Thyroid Doses in Children from Radioiodine following the Accident at the Fukushima Daiichi Nuclear Power Plant

Background: Huge amounts of radionuclides were released into the environment due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, which caused not only serious contamination on the ground, but also radiation exposure to the public. One problem that re-mains in performing the dose estimation is the difficulty of estimating the internal thyroid dose due to the intake of radioiodine (mainly, 131I) because of limitations to the human data available. Materials and Methods: The relevant papers were collected and reviewed by the authors. The results of thyroid dose estimates from different studies were tabulated for comparison.Results and Discussion: The thyroid dose estimates from the studies varied widely. The dose estimates by the United Nations Scientific Committee on the Effects of Atomic Radiation were higher than the others due to the ingestion dose being based on conservative assumptions. The dose estimates by Japanese experts were mostly below 20-30 mSv. The recent studies suggested that exposure on March 12, 2011 would be crucial for late evacuees from the areas near the FD-NPP because of the possible intake of short-lived radionuclides other than 131I. Further multilat-eral studies are vital to reduce uncertainties in the present dose estimations.Conclusion: The estimation of the thyroid doses to Fukushima residents still has many uncer-tainties. However, it is considered unlikely that the thyroid doses exceeded 50 mSv except in some extreme cases. Further multilateral studies are thus necessary to reduce the uncertainties in the present dose estimations.