TABLE 4-11 Comparison of Intakes from Drinking Watera from the Iowa Fluoride Study and IOM’s Upper Tolerable Intakes

 

 

Percentiles of Iowa Fluoride Study Distribution (mg/day)

Age, months

IOM Tolerable Upper Intake (mg/day)

75th

90th

Maximum

3

0.7

0.7

1.1

6.7

12

0.9

0.4

0.7

6.0

24

1.3

0.4

0.6

2.1

36

1.3

0.5

0.7

1.7

aFluoride concentrations in drinking water ranged from <0.3 to 2 mg/L.

SOURCE: Levy 2003.

infants have an average total fluoride intake (all sources except fluoride supplements) of 0.144 and 0.258 mg/kg/day at 2 and 4 mg/L fluoride in drinking water, respectively. Corresponding values are 0.090 and 0.137 mg/kg/day for children 1-2 years old and 0.082 and 0.126 mg/kg/day for children 3-5 years old. Furthermore, at EPA’s current default drinking water intake rate, the exposure of infants (nursing and non-nursing) and children 1-2 years old would be at or above the IOM limits at a fluoride concentration of 1 mg/L (Table 2-13). For children with certain medical conditions associated with high water intake, estimated fluoride intakes from all sources (excluding fluoride supplements) range from 0.13-0.18 mg/kg/day at 1 mg/L to 0.23-0.33 mg/kg/day at 2 mg/L and 0.43-0.63 mg/kg/day at 4 mg/L.

IOM’s tolerable upper limits were established to reduce the prevalence not only of severe fluorosis, but of moderate fluorosis as well, both of which ADA (2005) describes as unwanted effects. The present committee, in contrast, focuses specifically on severe enamel fluorosis and finds that it would be almost eliminated by a reduction of water fluoride concentrations in the United States to below 2 mg/L. Despite this difference in focus, the committee’s conclusions and recommendations with regard to protecting children from enamel fluorosis are squarely in line with those of IOM and ADA.

The current SMCL of 2 mg/L is based on a determination by EPA that objectionable enamel fluorosis in a significant portion of the population is an adverse cosmetic effect. EPA defined objectionable enamel fluorosis as discoloration and/or pitting of teeth. As noted above, the majority of the committee concludes it is no longer appropriate to characterize enamel pitting as a cosmetic effect. Thus, the basis of the SMCL should be discoloration of tooth surfaces only.

The prevalence of severe enamel fluorosis is very low (near zero) at fluoride concentrations below 2 mg/L. However, from a cosmetic stand-



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