Socioeconomic disparities in exposures to unregulated industrial contaminants in U.S. public drinking water supplies

Abstract

BACKGROUND AND AIMS Communities of color and low-income communities often face disproportionately high burdens of exposure to pollution. Previous studies investigating environmental justice and drinking water quality have focused on regulated contaminants with established standards, but many other unregulated contaminants are also present in drinking water. METHODS We evaluated associations between the presence of unregulated industrial contaminants and the demographics of communities served by U.S. public drinking water supplies (PWSs). We compiled data for four unregulated contaminants (1,4-dioxane, 1,1-dichloroethane, HCFC-22, PFAS) from U.S. EPA's Third Unregulated Contaminant Monitoring Rule (UCMR3). We analyzed data collected in 2013-2015 from 4,815 U.S. PWSs, serving 284 million people, that reported concentration data for at least one target contaminant. We also compiled information on PWS characteristics, county-level demographic data from the U.S. Census Bureau, and data on potential sources including airports, fire-training areas, wastewater treatment plants, and relevant contaminant releases reported in the U.S. EPA Toxic Release Inventory. RESULTS We found that PWSs serving counties with higher proportions of Hispanic residents and more urban households were more likely to have ≥1 target contaminant detected and were more likely to exceed a federal guideline for PFOA/PFOS or 1,4-dioxane, even after accounting for PWS characteristics and the presence of potential sources. Target contaminants were more frequently detected in large PWSs (>10,000 customers) compared to smaller systems and in groundwater systems compared to surface water systems. We did not find consistent associations between detection of UCMR3 contaminants and proportion of Black residents or proportion of residents considered deprived (according to the U.S. Census Bureau’s Multidimensional Deprivation Index). CONCLUSIONS Our findings provide new insight into the extent of socioeconomic disparities in exposures to drinking water contaminants and highlight the need to consider cumulative exposures to contaminants in drinking water. KEYWORDS Environmental justice, drinking water, contaminants, PFAS, industrial pollution