Assessment of the risk of medium-term internal contamination in Minamisoma City, Fukushima, Japan, after the Fukushima Dai-ichi nuclear accident

Environ Health Perspect. 2014 Jun;122(6):587-93. doi: 10.1289/ehp.1306848. Epub 2014 Mar 14.


Background: The Fukushima Dai-ichi nuclear disaster, the first level-7 major nuclear disaster since Chernobyl, raised concerns about the future health consequences of exposure to and intake of radionuclides. Factors determining the risk and level of internal radiation contamination after a nuclear accident, which are a key to understanding and improving current nuclear disaster management, are not well studied.

Objective: We investigated both the prevalence and level of internal contamination in residents of Minamisoma, and identified factors determining the risk and levels of contamination.

Methods: We implemented a program assessing internal radiation contamination using a whole body counter (WBC) measurement and a questionnaire survey in Minamisoma, between October 2011 and March 2012.

Results: Approximately 20% of the city's population (8,829 individuals) participated in the WBC measurement for internal contamination, of which 94% responded to the questionnaire. The proportion of participants with detectable internal contamination was 40% in adults and 9% in children. The level of internal contamination ranged from 2.3 to 196.5 Bq/kg (median, 11.3 Bq/kg). Tobit regression analysis identified two main risk factors: more time spent outdoors, and intake of potentially contaminated foods and water.

Conclusions: Our findings suggest that, with sensible and reasonable precautions, people may be able to live continuously in radiation-affected areas with limited contamination risk. To enable this, nuclear disaster response should strictly enforce food and water controls and disseminate evidence-based and up-to-date information about avoidable contamination risks.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Child
  • Environmental Exposure / statistics & numerical data*
  • Food Contamination, Radioactive
  • Fukushima Nuclear Accident*
  • Humans
  • Japan / epidemiology
  • Middle Aged
  • Radiation Dosage*
  • Radiation Monitoring*
  • Radioactive Hazard Release
  • Radioisotopes / analysis*
  • Risk Factors
  • Water Pollutants, Radioactive
  • Young Adult


  • Radioisotopes
  • Water Pollutants, Radioactive