Client alert: USEPA Proposed PFAS National Primary Drinking Water Regulations

On March 14, 2023, the United States Environmental Protection Agency (USEPA) proposed a National Primary Drinking Water Regulation (NPDWR) for six per- and polyfluoroalkyl substances (PFAS), together with their isomers and various salts.

Both enforceable maximum contaminant levels (MCLs) and maximum contaminant level goals (MCLGs) were proposed. An MCL is the maximum level allowed of a contaminant (or a mixture of contaminants) in water which is delivered to any user of a public water system (PWS). An MCLG is the maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, allowing for an adequate margin of safety.

USEPA’s proposed PFAS NPDWR includes perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) as individual contaminants, with MCLs of 4 parts per trillion (ppt, or nanograms/liter - ng/L) and MCLGs of zero for each. It also includes an MCL and an MCLG expressed as a hazard index (HI) of 1.0 for mixtures of the following four PFAS:

• Perfluorononanoic acid (PFNA)
• Hexafluoropropylene oxide dimer acid (HFPO-DA) and its ammonium salt, commonly known as GenX chemicals
• Perfluorohexane sulfonic acid (PFHxS)
• Perfluorobutane sulfonic acid (PFBS)

An HI is unitless and is the proposed approach to evaluate whether the combined levels of these four PFAS pose a potential risk to health. The HI calculation is described under the section Compliance calculations below. A PFAS mixture that is greater than the HI of 1.0 exceeds the MCL.

Monitoring frequency and compliance for PWS will be based on running annual averages (RAAs), system size, population served, and exceedances of trigger levels.

Following the publication of the proposed rule in the Federal Register (FR) on March 29, 2023, a 60-day period for public comment is open until May 30, 2023¹. USEPA anticipates finalizing the regulation by the end of 2023.

If finalized and issued, rules become enforceable three years after being published in the FR. Therefore, actions to comply with the NPDWR, such as installing treatment, should be achieved by the end of 2026 unless an exemption or extension is granted.

¹ Public comments can be provided at www.regulations.gov under Docket ID: EPA-HQ-OW-2022-0114.

The proposed NPDWR would set enforceable regulations for six PFAS, requiring those PWS with RAAs in drinking water that exceed the proposed standards to install or improve advanced treatment technologies or develop a new water source, possibly shifting the financial burden of PFAS mitigation onto utilities and ratepayers in some instances.

If finalized, affected PWS will be faced with demonstrating compliance, identifying and eliminating the sources of PFAS impacting their systems, and/or installing PFAS treatment.

Complexities associated with the proposed rule include the following:

• Initial and routine compliance monitoring and the associated compliance considerations
• Sampling requirements and compliance calculations
• Public notifications of violations
• Challenges complying with the proposed regulations

Within three years of the publication of the final rule, water systems will have to calculate a running annual average for each regulated PFAS per entry point to the distribution system (EPTDS). This can be satisfied with previously collected data such as UCMR5 or from other regulatory monitoring requirements performed after January 2023. Older data (from January 2019 through December 2022) can also be used if detections are below proposed trigger levels, i.e., 1.3 ppt for either PFOA or PFOS, and an HI of 0.33 for the other four PFAS included in the proposed regulations.

At a minimum, quarterly samples will be required from water systems to calculate the RAAs, unless reduced monitoring is approved based on the initial monitoring data and non-exceedance of trigger levels.

Key compliance status considerations include:

• A system is deemed out of compliance if a single EPTDS RAA exceeds any MCL
• While a single detection above the MCL will not necessarily bring the system out of compliance, a single sample may bring a RAA above the MCL if detections are high enough
• HI exceedances may be achieved even if only one of the four PFAS is present, if the measured PFAS exceeds its HBWC
• Systems may collect more samples per quarter to calculate their RAAs, averages must be calculated per sampling point (per EPTDS)

Samples must be analysed using USEPA-approved methods 533 or 537.1 for PFAS in drinking water by certified laboratories (including previous data permitted for initial monitoring). Composite samples (a mixture of various EPTDS in a single container) will not be allowed.

