Sodium Fluoride Is Added to Drinking Water in Some Municipalities

Short Answer

Sodium fluoride is added to drinking water in some municipalities to protect teeth against cavities. The target is to convert hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂, into more stable fluorapatite, Ca₁₀(PO₄)₆F₂. The EPA currently restricts the concentration of fluoride in drinking water to 4 mg/L. Express this concentration in parts per million (ppm).