A group of scientists have found abnormalities among
butterflies collected near the damaged Japanese nuclear plant after last year's disaster, reports said Tuesday.
"We conclude that artificial radionuclides from the Fukushima [Daiichi] Nuclear Power Plant caused physiological and genetic damage to this species," the scientists said in an article in Scientific Reports, an online journal of the Nature Publishing Group.
Butterflies are considered "useful environmental indicators," said the group led by Joji Otaki, associate professor at the University of the Ryukyus in Okinawa.
The team gathered collected 144 adult pale grass blue butterflies in areas in and outside Fukushima prefecture in mid-May 2011, two months after the start of the nuclear emergency.
They found abnormalities such as damaged eyes and smaller wings in 12.4 per cent of the total. But the figure rose to 18.3 per cent in a second generation.
The team also found the rate of abnormalities jumped to 33.5 per cent in the third generation produced through mating between those with abnormal traits and healthy ones.
The tests were conducted within labs on the southern island of Okinawa, 1,750 kilometres south-west from the Fukushima plant and one of the regions least affected by the nuclear fallout.
The scientists also collected another 238 butterflies in September 2011, and found abnormalities in 28.1 per cent of the total.
They also "observed frequent malformations of legs and antennae as well as wing colour-pattern aberrations," the group said.
The rate more than doubled to 59.1 per cent in a second generation of the butterflies collected in September.
The results showed the samples in September deteriorated compared with those in May, the team said, "possibly due to genetic damage caused by radiation from the Fukushima plant.
The plant released the massive amount of radioactive material into the environment and suffered meltdowns at three of its six reactors after the March 2011 earthquake and tsunami.
Tens of thousands of residents have been forced to leave areas around the complex. More residents in Fukushima have left the prefecture as they fear the health effects of radiation.
However, critics say the central and local governments have downplayed the possible effects of radiation and instead promoted the image of a safe Fukushima.
The city of Iwaki opened one of its beaches in mid-July, 65 kilometres south of the plant.
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