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EPA Finalizes Rule on PFAS in Drinking Water - What Lies Ahead for Drinking Water and Site Remediation Standards

Last month, the United States Environmental Protection Agency (EPA) issued a final rule establishing, for the first time, nationwide limits on the presence of six types of per- and polyfluoroalkyl substances (PFAS) in drinking water. This new National Primary Drinking Water Regulation (NPDWR) set maximum contaminant levels (MCL) and health-based maximum contaminant level goals (MCLG) addressing the following six PFAS: perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), hexafluoropropylene oxide dimer acid (HFPO-DA) (commonly known as GenX chemicals), perfluorononanoic acid (PFNA), and perfluorobutane sulfonic acid (PFBS).  The standards in the final rule also extend to and cover all salts, isomers and derivatives of the six listed PFAS chemicals, including derivatives other than the anionic (negatively charged) form which might be created or identified. The NPDWR will become effective on June 25, 2024 (with monitoring and compliance deadlines coming over the next three to five years).

EPA’s rule seeks to protect human health by limiting exposure to these PFAS in drinking water. The new MCL standards will have substantially broader impacts, however, given their use in other regulatory programs including as cleanup standards for contaminated sites. This expansive reach will have potentially significant regulatory and cost implications for public water systems and parties remediating PFAS contamination in soil and groundwater. EPA estimates that the cost for public water systems, alone, to implement the regulation will be approximately $1.5 billion annually. There are over 66,000 public water systems that are subject to the new rule. EPA has not estimated the potential costs for site remediation impacted by the new rule. 

EPA’s New PFAS MCLs and MCLGs
By way of background, an MCL is a legally enforceable standard that limits the level of a contaminant in drinking water provided by a public water system (PWS). An MCLG is a non-enforceable public health goal for a contaminant in drinking water that is set at a level below which there are no known or expected adverse health effects, while allowing for an adequate margin of safety.  EPA is required by the Safe Drinking Water Act (SDWA) to set the MCL as close to the MCLG as “feasible.”  Feasible means the use of the best technology and treatment approaches examined for effectiveness under field conditions, taking cost into consideration.         

The final MCLs and MCLGs set by EPA for the six PFAS compounds are as follows:

As noted in the table above, EPA is using a Hazard Index (unitless) as the MCL/MCLG for mixtures of two or more of PFHxS, PFNA, HFPO-DA, and PFBS. This approach has never before been used by EPA in setting drinking water standards, although it has been used by EPA in the federal Superfund program to better characterize the health risk from a chemical mixture. To calculate the Hazard Index, the measured concentration of each regulated PFAS chemical is divided by a health-based water concentration (HBWC) value for that chemical to create a ratio and then the ratios are then added together and compared against the Hazard Index of 1. 

Monitoring and Reporting
EPA’s NPDWR also includes monitoring and reporting requirements. Under the new rule, public water systems have three years to conduct initial monitoring for the six PFAS (by April 26, 2027).  Public water systems can use previously collected monitoring data, such as the currently ongoing Unregulated Contaminant Monitoring Rule 5 (UCMR5) data set, to satisfy the initial monitoring requirements. After this three-year period, public water systems must conduct compliance monitoring for the new PFAS MCLs at a frequency that is based on sample results. All public water systems will need to comply with the MCLs within five years (by April 26, 2029) with certain extensions and exemptions. Therefore, public water systems with exceedances of the new MCLs will need to implement changes, including capital improvements, to ensure compliance by April 26, 2029. 

Exceedances of the MCL are designated as “Tier 2” violations, which requires public notice no later than 30 days after the system learns of the violation. Violations of monitoring and testing requirements are designated as “Tier 3” violations, which requires public notice no later than one year after the system learns of the violation. The public water system is required to repeat the public notice annually for as long as the violation persists. Because the PFAS MCL does not become enforceable until April 26, 2029, the public notification requirements do not apply until that time. However, EPA encourages state agencies to require public notice to consumers prior to the MCL compliance date. EPA believes that the early notification will allow consumers to take actions to protect their health until the public water supplier can implement treatment. 

Many public water suppliers have expressed significant concerns with the public notification aspect of the rule, especially in light of ongoing UCMR 5 monitoring. Based on UCMR 5 sampling results to date, EPA believes that approximately 6 percent to 10 percent of public water suppliers covered by the rule would exceed the PFAS MCLs and will have to take action to reduce PFAS in their drinking water. Notably, UCMR 5 requires sampling for 29 different PFAS compounds, whereas EPA’s rule only addresses 6 PFAS compounds.  Public water suppliers that detect any of the 23 unregulated PFAS compounds will have to determine what information to provide to consumers about these unregulated PFAS compounds, what risks may be involved and what (if any) actions need to be taken to reduce levels of the unregulated compounds. 

Under the SDWA, community water systems are required to provide customers with an annual “Consumer Confidence Report” or “CCR.”  The CCR provides information on drinking water quality and the system’s compliance with drinking water regulations.  Public water systems are required to report certain detections (not just violations) of PFAS in their CCRs.  In addition, when any regulated PFAS is measured above the MCL, public water systems must include language in the CCR that explains the potential health effects of the particular PFAS. 

For systems that exceed MCLs, EPA states that PWSs would be required to reduce regulated PFAS levels in drinking water to meet MCLs either through treatment or other actions such a using an alternative water source. EPA has determined that the following represent best available treatment technologies and can effectively reduce the six PFAS in drinking water to below analytical detection limits: granular activated carbon, anion exchange resins, reverse osmosis, and nanofiltration. EPA notes that an added benefit of these technologies is that they can also remove other types of PFAS and contaminants that are currently unregulated. 

