Nuclear meltdowns make everything depressing, and this week, even butterflies and balloons have seen their normally cheery image marred by radioactivity.

First butterflies. A paper in the open-access journal Scientific Reports, shows mutations in butterfly populations around the Fukushima plant, which melted down in March of last year following a major earthquake and tsunami. The paper is impressively thorough: it examined 144 butterflies collected a month after the accident. While their behaviour was normal, they did suffer from small morphological defects, such as dented eyes and slightly deformed wings (see above). A second examination of butterflies caught six months later showed about twice the rate of mutation.

The group also conducted a series of laboratory experiments in which they induced mutations in normal butterflies through radiation exposure. The total dose received by the lab butterflies was 55 millisieverts (mSv) and 125 mSv, and mutations similar to those in the wild samples could be seen in both populations.

The results are consistent with low-dose radiation exposure. As butterflies breed in the radioactive environment, mutations will accumulate in the population. Another study has shown that the number of butterflies around Fukushima have dropped since the accident, and this could be one reason why.

It’s bad news for the environment, but should people be worried? Not really. As I reported in May the vast majority of civilians and workers have received less than 10 mSv of radiation. Those estimates are backed up by a paper out today in the Journal of the American Medical Assocaition showing that 3,051 residents surveyed received less than 1 mSv of internal exposure from caesium-137 six months after the accident (though they admit earlier exposure might be higher).

It is also worth mentioning that people are a lot bigger than butterflies; so even if they do receive higher doses, we wouldn’t expect the same response.

In separate balloon-related meltdown news, workers have flown a balloon inside the unit 1 reactor in a clever bid to get a better look at it. By floating it up through an equipment hatch, the crew hoped to get a look at the top of the reactor and the spent fuel pool, which contained used nuclear fuel before the accident and has been the subject of much speculation since. Unfortunately, they couldn’t get all the way to the top because of debris blocking the way. But they did manage to get a look at the fourth floor, and it wasn’t pretty.

There is a very small silver lining to all of this. On the butterfly front, it’s positive that there are scientists carefully examining the ecological impact of Fukushima (this kind of data was absent for years following the Chernobyl accident of 1984). And the balloon shows that the workers at the plant are coming up with creative ideas to try and deal with the situation.

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