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Current Grants & Projects.

Fluoride in Tooth Dentin and Neurodevelopmental Outcome in a Canadian Cohort

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 800 children; Aim 2. To test whether dentin fluoride concentrations in baby teeth is associated with lower IQ scores (n=610) and attention problems (n=898); Aim 3. To test whether the urinary and dentin fluoride concentrations impact thyroid hormones, and ultimately IQ scores and attention problems. 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 growth alters children’s IQ scores and behavioral problems. In addition, we will test the endocrine disrupting potential of fluoride during pregnancy. 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. The large sample size will let us find out if to child sex, timing of exposure, or exposure to powdered infant formula impact fluoride’s toxicity. Major contributions include: 1) quantification of exposure to fluoride during fetal development and early childhood using 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 resources, we will be able to accomplish this study efficiently and cost-effectively.


Impact of early life fluoride exposure on neurodevelopmental outcomes among children in the New Hampshire Birth Cohort

The benefits and risks of fluoride exposure have been debated for decades. The Centers for Disease Control hails water fluoridation as one of the greatest public health achievements while others argue that fluoride exposure causes adverse health effects. While it is undisputed that fluoride is toxic at high levels (e.g. >5 mg/L), studies examining neurodevelopmental outcomes in populations exposed to optimal levels of fluoride are disputed. Existing human studies are limited in their ability to examine dose-response relations due to the restricted range of fluoride typically found in areas with fluoridation. Only a few studies have measured biomarkers of fluoride exposure across critical periods of development. Moreover, given the widespread sources of fluoride, few studies have directly linked sources of exposure when studying fluoride neurotoxicity. This study capitalizes on the New Hampshire Birth Cohort Study (NHBCS), a large, prospective cohort designed to examine how contaminants in drinking water and food affect the health of pregnant women and their children. We will leverage existing data from this cohort to assess the association between early-life exposure to fluoride (pregnancy and infancy) and children's IQ and behavioral problems in 578 mother-child pairs. Novel to our work is the measurement of fluoride in biospecimens (urine samples and toenails) as well as in tap water samples that are known to vary in fluoride concentration from approximately 0.1 to 2.0 mg/L. We will use detailed dietary intake information to understand sources of fluoride exposure in pregnant women and their infants. Finally, we will determine whether there is an increased risk of lower IQ scores or behavioral difficulties in children resulting from the use of fluoridated water to reconstitute infant formula. Results of this study will directly impact decision making on the safety of fluoride exposure during early brain development at levels relevant to the U.S. and Canada.

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