For years, local water authorities have considered the addition of low concentrations of fluoride to drinking water a public health achievement. The Centers for Disease Control and Prevention recommends it, citing evidence showing that fluoride prevents cavities in children — the No. 1 chronic disease in kids.

The CDC calls the practice of adding fluoride to tap water systems one of the 10 greatest public health achievements of the last century.

Fluoride prevents cavities in a quarter of adults and children but excess and prolonged exposure can lead to health risks