abstract:Plutonium (Pu) is an artificial element, except for trace quantities of primordial 244Pu, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes.
From a public health perspective, the most important isotopes are short-lived isotopesof iodine (like Iodine-131), Cesium-137, Strontium-90, and possibly Plutonium-239.