Effect of high-fluoride water on intelligence in children

The Intelligence Quotient (IQ) was measured in 118 children, aged 10-12 years, who were life-long residents in two villages of similar population size and social, educational and economic background but differing in the level of fluoride in drinking water. The children in the high-fluoride area (drinking water fluoride 3.15 +/- 0.61 mg/L [ppm]) (mean +/- S.D.) had higher urinary fluoride levels (4.99 +/- 2.57 mg/L) than the children in the low-fluoride area (drinking water fluoride 0.37 +/- 0.04 mg/L) (urinary fluoride 1.43 +/- 0.64 mg/L). The IQ of the 60 children in the high-fluoride area was significantly lower, mean 92.27 +/- 20.45, than that of the 58 children in the low-fluoride area, mean 103.05 +/- 13.86. More children in the high-fluoride area, 21.6%, were in the retardation (<70) or borderline (70-79) categories of IQ than children in the low fluoride area, 3.4%. An inverse relationship was also present between IQ and the urinary fluoride level. Exposure of children to high levels of fluoride may therefore carry the risk of impaired development of intelligence.