Researchers analyzed a series of epidemiological studies that examined the adverse effects of high fluoride concentrations in drinking water and concluded that their results support the possibility of adverse effects of fluoride exposure on children’s neurodevelopment.
A 2006 report from the National Research Council (NRC 2006) had concluded that adverse effects of high fluoride concentrations in drinking water may be of concern and that additional research is warranted. Fluoride has been linked to causing neurotoxicity in laboratory animals, including effects on learning and memory.
Although acute fluoride poisoning may be neurotoxic to adults, most of the epidemiological information available on associations with children’s neurodevelopment is from China, where fluoride generally occurs in drinking water as a natural contaminant, and the concentration depends on local geological conditions. In many rural communities in China, populations with high exposure to fluoride in local drinking-water sources may reside in close proximity to populations without high exposure (NRC 2006).
Multiple epidemiological studies of developmental fluoride neurotoxicity were conducted in China because of the high fluoride concentrations that are substantially above 1 mg/L in well water in many rural communities, although microbiologically safe water has been accessible to many rural households as a result of the recent 5-year plan (2001–2005) by the Chinese government. It is projected that all rural residents will have access to safe public drinking water by 2020 (World Bank 2006). However, results of the published studies have not been widely disseminated. Four studies published in English were cited in a recent report from the NRC (2006), whereas the World Health Organization (2002) has considered only two in its most recent monograph on fluoride.
Fluoride readily crosses the placenta (Agency for Toxic Substances and Disease Registry 2003). Fluoride exposure to the developing brain, which is much more susceptible to injury caused by toxicants than is the mature brain, may possibly lead to permanent damage. In response to the recommendation of the NRC (2006), the U.S. Department of Health and Human Services (DHHS) and the U.S. EPA recently announced that DHHS is proposing to change the recommended level of fluoride in drinking water to 0.7 mg/L from the currently recommended range of 0.7–1.2 mg/L, and the U.S. EPA is reviewing the maximum amount of fluoride allowed in drinking water, which currently is set at 4.0 mg/L (U.S. EPA 2011).
The authors conclude that children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas.
Environ Health Perspect. 2012 October; 120(10): 1362–1368. Review
Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis
Anna L. Choi,1 Guifan Sun,2 Ying Zhang,3 and Philippe Grandjean.