Wikipedia: Health risk of radioactive Cesium

Health risk of radioactive caesium

Caesium-137 reacts with water producing a water-soluble compound (caesium hydroxide). The biological behavior of caesium is similar to that of potassium and rubidium. After entering the body, caesium gets more or less uniformly distributed throughout the body, with the highest concentrations in soft tissue.^[9]:114 The biological half-life of caesium is rather short at about 70 days.^[10] A 1972 experiment showed that when dogs are subjected to a whole body burden of 3800 μCi/kg (140 MBq/kg, or approximately 44 μg/kg) of caesium-137 (and 950 to 1400 rads), they die within thirty-three days, while animals with half of that burden all survived for a year.^[11]
Accidental ingestion of caesium-137 can be treated with Prussian blue, which binds to it chemically and reduces the biological half-life to 30 days.^{[12]
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https://en.wikipedia.org/wiki/Caesium-137#Health_risk_of_radioactive_caesium}