Japan’s Fukushima Daiichi nuclear power plant suffered three meltdowns last year. Paired with hydrogen explosions, these meltdowns allowed radioactive material to escape. So what's the effect on the environment and human health?

The first clues come from what’s called the pale grass blue butterfly. This delicate insect's wings change color and pattern in response to environmental changes.

The offspring of female butterflies caught in the Fukushima region six months after the meltdowns sported such color-pattern changes, as well as deformed legs, antennae, wings and even eyes. The deformities persisted and got worse in the second generation of offspring as well.

The same deformities were found in butterflies collected from the wild. And the researchers induced similar effects by exposing normal butterflies to radiation from cesium particles like those that escaped Fukushima Daiichi. The research is in the journal Nature Scientific Reports.

As for people, more than 3,000 individuals from a town 23 kilometers north of the stricken nuclear plant also bore detectable levels of radioactive cesium in their bodies. Their total dose of less than one milliSievert is considered safe, and no radiation sickness was observed. But, says a report in the Journal of the American Medical Association, the men, women and children exposed need to be watched for the long-term effects of the radiation—for the rest of their lives.

—David Biello

[The above text is a transcript of this podcast.]

[Scientific American is part of Nature Publishing Group.]