EPA Finalization of PFAS Water Quality Criteria Paves the Way for State Water Quality Standards

Originally published in the January/February 2025 issue of Bench & Bar of Minnesota Environmental Law Update, Minnesota State Bar Association.

The United States Environmental Protection Agency (EPA) recently published new water quality criteria for per- and polyfluoroalkyl substances (PFAS) compounds on October 7 and December 26, 2024. See 89 Fed. Reg. 81077 and 89 Fed. Reg. 105041. Water quality criteria are not binding, but once final, they provide national recommendations that states can use to establish their own enforceable water quality standards under the Clean Water Act (CWA). As of right now, there are very few state water quality standards for PFAS, however, these EPA publications could pave the way for that to change.

In the October 7, 2024, publication, EPA finalized aquatic life water quality criteria for the two most-studied PFAS as well as acute freshwater “benchmarks” for eight additional PFAS that states can now use to develop binding water quality standards and discharge limits under the CWA. The final PFAS criteria are generally more rigorous than what the agency proposed in 2022, in some cases by an order of magnitude. For example, the EPA’s 2022 proposal, the agency recommended water column acute freshwater criteria for perfluorooctanoic acid (PFOA) of 49 milligrams per liter (mg/L) and 0.094 mg/L for chronic exposure and the final PFOA criteria recommend a significantly stricter value of 3.1 mg/L for acute exposure and slightly less strict value of 0.10 mg/L for chronic exposure. The various tissue values remain similar to the proposal, with 1.18 milligrams per kilogram (mg/kg) wet weight (ww) for invertebrates, 6.49 mg/kg ww for fish whole body and 0.133 mg/kg ww for fish muscle. The final perfluorooctane sulfonic acid (PFOS) criteria are 0.071 mg/L for acute exposure and 0.00025 mg/L for chronic exposure. The final tissue values are 0.028 mg/kg ww for invertebrates, 0.201 mg/kg ww for fish whole body and 0.087 mg/kg ww for fish muscle.

The final PFOA and PFOS aquatic-life criteria recommendations are developed under CWA section 304(a)(1) and based on the latest scientific knowledge about protecting freshwater fish and other organisms from the effects of short-term and long-term exposure to PFOA or PFOS. EPA develops aquatic life benchmarks under CWA section 304(a)(2) when there is limited data on pollutants in freshwater or saltwater and the agency is not able to recommend water quality criteria. Similar to the criteria, these benchmarks are science-based concentrations above which exposure to certain pollutants negatively affect aquatic life.

For PFOA and PFOS in saltwater, the agency derived benchmarks of 7.0 mg/L and 0.55 mg/L, respectively. Furthermore, EPA derived freshwater benchmarks of 5.3 mg/L for perfluorobutanoic acid (PFBA), 4.8 mg/L for perfluorohexanoic acid (PFHxA), 0.65 mg/L for perfluorononanoic acid (PFNA), 0.5 mg/L for perfluorodecanoic acid (PFDA), 5.0 mg/L for perfluorobutane sulfonic acid (PFBS), 0.21 mg/L for perfluorohexanesulfonic acid (PFHxS), 0.037 mg/L for 2H-perfluoro-2-decenoic acid (8:2 FTUCA) and 0.012 mg/L for 2H,2H,3H,3H-pefluorodecanoic acid (7:3 FTCA).

Some state regulators raised concerns about EPA’s draft aquatic life criteria, but the EPA in a response to comments document defended the aquatic life values, disagreeing with comments from state regulators that largely questioned the toxicity data and technical approaches the agency used, as well as the lack of consideration of PFAS precursors and mixtures.

In the December 26, 2024, publication, EPA took a key step towards addressing human exposure to PFAS that states have been eagerly awaiting by releasing a draft human health water quality criteria for three PFAS. In a press release, EPA unveiled draft criteria for PFOA, Perfluorooctane PFOS and PFBS. These are risk-based measures that will assist states, tribes and other regulators in setting regulatory values for the three PFAS. The EPA explained that once final, the recommended criteria can be used by states and authorized tribes to set water quality standards that help protect people from exposure through consuming water, fish and shellfish from inland and nearshore waterbodies that may be polluted by these PFAS. The comment period for the public to submit a comment on the draft PFAS national recommended criteria ends on February 24, 2025, in Docket EPA-HQ-OW-2024-0454.

In a separate announcement on December 20, 2024, EPA also released its final Office of Research and Development Human Health Toxicity Value Assessment (HHTV) for 6:2 fluorotelomer sulfonic acid, a substance that is structurally similar to PFOS that is used in chrome plating operations and the manufacture of aqueous film-forming foam (AFFF). EPA’s HHTV sets a chronic reference dose (RfD) of 2 × 10⁻4 mg/kg-day that represents the agency’s estimate of the largest amount of a chemical that a person can ingest daily over a lifetime without expected non-cancer health effects. The HHTV was crafted by EPA’s research office at the request of the agency’s waste, air, enforcement, children’s health and Region 5 offices, according to the assessment.

The EPA’s technical fact sheet provides that the draft human health criteria (HHC) include two values for each contaminant — a “water plus organism” HHC and an “organism only” HHC — and if not exceeded, the criteria will protect the general population from adverse health effects due to ingesting water, fish and shellfish from inland and nearshore waterbodies. The fact sheet explains that in the draft criteria, the EPA provides an illustrative example for states or Tribes interested in developing a water quality standard for a mixture of two or more PFAS for which HHC have been developed using the hazard index (HI) approach.

For PFOA, the draft value for the water plus organism HHC is 0.0009 parts per trillion (ppt) or nanograms per liter (ng/L), and the draft value for the organism only HHC is 0.0036 ppt or ng/L. For PFOS, the draft value for the water plus organism HHC is 0.06 ppt or ng/L, and the draft value for the organism only HHC is 0.07 ppt or ng/L. The draft value for the water plus organism HHC for PFBS is 400 ppt or ng/L while the draft value for the organism only HHC is 500 ppt or ng/L. EPA in its technical fact sheet says it is presenting the values with both types of units to make it easier to compare them to the method detection limit (MDL) for the chemicals. The pooled MDL values, derived from a multi-laboratory validation study, are 0.54 ng/L for PFOA, 0.63 ng/L for PFOS and 0.37 ng/L for PFBS.

State regulators and water dischargers have criticized EPA’s decision to develop the aquatic life criteria first, noting states’ greater interest in HHC. However, former EPA official Betsy Southerland told the Inside PFAS Policy news service in October 2024 that the aquatic life criteria were a necessary prerequisite for HHC. Southerland went on to explain that a human health criterion is developed using two sources of exposure for a person living on that water body: (1) eating fish and (2) drinking water. So, the intention behind putting the criteria and benchmarks in place and make them legally enforceable was to reduce one of the two routes of exposure in a human health criterion.