The Fukushima nuclear accident and the pale grass blue butterfly: evaluating biological effects of long-term low-dose exposures

Abstract

BackgroundOn August 9th 2012, we published an original research article in Scientific Reports, concluding that artificial radionuclides released from the Fukushima Dai-ichi Nuclear Power Plant exerted genetically and physiologically adverse effects on the pale grass blue butterfly Zizeeria maha in the Fukushima area. Immediately following publication, many questions and comments were generated from all over the world. Here, we have clarified points made in the original paper and answered questions posed by the readers.ResultsThe following points were clarified. (1) There are many advantages to using the pale grass blue butterfly as an indicator species. (2) The forewings of the individuals collected in Fukushima were significantly smaller than in the northern and southern localities. (3) We observed growth retardation in the butterflies from the Fukushima area. (4) The aberrant colour patterns in the butterflies obtained in the Fukushima area were different from the colour patterns induced by temperature and sibling crosses but similar to those induced by external and internal exposures to the artificial radionuclides and by a chemical mutagen, suggesting that genetic mutations caused the aberrations. (5) This species of butterfly has been plentiful in Fukushima area for at least half a century. We here present specimens collected from Fukushima Prefecture before the accident. (6) Mutation accumulation was detected by the increase in the abnormality rates from May 2011 to September 2011. (7) The abnormal traits were heritable. (8) Our sampling localities were not affected by the tsunami. (9) We used a high enough number of samples to obtain statistically significant results. (10) The standard rearing method was followed, producing normal adults in the control groups. (11) The exposure experiments successfully reproduced the results of the field work. This species of butterfly is vulnerable to long-term low-dose internal and external exposures; however, insect cells are known to be resistant to short-term high-dose irradiation. This discrepancy is reconcilable based on the differences in the experimental conditions.ConclusionsWe are just beginning to understand the biological effects of long-term low-dose exposures in animals. Further research is necessary to accurately assess the possible biological effects of the accident.

The biological impacts of ingested radioactive materials on the pale grass blue butterfly

“…Another study indicated a high incidence of morphological abnormality in gall-forming aphids14. Consistent with these studies, we have demonstrated that the Japanese pale grass blue butterfly, Zizeeria maha ( Yamato shijimi in Japanese), was affected physiologically and genetically in the polluted area, likely due to the artificial radionuclides released from the Fukushima Dai-ichi NPP1516. In one of a series of experiments, we have shown a decrease in the survival rate of this butterfly in accordance with the level of radioactivity of cesium in the diet (i.e., the leaves of the host plant, Oxalis corniculata )1516 under our standard rearing conditions17.…”

“…We found that the levels of ingested cesium from the 4 localities (i.e., Hirono, Fukushima, Iitate-flatland, and Iitate-montane) were much higher than that from Ube, a control locality; thus, it is not surprising that harmful biological effects were clearly detected in previous studies1516. However, we do not know if our results can be directly compared to other studies on natural radiation or other nuclear accidents.…”

Low-dose radiation, scientific scrutiny, and requirements for demonstrating effects

“…In a rebuttal Hiyama et al . [10] provided extensive evidence that supports their initial conclusions (Table 2). In particular, they have shown five important findings: the color patterns obtained in Fukushima differed from color patterns produced by aberrant temperatures and sibling crosses; the minor morphological abnormalities were not present at high frequency in Fukushima before the accident, as shown by older specimens in collections; the abnormal traits were heritable; mutation accumulation occurred from May to September 2011; and finally, positive controls produced normal adults.…”

Radioecological impacts of tin mining

“…Although the IAEA generally assumes limited impacts to organisms from dose rates B50 lGy h -1 , there is considerable discussion of these arbitrary thresholds given the lack of sufficient information concerning unknown individual and species variation in sensitivity, the role of multigeneration exposures, and the importance of complex community interactions in determining individual-, population-, and ecosystem-level responses to radiation sources. Recent analyses of organisms inhabiting Chernobyl, Fukushima, and other naturally radioactive regions around the world point to measurable, biologically significant impacts at what are much lower dose rates than those recommended by IAEA (e.g., Mousseau 2009, 2015;Hiyama et al 2012Hiyama et al , 2013Yamashiro et al 2013;Møller et al 2014). Clearly, further research is needed.…”