[valarauko]

Agree with everything you're saying. For what it's worth, the concerns about the high fluoride in groundwater are almost entirely about unborn infants - adults seem to suffer no severe issues from drinking it. With teeth, high fluoride exposure causes blotchy teeth before they erupt - once the (adult) teeth have erupted, the fluoride seems to help. It's also a continuum - some regions have such high levels that it's considered unsafe for consumption, period. These are the regions where developmental issues are seen.