© 2025 American Dental Association l 73
Fluoridation Facts
• Farmus et al. (2021): This Canadian study used repeated exposures from mother-child pairs
in the MIREC pregnancy and birth cohort to assess the association between fluoride and IQ
scores across prenatal and postnatal exposure windows. Researchers analyzed the data by using
generalized estimating equations for repeated exposure variables and adjusted for multiple
hypothesis testing. This study found that the associations between fluoride exposure and PIQ
differed based on the timing of exposure, and therefore concluded that the prenatal window
may be critical for boys. In contrast, infancy may be a critical window for girls.334 However,
samples were taken from six cities and each city had a different IQ assessor, and this study did
not account for a possible lack of measurement reliability among those assessors. When this
was considered by including the variable city and corrected for multiple comparisons, fluoride
exposures during pregnancy, infancy, or childhood were not associated with IQ outcomes.335
• Farmus et al. (2022): In an addendum to their previous study,334 this study found that exposures
during the trimesters of pregnancy, infancy, and childhood were not significantly associated with
IQ outcomes once the variable city was controlled and the false discovery rate was applied.335
Fluoride and Attention Deficit Hyperactivity Disorder
Some reports have linked fluoride to attention deficit hyperactivity disorder (ADHD), a neurodevelopmental
disorder. Fiore et al.28 conducted a systematic review of studies conducted before March 31, 2023,
to assess whether fluoride increased the risk of ADHD development in children and adolescents. The
authors concluded that the current evidence did not allow them to conclusively confirm that fluoride
exposure was specifically linked to ADHD development.
Ibarluzea and colleagues subsequently published the results of a prospective birth cohort study conducted
in Spain.336 They did not find any significant association between fluoride exposure during pregnancy
and ADHD symptoms. Interestingly, higher levels of maternal urinary fluoride adjusted for creatinine
in pregnant women were associated with a lower risk of inattention problems at 11 years of age.
Limitations to Fluoride Studies
Those opposed to water fluoridation have promoted studies that reportedly show fluoride causes a
lower IQ in children. The cited studies are primarily from China, Mexico, India, or Iran, where social,
nutritional, and environmental conditions are significantly different from those in the United States.29
The vast majority of these studies have not been published in peer-reviewed English language journals.
The consensus of those who have reviewed these studies is that their quality does not stand up to
scientific scrutiny.28,192 The studies are of low quality, have a high risk of bias, and use a study design
unsuited to prove or disprove theories. They generally do not adequately account for other factors
that are known to cause a lowering of IQ such as nutritional status, socioeconomic status, iodine
deficiency, and consumption of other harmful elements in ground water such as arsenic or lead.
Fluoridation Facts
• Farmus et al. (2021): This Canadian study used repeated exposures from mother-child pairs
in the MIREC pregnancy and birth cohort to assess the association between fluoride and IQ
scores across prenatal and postnatal exposure windows. Researchers analyzed the data by using
generalized estimating equations for repeated exposure variables and adjusted for multiple
hypothesis testing. This study found that the associations between fluoride exposure and PIQ
differed based on the timing of exposure, and therefore concluded that the prenatal window
may be critical for boys. In contrast, infancy may be a critical window for girls.334 However,
samples were taken from six cities and each city had a different IQ assessor, and this study did
not account for a possible lack of measurement reliability among those assessors. When this
was considered by including the variable city and corrected for multiple comparisons, fluoride
exposures during pregnancy, infancy, or childhood were not associated with IQ outcomes.335
• Farmus et al. (2022): In an addendum to their previous study,334 this study found that exposures
during the trimesters of pregnancy, infancy, and childhood were not significantly associated with
IQ outcomes once the variable city was controlled and the false discovery rate was applied.335
Fluoride and Attention Deficit Hyperactivity Disorder
Some reports have linked fluoride to attention deficit hyperactivity disorder (ADHD), a neurodevelopmental
disorder. Fiore et al.28 conducted a systematic review of studies conducted before March 31, 2023,
to assess whether fluoride increased the risk of ADHD development in children and adolescents. The
authors concluded that the current evidence did not allow them to conclusively confirm that fluoride
exposure was specifically linked to ADHD development.
Ibarluzea and colleagues subsequently published the results of a prospective birth cohort study conducted
in Spain.336 They did not find any significant association between fluoride exposure during pregnancy
and ADHD symptoms. Interestingly, higher levels of maternal urinary fluoride adjusted for creatinine
in pregnant women were associated with a lower risk of inattention problems at 11 years of age.
Limitations to Fluoride Studies
Those opposed to water fluoridation have promoted studies that reportedly show fluoride causes a
lower IQ in children. The cited studies are primarily from China, Mexico, India, or Iran, where social,
nutritional, and environmental conditions are significantly different from those in the United States.29
The vast majority of these studies have not been published in peer-reviewed English language journals.
The consensus of those who have reviewed these studies is that their quality does not stand up to
scientific scrutiny.28,192 The studies are of low quality, have a high risk of bias, and use a study design
unsuited to prove or disprove theories. They generally do not adequately account for other factors
that are known to cause a lowering of IQ such as nutritional status, socioeconomic status, iodine
deficiency, and consumption of other harmful elements in ground water such as arsenic or lead.
