A new study suggests a link between high levels of fluoride and lowered IQ. It's heating up arguments over fluoridating drinking water, which dentists say is critical for protecting teeth.

Florida's surgeon general, Dr. Joseph Ladapo, cited developmental concerns from higher levels of fluoride than are found in most U.S. water supplies.

The Richmond, Vt., water superintendent revealed in his resignation letter that fluoride levels have not been in the state-recommended range for over a decade — far longer than previously disclosed.

Residents of a small Vermont community were blindsided by news that a water department official lowered fluoride levels nearly four years ago, giving rise to worries about children's dental health.