The FMU and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) concluded that the high incidence of thyroid cancer after the Fukushima nuclear accident was not the result of radiation exposure, but rather might have been overdiagnosis based on the low thyroid dose estimated in the UNSCEAR 2020/2021 report. In this study, the origin of increased PTC in Fukushima was examined based on the thyroid dose estimated by UNSCEAR. The dose–response relationship of the incidence rate per person-years (PY) was analyzed for four areas in Fukushima prefecture via regression analysis. The linear response of the annual incidence rates to thyroid dose in the first six years showed that the dominant origin of childhood thyroid cancer was radiation exposure. Excess absolute risk (EAR) proportionally increased with thyroid dose, with an EAR/104PY Gy of 143 (95%CI: 122, 165) in the second TUE (p< 0.001), which is approximately 50–100 times higher than the EAR/104PY Gy ≒ 2.3 observed after the Chernobyl accident. This suggests an underestimation of the thyroid dose by UNSCEAR of approximately 1/50~1/100 compared with the thyroid dose for Chernobyl. The increased childhood thyroid cancer in Fukushima was found to arise from radioactive iodine exposure, which was comparable to that in Chernobyl.
福岛医科大学与联合国原子辐射效应科学委员会（UNSCEAR）指出，福岛核事故后甲状腺癌高发并非辐射暴露所致，而可能是基于UNSCEAR 2020/2021报告中估算的较低甲状腺剂量导致的过度诊断。本研究依据UNSCEAR估算的甲状腺剂量，探讨了福岛地区甲状腺乳头状癌（PTC）增加的根源。通过回归分析，对福岛县四个区域的人年发病率与剂量反应关系进行了分析。前六年中年发病率与甲状腺剂量的线性响应表明，儿童甲状腺癌的主要成因是辐射暴露。超额绝对风险（EAR）随甲状腺剂量成比例增加，在第二次甲状腺超声检查中EAR/10⁴人年·戈瑞达到143（95%CI：122, 165）（p<0.001），约为切尔诺贝利事故后观测值EAR/10⁴人年·戈瑞≒2.3的50-100倍。这表明UNSCEAR对甲状腺剂量的低估程度约为切尔诺贝利剂量的1/50~1/100。研究发现，福岛儿童甲状腺癌的增加源于放射性碘暴露，其影响程度与切尔诺贝利事故相当。
肿瘤(癌症)患者之家