Future PFAS MCLs/MCLGs
The new PFAS MCLs/MCLGs apply to six PFAS substances (including all salts, isomers and derivatives), however, there are thousands of other PFAS substances that are not yet subject to regulation and for which scientific and health effects information is not yet known or available.   

EPA recognizes, in its preamble, that PFAS-related science and information is still developing but asserts that the SDWA allows it to move forward in the face of imperfect information. It states that the SDWA gives it authority to regulate based upon the best available science and information and it provides a mechanism for EPA to update standards as more science becomes available. For the PFAS covered by the rulemaking, EPA has concluded that that the state of science and information has advanced sufficiently to satisfy the statutory requirements, noting that the final rule is based upon the best available peer-reviewed science. The SDWA directs EPA to establish MCLs and MCLGs if it determines: (i) the contaminant may have an adverse effect on the health of persons; (ii) the contaminant is known to occur or there is a substantial likelihood that the contaminant will occur in public water systems with a frequency and at levels of public health concern; and (iii) in the sole judgment of the Administrator, regulation of such contaminant presents a meaningful opportunity for health risk reduction for persons served by public water systems.

EPA expects to build upon this first PFAS MCL rulemaking as science and information develops. In this final rulemaking, EPA issued its final determination to individually regulate PFHxS, PFNA, and HFPO-DA, adding to a prior final determination to regulate PFOA and PFOS.  However, EPA deferred making a final determination to regulate PFBS when it occurs individually.  EPA notes that, as more information becomes available, the agency will continue to evaluate PFBS and other PFAS for potential future determinations to regulate them under the SDWA.  EPA has also commented that it believes the Hazard Index approach provides an adaptive and flexible framework for considering regulation of additional PFAS.

Under the SDWA, EPA is required to review and revise, as appropriate, its NPDWRs at least once every six years. Information typically considered by EPA in the review process may relate to health effects, treatment technologies, analytical methods, occurrence and exposure, implementation and/or other factors that provide a health or technical basis to support a regulatory revision that will strengthen or improve public health. EPA considers potential revision to a NPDWR “appropriate” if it presents a meaningful opportunity to improve the level of public health protection or achieve cost savings while maintaining or improving the level of public health protection. 

Notably, in a major development, EPA’s Contaminant Candidate List 5 issued in November 2022 (CCL 5), included “PFAS” as a group, rather than additional individual PFAS chemicals. According to EPA’s current structural definition of PFAS, this would include over 10,000 individual PFAS chemicals. CCL 5 included 66 chemicals and three chemical groups (one being PFAS).  After a CCL is published, EPA must determine whether or not to regulate at least five contaminants from the CCL in a separate process called a Regulatory Determination. EPA will make a Regulatory Determinations for five or more CCL 5 contaminants by 2027.    

State Drinking Water Standards
State agencies authorized to implement and enforce the SDWA program (primacy agencies) will have two years to adopt requirements that align with the new NPDWR and apply to EPA for approval (extensions also may be requested in certain circumstances). States that have already established PFAS limits for drinking water will need to review their standards to ensure they are at least as stringent as the federal NPDWR issued by EPA. New Jersey and Pennsylvania have each previously established state based MCLs for certain PFAS and, thus, will each need to review and update their programs in order to ensure they are no less stringent than the regulations promulgated by EPA.  

Site Remediation Program Impacts
Ripple effects from EPA’s NPDWR will also extend to site remediation and brownfield cleanup programs, as soil and groundwater cleanup standards are often based on MCLs.

For example, under Pennsylvania’s Act 2 program, Federal or State MCLs automatically become the new Medium Specific Concentrations (MSC) under the Statewide Health Standard (SHS) after the MCLs become effective. Thus, when Pennsylvania established its own state based MCLs for PFOA (0.014 ug/L) and PFOS (0.018 ug/L) on January 14, 2023, those values automatically became effective as the new groundwater MSCs under Act 2.  Prior to that, the Pennsylvania Department of Environmental Protection (PADEP) had already established soil and groundwater standards for PFOS, PFOA and PFBS. PADEP is planning to propose certain revisions to its MSCs for at least three new PFAS later this year such as GenX, PFBA, and Perfluorohexanoic acid (PFHxA). It is still determining how it plans to address the NPDWR with respect to Act 2 standards. 

Similarly, at the federal level, under the Superfund program, EPA uses MCLs as a basis for Regional Screening Levels (RSLs). The RSL in EPA Region 3 were updated on May 14, 2024, to reflect the federal MCLs and the latest in PFAS science. RSLs are used for site "screening" and as initial cleanup goals, if applicable, to help identify areas, contaminants, and conditions that require further federal attention at a particular site. Generally, at sites where contaminant concentrations fall below RSLs, no further action or study is warranted under the Superfund program, so long as the exposure assumptions at a site match those taken into account by the RSL calculations.   

Finally, EPA’s new MCLs may also become potentially Applicable or Relevant and Appropriate Requirements (ARARs) for Superfund sites. CERCLA section 121(d)(2)(A)(i) requires on-site CERCLA remedies to attain standards or levels of control established under the SDWA (where they are applicable or relevant and appropriate).  CERCLA also requires on-site remedies to attain MCLGs where relevant and appropriate under circumstances of the release in question.  EPA believes that MCLGs set at levels above zero should be attained, where relevant and appropriate, as cleanup levels for ground or surface waters that are current or potential sources of drinking water.

If you have questions about this article or PFAS regulatory developments, please contact Bryan Franey (484-430-2308), Brenda Gotanda (484-430-2327) or Mike Nines (484-430-2350).