A comprehensive dose evaluation project concerning animals affected by the Fukushima Daiichi Nuclear Power Plant accident: its set-up and progress

摘要

Explosions at the Fukushima Daiichi Nuclear Power Plant (FNPP) occurred after the Great East Japan disaster, and they released a huge amount of artificial radioactive substances into the environment; most of them were dispersed on 15 March 2011. Since then, people globally have been concerned about the late effects of radiation decades after the accident; even the acute effects were not detected. The evacuation zone was defined on 22 April 2011 as within a 20-km radius of the FNPP, and since then no one has been allowed to enter the area without permission from the Anti-Disaster Headquarters. Since April 2012, rearrangements of the restricted areas, including the evacuation zone, have been performed several times. We, therefore, term the area within a 20-km radius of the FNPP the ex-evacuation zone. On 12 May 2011, the Prime Minister ordered the Governor of Fukushima to euthanize livestock within the evacuation zone, preventing people from eating meats contaminated with radionuclides. With the intention of increasing understanding of the biological and human effects of both internal and external radiation exposure and of the spatio-temporal changes occurring after radioactive contamination, the aim of this project was to establish an archive system, to accurately evaluate radiation doses to individual organs from euthanized animals and to the environment at the contaminated site, and to preserve sample materials with data for future generations. There is no doubt that the technology associated with radiation measurement and analysis of biological effects will develop further in the future. This archive will become crucial to our understanding of the effects of radiation on humans and on the earth. We organized a research group entitled the ‘Group for Comprehensive Dose Evaluation in Animals from the Area Affected by the FNPP Accident' and started the research activity after overcoming many difficulties and obstacles. We had to obtain finances for?the project and also obtain permission to enter the ex-evacuation zone and to bring out organ samples (Fig.?1). Since 29 August 2011, we have been performing sampling of organs and peripheral blood from animals left behind in and around the ex-evacuation zone of the FNPP accident. Euthanasia and sampling began from the livestock about which consent was obtained from dairy farmers. After euthanasia was performed (by veterinarians from the Fukushima prefecture), peripheral blood was obtained from the jugular vein. Carcasses were carried by dump trucks to the burying place and put into the trench dug for burying them. Dissection was carried out in the trench, and the organs were divided into four groups: one for the measurement of radioactivity, one for histological examination and two for molecular study (Fig.?2). For molecular analysis, duplicates of frozen tissues were stored in two different laboratories (where electricity was supplied by two independent power companies) in case of power failure. We also separated the plasma from the blood cells on the dissection site. All samples were collected and divided according to the purpose of analysis (Fig.?3). All the materials were itemized?and linked to their information via a barcode issued for each individual animal (Fig.?4). Each barcode was printed on a piece of tape by a PT-9800PCN desktop network thermal label printer (Brother Industries, Nagoya, Japan), using its attached software, P-touch editor. The barcode label was laminated and was put into a plastic freezer bag with the registered organ tissue samples associated with the particular animal. All sample data were compiled and organized into a chart on a Microsoft Excel spreadsheet controlled by a barcode system (Fig.?5).