Yeah this one is a heads up - I've always thrifted and sourced my pans at flea markets. I would imagine that sandblasting the pan and re seasoning might mitigate?
not all sandblasting is ghost busters style though. Plenty of smaller units in use that have some pretty extensive filtration add'ons for just this type of situation (think sci-fi medical glass-box with glove inserts you stick you hands into and where the alien eventually breaks out of).
Depends if the lead is just a later contamination on the surface or is already in the material since the beginning. For first one your idea might work, second one definitely not.