The CDC requires drinking water to have less than 4mg/liter fluoride. There is a guideline of less than 2mg/liter. Fluoridation for dental health is done at 0.

The CDC requires drinking water to have less than 4mg/liter fluoride. There is a guideline of less than 2mg/liter. Fluoridation for dental health is done at 0.7mg/liter. The only health effects observed at 4mg/liter are dental fluorosis, staining of teeth as they form in children. There are places in the United States where the natural drinking water exceeds 4mg/liter. King Hill, Idaho (population 100) wins with 16mg/liter.