Really makes you empathize with religious writers trying to communicate often second hand divine truths that people thousands of years later will have to figure out without the understanding the original prophet had.
Of course, the real problem with this endeavor is that human nature is going to be that explorers ignorant of The Old World will happily ignore any signs saying "Danger! Keep Out! We Really Mean It! This Will Kill You (Slowly)!" looking for treasure. That's exactly what happened with the pyramids--they were looted within a few centuries of being constructed. If humanity regresses to a point that they don't understand radiation poisoning, they are not going to be stopped by even the clearest explanation of what will befall them because they won't believe it.
A machine that can reanimate the dead perhaps? Energy that can turn bones into a living person?
Why not say "nuclear" or "radiation"? It seems very unlikely that the entire species will completely forget about the concept of nuclear radiation.
We don't sit around moping that Marie Curie & co died doing research, everyone involved gets recognised for helping to usher in a new age of scientific progress.
That it isn't fiction is what gives it salience, and the requisite paternalistic 'talking down' to a pre-technical future aspect provides emotional and/or moralistic flavor, if you like that sort of thing.
Eventually, it turns into bike-shedding scary apocalyptic artworks.