Distribution of artificial radionuclides in animals in and around the evacuation zone of the Fukushima Daiichi Nuclear Power Plant

The Fukushima Daiichi Nuclear Power Plant (FNPP) accident released large amounts of radioactive substances into the environment. We collected organ specimens from over 200 cattle, 50 pigs and 100 monkeys within and adjacent to the 20-km radius previously set as the evacuation zone of FNPP. We have been performing determination of the concentration of radionuclides in the organs of animals. In all the specimens examined, both Cesium-134 (¹³⁴Cs) and ¹³⁷Cs were detectable in a gamma-ray spectrometer and the level of their radioactivity concentrations in each organ was quite similar after the decay correction to March 15, 2011, the day of major release of radionuclides. Linear correlation was found between radioactivity concentration of ¹³⁷Cs in whole peripheral blood (PB) and that in each organ. The slope of the regression line was organ dependent and was the highest in the skeletal muscles. The level of ¹³⁷Cs in an organ of both fetus and infants was higher than that of the corresponding maternal organ. Over all levels of radioactivity concentration of ¹³⁷Cs were dependent on the geological location, the environment and species. Organ-specific deposition of radionuclides with the relatively short half-life was detected, such as ^110mAg in the liver and ^129mTe in the kidney of adult cattle. However both ^110mAg and ^129mTe were not detectable in any organ of pigs or monkeys. This study is the first to reveal in detail the distribution of radionuclides attributed to the FNPP accident through the entire body of animals. (author)