Demonstrating the undermining of science and health policy after the Fukushima nuclear accident by applying the Toolkit for detecting misused epidemiological methods

Abstract

It is well known that science can be misused to hinder the resolution (i.e., the elimination and/or control) of a health problem. To recognize distorted and misapplied epidemiological science, a 33-item “Toolkit for detecting misused epidemiological methods” (hereinafter, the Toolkit) was published in 2021. Applying the Toolkit, we critically evaluated a review paper entitled, “Lessons learned from Chernobyl and Fukushima on thyroid cancer screening and recommendations in the case of a future nuclear accident” in Environment International in 2021, published by the SHAMISEN (Nuclear Emergency Situations - Improvement of Medical and Health Surveillance) international expert consortium. The article highlighted the claim that overdiagnosis of childhood thyroid cancers greatly increased the number of cases detected in ultrasound thyroid screening following the 2011 Fukushima nuclear accident. However, the reasons cited in the SHAMISEN review paper for overdiagnosis in mass screening lacked important information about the high incidence of thyroid cancers after the accident. The SHAMISEN review paper ignored published studies of screening results in unexposed areas, and included an invalid comparison of screenings among children with screenings among adults. The review omitted the actual state of screening in Fukushima after the nuclear accident, in which only nodules > 5 mm in diameter were examined. The growth rate of thyroid cancers was not slow, as emphasized in the SHAMISEN review paper; evidence shows that cancers detected in second-round screening grew to more than 5 mm in diameter over a 2-year period. The SHAMISEN consortium used an unfounded overdiagnosis hypothesis and misguided evidence to refute that the excess incidence of thyroid cancer was attributable to the nuclear accident, despite the findings of ongoing ultrasound screening for thyroid cancer in Fukushima and around Chernobyl. By our evaluation, the SHAMISEN review paper includes 20 of the 33 items in the Toolkit that demonstrate the misuse of epidemiology. The International Agency for Research on Cancer meeting in 2017 and its publication cited in the SHAMISEN review paper includes 12 of the 33 items in the Toolkit. Finally, we recommend a few enhancements to the Toolkit to increase its utility.

Individual Dose Response and Radiation Origin of Childhood and Adolescent Thyroid Cancer in Fukushima II: Possibility of High I-131 Exposure as in Chernobyl

“…It seems better to compare the dose dependence of EAR/PY than ERR/Gy among nuclear accidents if thyroid dose was not measured directly as in Fukushima. [7]. They proposed the need for alternative measurements of thyroid dose, such as the incidence of childhood thyroid cancer, owing to the large gap among the estimates, ranging from less than 1 mSv to more than 1000 mSv.…”

“…Thyroid doses in Chernobyl were based on 350,000 direct thyroid dose measurements performed after the Chernobyl accident (B35) [6]. On the other hand, in Fukushima, only 1080 thyroid monitoring was carried out outside the evacuation zone by the use of a less-sensitive survey meter [7]. The measurements might have been a great underestimation because 55% of measured thyroid doses were negative or zero, suggesting that some doses other than background were subtracted from the measurements (A135,136, Table A20) [2].…”

Response to Toshihide Tsuda, Yumiko Miyano and Eiji Yamamoto [1]

“…We welcome the suggestion by Tsuda et al [1] that the items in Part A (i.e., method-related misuses) of the Toolkit [2] be rearranged in the order of how a study is designed, conducted, analyzed, and reported. This could help other potential users of the Toolkit navigate through all of the items.…”

“…A year after publication of our Toolkit article [2], not only do we see its application by Tsuda et al [1] in the field of Epidemiology, but now, a few weeks later in Conservation Letters, a journal of the Society for Conservation Biology, our Toolkit is seen to have inspired its authors to fashion it for use in the Biological Sciences [9]. Burgman et al [9] have used our Toolkit [2] as a starting point and adapted the items to reflect issues of special relevance to Conservation Biology, focusing on issues that are relevant in conservation and environmental science.…”

“…Tsuda et al [1] recently applied our Toolkit for detecting misused epidemiological methods [2] that serves to organize and formalize the transparent evaluation of research papers or reports. Our focus in this comment is not on the specialized content area of Tsuda et al, but rather on the recommendations made by them to improve and manage the Toolkit.…”