A new review of research finds strong evidence that fluoride exposure, especially during fetal development and infancy, can lead to decreased IQ and other neurotoxic effects.
While fluoride may help prevent dental cavities when applied topically, ingesting elevated levels early in life appears to pose risks to long-term brain health.
Key facts:
- Multiple recent studies suggest fluoride can negatively impact children’s cognitive development and IQ at levels below the EPA’s current safe drinking water standards.
- Both human and animal research indicates the fetal and infant brain is particularly vulnerable to neurotoxicants like fluoride.
- Higher fluoride exposure correlates with lower IQ scores in prospective studies that measured maternal urine fluoride levels during pregnancy.
- Dose-response data indicates safe levels may need to be below 0.2 mg fluoride per liter in drinking water, dramatically lower than the current EPA standard of 4 mg/L.
- Topical fluoride products like fluoridated toothpaste provide dental benefits with less risk than systemic fluoride ingestion.
- More research is still needed, but evidence suggests pregnant women and young children should minimize fluoride ingestion from water, tea, and other sources.
Source: Environ Health
The Ongoing Debate Over Water Fluoridation
The practice of adding fluoride compounds to public drinking water to prevent tooth decay has been hailed by many public health experts as one of the top medical achievements of the 20th century.
However, water fluoridation has also become controversial due to concerns about potential adverse effects, including neurological toxicity.
To settle the debate, researchers have increasingly focused on high-quality epidemiological studies examining fluoride’s effects on brain development.
A 2012 meta-analysis of 27 studies from China found children in areas with high water fluoride levels averaged nearly 7 IQ points less than those exposed to lower levels.
This new review led by Grandjean of the University of Southern Denmark analyzes 14 major studies since 2012 along with other evidence to provide an updated assessment of fluoride’s developmental neurotoxicity.
Multiple New Studies Link Fluoride to Cognitive Deficits
The review found consistent evidence from around the world linking elevated fluoride exposure in early childhood to lower IQ and impaired cognitive function.
Of particular importance are three recent prospective cohort studies measuring individual fluoride exposures during pregnancy and relating it to children’s later test scores.
These high-quality studies in Mexico and Canada found that higher maternal urine fluoride levels correlated with significantly lower IQ in offspring.
The consistent dose-response relationship observed argues against the results being due to chance or confounding factors.
Other new cross-sectional studies in children provide additional evidence, with a large study of over 2500 children in China finding a 4.5 point lower IQ score associated with each 0.5 mg/L increase in both fluoride content in local water supplies and urine fluoride levels.
Studies using dental fluorosis as an indicator of early fluoride exposure found similar inverse relationships between fluorosis severity and children’s cognitive measures.
Overall, the review concluded that fluoride appears capable of causing neurotoxicity at levels below 1 mg/L in water, the level often used for artificial fluoridation of municipal supplies.
The Developing Brain is Particularly Vulnerable
The evidence for fluoride’s neurotoxicity accords with a large body of research showing the fetal and infant brain is far more susceptible to chemical exposures than the mature brain.
Animal studies also confirm the placental transfer of fluoride and its ability to cross the blood-brain barrier.
Autopsy studies have even found elevated fluoride levels in aborted fetuses in high-exposure areas.
Grandjean argues that just as very low levels of lead or mercury are understood to affect neurodevelopment, the new research suggests fluoride’s “safe” dose for neurological effects may need to be significantly lowered, especially for protecting early brain development.
His benchmark dose analysis estimated safe exposure levels may need to be below 0.2 mg/L in drinking water.
Topical Fluoride Safer Than Ingestion for Dental Health
Importantly, Grandjean emphasizes that while fluoride ingestion appears to pose neurotoxicity risks, topical application directly onto teeth continues to provide dental health benefits with less systemic exposure or risks.
This accords with modern understanding that fluoride’s primary benefit comes from direct surface contact with enamel rather than ingestion.
Given this, he argues community water fluoridation programs are difficult to justify given their wide-ranging increase in total fluoride intake for all residents.
Targeted use of fluoridated toothpastes and mouthwashes may achieve the same dental benefits with lower risks, though parents should still take care to minimize swallowing by younger children.
Minimizing Fluoride Exposure in Pregnancy and Childhood
The overall body of evidence, while not definitive, suggests pregnant women and young children should take reasonable steps to minimize fluoride ingestion until more conclusive research is available.
Elevated fluoride consumption should be avoided, especially from drinking water containing ≥0.7 mg/L as well as excessive tea intake.
Formula made with fluoridated water also appears to be a substantial risk factor when reconstituted at fluoride levels above 0.2 mg/L.
While the EPA is unlikely to dramatically revise drinking water standards anytime soon, this new review indicates pregnant women and parents of infants should consider avoiding artificially fluoridated municipal water if feasible, especially when formula-feeding.
Further research on windows of heightened vulnerability is still needed, but minimizing exposure during pregnancy and early childhood appears prudent given the possible lifelong consequences.
References
- Study: Developmental fluoride neurotoxicity: an updated review
- Author: Philippe Grandjean (2019)
