Does fluoride in drinking water cause neurotoxicity?

From the Guidelines

No, fluoride in water at the levels used for community water fluoridation does not cause brain damage, according to the most recent and highest quality study available 1. The concentration of fluoride added to public water supplies is carefully regulated and has been extensively studied for safety. While extremely high fluoride exposure (much higher than levels in fluoridated water) may potentially affect neurological development, the scientific consensus from decades of research indicates that fluoridated water at recommended levels poses no risk of brain damage. Some studies have suggested a potential link between high levels of fluoride exposure and reduced intelligence in children 1, but these findings are based on high levels of fluoride exposure, not the levels typically used in community water fluoridation. The practice of water fluoridation has been implemented for over 75 years to prevent tooth decay, with substantial evidence showing its effectiveness in reducing cavities by about 25% in both children and adults. The benefits of fluoridated water for dental health far outweigh any theoretical risks, and major health organizations worldwide continue to support this public health measure as safe and effective. Key points to consider include:

• The optimal concentration of fluoride in community drinking water to maximize caries prevention and limit enamel fluorosis is between 0.7 ppm and 1.2 ppm 1.
• The US Environmental Protection Agency sets a maximum allowable limit for fluoride in community drinking water at 4 ppm and a secondary limit at 2 ppm 1.
• Fluoride can be safely provided in enteral nutrition at doses of up to about 3 mg/day, and in parenteral nutrition at a dose of 0.95 mg without any side effects 1. However, it is essential to note that the need for adding fluoride to parenteral nutrition is debated, especially in the USA 1. In real-life clinical practice, the benefits of fluoridated water for dental health outweigh any theoretical risks, and it is recommended to continue using fluoridated water at recommended levels.

From the Research

Fluoride in Water and Brain Damage

• The relationship between fluoride in water and brain damage is a topic of ongoing research and debate 2, 3, 4, 5, 6.
• Some studies suggest that high levels of fluoride exposure may be associated with reduced IQ scores in children 2, 3, 5.
• A systematic review of epidemiological and toxicological evidence found that the weight of evidence for a reduction in IQ scores in children was strong, but with some uncertainty in the causal weight of evidence 2.
• Another systematic review and meta-analysis found that high levels of fluoride exposure were associated with IQ impairment, but the evidence was classified as very low-level 3.
• Experimental studies have shown that fluoride can accumulate in the body and cause damaging effects on the nervous system, particularly in children 4.
• A review of the principles of fluoride toxicity found that high concentrations of fluoride can result in oxidative stress, organelle damage, and apoptosis in single cells, and skeletal and soft tissue damage in multicellular organisms 6.

Key Findings

• The National Toxicology Program (NTP) conducted a systematic review of the evidence linking fluoride exposure to neurodevelopmental and cognitive effects in humans, and found that higher estimated fluoride exposures were consistently associated with lower IQ in children 5.
• The NTP review also found that the body of evidence from studies in adults was limited and provided low confidence that fluoride exposure was associated with adverse effects on adult cognition 5.
• A review of the current state of evidence associating fluoride exposure with cognitive or neurodevelopmental health effects found that the benefits of fluoride with respect to oral health were not addressed, and that the bodies of experimental animal studies and human mechanistic evidence did not provide clarity on the association between fluoride exposure and cognitive or neurodevelopmental human health effects 5.

Evidence Limitations

• The evidence on the association between fluoride exposure and brain damage is limited by the heterogeneity of the studies and the lack of high-quality data 3, 5.
• More studies are needed to fully understand the potential for lower fluoride exposure to affect children's IQ and to clarify the relationship between fluoride exposure and neurodevelopmental and cognitive effects in humans 5.