Whole-body counter surveys of over 2700 babies and small children in and around Fukushima Prefecture 33 to 49 months after the Fukushima Daiichi NPP accident

TL;DR

This study used a newly developed whole body counter to scan over 2700 children in Fukushima, finding no detectable radioactive cesium and concluding internal radiation exposure risks are negligible.

Contribution

The paper reports the deployment of a new WBC device for small children and provides extensive data on internal contamination levels post-Fukushima accident.

Findings

No children had detectable radioactive cesium levels.

Maximum estimated dose from residual cesium is about 16 μSv/year.

No correlation between local food consumption and internal contamination.

Abstract

BABYSCAN, a whole body counter (WBC) for small children was developed in 2013, and units have been installed at three hospitals in Fukushima Prefecture. Between December, 2013 and March, 2015, 2707 children between the ages of 0 and 11 have been scanned, and none had detectable levels of radioactive cesium. The minimum detectable activities (MDAs) for $^{137}$Cs were $\leq 3.5$ Bq kg$^{-1}$ for ages 0-1, decreasing to $\leq 2$ Bq kg$^{-1}$ for ages 10-11. Including the $^{134}$Cs contribution, these translate to a maximum committed effective dose of $\sim 16 \mu$Sv y$^{-1}$ even for newborn babies, and therefore the internal exposure risks can be considered negligibly small. Analysis of the questionnaire filled out by the parents of the scanned children regarding their families' food and water consumption revealed that the majority of children residing in the town of Miharu regularly consume local or home-grown rice and vegetables, while in Minamisoma, a majority avoid tap water and produce from Fukushima. The data show, however, no correlation between consumption of locally produced food and water and the children's body burdens.