Evaluating the effect of water fluoridation on adverse birth outcomes

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Project Summary/Abstract The objective of this K99/R00 proposal is to estimate the effect of community water fluoridation on adverse birth outcomes in California and identify whether there are subpopulations who are especially vulnerable to fluoride exposure during pregnancy. Fluoride has been added to water supplies to promote dental health in the United States since 1945, but the impacts on pregnancy outcomes have never been assessed. It is possible that maternal and in-utero fetal exposure to fluoride increases risk of preterm birth and small-for- gestational age. A small number of studies in other countries suggest there is an increased risk of adverse birth outcomes associated with drinking water with naturally high levels of fluoride, and evidence suggests fluoride consumption can affect thyroid function and cardiovascular systems, both of which play important roles in regulating and maintaining a healthy pregnancy. Since 1995, California has required water systems with at least 10,000 service connections to fluoridate their water, but systems were only required to implement a fluoridation program once the funds were allocated. Therefore, there is a substantial amount of variability in which water systems have added fluoride over the last 25 years, and when they did so. We will leverage this variation in water fluoridation practices in California to (1) identify the effects of changes in water fluoridation on adverse birth outcomes during 2006-2017 and (2) evaluate whether there are heterogeneous exposure effects by maternal/fetal characteristics and environmental co-exposures. Furthermore, we will use the ECHO.CA.IL pregnancy cohort, which is composed of pregnant women and their children in San Francisco and Illinois, to (3a) assess whether maternal urinary fluoride during the second trimester is associated with reduced gestational age or lower birthweight-for-gestational-age-z-scores at birth and (3b) evaluate whether there are heterogeneous effects of exposure by maternal/fetal characteristics and environmental co-exposures. The research plan is bolstered by an exceptional mentorship team and training plan at the University of San Francisco, California. The proposed project builds on the applicant’s background in perinatal epidemiology and provides training in new statistical methods to identify heterogeneous exposure effects and education in the biological processes of gestation and parturition, exposure assessment of environmental chemicals, and translating scientific findings to policymakers. The combined research and training plans will enable the candidate to transition into an independent researcher of policy-relevant social and environmental factors that shape perinatal health. This research aligns with NIEHS’s strategic goals to evaluate health effects of the exposome, identify individual susceptibilities to environmental hazards, utilize data science techniques, and generate evidence that can be utilized by policymakers to improve population health.