Commentary on study Till C, Green R, Flora D, Hornung R, Martinez-Mier EA, Blazer M, et al. Fluoride exposure from infant formula and child IQ in a Canadian birth cohort. Environ Int 2020;134:105315.

Question Among otherwise normal preschool children, what is the association between fluoridated water used to constitute formula as infants/toddlers and IQ?

Design Multicenter, prospective study drawn from participants in the Maternal-Infant Research on Environmental Chemicals (MIREC) program.

Setting 6 cities across Canada.

Participants 398 mother-child dyads, the children of which were 3-4 years old.

Intervention Wechsler Primary and Preschool Scale of Intelligence-
III.

Outcomes IQ score.

Main Results 38% of the dyads lived in cities with fluoridated water. An increase of 0.5 mg/L in water fluoride concentration corresponded to a 9.3- and 6.2-point decrement in Performance IQ among both formula-fed (95% CI:
13.77 to 4.76) and breast-fed children (95% CI: 10.45 to 1.94), respectively.

Conclusions Ingestion of formula constituted from fluoridated water is associated with Performance IQ deficits.

Commentary This study by Till et al used data from the MIREC Study to demonstrate that fluoride intake from infant formula constituted from tap water is associated with lower performance IQ at age 3-4 years. Despite some limitations, eg, the use of estimated vs directly measured exposures to fluoride, the possibility of bias or confounding appears low. The results are consistent with increasing evidence suggesting that early life exposure to fluoride (prenatal and infancy) is associated with adverse neurobehavioral impacts. Evidence includes experimental studies in rodents as well as 3 recent longitudinal birth cohort studies (1 involving MIREC and 2 involving ourselves and colleagues) demonstrating significant associations between individual measures of prenatal fluoride exposure and lower performance on offspring measures of intelligence and behavior.^1-3 Overall, these studies inform the ongoing debate over the benefits vs risks associated with the fluoridation of water. Clearly, more research is needed. Meanwhile, since the beneficial effects of fluoride predominantly occur at the tooth surface after teeth have erupted, whereas fluoride is not essential for growth and development, a cautious step could be avoidance of fluoridated products and water by women during pregnancy and by infants during the first 6 months of life.

Morteza Bashash, PhD, MS
University of Toronto
Toronto, Ontario, Canada

and

Howard Hu, MD, MPH, ScD
University of Washington
Seattle, Washington

References

1. Green R, Lanphear B, Hornung R, Flora D, Martinez-Mier EA, Neufeld R, et al. Fluoride exposure during fetal development and intellectual abilities in a Canadian birth cohort. JAMA Pediatr 2019;173:940-8.

2. Bashash M, ThomasD, HuH, Martinez-MierEA, Sanchez BN, Basu N, et al. Prenatal fluoride exposure and cognitive outcomes in children at 4 and 6-12 years of age in Mexico. Environ Health Perspect 2017;125:097017.

3. Bashash M, Marchand M, Hu H, Till C, Martinez-Mier EA, Sanchez BN, et al. Prenatal fluoride exposure and attention deficit hyperactivity disorder (ADHD) symptoms in children at 6-12 years of age in Mexico City. Environ Int 2018;121(Pt 1):658-66.

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*Original Commentary online at https://www.jpeds.com/article/S0022-3476(20)30467-4/fulltext

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