NTP monograph on the state of the science concerning fluoride exposure and neurodevelopment and cognition: a systematic review.
Level 1 - systematic review of randomized trials
Systematic review of observational epidemiological studies and experimental literature
PubMed 39172715 · doi:10.22427/NTP-MGRAPH-8
What was done
The National Toxicology Program (NTP) conducted a systematic review following the standardized OHAT framework to evaluate human, experimental animal, and mechanistic evidence regarding fluoride exposure and neurodevelopmental or cognitive outcomes. Exposure metrics assessed included drinking water concentrations and biomarkers such as urinary fluoride. Studies were evaluated separately for adults and children, with predefined assessments of study quality and confidence levels. Oral health benefits were not evaluated.
What was found
Animal and human mechanistic studies were too limited and heterogeneous to clarify biological plausibility. In adults, evidence was restricted to 2 high-quality cross-sectional studies (low confidence). In children, 8 of 9 high-quality studies assessing non-IQ cognitive or neurodevelopmental outcomes reported associations with fluoride exposure (low confidence due to outcome heterogeneity). For children's IQ, 72 studies were evaluated: 18 of 19 high-quality studies (3 prospective cohorts, 15 cross-sectional across 5 countries) and 46 of 53 low-quality studies reported an inverse association between estimated fluoride exposure and IQ. The review concluded with moderate confidence that higher estimated fluoride exposure (e.g., drinking water concentrations >1.5 mg/L) is consistently associated with lower IQ in children.
Why it matters
This comprehensive federal review establishes moderate-confidence evidence that elevated fluoride exposure (>1.5 mg/L) is linked to reduced IQ in children, providing a key benchmark for environmental and drinking water standards.
Limits
The human evidence is observational (mostly cross-sectional), precluding definitive causal conclusions. Data remain insufficient to evaluate risks at lower exposure levels (<1.5 mg/L), confidence is low for adult cognition and non-IQ pediatric outcomes, and the abstract does not report the total number of studies across all evidence streams.
Cited by
- partial The National Toxicology Program (NTP) reviewed 55 studies on fluoride and concluded that exposure poses neurodevelopmental risks with no safe level.