BBK Firm Attorneys at Law logoRegulations Impose New Monitoring Requirements and Maximum Contaminant Levels, Requires Attainment by 2029

On April 10, 2024, the U.S. Environmental Protection Agency (EPA) issued final new national primary drinking water regulations for six per- and polyfluroralkyl substances (PFAS). The regulations impose Maximum Contaminant Levels and monitoring requirements for the nation’s water systems for six PFAS chemicals under the Safe Drinking Water Act.

Maximum Contaminant Levels

The final rule sets the following Maximum Contaminant Levels:

Chemical Maximum Contaminant Level
PFOA 4 parts per trillion (ppt)
PFOS 4 ppt
PFHxS 10 ppt
HFPO-DA (GenX Chemicals) 10 ppt
PFNA 10 ppt


The final rule also sets a Maximum Contaminant Level that uses a Hazard Index approach for any combination of PFHxS, GenX Chemicals, PFNA, and PFBS. Under the Hazard Index approach, a combination of two or more of those PFAS chemicals can exceed the Maximum Contaminant Level based on the fractions of detected amounts compared to 10 ppt for PFHxS, GenX Chemicals, and PFNA, and compared to 2000 ppt for PFBS. Although EPA has used a Hazard Index approach under other statutes, its use is new under the Safe Drinking Water Act.

Monitoring Requirements

The final rule requires all surface water systems and groundwater systems serving more than 10,000 people to initially conduct quarterly sampling within a 12-month period. Smaller groundwater systems will only need to monitor twice within a 12-month period. Systems that previously sampled under Unregulated Contaminant Monitoring Rule 5 (UCMR-5) or a comparable state requirement may use those lab results to satisfy the initial monitoring requirements.

The final rule gives state regulators the authority to reduce PFAS monitoring requirements if initial monitoring results are below the following trigger levels for all regulated PFAS: 2 ppt for PFOA and PFOS, 5 ppt for PFHxS, PFNA, and GenX Chemicals, and one-half of the Hazard Index for mixtures of PFHxS, GenX Chemicals, PFNA and PFBS. Reduced monitoring for small systems is once every three years. Larger systems serving over 3,300 people will need to sample twice in one calendar year every three years.

Public Notification Requirements

The final rule requires community water systems to report detections of PFOA, PFOS, PFHxS, GenX Chemicals, and PFNA (and mixtures containing two or more of PFHxS, GenX Chemicals, PFNA, and PFBS) beginning with their 2027 annual Consumer Confidence Reports. Once the Maximum Contaminant Levels take effect in 2029, water systems will be required to provide notification of violations as soon as practicable but no later than 30 days after the system learns of the violation, and then repeat the notification every three months until the violation is remedied.


The final regulation requires water systems to comply with PFAS monitoring and reporting requirements within 3 years of its publication in the Federal Register (by 2027), and to comply with the Maximum Contaminant Levels within 5 years of publication (by 2029). (The proposed regulation had proposed a tighter deadline of 3 years to comply with the Maximum Contaminant Levels.)

Final vs. Proposed Regulation

The final regulation is largely consistent with the 2023 proposal. The most significant change is that the final regulation allows 2 additional years (until 2029) for water systems to achieve compliance with the Maximum Contaminant Levels.

Other minor changes include:

  • The final regulation sets individual Maximum Contaminant Levels of 10 ppt for PFHxS, GenX Chemicals, and PFNA. The proposed rule had only included these PFAS chemicals in the Hazard Index for combinations of chemicals, and had requested comment on individual Maximum Contaminant Levels.
  • The final health-based water concentration for PFHxS in the HI has been adjusted to 10 ppt. The proposed rule had a health-based water concentration for PFHxS set at 9 ppt.
  • The final regulation set the trigger level for continued quarterly monitoring requirements at one half of the Maximum Contaminant Levels for each regulated PFAS chemical. The proposed regulation’s trigger level was one third of the Maximum Contaminant Levels.

