# Which is the most toxic isotope of plutonium and what makes it toxic? [closed]

Some sources say plutonium is one of the most toxic substances known, while this challenge from Bernard Cohen to Ralph Nader challenges the toxicity. I heard that only one of its isotopes is toxic, I think the one that powers some space craft by thermo-radioactivity to electric generation. Is there any truth to plutonium's alleged extreme toxicity? Which isotope is the most toxic and why? I think different isotopes have different half lives and thus lingering toxic effects.

## closed as off-topic by JMac, John Rennie, Jon Custer, stafusa, knzhouSep 29 '17 at 16:14

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• I'm voting to close this question as off-topic because this primarily deals with biology and chemistry. – JMac Sep 26 '17 at 15:38
• For radiation risk, you might compare to polonium. Note that many heavy metals (such as lead) are toxic for reasons to do purely with chemistry. – rob Sep 26 '17 at 15:47
• – dmckee Sep 26 '17 at 17:03

1. Plutonium is radioactive. All of its isotopes are. Some of them not very strongly, but all of them are more radioactive as the practically problem-free ${}^{238} \mathrm{U}$. Ingesting it, inhaling its dust, causes radioactive damage. The radioactivity is not toxicity, it is a damage, like the burns. The term "radioactive poison" is used essentially falsely in most cases.
The most stable isotope of the Plutonium is the ${}^{244} \mathrm{Pu}$, its long ($\approx$ 80 million year) half-life makes its radioactivity practically not dangerous, or very low risky. (As a rule of thumb, the danger of the radioactivity of an isotope is roughly inversely proportional with its half life.)
The least stable Pu-isotope in this list is the ${}^{243m2} \mathrm{Pu}$, with its half life of nanoseconds. We could say that it is the most "toxic". Although it decays faster as the light would reach from it your eye. Thus, you can't eat it.