Estimation of internal dose from tap water after the Fukushima Daiichi Nuclear Power Station accident using newly obtained data.

Massive release of radioactive materials into the atmosphere occurred due to the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in March 2011. The World Health Organization (WHO) and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reported the results of dose estimation to assess the health effect of the accident and both reports state that their assessments of internal and external exposure doses contain certain uncertainties due to uncertainties inherent to the basic data. Therefore, estimation of the internal dose from tap water was conducted in this study by utilizing a database of deposition calculated by an atmospheric transfer, dispersion and deposition model (ATDM) in conjunction with the newly obtained data on the volume of daily water intake obtained by a web-based survey. The median mean and 95-percentile of thyroid equivalent doses were estimated for 1-year and 10-year children and adults in 12 municipalities in the evacuation area in Fukushima prefecture. The present mean thyroid dose estimations for 1-year children (0.4-16.2 mSv) are smaller than the corresponding values in the UNSCEAR 2013 report (1.9-49 mGy). Dose-modifying factors in the Japanese or local community are discussed.