Results: The standardized weighted mean difference in IQ score between exposed and reference populations was –0.45 (95% confidence interval: –0.56, –0.35) using a random-effects model. Thus, children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas. Subgroup and sensitivity analyses also indicated inverse associations, although the substantial heterogeneity did not appear to decrease.
https://ehp.niehs.nih.gov/doi/10.1289/ehp.1104912 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6923889/