Background: People of all ages are exposed to fluoride from a variety of sources including dental products, drinking water, food, beverages and pharmaceuticals. In some developed countries, fluoride is added to municipal water systems to prevent tooth decay.
Methods: The National Toxicology Program (NTP) conducted a systematic review of the human, experimental animal, and mechanistic literature to evaluate the evidence and develop hazard conclusions about whether fluoride exposure is associated with neurodevelopmental and cognitive effects.
Results: The literature search and screening process identified 185 published human studies, 339 published experimental animal studies, and 60 in vitro/mechanistic studies.
Conclusion: Although draft conclusions were reached by integrating evidence from human and animal studies with consideration of relevant mechanistic data, the conclusions are based primarily on the human evidence. The body of human evidence provides a consistent pattern of findings, across several different populations, that high fluoride exposure is associated with lower intelligence quotient (IQ) in children. These consistent findings are based primarily on studies with higher levels of fluoride exposure (i.e., >1.5 ppm in drinking water). When focusing on findings from studies with exposures in ranges typically found in the United States (approximately 0.03 to 1.5 ppm in drinking water) that can be evaluated for dose response, effects on cognitive neurodevelopment are inconsistent, and therefore unclear. There is inadequate evidence to determine whether fluoride exposure lowers IQ or impairs cognitive function in adults. The evidence from animal studies is inadequate to inform conclusions on cognitive effects, and the mechanisms underlying fluoride-associated cognitive neurodevelopmental effects are not well characterized. The NTP will develop hazard conclusions for children and adults on a 4-level scale for hazard classification (“known”, “presumed”, “suspected”, “not classifiable”).
This abstract was presented in SYMPOSIUM 20 at the virtual 32nd Conference of ISEE.
Authors affiliation: Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA