Scientists have found abnormalities in some butterflies collected near Fukushima. It's the first time such physiological damage has been observed in the area around the nuclear plant stricken by last year's tsunami.
A team gathered 144 adult pale grass blue butterflies in areas within and around the fallout zone in Fukushima prefecture in mid-May 2011, two months after the start of the nuclear emergency. Abnormalities such as damaged eyes and smaller wings were found in roughly 12.4 percent of the total.
The insects were then mated in a laboratory far away from the fallout zone and 18.3 percent of the offspring displayed similar problems, said Joji Otaki, associate professor at Ryukyu University on the island of Okinawa. Okinawa is in the South China Sea, over 500 kilometers (310 miles) to the south-west of main Japanese island, Kyushu.
The third generation of affected butterflies continued the upward trend, with 33.5 percent found to have abnormalities.
"We conclude that artificial radionuclides from the Fukushima Daiichi Nuclear Power Plant caused physiological and genetic damage to this species," the scientists wrote in the online journal "Scientific Reports."
In a second experiment, the researchers collected 240 butterflies in Fukushima in September last year, six months after the disaster. Abnormalities were recorded in 59.1 percent of their offspring. In the second experiment, the scientists also "observed frequent malformations of legs and antennae as well as wing color-pattern aberrations," the group said.
Otaki told the AFP news agency that "we have reached the firm conclusion that radiation released from the Fukushima Daiichi plant damaged the genes of the butterflies."
The scientists' findings raise fears over the long-term effects of the nuclear plant's radiation leaks on people who were exposed in the days and weeks after the accident, as radiation spread and authorities were forced to evacuate the area around the plant. Some have claimed the effects of nuclear exposure have already been observed on successive generations of descendants of people who lived in Hiroshima and Nagasaki when the US dropped atomic bombs on the cities during the closing days of World War II.
Long-term effects unknown
Otaki cautioned it was too soon to jump to conclusions, saying his team's findings on the butterflies could not be directly applied to humans. He said that he and other scientists would conduct follow-up studies, including similar tests on other animals.
Otaki's caution was echoed by Kunikazu Noguchi, an associate professor in radiological protection at Nihon University School of Dentistry, who told AFP that more data was needed to determine the impact of the Fukushima disaster on animals.
"This is just one study," Noguchi was quoted as saying. "We need more studies to verify the entire picture of the impact on animals."
The Fukushima Daiichi Nuclear Power Plant suffered meltdowns at three of its six reactors following the March 2011 earthquake and tsunami.
Tens of thousands of Japanese fled their homes around the nuclear complex. According to some experts, it may be decades until radiation levels near the plant are reduced enough for permanent human habitation again.
The March 11, magnitude 9.0 off-shore earthquake triggered a tsunami that killed an estimated 15,867 people. According to the Japanese National Police Agency, more than 2,900 people are still missing. The World Bank estimated the cost of the damage at $235 billion (190 billion euros), which would make it the most expensive natural disaster in human history.
bm/msh (AFP, dpa)