Fluoride occurs naturally in Cheyenne’s water sources. It comes from fluoride rich minerals located in the rocks and soils in the mountains and plains west of Cheyenne. Cheyenne’s water can have between 0.3 milligrams per liter (mg/L) and 0.7 mg/L of fluoride from these natural sources.

The Centers for Disease Control and Prevention (CDC) recommends an optimal fluoride concentration of 0.7 mg/L in drinking water. At this concentration, the CDC has determined that the fluoride helps protect teeth. For more information on fluoride, please visit the CDC's website.

When the water from Cheyenne's sources is below 0.5 mg/L of fluoride, the BOPU adds a small amount of fluoride that was mined from natural deposits to reach the CDC’s recommended concentration.