Grant: Project Grant

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.