Environmental Justice and Drinking Water Quality in U.S. Public Water Supplies

Abstract

Low-income and minority communities often face disproportionate burdens of exposure to pollution, and associations with race and ethnicity persist even after accounting for income. However, few studies have investigated links between drinking water quality and environmental justice. The goal of our study was to evaluate associations between drinking water quality and characteristics of public water supplies and demographics of the communities they serve. We compiled county-level demographic data from the U.S. Census Bureau and water system characteristics from U.S. EPA’s Safe Drinking Water Information System. We obtained data for regulated contaminants (lead, TCE, trihalomethanes) in around 40,000 community water systems (CWSs) from individual state drinking water programs. Data for 17 unregulated contaminants were gathered from EPA's Unregulated Contaminant Monitoring Rule (UCMR) program (2013–2015), which included 4,650 CWSs serving 240 million people (every large supply serving >10,000 customers and a subset of small supplies). We found that percent of Hispanic residents and percent of residents living in urban areas were associated with increased likelihood of detection, or exceedance of health guidelines, for a variety of unregulated industrial (e.g., 1,4-dioxane, PFASs) and inorganic (e.g., chromium) contaminants and disinfection byproducts (e.g., chlorate). Percent Hispanic and percent urban residents were also associated with increased likelihood of at least one exceedance of a health guideline for the UCMR contaminants in our analysis. We further observed positive associations between wealth-related factors (lower rates of poverty, higher rates of homeownership) and industrial, inorganic, and disinfection-related UCMR contaminants. The relationships we identified between demographics and levels of unregulated contaminants are similar to those that we previously observed for nitrate; future work will extend these analyses to lead, TCE, and trihalomethanes.