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
Accident rating of the Fukushima Daiichi nuclear disaster radioactive material have also been released into ground and ocean waters. Measurements taken by the Japanese government 30–50 km from the plant showed caesium-137 levels high enough to cause concern, leading the government to ban the sale of food grown in the area. Tokyo officials temporarily recommended that tap water should not be used to prepare food for infants. In May 2012, TEPCO reported that at least 900 PBq had been released "into the atmosphere in March last year [2011] alone". Several of the plant's workers were severely injured or killed by the disaster conditions resulting from the earthquake. There