72 l © 2025 American Dental Association
Section 2: Safety
• Veneri et al. (2023): This systematic review and dose-response meta-analysis observed that
although the negative association between fluoride exposure and IQ was particularly strong in the
studies at high risk of bias, no association was found in the only study judged at low risk of bias.327
• Gopu et al. (2022): This systematic review investigated the association between fluoride
exposure and cognitive outcomes from gestation to adulthood. Evidence from this review indicated
that fluoride exposure at levels exceeding 2 mg/L in drinking water may be associated with impaired
cognitive outcomes in children. However, the reliance on numerous low-quality studies and the
absence of accurate estimates of fluoride exposure from all sources limited the ability to draw
definitive conclusions.328
• Miranda et al. (2021): This systematic review and meta-analysis assessed the association
between fluoride exposure and neurological disorders. According to the authors, “The
methodological quality analyses of the studies detected serious problems related to the quality
of sample, measurements, and outcomes. There were also problems related to the absence of
randomization, sample size calculation, and blinding, which increase the risk of bias and limit the
inference capacity of studies on the neurotoxic effects of fluoride.”329
• Guth et al. (2020): This was a critical evaluation of evidence on the toxicity of fluoride. Based on
the available evidence, the review did not support the presumption that fluoride should be assessed
as a human developmental neurotoxicant at the current exposure levels in Europe.187
• Canadian Agency for Drugs and Technologies in Health (2019): This systematic review
reported that there was not conclusive evidence for an association between water fluoridation at
recommended Canadian levels (optimum at 0.7 mg/L) and IQ, cognitive function, or neurological
development in children and adolescents.330
Additional Studies
The following studies provide further evidence that the consumption of fluoridated water at levels
recommended in the United States (0.7 mg/L) does not lower IQ or cause behavior problems in children:
• Aggeborn and Ohman (2021): This ecological study used Swedish registry data of 80,000
individuals to study the causal effects of fluoride in drinking water. Results of this study found
“zero effect” of fluoride on cognitive ability.331
• Lin et al. (2023): This cross-sectional study from Taiwan found that dental fluorosis and urinary
fluoride levels were not significantly associated with the IQ of schoolchildren living in low-fluoride
areas.332
• Till et al. (2020): This Canadian study examined mother-child dyads in the MIREC cohort who
reported drinking tap water. Researchers found that infant fluoride intake was not consistently
associated with IQ deficits in multiple analyses of fluoride and FSIQ scores. Prenatal exposure was
not associated with FSIQ in boys or girls. However, exposure to higher fluoride levels in tap water
was associated with diminished performance IQ (PIQ), that is, nonverbal intellectual abilities. That
association was more pronounced among formula-fed children such that a 0.5 mg/L increase
in water fluoride level was associated with a decrement in PIQ of 9.3 points in the formula-fed
and 6.2 points in the breastfed group. In these analyses, the authors did not account for the
correlation between exposures during pregnancy and infancy and did not adjust the statistical
significance level for multiple comparison hypothesis testing. Such analytic flaws often result in
false positive findings.333
Section 2: Safety
• Veneri et al. (2023): This systematic review and dose-response meta-analysis observed that
although the negative association between fluoride exposure and IQ was particularly strong in the
studies at high risk of bias, no association was found in the only study judged at low risk of bias.327
• Gopu et al. (2022): This systematic review investigated the association between fluoride
exposure and cognitive outcomes from gestation to adulthood. Evidence from this review indicated
that fluoride exposure at levels exceeding 2 mg/L in drinking water may be associated with impaired
cognitive outcomes in children. However, the reliance on numerous low-quality studies and the
absence of accurate estimates of fluoride exposure from all sources limited the ability to draw
definitive conclusions.328
• Miranda et al. (2021): This systematic review and meta-analysis assessed the association
between fluoride exposure and neurological disorders. According to the authors, “The
methodological quality analyses of the studies detected serious problems related to the quality
of sample, measurements, and outcomes. There were also problems related to the absence of
randomization, sample size calculation, and blinding, which increase the risk of bias and limit the
inference capacity of studies on the neurotoxic effects of fluoride.”329
• Guth et al. (2020): This was a critical evaluation of evidence on the toxicity of fluoride. Based on
the available evidence, the review did not support the presumption that fluoride should be assessed
as a human developmental neurotoxicant at the current exposure levels in Europe.187
• Canadian Agency for Drugs and Technologies in Health (2019): This systematic review
reported that there was not conclusive evidence for an association between water fluoridation at
recommended Canadian levels (optimum at 0.7 mg/L) and IQ, cognitive function, or neurological
development in children and adolescents.330
Additional Studies
The following studies provide further evidence that the consumption of fluoridated water at levels
recommended in the United States (0.7 mg/L) does not lower IQ or cause behavior problems in children:
• Aggeborn and Ohman (2021): This ecological study used Swedish registry data of 80,000
individuals to study the causal effects of fluoride in drinking water. Results of this study found
“zero effect” of fluoride on cognitive ability.331
• Lin et al. (2023): This cross-sectional study from Taiwan found that dental fluorosis and urinary
fluoride levels were not significantly associated with the IQ of schoolchildren living in low-fluoride
areas.332
• Till et al. (2020): This Canadian study examined mother-child dyads in the MIREC cohort who
reported drinking tap water. Researchers found that infant fluoride intake was not consistently
associated with IQ deficits in multiple analyses of fluoride and FSIQ scores. Prenatal exposure was
not associated with FSIQ in boys or girls. However, exposure to higher fluoride levels in tap water
was associated with diminished performance IQ (PIQ), that is, nonverbal intellectual abilities. That
association was more pronounced among formula-fed children such that a 0.5 mg/L increase
in water fluoride level was associated with a decrement in PIQ of 9.3 points in the formula-fed
and 6.2 points in the breastfed group. In these analyses, the authors did not account for the
correlation between exposures during pregnancy and infancy and did not adjust the statistical
significance level for multiple comparison hypothesis testing. Such analytic flaws often result in
false positive findings.333
