In this study, 512 children aged 8-13 years in two Chinese villages were studied and tested – Wamaio with an average of 2.47 mg/L water fluoride (range 0.57-4.50 mg/L) and Xinhuai averaging 0.36 mg/L (range 0.18-0.76 mg/L).
The authors eliminated both lead exposure and iodine deficiency as possible causes for the lowered IQs. They also excluded any children who had a history of brain disease or head injury and none drank brick tea, known to contain high fluoride levels. Neither village is exposed to fluoride pollution from burning coal or other industrial sources.
About 28% of the children in the low-fluoride area scored as bright, normal or higher intelligence compared to only 8% in the "high" fluoride area of Wamaio.
In the high-fluoride city, 15% had scores indicating mental retardation and only 6% in the low-fluoride city.
The study authors write: "In this study we found a significant dose-response relation between fluoride level in serum and children's IQ."
In addition to this study, and the 23 other IQ studies, there have been over 100 animal studies linking fluoride to brain damage (all the IQ and animal brain studies are listed in Appendix 1 in The Case Against Fluoride available online at http://fluoridealert.org/caseagainst...ppendices.html