In response to the 2006 National Research Council (NRC) report: Fluoride in Drinking Water: A Scientific Review of EPA's Standards, the U.S. EPA Office of Water (OW) began a reassessment of the dose-response associated with the effects of ingested fluoride on severe dental fluorosis and bone structure. This report is a culmination of that effort. At low intake levels, fluoride has been shown to have therapeutic value in the prevention of dental caries; however, slightly higher levels, particularly in children during the period of enamel development can lead to dental fluorosis, a condition in which the enamel covering of the teeth fails to crystallize properly. Possible resulting problems include enamel defects ranging from barely discernable markings to brown stains and surface pitting. Prolonged high intake of fluoride, at any age, can result in skeletal fluorosis, a condition which may increase bone brittleness, and in a potential increase in risk of bone fracture. In high-dose cases, severe bone abnormalities can develop, crippling the affected individual.