70 l © 2025 American Dental Association
Section 2: Safety
41. Does ingestion of water fluoridated at recommended levels have
an adverse effect on neurodevelopment or intelligence (IQ) or
behavioral disorders in children?
Answer
No. The best available scientific evidence does not establish a causal relationship between
consumption of water fluoridated at recommended levels and lowered intelligence (IQ) or
behavioral disorders in children.
Fact
Several systematic reviews, meta-analyses, and individual studies provide evidence that the consumption
of optimally fluoridated water at levels recommended in the United States (0.7 mg/L) does not lower IQ
or cause behavior problems in children.
Several systematic reviews, meta-analyses, and individual studies provide evidence
that the consumption of optimally fluoridated water at levels recommended in the
United States (0.7 mg/L) does not lower IQ or cause behavior problems in children.
NTP Monograph
The NTP monograph systematically reviewed human, animal, and mechanistic studies to evaluate
potential associations between fluoride exposure and neurodevelopmental effects such as IQ
deficits.301 A National Academies of Science, Engineering, and Medicine (NASEM) committee
reviewed two earlier drafts of an NTP monograph and concluded that the evidence did not support
their conclusion about neurodevelopmental effects.192 Therefore, the NTP monograph removed
the neurodevelopmental hazard statement.301 The monograph found an association between high
fluoride concentrations and lower IQ in children however, these findings were based on exposures
exceeding WHO guidelines (1.5 mg/L) and are not relevant to US fluoridation practices. “The
monograph and addendum do not address whether the sole exposure to fluoride added to
drinking water in some countries (i.e., fluoridation, at 0.7 mg/L in the United States and
Canada) is associated with a measurable effect on IQ.” The NTP report found no evidence that
fluoride exposure negatively impacts adult cognition. The review also highlighted limited mechanistic
insight because animal studies were of poor quality and human studies lacked clarity on biological
pathways. Significant methodological limitations, such as biases and the use of cross-sectional study
designs, further weakened causal conclusions. The monograph did not assess the benefits of the use
of fluorides in oral health or provide a risk/benefit analysis.301
Systematic Reviews and Meta-Analyses
Most studies of fluoride-IQ association were conducted in high-fluoride areas of China, Iran,
and India, which exceeded the WHO guideline value of 1.5 mg/L.321 Many of these studies found
associations between high fluoride exposure and IQ deficits, but these are mostly cross-sectional
studies in impoverished communities where access to clean water is a significant problem. Cross-
sectional studies cannot be used to establish cause and effect relationships and can help in generating
hypotheses. According to Kumar et al.,29 the authors need to analyze and present much more data
to judge that the socioeconomic status and education of parents in the high-fluoride areas are
Section 2: Safety
41. Does ingestion of water fluoridated at recommended levels have
an adverse effect on neurodevelopment or intelligence (IQ) or
behavioral disorders in children?
Answer
No. The best available scientific evidence does not establish a causal relationship between
consumption of water fluoridated at recommended levels and lowered intelligence (IQ) or
behavioral disorders in children.
Fact
Several systematic reviews, meta-analyses, and individual studies provide evidence that the consumption
of optimally fluoridated water at levels recommended in the United States (0.7 mg/L) does not lower IQ
or cause behavior problems in children.
Several systematic reviews, meta-analyses, and individual studies provide evidence
that the consumption of optimally fluoridated water at levels recommended in the
United States (0.7 mg/L) does not lower IQ or cause behavior problems in children.
NTP Monograph
The NTP monograph systematically reviewed human, animal, and mechanistic studies to evaluate
potential associations between fluoride exposure and neurodevelopmental effects such as IQ
deficits.301 A National Academies of Science, Engineering, and Medicine (NASEM) committee
reviewed two earlier drafts of an NTP monograph and concluded that the evidence did not support
their conclusion about neurodevelopmental effects.192 Therefore, the NTP monograph removed
the neurodevelopmental hazard statement.301 The monograph found an association between high
fluoride concentrations and lower IQ in children however, these findings were based on exposures
exceeding WHO guidelines (1.5 mg/L) and are not relevant to US fluoridation practices. “The
monograph and addendum do not address whether the sole exposure to fluoride added to
drinking water in some countries (i.e., fluoridation, at 0.7 mg/L in the United States and
Canada) is associated with a measurable effect on IQ.” The NTP report found no evidence that
fluoride exposure negatively impacts adult cognition. The review also highlighted limited mechanistic
insight because animal studies were of poor quality and human studies lacked clarity on biological
pathways. Significant methodological limitations, such as biases and the use of cross-sectional study
designs, further weakened causal conclusions. The monograph did not assess the benefits of the use
of fluorides in oral health or provide a risk/benefit analysis.301
Systematic Reviews and Meta-Analyses
Most studies of fluoride-IQ association were conducted in high-fluoride areas of China, Iran,
and India, which exceeded the WHO guideline value of 1.5 mg/L.321 Many of these studies found
associations between high fluoride exposure and IQ deficits, but these are mostly cross-sectional
studies in impoverished communities where access to clean water is a significant problem. Cross-
sectional studies cannot be used to establish cause and effect relationships and can help in generating
hypotheses. According to Kumar et al.,29 the authors need to analyze and present much more data
to judge that the socioeconomic status and education of parents in the high-fluoride areas are
