I know Kryptonite is stated to be very rare on Earth but surely the very rich/powerful (presidents, monarchs) would have carried it everywhere to protect them from skin cancer?
Was it just the risk to Superman that prevented them from using it? (e.g. saving from natural disasters, automobile accidents and supervillains) or is there some inherent danger in constant exposure?
Is there a canonical use of kryptonite as some form of radiotherapy/cancer treatment?
Kryptonite affects Kryptonian physiology by forcing stored solar radiation, used as a catalyst for superhuman feats, out of the cells of Kryptonians who are under a yellow sun.
During this event, the Kryptonian cannot perform feats of superhuman activity and can only writhe helplessly unless rescued by a third party.
This effect is damaging to Kryptonian physiology and acts as a deadly exposure to radiation would on human beings, eventually killing the Kryptonian in as little as an hour.
This effect does not happen to humans exposed to Kryptonite because Human cells do not absorb solar radiation for feats of superhuman capability.
Kryptonite, instead acts as a mildly radioactive substance eventually CAUSING cancer if a Human is exposed to it for an extended period.
Lex Luthor, in the previous DC continuity developed cancer after wearing Kryptonite as a piece of jewelry to harass Superman.
