Chemicals, Regulatory Developments, Sustainability

National Drinking Water Standard for PFAS

On March 14, 2023, the Biden-Harris administration announced its proposal for a first-ever National Primary Drinking Water Regulation (NPDWR) for six per- and polyfluoroalkyl substances (PFAS). The legally proposed enforceable limits are 4 parts per trillion (ppt) for perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). If finalized as proposed, public water systems (PWSs) have 3 years to bring their systems into compliance.

PFAS, also known as “forever chemicals” due to a strong chemical bond that makes them hard to break down, are a category of manufactured chemicals that can cause serious health problems, including cancer, if people are exposed to them over a long period of time. When drinking water is contaminated with PFAS, it can be a significant portion of a person’s total PFAS exposure.

“PFAS tend to co-occur with each other,” according to the EPA PFAS website. “This regulation will also remove many other PFAS when they co-occur with these six regulated PFAS. EPA is following recent peer-reviewed science that indicates that mixtures of PFAS can pose a health risk greater than each chemical on its own. Concurrent with the proposed PFAS NPDWR, which was published in the Federal Register on March 29, 2023, the EPA also announced it is making preliminary regulatory determinations for [perfluorononanoic acid (PFNA)], GenX Chemicals, [perfluorohexane sulfonate (PFHxS)], and [perfluorobutanesulfonic acid (PFBS)] in accordance with the Safe Drinking Water Act regulatory development process. EPA proposes to regulate PFNA, GenX Chemicals, PFHxS, and PFBS using a Hazard Index formula.”

If finalized, the proposed rule would establish:

  1. Maximum contaminant levels (MCLs) and maximum contaminant level goals (MCLGs) for PFOS and PFOA;
  2. A Hazard Index for PFHxS, GenX chemicals, PFNA, and PFBS;
  3. Monitoring requirements for PWSs;
  4. Reporting requirements for PWSs that are community water systems; and
  5. Treatment requirements for reducing PFAS levels for PWSs.

MCLGs and MCLs

“MCLGs are non-enforceable public health goals,” states the EPA Fact Sheet on the proposal. “MCLGs consider only public health, not the limits of detection and treatment technology effectiveness. Therefore, they are sometimes set at levels which water systems cannot meet because of technological limitations. For example, if a contaminant is a known or likely carcinogen, EPA sets the MCLG at 0.  MCLGs also consider adverse health risks to sensitive groups, including infants, children, the elderly, and immuno-compromised individuals. Once the MCLG is established, EPA determines the MCL. MCLs are enforceable standards. An MCL is the maximum level of a contaminant allowed in drinking water, which can be delivered to users of a [PWS]. For this rule proposal, EPA evaluated available methods and treatment technologies, that are shown to measure and remove these six PFAS and set the proposed MCLs as close as possible to the MCLGs. EPA also evaluated costs and benefits in determining the proposed MCLs.”

Under the proposed rule, when a PWS discovers an MCL violation, it would be required to provide public notification within 30 days and to bring the system into compliance.

“However, a one-time exceedance will not necessarily result in an MCL violation under the proposed rule—compliance would be calculated using a running annual average approach,” advises a Lexology article by Vorys, Sater, Seymour and Pease LLP. “For example, if a PWS has a quarterly monitoring obligation, and the PWS had a sample result of PFOA at 5.0 ppt and the remaining quarter sample results were all 2.0 ppt each, the PWS would not in be violation as the quarterly average would be less than 4 ppt.”

Hazard Index for PFHxS, GenX chemicals, PFNA, and PFBS

The Hazard Index is a long-established tool the EPA regularly uses—for example, in the Superfund program—to understand the health risk from chemical mixtures. The EPA is proposing a Hazard Index MCL to limit any mixture containing one or more PFNA, PFHxS, PFBS, and/or GenX chemicals. The Hazard Index considers the different toxicities of PFNA, GenX chemicals, PFHxS, and PFBS. For these PFAS, water systems would use a Hazard Index calculation to determine if the combined levels of these PFAS in the drinking water pose a potential risk and require action.

To calculate the Hazard Index, it’s important to understand it’s made up of a sum of fractions. Each fraction compares the level of each PFAS measured in the water with the highest level determined not to have a risk of health effects.

To see an example of what this equation looks like, see the EPA Hazard Index Fact Sheet.

“Although the Hazard Index is intended to account for PFAS mixtures, the Index would apply to any combination of the four PFAS and could be exceeded even when just one of the four PFAS is present,” adds Vorys, Sater, Seymour and Pease. “Like the PFOS and PFOA MCLs, however, compliance with the Hazard Index MCL would be calculated using a running annual average approach under the proposed rule.”

