EPA Releases Preliminary Results of PFAS Sampling in Public Water Systems Under UCMR 5

On August 17, 2023, the U.S. Environmental Protection Agency (EPA) released preliminary results from the fifth Unregulated Contaminant Monitoring Rule (UCMR) under Section 1445(a)(2) of the Safe Drinking Water Act (SDWA). The UCMR provides a mechanism for the EPA to collect data regarding impacts to public water systems from “emerging contaminants,” for which the SDWA does not otherwise require sampling and mitigation. The purpose of the UCMR is to allow the agency to collect data regarding the scope and magnitude of impacts to potable water supplies that can serve as the basis for science-based decisions regarding future regulations. Notably, the EPA has indicated that it will interpret the data obtained from the fifth UCMR—or UCMR 5, as it is called—with an eye toward environmental justice.

Sampling activities under UCMR 5 went into effect in 2022 and will continue into 2026. In all, some 10,311 public water systems will be sampled, of which 800 are “small systems” (within the meaning of the SDWA) servicing fewer than 3,300 individuals, 5,147 are small systems servicing between 3,300 and 10,000 individuals, and 4,364 are large systems, servicing more than 10,000 individuals. Notably, the contaminant list for UCMR 5 adds 29 PFAS chemicals, as well as lithium, to the analytes sampled under prior UCMRs.

The preliminary results that were just released cover 2,000 public water systems and represent 7% of the total data expected to be obtained as part of the UCMR 5 sampling cycle. In addition to showing a distribution of the 29 new PFAS chemicals in 439 of the sampled systems, the preliminary data shows that approximately 220 public water systems (greater than 10% of those sampled to date as part of UCMR 5) contain perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), the two most studied PFAS chemicals and those at the heart of recent litigation and governmental enforcement efforts. In 8% of the sampled public water systems (servicing up to 26 million individuals), these two PFAS were present at concentrations exceeding their proposed MCLs of 4 ppt.

UCMR data can serve as major drivers for PFAS regulation and litigation. Ingestion through drinking water is the principal exposure pathway of concern for PFAS, and the recent wave of PFAS lawsuits, regulations and enforcement actions may be traced back to 2016, when the EPA presented the results of UCMR 3. That UCMR included six PFAS on its analyte list—PFOA, PFOS, perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), perfluoroheptanoic acid (PFHpA) and perfluorononanoic acid (PFNA). Most of these six PFAS—and, in particular, PFOA and PFOS—have since been the focus of regulatory efforts at both the federal and state levels. The current UCMR stands to expand the field of PFAS prioritized for regulation fivefold. Although it remains to be seen how the EPA and the states will process the data from UCMR 5, businesses may find it beneficial to closely track the results as they are rolled out, and to begin accounting for the 29 PFAS subject to the rule for purposes of ascertaining potential PFAS-related liability exposures.

Additionally, entities that own or operate SDWA “consecutive public water systems,” as defined under the SDWA, may find it beneficial to assess whether they qualify for any exemptions from having to comply with the primary drinking water regulations in the event that any additional PFAS MCLs are proposed and analyzed. As to PFOA and PFOS, the EPA is currently targeting a December 2023 date for finalizing the proposed MCLs.


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