Nationwide geospatial analysis of county-level racial/ethnic composition and public drinking water arsenic and uranium

Background:There is no safe level of exposure to inorganic arsenic or uranium. Both metals are frequently detected in community water systems (CWSs), which serve 90% of the US population. Sociodemographic and regional inequalities in CWS arsenic and uranium have been identified at the CWS level, but nationwide studies of disparities by racial/ethnic composition are critically needed. We conducted the first nationwide geospatial assessment of the county-level association between racial/ethnic composition and CWS arsenic and uranium concentrations(2000-2011) for 2,631 conterminous counties. Methods:First, we assessed spatial autocorrelation via Moran’s I and identified Local Indicators of Spatial Association(LISA) clusters. Then, we estimated the geometric mean ratio(GMR) of county-level CWS metal concentrations per 10% higher proportion of each racial/ethnic group via spatial lag regression, adjusting for population density, percentage of public water sourced from groundwater, household income, and education. We evaluated spatial non-stationarity in the strength and direction of the association via geographically weighted regression. Results:In fully adjusted nationwide models, for a 10% higher county proportion of Hispanic/Latino and American Indian/Alaskan Native residents, the geometric mean (95% CI) of CWSs metal concentration was higher by 6% (4, 8) and 7% (3, 11) respectively for arsenic, and by 17% (13, 22) and 2% (-4, 8), respectively, for uranium. Nationwide associations were inverse for non-Hispanic White and non-Hispanic Black residents, although geographically weighted regression identified a positive relationship between a higher proportion of non-Hispanic Black residents and CWS metals in the Midwestern and Southwestern US. Conclusion:Racial/ethnic composition is associated with public drinking water metal concentrations, adding to a growing body of literature characterizing nationwide environmental and racial injustices in US public drinking water contaminants. Findings from this study can advance environmental justice initiatives by informing infrastructure investment and regulatory action to protect communities disproportionately exposed to major environmental contaminants. Keywords:arsenic, uranium, drinking water, racism, environmental justice.