Methodology for Determining Exceedances

Consistent with the proposed rule, compliance with the final rule’s Maximum Contaminant Levels will be determined using a running annual average. Therefore, a system that monitors for the regulated PFAS on a quarterly basis will not necessarily be in violation until the annual average exceeds the applicable Maximum Contaminant Level. EPA has also provided a buffer when computing the annual average by allowing systems to use zero (0) for sample results below the Practical Quantitation Limit (PQL). The PQL is the “lowest concentration of analyte that can be reliably measured within specified limits of precision and accuracy during routine laboratory conditions.” The final rule’s PQLs matched those of the proposed rule:

Chemical PQL
PFOA 4 ppt
PFOS 4 ppt
PFHxS 3 ppt
Gen X Chemicals 5 ppt
PFNA 4 ppt
PFBS 3 ppt


Costs for Public Water Agencies and Ratepayers

The new monitoring requirements apply to the nation’s 66,000 public water agencies, and EPA estimates that the number of water agencies that will need to reduce regulated PFAS to comply with the new Maximum Contaminant Levels ranges between 4,100 and 6,700, serving between 83 million and 105 million people. The final regulation and supporting analysis estimate that the new regulation will cost $1.63 billion per year – an increase from the proposed rule’s estimate of $1.2 billion per year that was largely based on inflation and increased costs for materials. Public water agencies commented that EPA’s range of estimated impacts and costs were lower than the water agencies’ projections. But even EPA’s total cost estimate is significant – more than $128 billion, which EPA annualized over 82 years. For the nation’s public water agencies with water that exceeds Maximum Contaminant Levels, those $128 billion in cost increases won’t be spread evenly over 82 years. They will come as generational planning and capital investments in the immediate five years – EPA estimates more than $15 billion in 2029 alone – followed by a stream of increased operations and maintenance costs in perpetuity. EPA’s announcement refers to $9 billion in funding provided in the Bipartisan Infrastructure Law. This funding will provide some help for public water agencies, but is significantly less than EPA’s projected cost increases.

Further Actions on PFAS to be Taken by EPA

The new drinking water standards fulfill one aspect of EPA’s larger PFAS Strategic Roadmap. In addition to the new MCLs, EPA is expected to finalize rules that would designate certain PFAS as hazardous constituents under the Resource Conservation and Recovery Act (RCRA) and hazardous substances under the Comprehensive Environmental Response, Compensation and Liability Act (CERLCA). Both rules could significantly impact water systems that must now filter and dispose of PFAS under the new drinking water standards. Lastly, EPA has released interim guidance on the destruction and disposal of PFAS – once published in the Federal Register will be available for comment for 180 days. The guidance focuses on the disposal of some PFAS and PFAS-containing materials and primarily analyzes three currently used technologies: underground injection; landfills; and thermal treatment (including incineration).

BBK has a coalition of clients that has advocated and shared insights into each of the proposed rules. BBK will be preparing comments on the interim destruction and disposal guidance as well. If you would like to be a part of this coalition please contact one of the authors of this Alert.

About PFAS

First developed in the 1940s, PFAS or “forever chemicals” are a family of synthetic chemicals known for their unique properties that make them durable, heat resistant, and water resistant. PFAS are found in almost every manufactured good today, including but not limited to automobiles, military equipment, medical equipment, electronics, clothes, packaging, cookware, and furniture. PFAS are highly stable and can persist in the environment forever.

While PFOA and PFOS are no longer manufactured in the United States, decades of use has resulted in widespread contamination. Scientific studies link these two chemicals to “significant and diverse” adverse health impacts, including cancer and liver cell death. Studies on the other regulated PFAS—PFHxS, HFPO-DA, PFNA, and PFBS—linked them to, among other things, liver and thyroid toxicity. However, due to limited data, the full scope of their human health effects is unknown.

Click here to view the Pre-Publication Version of the new regulation.

Click here to view the FAQ on the new regulation.