Low-dose radiation risk and individual variation in radiation sensitivity in Fukushima

Precision Radiotherapy and Radiation Risk Assessment: How Do We Overcome Radiogenomic Diversity?

Precision medicine is a rapidly developing area that aims to deliver targeted therapies based on individual patient characteristics. However, current radiation treatment is not yet personalized; consequently, there is a critical need for specific patient characteristics of both tumor and normal tissues to be fully incorporated into dose prescription. Furthermore, current risk assessment following environmental, occupational, or accidental exposures to radiation is based on population effects, and does not account for individual diversity underpinning radiosensitivity. The lack of personalized approaches in both radiotherapy and radiation risk assessment resulted in the current situation where a population-based model, effective dose, is being used. In this review article, to stimulate scientific discussion for precision medicine in both radiotherapy and radiation risk assessment, we propose a novel radiological concept and metric - the personalized dose and the personalized risk index - that incorporate individual physiological, lifestyle-related and genomic variations and radiosensitivity, outlining the potential clinical application for precision medicine. We also review on recent progress in both genomics and biobanking research, which is promising for providing novel insights into individual radiosensitivity, and for creating a novel conceptual framework of precision radiotherapy and radiation risk assessment.

Developmental and hemocytological effects of ingesting Fukushima's radiocesium on the cabbage white butterfly Pieris rapae

High morphological abnormality and mortality rates have been reported in the pale grass blue butterfly, Zizeeria maha, since the Fukushima nuclear accident. However, it remains uncertain if these effects are restricted to this butterfly. Here, we evaluated the effects of ingesting cabbage leaves grown with contaminated soils from Fukushima on the development and hemocytes of the cabbage white butterfly, Pieris rapae. Contaminated cabbage leaves containing various low levels of anthropogenic ¹³⁴Cs and ¹³⁷Cs radioactivity (less than natural ⁴⁰K radioactivity) were fed to larvae from Okinawa, the least contaminated locality in Japan. Negative developmental and morphological effects were detected in the experimental groups. The cesium (but not potassium) radioactivity concentration was negatively correlated with the granulocyte percentage in hemolymph, and the granulocyte percentage was positively correlated with the pupal eclosion rate, the adult achievement rate, and the total normality rate. These results demonstrated that ingesting low-level radiocesium contaminants in Fukushima (but not natural radiopotassium) imposed biologically negative effects on the cabbage white butterfly, as in the pale grass blue butterfly, at both cellular and organismal levels.

Current Status of the Blue Butterfly in Fukushima Research

Adverse biological impacts of the Fukushima nuclear accident have been revealed using the pale grass blue butterfly, Zizeeria maha, since 2012, which were often considered incompatible with the conventional understanding of radiation biology. This discrepancy likely originates from different system conditions and methodologies. In this article, we first respond to comments from the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) regarding our study; "technical errors" in unit usage and mathematical models noted by UNSCEAR are not errors but reflect our research philosophy not to introduce theoretical assumptions associated with unit conversion and mathematical fit. Second, we review our recent studies to support the original 2012 conclusions. Because the high morphological abnormality rate and small body size detected in Fukushima in 2011 have already ceased, likely through adaptive evolution, their present geographical distributions were investigated throughout Japan. Local populations showing relatively high abnormality rates and small body sizes were rare and basically restricted to Miyagi and its northern populations excluding the Fukushima populations, supporting the causal involvement of the accident. Lastly, we stress the importance of understanding the whole picture of the biological impacts of the Fukushima accident. In addition to the direct radiation impacts, indirect impacts through unknown radiation-associated mechanisms, such as immunological responses to insoluble particulate matter and nutritional deficiencies in plants and animals, would be in effect. Further environmental studies beyond conventional radiation biology and physics are necessary to understand the complex responses of organisms, including humans, to the Fukushima nuclear accident.

Fukushima's lessons from the blue butterfly: A risk assessment of the human living environment in the post-Fukushima era

A series of studies on the pale grass blue butterfly that were carried out to assess the biological effects of the Fukushima nuclear accident teach 3 important lessons. First, it is necessary to have an environmental indicator species, such as the pale grass blue butterfly in Japan, that is common (not endangered), shares a living environment (air, water, and soil) with humans, and is amenable to laboratory experiments. The monitoring of such indicator species before and immediately after a nuclear accident likely reflects acute impacts caused by initial exposure. To assess transgenerational and chronic effects, continuous monitoring over time is encouraged. Second, it is important to understand the actual health status of a polluted region and comprehend the whole picture of the pollution impacts, rather than focusing on the selected effects of radiation alone. In our butterfly experiments, plant leaves from Fukushima were fed to larval butterflies to access whole-body effects, focusing on survival rate and morphological abnormalities (rather than focusing on a specific disease or biochemical marker). Our results revealed that ionizing radiation is unlikely to be the exclusive source of environmental disturbances. Airborne particulate matter from a nuclear reactor, regardless of its radioactivity, is likely equally important. Finally, our butterfly experiments demonstrate that there is considerable variation in sensitivities to nuclear pollution within a single species or even within a local population. Based on these results, it is speculated that high pollution sensitivity in humans may be caused not only by low levels of functional DNA repair enzymes but also by immunological responses to particulate matter in the respiratory tract. These lessons from the pale grass blue butterfly should be integrated in studying future nuclear pollution events and decision making on nuclear and environmental policies at the local and international levels in the postFukushima era. Integr Environ Assess Manag 2016;12:667-672. © 2016 SETAC.