Chernobyl disaster substantial levels of caesium, which were believed to have been passed onto them during their consumption by wild boars, a significant number of which already contained radioactive particles above the allowed level. Like many other releases of radioactivity into the environment, the Chernobyl release was controlled by the physical and chemical properties of the radioactive elements in the core. Particularly dangerous are the highly radioactive fission products, those with high nuclear decay rates that accumulate in the food chain, such as some of the isotopes of iodine, caesium and strontium. Iodine-131 and caesium-137 are responsible for most of the radiation
Fukushima Daiichi nuclear disaster experimental agricultural research fields around the affected area) has noted that "the fallout was found at the surface of anything exposed to air at the time of the accident. The main radioactive nuclides are now caesium-137 and caesium-134", but these radioactive compounds have not dispersed much from the point where they landed at the time of the explosion, "which was very difficult to estimate from our understanding of the chemical behavior of cesium". In February 2018, Japan renewed the export of fish caught off Fukushima's nearshore zone. According to prefecture officials, no seafood had been found with radiation levels exceeding