I think that's more of a concern for people who aren't genocidal maniacs out to destroy the species. Like I said, we already have examples of people who wanted to usher in an apocalypse, some of them even gave it the good old college try, but they lacked resources. If you gave Shoko Asahara a few hundred billion to play with, who knows what Aum would have come up with. At the very least their sarin would have been pure.