PWS monitoring and reporting requirements

If finalized, the proposed regulation will require PWSs to monitor for these chemicals, as well as require systems to notify the public and reduce PFAS contamination if levels exceed the proposed regulatory standards. The EPA anticipates, if fully implemented, the rule will, over time, prevent thousands of deaths and reduce tens of thousands of serious PFAS-attributable illnesses. This action establishes nationwide protection from PFAS pollution for all people, including environmental justice communities.

PWSs have 3 years to conduct initial monitoring under the proposal, which also suggests a monitoring frequency of biannually or quarterly, depending on the size of the system.

PWSs that have previously collected monitoring data using approved EPA Methods 533 or 537.1 would be able to satisfy the initial monitoring requirements with this previous data, according to Vorys, Sater, Seymour and Pease. “PWSs would be eligible for reductions in compliance monitoring frequency if their monitoring results are below ‘trigger levels.’ The proposed rule sets the trigger level at 1.3 ppt for PFOA and PFOS, and a 0.33 Hazard Index (unitless) for mixtures of PFHxS, GenX Chemicals, PFNA, and PFBS. … PFOA and PFOS cannot be reliably detected below 4 ppt—USEPA, however, states in the proposed rule that these less definitive measurements are appropriate for establishing monitoring frequency.”

The proposed rule doesn’t allow the use of composite samples and doesn’t allow state agencies to grant monitoring waivers.

PWSs are already required to provide annual water quality reports to their customers. The proposed rule will require the addition of information regarding measured levels of PFOA, PFOS, PFHxS, GenX chemicals, PFNA, and PFBS, as well as the Hazard Index for the mixtures of PFHxS, GenX chemicals, PFNA, and PFBS to those annual reports.

State enforcement under the proposed rule will require states “to develop state regulations that are no less strict than the proposed rule within two years of the rule being finalized,” continues Vorys, Sater, Seymour and Pease.

PWS funding

Reducing PFAS in drinking water will likely require investments in water infrastructure. The Bipartisan Infrastructure Law provides $9 billion to invest in drinking water systems impacted by PFAS and other emerging contaminants. The EPA will ensure that states, tribes, and communities get their fair share of this federal water infrastructure investment, especially in disadvantaged communities. These funds include:

  • $4 billion in investment through the Drinking Water State Revolving Funds, including a requirement that states dedicate 25 percent of these resources to disadvantaged communities or PWSs serving fewer than 25,000 people.
  • $5 billion to communities as grants through the EPA’s new Emerging Contaminants in Small or Disadvantaged Communities (EC-SDC) Grant Program. This program will promote access to safe and clean water in small, rural, and disadvantaged communities while supporting local economies. In February 2023, the EPA announced the availability of the first $2 billion of this funding.

Several sources report PWSs are concerned about the cost of compliance.

“Iyala Simba, city programs director at the Illinois Environmental Council, says PFAS are miniscule chemical compounds that are impossible to see and impossible to avoid,” reports The Center Square. “‘This is something that a lot of water treatment plants are really afraid of because they can’t begin to cover the costs,’ Simba said.

“Municipalities are expected to initiate lawsuits against PFAS producers, including the U.S. military, which uses firefighting foam at airports and training facilities, and chemical companies DuPont, Chemours and 3M, which use PFAS in hundreds of applications from non-stick cookware and rain gear to construction materials and packaging,” The Center Square continues. “Previous guidelines for forever chemicals in drinking water were 70 parts per trillion. … Scientists say that 4ppt is a huge improvement, but they emphasize that no traceable level of forever chemicals in drinking water is ‘safe.’”

“I have long supported the implementation of a national drinking water standard to ensure that the water in our communities is clean and safe for consumption,” said Congressman Brian Fitzpatrick, co-chair of the Bipartisan Congressional PFAS Taskforce, in an EPA news release. “Today’s announcement is a step in the right direction as we work to prevent the future contamination of PFAS ‘forever chemicals’ in our water and I look forward to continuing to work with the Administration to enforce a high standard of water quality.”

The EPA requests input on the proposal from all stakeholders, including the public, water system managers, and public health professionals. Comments may be submitted through the public docket, identified by Docket ID No. EPA-HQ-OW-2022-0114, at

The EPA will also be holding a public hearing on May 4, 2023, which members of the public can register to attend and provide verbal comments to the EPA on the rule proposal. Registration is required, and the last day to register to speak at the hearing is April 28, 2023. For questions related to the public hearing, contact

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