> The substances listed in the comment I replied to are stable elements. The comment you replied to said "more mundane sorts of toxic waste". That would usuall

> The substances listed in the comment I replied to are stable elements. The comment you replied to said "more mundane sorts of toxic waste". That would usually be molecules, i.e. built from multiple atoms, probably multiple elements. And every chemical transformation works both ways, and while the probability for a molecule to fall apart or recombine with other molecules might be low, it will never be zero. So to the best of my understanding there's no such thing as a completely stable molecule, the question is simply how long of a time that you consider. Which leads me back to the question what references you have for (toxic, nonetheless, thus probably somewhat reactive) molecules that have a molecular (not radioactive) half life longer than those for the radioactive decay you compare them to. To restate my point: molecules may be less stable than the atoms they are made of, and less stable than the radioactive elements you compare them to.