Research will help determine the safety of chronic fluoride exposure in developing brains

Water running from a kitchen tap

Emerging research from York University aims to address rising concerns about the safety of early-life exposure to fluoride, and whether chronic exposure to fluoride at current population levels could contribute to lower IQ and behavioural problems in children.

By Krista Davidson

Christine Till
Christine Till

Associate Professor at the Faculty of Health, Christine Till, and her team, are collaborating with Professor Bruce Lanphear at Simon Fraser University’s Faculty of Health Sciences and the Manish Arora at Mount Sinai School of Medicine in New York, to measure fluoride exposure levels using baby teeth collected in a Canadian birth cohort. Tooth dentin – the tissue that lies beneath enamel – forms between 16 weeks’ gestation up to 2.5 years of age. As teeth mineralize, they accumulate chemicals that have been ingested, including fluoride from drinking water. Using modern techniques, the team will extract a historical record of exposure by measuring fluoride in layers of hydroxyapatite, similar to how tree rings accumulate to indicate the passage of time.

“Sampling tooth layers that correspond to specific life stages will provide critical information for when exposure occurred and how much reached the developing brain,” explains Till.

“Most toxic chemicals, like lead and pesticides, are promoted by industry. Fluoride is promoted by health agencies, so it is imperative to verify if fluoride is toxic to the developing brain,” says Lanphear.

The research, which received close to $2 million in funding from the National Institutes of Health, builds on the findings of an earlier study published by Till’s team, including York graduate student, Rivka Green, in JAMA Pediatrics in 2019. This study examined 512 mother-child pairs from six cities in Canada using data from the Maternal Infant Research on Environment Chemicals (MIREC). The researchers found that higher fluoride exposure in pregnancy was associated with lower IQ in children. The study was the first of its kind to be conducted in children and women living in communities where fluoride is intentionally added to drinking water or not.

“Our earlier research measured urinary fluoride levels in pregnant women, which does not tell us how much fluoride reached the fetus and when,” says Till. “The tooth dentin is an optimal biomarker because it will provide evidence that fluoride crosses the placenta. This will give a better understanding of the critical window of when exposure becomes harmful to the developing brain.”

In addition to assessing the neurotoxicity of early-life exposure to fluoride using teeth, the team is assessing the thyroid-disrupting effects of fluoride in pregnancy. This work will shed light on potential mechanisms of fluoride neurotoxicity.

Till and her team, together with researchers in Toronto and Mexico, have contributed some of the key studies related to fluoride neurotoxicity in the prenatal and early postnatal period. Still, more research is needed to fully understand the impact of low-level exposure to fluoride on cognitive development.

“The question is whether fluoride ingestion is safe for everyone, including fetuses and young infants, and this research aims to develop a solid understanding to support evidence-based decision-making around the safety of fluoride,” says Till.