Unregulated and Emerging Contaminants in Tribal Water

Emerging contaminants in Tribal water have been unexplored until implementation of the Unregulated Contaminant Monitoring Rule (UCMR) campaigns, which mandated the analysis of up to 30 new contaminants in drinking water every five years. As additions to the Safe Water Drinking Act (SDWA), the UCMR1 - 3 were created to assess contaminants which have not yet been assigned a maximum contaminant level (MCL) but may be regulated in the future to protect human health. While a handful of Tribes (n = 6) participated in UCMR1, public water systems (PWS) within reservation boundaries were intentionally included in representative nation-wide sampling beginning with UCMR2 after a period of Tribal consultation. Still, less than 3% of Tribal PWS were surveyed. The results from UCMR2 revealed that samples from all surveyed Tribal PWS fell below the method detection limits. Target analytes shifted to metals, perfluorinated chemicals, hormones, volatile organic compounds (VOCs), dioxane, and chlorate under UCMR3. Detectable levels of metals (chromium, hexavalent chromium, strontium, and vanadium), chlorate, and dioxane were observed, and in some cases, at concentrations greater than the U.S. Environmental Protection Agency's (EPA's) recommended health reference limit (HRL). The presence of elevated levels of vanadium, strontium, 1,4-dioxane, perfluorooctanesulfonate (PFOS), and chlorate defines a new set of emerging contaminants that needs to be considered with regards to risk, reporting and monitoring, and water treatment in Tribal drinking water.