11.22.21 Last week, EPA transmitted four important documents to the EPA Science Advisory Board (SAB) for peer review that included updated health assessments for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). This peer review, which will start on December 16, will inform EPA’s development of a Maximum Contaminant Level (MCL) Goal and a future, legally enforceable National Primary Drinking Water Regulation for PFOA and PFOS under the Safe Drinking Water Act. As noted in the PFAS Strategic Roadmap: EPA’s Commitments to Action 2021-2024, EPA intends to release a proposed drinking water regulation for PFOA and PFOS in fall 2022. These scientific documents will provide the underpinnings for that important regulation.
The transmitted documents propose new (and lower) allowable levels for ingestion of PFOA and PFOS. Once the peer review is complete, these assessments will also inform updated health advisories for PFOA and PFOS, which will be used to inform EPAs preliminary remediation goals (PRGs) for contaminated groundwater that is a current or potential source of drinking water. This can include sites being evaluated and addressed under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund) and the Resource Conservation and Recovery Act (RCRA) corrective action program. Thus, the implications are broad and this review will be one worth watching.
What Did EPA Transmit to the SAB?
In addition to sending ten pages of questions for the SAB to answer, the EPA Office of Water sent four scientific documents to the SAB for their review.
Documents 1 and 2, Health Effects: EPA submitted two documents to the SAB that propose an approach for deriving the MCL Goal for PFOA and PFOS. These lengthy documents (over 700 pages each) provide updated toxicity assessments for each chemical, including a proposed non-cancer Reference Dose (RfD) (which is the safe level for ingestion due to non-cancer effects) and a cancer assessment. The documents also provide an evaluation of the relative source contribution (RSC), which is the proportion of the total daily exposure, through ingestion, to a chemical that is attributed to or allocated to drinking water (accounting for multi-route exposures).
The non-cancer assessment: For the non-cancer assessment, for both PFOA and PFOS, EPA relies upon decreased serum anti-diphtheria and decreased serum anti-tetanus antibody concentrations in children as the critical effect of PFOA/PFOS exposure. Although this is not an “adverse effect,” EPA states that decreases in these antibodies may lead to decreases in the prevention of diphtheria and tetanus infections in children. The table below shows the new proposed non-cancer values along with the existing values for PFOA and PFOS and the safe ingestion levels for three other PFAS EPA has evaluated to date.
Using the 2016 values for PFOA and PFOS, EPA set the lifetime health advisories for these chemicals at 70 ppt. Using the same approach EPA used in 2016, with the new proposed values, the lifetime health advisory could be as low as 0.006 ppt (or 6 parts per quadrillion (ppq)). It is unlikely that the available EPA test methods are capable of detecting PFOA and PFOS at these low levels.
The cancer assessment: While the 2016 health assessments for PFOA and PFOS determined the cancer evidence to show “suggestive evidence of carcinogenic potential,” the PFOA assessment released last week proposes that the evidence is now more supportive of carcinogenic potential. EPA states that PFOA is “likely to be carcinogenic to humans.” For PFOS, EPA is maintaining the “suggestive” cancer classification. If the “likely” classification of PFOA is maintained, then a non-enforceable MCL Goal may be set for PFOA at zero.
The relative source contribution: EPA applies a relative source contribution (RSC) when calculating an MCL Goal to provide a margin of safety that an individual’s total exposure (including non-drinking water sources) does not exceed the RfD. In the new assessments, EPA continues to support a 20% RSC, as was used in 2016.
Document 3, Cardiovascular Risk Reduction: EPA submitted a document to the SAB that correlates cardiovascular disease risk reduction with reduced PFOA and PFOS exposure. This analysis will inform the health risk reduction and cost analysis that is required by the Safe Drinking Water Act (SDWA). As PFOA and PFOS are known to increase cholesterol levels which in turn impacts cardiovascular disease, EPA presents a methodology to evaluate avoided cases of cardiovascular disease with decreases in PFOA and PFOS. Once the peer review is complete, EPA intends to use this methodology to quantify the cardiovascular risk-reduction benefits associated with the new regulation for the population served by public drinking water systems. As this evaluation is novel, EPA is asking the SAB to comment on whether the approach is scientifically supported.
Document 4, A Framework for PFAS Mixtures: EPA’s fourth document submitted to the SAB provides a draft framework for estimating non-cancer health risks associated with mixtures of PFAS. EPA intends for this framework to provide a flexible and data-driven approach that is based on the concept of dose-additivity. A dose additivity approach means that, assuming a common mode of action, the dose of the mixture can be represented by a linear combination of the component doses.
What Are the Next Steps?
The SAB will begin their review on December 16 and will hold four half-day virtual meetings to discuss their comments and to respond to the questions that EPA provided. The details on the meetings and a link to participate can be found here. At the public meetings, EPA will allow oral statements from stakeholders, limited to three minutes per speaker. In addition, written statements can be provided to the SAB by December 30. Comments received after this date, may not be considered by the SAB review panel, although they will be accepted. The details in the Federal Register notice describing the review and comment process seem to suggest that while the SAB will consider the public comments, EPA will not be providing responses to the comments received.