I once read that 1 kg of plutonium burning up in the higher atmosphere would be enough to kill the entire population of the earth. I'm not enough of an expert t

I once read that 1 kg of plutonium burning up in the higher atmosphere would be enough to kill the entire population of the earth. I'm not enough of an expert to know if that's really true, but I suspect there's a good reason why experts don't consider this a good option. Or at least not yet.