A citizens' group has discovered radioactive strontium in soil in three locations in Tokyo, peaking at 51 becquerels per kilogram.
The group took measurements throughout Tokyo and Yokohama, and found radioactive mud in several locations, Sankei Shimbun reported Friday. In one case, a soil sample weighing one kilogram was found to be emitting 51 becquerels.
The group said they gathered soil through Oct 31 from various locations and then had them examined at an isotope research facility, Sankei said. The group claimed that a sample taken near the Ministry of Economy, Trade and Industry building in Kasumigaseki emitted 48 becquerels, one taken from outside the Tokyo International Forum in Yurakucho gave off 51 becquerels, and a third sample taken outside Kiyosumi-shirakawa Station in Koto Ward measured 44 becquerels per kilogram.
The group is the same one that discovered radioactive strontium 90 in sediment on the roof of a condominium in Yokohama in mid-October. In that case, the level of radioactive strontium was 195 becquerels, which is 95 becquerels per kilogram above the government standard.
It was the first time that radioactive strontium with a level higher than the government benchmark has been found so far from the stricken Fukushima Daiichi nuclear power plant.
Strontium 90 is a radioactive isotope of strontium, with a half-life of 28.8 years. Its presence in bones can cause bone cancer, cancer of nearby tissues and leukemia.
However, the Ministry of Education, Culture, Sports, Science and Technology said Thursday that the Yokohama strontium most likely did not come from the Fukushima Daiichi nuclear power plant. NHK quoted a ministry spokesperson as saying the isotope research did not detect strontium 89 with a half-life period of around 50 days, which would have been the case if it was linked to Fukushima. The ministry said the test detected 0.82 to 1.1 becquerels per kilogram of strontium 90 with a half-life of around 29 years, NHK reported.© Japan Today