Caesium-137 alienation around the Chernobyl nuclear power plant. Together with caesium-134, iodine-131, and strontium-90, caesium-137 was among the isotopes distributed by the reactor explosion that constitute the greatest risk to health. The mean contamination of caesium-137 in Germany following the Chernobyl disaster was 2000 to 4000 Bq/m. This corresponds to a contamination of 1 mg/km of caesium-137, totaling about 500 grams deposited over all of Germany. In Scandinavia, some reindeer and sheep exceeded the Norwegian legal limit (3000 Bq/kg) 26 years after Chernobyl. As of 2016 the Chernobyl caesium-137 has decayed by half, but could have been locally concentrated by much
Radiation effects from the Fukushima Daiichi nuclear disaster in the unit-3 spent-fuel pool were reported at 140 kBq of radioactive caesium-134 per cubic centimeter, 150 kBq of caesium-137 per cubic centimeter, and 11 kBq per cubic centimeter of iodine-131 on 10 May. TEPCO have reported at three sites 500 meters from the reactors that the caesium-134 and caesium-137 levels in the soil are between 7.1 kBq and 530 kBq per kilo of undried soil. Small traces of plutonium have been found in the soil near the stricken reactors: repeated examinations of the soil suggest that the plutonium level is similar to the background level caused by atomic bomb