The PanOrient News site reported this morning:
Radioactive strontium exceeding normal quantities has been detected in sediment from atop an apartment building in Yokohama…. The strontium 90 was detected in Yokohama, some 250 kilometers from the damaged Fukushima Daiichi nuclear power plant, by a private agency that conducted the test upon the request of a resident. This is the first time strontium at a concentration of over 100 becquerels per kilogram has been found beyond 100 km from the Fukushima plant.
PanOrient said the level of contamination was 195 becquerels per kilogram.
The radiation exceeded the background levels found in Japan:
Strontium 90 has been detected at concentrations roughly between 10 to 20 becquerels at various places across Japan prior to the nuclear crisis triggered by the March 11 earthquake and tsunami.
The PanOrient article included a second case of strontium contamination, this one near Tokyo:
…officials of Setagaya Ward, west of Tokyo, said Wednesday that radiation levels as high as 2.707 microsieverts per hour have been detected on a local sidewalk. The reading was taken in the Tsurumaki 5-chome area of the western Tokyo ward after being told by a resident that a local place had high radiation levels.
The aritcle details the health effects of strontium exposure:
In adults, strontium mostly attaches to the surfaces of bones. In children, strontium may create the hard bone mineral itself, thus being stored in the bones for many years. Eventually, strontium will dissolve from the bones and return to the blood to be used again to grow bone, or to be expelled through urine, waste matter or sweat. The harmful effects of strontium-90 are caused by the high energy effects of radiation.
Since radioactive strontium is taken up into bone, the bone itself and nearby soft tissues may be damaged by radiation released over time. Bone marrow is the most important source of red blood cells, which are depleted if the strontium-90 level is too high. Problems from lowered red blood cell counts include anemia, which causes excessive tiredness, blood that does not clot properly, and a decreased resistance to fight disease.