Frame said the ring likely used polonium-210 because it was the most accessible substance that could produce the alpha particles required to make the effect work. However, polonium-210 has a relatively short half-life of 138 days, meaning that approximately half the polonium in the ring would have been gone within about four and a half months. In other words, a vintage Atomic Bomb Ring isn't going to be producing any scintillations.
Even while the ring's effect was still happening, though, kids weren't really in danger. Alpha radiation can be dangerous when ingested, but it's also the easiest type of radiation to block — even a sheet of paper is enough
