital, Minamisoma, Fukushima, Japan.
authors.forename: Claire
authors.initials: C
authors.lastname: Leppold
authors.affiliation: Faculty of Policy Management, Keio University, Fujisawa, Kanagawa, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Furutani
authors.affiliation: Department of Radiation Protection, Soma Central Hospital, Soma, Fukushima, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Morita
authors.affiliation: Department of Radiation Protection, Minamisoma Municipal General Hospital, Minamisoma, Fukushima, Japan.
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Oikawa
authors.affiliation: Department of Radiation Protection, Minamisoma Municipal General Hospital, Minamisoma, Fukushima, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Kanazawa
mesh_terms: D002588:Cesium Radioisotopes / Q000009:adverse effects / Q000032:analysis* / Q000633:toxicity; D004781:Environmental Exposure / Q000032:analysis*; D005260:Female; D062406:Fukushima Nuclear Accident; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D000069079:Radiation Exposure / Q000009:adverse effects / Q000032:analysis*; D011834:Radiation Monitoring; D012990:Soil Pollutants, Radioactive / Q000009:adverse effects / Q000032:analysis* / Q000633:toxicity; D017741:Survivors; D013997:Time Factors; D014915:Whole-Body Counting / Q000295:instrumentation*
chemical_list: D002588:Cesium Radioisotopes; D012990:Soil Pollutants, Radioactive
keywords: Cs-134; Cs-137; countermeasure; internal radiation exposure; transfer factor; whole body counter