Fluoride in Drinking Water

Fluoride in drinking water comes from two main sources: intentional addition by water utilities (community water fluoridation, typically at 0.7 mg/L) to prevent tooth decay, and natural occurrence from the dissolution of fluoride-containing minerals in the Earth's crust. The public health debate around fluoride is one of the longest-running in water treatment history. At low concentrations (around 0.7 mg/L), fluoride has been shown to reduce cavities, particularly in children who may not have access to dental care. However, at higher levels, fluoride can cause health problems.

The EPA sets the maximum contaminant level for fluoride at 4.0 mg/L based on the risk of skeletal fluorosis -- a painful bone disease that can develop after long-term exposure to high fluoride levels. At somewhat lower levels (above 2.0 mg/L), children can develop dental fluorosis, which causes discoloration and pitting of the teeth. The EPA has set a secondary standard of 2.0 mg/L to protect against dental fluorosis, though this is a non-enforceable guideline. Recent research has also raised questions about potential neurological effects, particularly in developing brains, leading the National Toxicology Program to conclude that fluoride exposure above 1.5 mg/L is associated with lower IQ in children.

If you're on a public water system that practices fluoridation, your levels are typically well-controlled around 0.7 mg/L -- far below the MCL. The concern arises primarily with well water in areas with naturally high fluoride geology, or in communities with inadequate monitoring. If you have young children and are concerned about fluoride, testing your water is straightforward and inexpensive.