RAAs are calculated considering detections below the practical quantitation levels (PQL) as zeros. PQLs were defined as 5 ppt for HFPO-DA/GenX, 4 ppt for each of PFOA, PFOS and PFNA, and as 3 ppt for PFBS. The HI is calculated by summing the ratios of each regulated PFAS concentration in the sample by its health-based water concentration (HBWC) according to the formula:

HI MCL= HFPO-DA/ 10 ng/L + PFBS/ 2000 ng/L + PFNA/ 10 ng/L + PFHxS/ 9 ng/L

Public notification of MCL violations should be provided at the earliest opportunity, but no later than 30 days after a violation is detected. Consumer confidence reports (CCR) must be provided annually to customers and list detections of the six PFAS, even if below the PQLs.

There will be numerous challenges complying with the proposed rule, if approved. Even just conducting the analyses to demonstrate compliance could be problematic. Examples of analytical challenges include:

• Limited data available on matrix effect of salinity or organic materials potentially affecting results
• Quality control, contamination, risk of triggering non-compliance or monitoring due to inaccurate sample collection and processing
• Limited availability of certified laboratories causing longer turn-around times which could result in extended noncompliance durations
• Compliance is determined by RAAs, implying that a year of data should be available before the compliance period starts
• The cost of sample collection and analyses could be significant

In addition to analytical challenges, the proposed best available technologies (BATs) that USEPA determined feasible for meeting the MCLs are granular activated carbon (GAC), anion exchange resins (AIX), nanofiltration (NF) and reverse osmosis (RO).

These treatment systems can require considerable initial capital investment, have elevated maintenance costs, and operational challenges. For example, there may be rapid exhaustion of GAC due to competition with other pollutants or organic matter; fouling or degradation of the AIX resins due to minerals, chlorine and other dissolved compounds; and membrane fouling and potential low recovery rates for NF and RO. Furthermore, the proposed BATS are removal technologies, producing significant PFAS-concentrated waste requiring further treatment and/or disposal.

Recent USEPA-proposed PFAS actions and regulations, including this NPDWR, signal an intent to stringently regulate PFAS, not only as individual chemicals but potentially as a mixture of chemicals.

Examples include:

• Lowering the health advisories (HA) of PFOA and PFOS by several orders or magnitude to near zero (interim HAs of 0.004 and 0.02 ppt, respectively)
• Proposing the designation of PFOA and PFOS as hazardous substances under CERCLA section 102(a). This section considers potential danger to health or the environment, regardless of cost or proof of harm, and has not been previously employed by the agency to designate a hazardous substance
• Setting a HI considering a mixture of four PFAS as an MCL is first-of-a-kind for SDWA regulations
• Setting MCLGs for PFOA and PFOS at zero
• Setting MCLs for PFOA and PFOS at the same levels as the PQLs

AIX – anion exchange resin ARAR – applicable or relevant and appropriate requirement BAT – best available technology CERCLA – Comprehensive Environmental Response, Compensation and Liability Act (commonly referred to as Superfund) CCR – consumer confidence report CWA – Clean Water Act ELG – effluent guideline EPTDS – entry point to the distribution system FR – federal register GAC – granular activated carbon HA – health advisory HFPO-DA – hexafluoropropylene oxide dimer acid and its ammonium salt (commonly known as GenX chemicals) HI – hazard index MCLG – maximum contaminant level goal MCL – maximum contaminant level NF – nanofiltration NPDES – National Pollutant Discharge Elimination System NPDWR – National Primary Drinking Water Regulation PFAS – per- and polyfluoroalkyl substances PFBS – perfluorobutane sulfonic acid PFHxS – perfluorohexane sulfonic acid PFNA – perfluorononanoic acid PFOA – perfluorooctanoic acid PFOS – perfluorooctane sulfonic acid PQL – practical quantitation level PWS – public water system RAA – running annual average RO – reverse osmosis SDWA – Safe Drinking Water Act USEPA – United States Environmental Protection Agency

The information contained and opinions expressed herein: (i) are for discussion/informational purposes only, without representation or warranty; (ii) are general in nature, may not be applicable to your particular circumstances, and cover subject matters for which information and practices may change/develop quickly over time; and, therefore, (iii) should not be relied upon for any particular circumstances without consulting an environmental professional experienced in both PFAS and the specific issues related to your matter.