Socioeconomic vulnerability and public water arsenic concentrations across the US

Abstract

Background/Aim: Inorganic arsenic is known human carcinogen and is routinely detected in community water systems (CWSs) across the US. Significant inequalities in CWS arsenic concentrations exist across broad sociodemographic subgroups of the US population. We evaluated the county-level association between socioeconomic vulnerability and CWS arsenic concentrations across the conterminous US. Methods: We evaluated previously developed, population-weighted, county-level CWS arsenic concentrations (2006-2011), the Centers for Disease Control and Prevention’s county-level socioeconomic vulnerability score (range: 0-1), median household income, and the proportion of adults with a high school diploma for 2,604 conterminous US counties. We used spatial lag models and evaluated the adjusted geometric mean ratio (GMR) of county-level CWS arsenic concentrations per interquartile range increase in socioeconomic vulnerability domain and in flexible spline models. We also stratified by region and by United States Department of Agriculture Rural-Urban Continuum Codes to assess potential effect measure modification by region and rurality. Results: Associations between socioeconomic vulnerability and CWS arsenic were modified by region, rurality, and socioeconomic domain. The fully adjusted GMR (95% CIs) of CWS arsenic per interquartile range increase in the proportion of adults with a high school education was 0.83 (0.71, 0.98) or 17% in the Southwest, 0.82 (0.71, 0.94) or 18% in the Eastern Midwest, and 0.65 (0.31, 1.36) or 35% in New England. Higher overall socioeconomic vulnerability was significantly associated with lower CWS arsenic, but only in counties in the Central Midwest and those with total populations less than 20,000. Conclusions: Higher educational attainment was associated with lower CWS arsenic in the Southwest, Eastern Midwest, and New England regions. Findings likely reflect regional/local differences in both socioeconomic/socio-cultural context and regulated drinking water contaminant concentrations. Region-specific analyses at finer geographic resolutions evaluating components of overall socioeconomic vulnerability are needed to adequately characterize the association. arsenic; drinking water; environmental justice