What's in the water? Long-run effects of fluoridation on health and economic self-sufficiency.

Community water fluoridation has been named one of the 10 greatest public health achievements of the 20th century for its role in improving dental health. Fluoride has large negative effects at high doses, clear benefits at low levels, and an unclear optimal dosage level. I leverage county-level variation in the timing of fluoride adoption, combined with restricted U.S. Census data that link over 29 million individuals to their county of birth, to estimate the causal effects of childhood fluoride exposure. Children exposed to community water fluoridation from age zero to five are worse off as adults on indices of economic self-sufficiency (-1.9% of a SD) and physical ability and health (-1.2% of a SD). They are also significantly less likely to graduate high school (-1.5 percentage points) or serve in the military (-1.0 percentage points). These findings challenge existing conclusions about safe levels of fluoride exposure.