A team of international researchers has found that levels of radioactive material in farmland in parts of northeastern Japan exceed safety standards.
The study, published in the Proceedings of the National Academy of Sciences journal, found that Fukushima prefecture was “highly contaminated” after the Fukushima Daiichi nuclear power plant was damaged in the March 11 earthquake and tsunami.
The level of radioactive material found in neighboring prefectures, such as Miyagi, Tochigi and Ibaraki, was lower but could still pose a threat to food production in some areas, the researchers said.
The study, led by Teppei Yasunari of the Universities Space Research Assn. in Maryland, looked at levels of cesium-137, which is of particular concern because it takes decades to decay.
The researchers used daily measurements collected in most prefectures along with computer-generated models of particle dispersion based on weather patterns to estimate the level of contamination across Japan.
The legal limit in Japan for concentrations of cesium-137 and cesium-134 in farm soil is 5,000 becquerels per kilogram (2.2 pounds). Cesium-137 makes up about half of the total for the concentrations, which are produced together.
The study found that the level of contamination in east Fukushima exceeded the safety limits. Results from neighboring prefectures were within the legal limits, but the researchers advised local authorities to conduct supplementary soil sampling.
TOKYO – JAPAN banned the shipment of green tea leaves grown in four prefectures around Tokyo on Thursday after radioactive caesium above legal levels was found in samples, a media report said.
It was the latest produce shipment ban since the massive March 11 seabed quake and tsunami crippled the Fukushima nuclear plant northeast of Tokyo, which has since leaked radiation into the ground, air and sea.
The ban covers tea leaves from parts of the Tochigi, Chiba and Kanagawa prefectures and all of Ibaraki prefecture, the Ministry of Health, Labour and Welfare said, Kyodo News agency reported.
Kanagawa, southwest of Tokyo, said in early May it had detected radiation above the legal limit in tea grown there and blamed it on the stricken Fukushima nuclear power plant, which suffered partial meltdowns.
Kanagawa prefecture then started a recall of the tea after measuring about 570 becquerels of caesium per kg in leaves grown in the city of Minamiashigara. The legal limit is 500 Bq/kg.
The Fukushima Daiichi plant is located some 220km north-east of Tokyo and 280km from Minamiashigara. — AFP