In Shanxi Province, China, children living in the endemic fluoride village of Sima (water supply F = 4.12 mg/L) located near Xiaoyi City had average IQ (97.69) significantly lower (p < 0.02) than children living to the north in the nonendemic village of Xinghua (F = 0.91 mg/L; average IQ = 105.21). These differences were not associated with gender, but the IQ scores were directly related to educational level of the parents.
The results of this study indicate that intake of high-fluoride drinking water from before birth has a significant deleterious influence on children’s IQ in one of two similar villages. No real differences were found for gender. In the high-fluoride village of Sima the number of children with IQ of 69 or below was six times that in the healthier low-fluoride village of Xinghua. There were also fewer children (20) in Sima with superior IQ scores of 120 or higher than the number (27) in Xinghua. Moreover, the fact that the IQ scores increased more slowly with age in Sima than in Xinghua supports the view that exposure to high levels of fluoride in utero exerts a cumulative adverse effect that is not overcome with increasing age in a high-fluoride community.
As expected, and also found here, the educational level of the parents has a significant positive influence on the children’s IQ. However, other factors that might affect children’s IQ need to be considered as well, and further studies are therefore needed both to confirm the present findings and to elucidate the mechanism of fluoride involvement.