@farmerman,
Perhaps Quahog doesnt understnd that, there are areas where F exceeds a recc limit for effective dental protection. If that does occur, (especially where ground water is used in public supplies, the water is DEFLOURIDATED by perking the product water through beds of activated alumina.
A recc dosage is at or slightly less than a ppm.
Hormetic effects occur with many substances , even table salt.