Japan radiation cited in changes to butterflies

TOKYO -- Radiation that leaked from the Fukushima nuclear plant after last year's tsunami caused mutations in some butterflies, including dented eyes and stunted wings, though humans seem relatively unaffected, researchers say.

The mutations are the first evidence that the radiation has caused genetic changes in living organisms. They are likely to add to concerns about potential health risks among humans, though there is no evidence of it yet. Scientists say more study is needed to link human health with the Fukushima disaster.

The catastrophic meltdowns in three reactors of Fukushima Dai-ichi power plant after it was damaged by the 9.0-magnitude earthquake and tsunami on March 11, 2011, prompted a public backlash against nuclear power, and forced the government to reassess resource-scarce Japan's entire energy strategy.

But the most visible example of the radiation's effect was claimed by a group of Japanese researchers who found radical physical changes in successive generations of a type of butterfly, which they said was caused by radiation exposure. They said that the threat to humans, a much larger and longer-lived species, remains unclear.

"Our findings suggest that the contaminants are causing ecological damage. I do not know its implication to humans," Joji Otaki of the University of the Ryukyus in Okinawa, a member of the research team, said in an email.

A separate study, released this week, found very low levels of radioactivity in people who were living near the Fukushima plant when it suffered the meltdowns.

The paper, published in the Journal of the American Medical Association, measured cesium levels in 8,066 adults and 1,432 children and found average doses of less than 1 millisievert, which are considered safe. It was the first such study measuring internal exposures to cesium in a large number of people from the disaster.