enamel fluorosis, and about one-half of the cases were classified as moderate or severe.

Because the cosmetic effects of the milder forms of enamel fluorosis are not readily apparent, moderate enamel fluorosis was selected as the critical adverse effect for susceptible age groups (infants, toddlers, and children through the age of 8 years). Thus, a fluoride intake of 0.10 mg/kg/day was identified as a LOAEL for moderate enamel fluorosis in children from birth through the age of 8 years, at which age the risk of developing fluorosis of the anterior teeth is over.

Uncertainty Assessment. The relationship between fluoride intake and enamel fluorosis is based on results from human studies and enamel fluorosis is considered a cosmetic effect rather than an adverse functional effect. Therefore, an uncertainty factor (UF) of 1 was selected.

Derivation of the UL. Based on a LOAEL of 0.10 mg/kg/day for moderate enamel fluorosis and a UF of 1, a Tolerable Upper Intake Level (UL) of 0.10 mg/kg/day was established for infants, toddlers, and children through 8 years of age. The extensive epidemiological research conducted in the United States during the 1930s and 1940s (Dean, 1942) established, with a high degree of certainty, that a chronic fluoride intake of less than 0.10 mg/kg/day by children at risk of enamel fluorosis was associated with a low prevalence (for example, approximately 10 percent) of the milder forms of the condition.

Based on a UL of 0.10 mg/kg/day of fluoride and a reference weight for infants ages 0 through 6 months of 7 kg (Table 1-3), the UL is 0.7 mg/day. For children ages 7 through 12 months with a reference weight of 9 kg, the UL is 0.9 mg/day.

Based on a UL of 0.10 mg/kg/day of fluoride and a reference weight for children ages 1 to 3 years of 13 kg (Table 1-3), the UL is 1.3 mg/day for children ages 1 through 3 years. For children ages 4 through 8 years with a reference weight of 22 kg, the UL is 2.2 mg/day.