Source : Kyodo News International, Inc., Februray 6 2012
"Earthworms collected in Kawauchi, a village near the Fukushima Daiichi nuclear power plant, were found to contain high levels of cesium averaging some 20,000 becquerels per kilogram, governmental researchers said Monday.
The finding indicates that the radioactive substance "may accumulate in other animals through a food chain," Motohiro Hasegawa, senior researcher at the Department of Forest Entomology, Forestry and Forest Products Research Institute, said, noting that earthworms are eaten by birds, hogs and other wild animals.
Last August and September, Hasegawa and other researchers from the institute, based in Tsukuba, Ibaraki Prefecture, collected earthworms in national forests in Kawauchi, located 20 kilometers away from the crippled nuclear power plant, and two other places in Fukushima Prefecture -- Otama Village and Tadami Town located 60 km and 150 km from the plant, respectively.
The researchers analyzed average cesium levels in five earthworms gathered each in the three locations. Worms from Otama and Tadami were found to have some 1,000 and 300 becquerels of cesium per kilogram, respectively, compared with the central government-set allowable limit of 500 becquerels, according to them.
Fallen leaves come into contact with radioactive substances, leaked from the Fukushima nuclear plant, and decompose into the soil before earthworms eat it, the searchers said, explaining how the animals have come to contain cesium.
Cesium levels in the soil where earthworms were collected stood at some 1.38 million becquerels per square meter in Kawauchi, 80,000 to 120,000 becquerels in Otama and 20,000 becquerels in Tadami, they added."