Fluoride in drinking water has no effect on IQ or brain function, long-term study shows
(twin-cities.umn.edu)
why can't we have both?
Because drinking water is a basic need and should not be medicated when it’s not even a great way to apply the medicine.
Note that while the risk of issues from proper dosing is low. Improper dosing can and does occur. Sandy City, Hooper Bay, Richmond to list a few. When you improperly dose community water you’re affecting everyone using the water.
If toothpaste or mouthwash was improperly dosed, it would be mostly spit out and the risk is minimized while also maximizing exposure to the enamel.