Nationwide Inequalities in Public Drinking Water Fluoride Exposure, 2006-2011 Open Access

Abstract

Background: Fluoride has been added to public drinking water systems in the US for decades to prevent and reduce dental disease, and recent epidemiologic evidence suggests fluoride exposure may be associated with adverse child neurodevelopment. Yet nationwide estimates of public water fluoride exposure are not currently available. Our objective was to estimate public water fluoride exposure across the US and identify potential exposure inequalities across geographic or sociodemographic groups in geospatial regression models.

Methods: We generated CWS-level and weighted county-level public water fluoride exposure estimates across the US using 256,237 routine compliance monitoring records for fluoride from 32,495 community water systems (CWSs). Data was collected from the Environmental Protection Agency’s (EPA) Third Six-Year Review of Contaminant Occurrence dataset, 2006-2011. We compared fluoride distributions and the percent of CWSs exceeding EPA’s maximum contaminant level (MCL) and the World Health Organization’s Guideline for drinking water quality (WHO GDWQ) across major subgroups served by CWSs including region, population size served, and community sociodemographic characteristics. We further evaluated geometric mean ratios (GMRs) of CWS fluoride in spatial lag regression models per 10% increase in the proportion of residents belonging to a given racial/ethnic subgroup.

Results: A total of 4.5% of CWSs had mean 2006-2011 fluoride concentrations that exceeded WHO’s GDWQ of 1,500 µg/L. Arithmetic mean, 75^th, and 95^th percentile contaminant concentrations were greatest in CWSs reliant on groundwater, CWSs in the Southwest, and CWSs serving Semi-Urban, Hispanic communities. In fully adjusted spatial lag models, the GMR (95% CI) of CWS fluoride per a (10%) increase in the proportion of county residents that were Hispanic/Latino was 1.16 (1.10, 1.23).

Conclusions: Fluoride is often present in CWSs at concentrations that exceed the EPA MCL and WHO GDWQ, indicating that fluoride may be an understudied contaminant in public water systems. Fluoride concentrations were significantly greater in Hispanic communities even after adjusting for other sociodemographic and geographic characteristics. Public drinking water exposure estimates for fluoride derived in this study may support future epidemiologic work to address environmental health disparities through assessing optimal concentrations of fluoride in public water systems.

Table of Contents

Introduction………………………………………………………………...…………..….1 

Materials and Methods…………………….………………….…………...…………....4 

Results………………..…………………….……………………...………………………..9 

Discussion………….…………………………………………………………...….……...11

Tables………………..……………………………………………………………...…..….16

Figures and Legends…………….…………..…………………………………………...20

References……………..…………………………………………………………………...21

About this Master's Thesis

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School	Rollins School of Public Health
Department	Environmental Health
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Environmental Health Health Sciences, Epidemiology Health Sciences, General
Keyword	community water system public drinking water epa exposure environmental justice spatial lag regression sociodemographic fluorosis inequalities fluoride exposure inequalities
Committee Chair / Thesis Advisor	Dr. Jeremy Sarnat, Emory University
Committee Members	Dr. Anne Nigra, Columbia University

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