Disparities in drinking water quality across the United States

Access to safe and affordable drinking water is fundamental to the health of communities across the United States, yet research has documented disparities across income and racial/ ethnic groups in access to safe drinking water. Data limitations, however, have made it difficult for researchers to conduct national analyses on disparities in drinking water quality. In this paper, we build on previous work by characterizing socioeconomic and regional inequalities for seven key drinking water quality indicators. These indicators include arsenic, bacterial detection, disinfection byproduct formation, lead, nitrates, PFAS, and health-based violations of the Safe Drinking Water Act. We use a national dataset of water system service areas to estimate drinking water quality experienced by different demographic groups, allowing for some of the first nationwide estimates of the unequal water quality burden faced by households with heightened socioeconomic vulnerability in the US at the water system-level. We find disparities in drinking water quality with respect to every indicator of water quality included in this analysis. Notably, our analysis suggests that some of the largest disparities in water quality exist for American Indian populations, who are served by systems with 2–3 times more health-based violations and twice the typical arsenic concentrations than a reference population of non-Hispanic white individuals. We also find more acute differences between racial and ethnic categories than between low-income and higher-income communities. We document these disparities using a diverse set of methods and data visualizations including bivariate maps, Lorenz curves, prevalence ratios, and regression analysis.