Fluoride exposure from infant formula and child IQ in a Canadian birth cohort

Christine Till, Rivka Green, David Flora, Richard Hornung, E. Angeles Martinez-Mier, Maddy Blazer, Linda Farmus, Pierre Ayotte, Gina Muckle, Bruce Lanphear

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4 Scopus citations


Background: Infant consumption of formula reconstituted with fluoridated water can lead to excessive fluoride intake. We examined the association between fluoride exposure in infancy and intellectual ability in children who lived in fluoridated or non-fluoridated cities in Canada. Methods: We examined 398 mother-child dyads in the Maternal-Infant Research on Environmental Chemicals cohort who reported drinking tap water. We estimated water fluoride concentration using municipal water reports. We used linear regression to analyze the association between fluoride exposure and IQ scores, measured by the Wechsler Primary and Preschool Scale of Intelligence-III at 3–4 years. We examined whether feeding status (breast-fed versus formula-fed) modified the impact of water fluoride and if fluoride exposure during fetal development attenuated this effect. A second model estimated the association between fluoride intake from formula and child IQ. Results: Thirty-eight percent of mother-child dyads lived in fluoridated communities. An increase of 0.5 mg/L in water fluoride concentration (approximately equaling the difference between fluoridated and non-fluoridated regions) corresponded to a 9.3- and 6.2-point decrement in Performance IQ among formula-fed (95% CI: −13.77, −4.76) and breast-fed children (95% CI: −10.45, −1.94). The association between water fluoride concentration and Performance IQ remained significant after controlling for fetal fluoride exposure among formula-fed (B = −7.93, 95% CI: −12.84, −3.01) and breastfed children (B = −6.30, 95% CI: −10.92, −1.68). A 0.5 mg increase in fluoride intake from infant formula corresponded to an 8.8-point decrement in Performance IQ (95% CI: −14.18, −3.34) and this association remained significant after controlling for fetal fluoride exposure (B = −7.62, 95% CI: −13.64, −1.60). Conclusions: Exposure to increasing levels of fluoride in tap water was associated with diminished non-verbal intellectual abilities; the effect was more pronounced among formula-fed children.

Original languageEnglish (US)
Article number105315
JournalEnvironment International
StatePublished - Jan 2020


  • Fluoride
  • Formula
  • Infants
  • Intellectual function
  • Water fluoridation

ASJC Scopus subject areas

  • Environmental Science(all)

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    Till, C., Green, R., Flora, D., Hornung, R., Martinez-Mier, E. A., Blazer, M., Farmus, L., Ayotte, P., Muckle, G., & Lanphear, B. (2020). Fluoride exposure from infant formula and child IQ in a Canadian birth cohort. Environment International, 134, [105315]. https://doi.org/10.1016/j.envint.2019.105315