This is another post responding to misinformation promulgated by HHS Secretary Robert Kennedy Jr. Misinformation seems to proliferate faster that true science-based information. Perhaps one way to combat this is for readers of these blog posts to share them as widely as possible to people they know.
Secretary Kennedy is opposed to adding fluoride to public water supplies. He maintains that adding fluoride to public water supplies causes lower IQ’s in children. Two states, Utah and now Florida have already banned fluoridation of public water supplies, mostly in response to his claims about the evils of water fluoridation. I will examine the evidence for these claims in this post
Positive effects of water fluoridation
The US Public Health Service recommends public water fluoridation at a level of 0.7 mg per liter. This level of fluoride in water reduces tooth decay in children by 25% even in children who do not brush or floss regularly. This therefore most benefits poor and marginalized populations for whom dental hygiene can be difficult. Public water fluoridation at this level is one of the most effective public health interventions. Tooth decay can lead to chronic inflammation, which can lead to many other diseases including heart disease.
Sources of natural fluoride
Fluoride occurs naturally in almost all water supplies through the erosion of rocks and soil containing fluoride. The levels of natural fluoride are usually too low to prevent tooth decay, but some water supplies have much higher levels of natural fluoride up to as much as 50 mg per liter in some mountainous and volcanic regions.
Adverse effects of high natural fluoride
Fluorosis
Fluorosis has two components. At fluoride levels greater than 1.5 mg/L children who have growing teeth can develop brown discoloration of teeth. This is called dental fluorosis and is mostly a cosmetic problem. Long term exposure to fluoride levels greater than 10 mg/L can lead to skeletal fluorosis, which is a much more serious condition. In skeletal fluorosis the bones are generally weaker than normal with stiffness and pain in the joints as the early symptoms. In severe cases, muscles are impaired and bones in the central skeleton are irregularly thickened.
Lower IQ in children
In January of 2025 JAMA (Journal of the American Medical Association) published an analysis of combined data from many international studies that showed lower IQ scores in children exposed to higher levels of fluoride from all sources: Fluoride Exposure and Children’s IQ Scores. The study found that the higher the exposure to fluoride, the lower were the children’s IQ scores. This finding was statistically significant for levels above 1.5 mg/L but not at or below this level. None of these studies were done in the United States. The US Public Health recommendation of 0.7 mg/L is well below the threshold for association of lower IQ in children.
Other sources of fluoride
The most significant other sources of fluoride are supplements, toothpaste and oral rinses. For children who have fluoride at 0.7 mg\l in drinking water, fluoride containing supplements should not be given. Most toothpastes contain fluoride, so children with fluoride in the water supply should use only a pea sized amount of toothpaste per brushing and should be encouraged to spit out the toothpaste after brushing. If the water supply has not been fluoridated and contains only trace amounts of natural fluoride, then supplements should be given to children.
Bottom Line
Fluoridation of public water systems at the recommended concentration of 0.7 mg/L is safe and effective at markedly reducing tooth decay in children. There is no evidence that fluoride in water at this level has any adverse effects. There is some evidence that concentrations of higher than 1.5 mg/L are associated with modest decreased IQ in children. Elimination of fluoride from public water systems will increase tooth decay in the most vulnerable populations and will not have any benefit. Children who live in communities with fluoridated water should not take fluoride supplements, should use only small amounts of fluoridated toothpaste, and should be encouraged to spit out toothpaste after brushing and not swallow it. Communities who have high natural levels of fluoride in drinking water can reduce fluoride to safe levels by reverse osmosis or charcoal filter systems.