The U.S. Environmental Protection Agency (EPA) this week added five PFAS chemicals for a total of six PFAS chemicals to a list of risk-based values. EPA uses these values to determine if response or remediation activities are needed. The five PFAS additions include: hexafluoropropylene oxide dimer acid and its ammonium salt (HFPO-DA — sometimes referred to as GenX chemicals), perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorohexanesulfonic acid (PFHxS). EPA added the first PFAS substance, perfluorobutanesulfonic acid (PFBS), to the Regional Screening Level (RSL) and Regional Removal Management Level (RML) lists in 2014 and updated it in 2021 when EPA released its updated toxicity assessment for PFBS.

For PFOA, PFOS, PFNA, and PFHxS, EPA selected levels using what it contends is the most updated final peer-reviewed information developed from Minimal Risk Levels from the Agency for Toxic Substances and Disease Registry’s (ATSDR) 2021 toxicological profile. For the fifth chemical, HFPO-DA, EPA used a final peer-reviewed EPA toxicity value. RSL’s are used to identify contaminated media (i.e., air, tap water, and soil) at a site that may need further investigation. Typically, if a contaminant concentration is below the screening level, no further action or investigation is needed. If the concentration is above the screening level, further investigation may be needed to determine if some action is required. EPA uses RML’s to justify undertaking a removal action under CERCLA, or remediation of contaminated media, if proven to be necessary.

Though the updates to the two sets of screening levels derive from ATSDR levels for PFOA and PFOS, those levels triggered significant controversy when first proposed in 2018. At the time, EPA and other agencies expressed concern that the levels were stricter than values EPA adopted to set nonbinding drinking water advisory levels in 2016.

While EPA attempts to regularly review and update screening levels twice a year, the agency action against the backdrop of EPA plans to beef up efforts to remediate PFAS. While agency enforcement officials are currently investigating scores of facilities’ current and past uses of more than a dozen PFAS, the agency hopes to adopt a rule to designate PFOA and PFOS — the two PFAS compounds predominantly studied — as “hazardous substances” under the Superfund law. A final designation rule would trigger multiple industry responsibilities and potential liabilities, including by example release reporting and cost recovery and contribution claims to recoup cleanup costs.

EPA’s move to add additional compounds and levels was met with praise from advocacy groups that criticized the White House in 2019 for dropping from the interim PFAS groundwater cleanup guide a default threshold above which regulators could order removals, saying it was not clear if EPA would undertake an emergency removal action to respond to groundwater contamination.