Fluoride in Tooth Dentin and Neurodevelopmental Outcome in a Canadian Cohort

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Project Summary / Abstract Water fluoridation is controversial. Over the past decade, concern about the potential toxicity of fluoride has grown, but there are still questions. Most human studies of fluoride toxicity only studied children who were exposed to high levels of fluoride and only a few studies measured fluoride exposure during critical periods of development. Urine, which is commonly used to quantify a person’s exposure to fluoride, reflects recent exposure and requires serial sampling to measure fluoride during different periods of development. Our proposed study will analyze tooth dentin – the tissue that lies beneath enamel – to measure the level and timing of fluoride exposure. Tooth dentin is an optimal biomarker because it provides a historical record of both serial and cumulative exposure to ingested fluoride. We will test the following specific aims: Aim 1. To quantify prenatal, early childhood, and cumulative fluoride exposure levels using shed baby teeth collected from 360 children; Aim 2. To examine the association between prenatal and postnatal fluoride levels in baby teeth (dentin) and neurodevelop- mental outcomes in infants and children (n=300 with tooth and behavioral data). This study is innovative because it will employ state-of the-art analytical methods to measure the level and precise timing of exposures to fluoride and toxic metals in tooth dentin. The study capitalizes on an existing Canadian pregnancy and birth cohort, the Maternal-Infant Research on Environmental Chemicals. We will leverage existing data from our ongoing NIH-funded study to find out if fluoride exposure during early brain development alters children’s IQ scores and behavioral problems. Our measurement of fluoride exposure in tooth dentin and serial urine samples offers an unprecedented opportunity to test for neurotoxic effects of early-life exposure to fluoride. Major contributions include: 1) quantification of exposure to fluoride during fetal development and early childhood using tooth dentin; and 2) results that will directly impact decision making concerning the safety of fluoride exposure during fetal development and early childhood at levels relevant to the U.S. and Canada. Given our archived specimens collected during pregnancy, we will be able to accomplish this study efficiently and cost-effectively.