Site loading image

Regulatory Updates

EPA Announces Updated Drinking Water Health Advisories for Four PFAS Chemicals: PFOS, PFOA, PFBS, & GenX

Emily Larson, Elizabeth Denly, & Catriona Smith | June 27, 2022

On June 15, 2022, the U.S. Environmental Protection Agency (EPA) released updated Health Advisory (HA) Levels for four per- and polyfluoroalkyl substances (PFAS) in drinking water, replacing the HAs that EPA previously issued in 2016. HA Levels are non-regulatory, non-enforceable, chemical-specific drinking water levels where exposure at or below is not anticipated to cause adverse human health effects. This action is in accordance with EPA’s PFAS Strategic Roadmap and is in support of EPA’s development of the National Primary Drinking Water Regulation (NPDWR) for PFAS.

The new PFAS HAs are shown below for the four PFAS including, perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorobutane sulfonic acid (PFBS) and hexafluoropropylene oxide dimer acid (HFPO-DA) and its ammonium salt (known as “GenX” chemicals). Additionally, the current lowest analytical reporting limit (the lowest concentration that current analytical technology can accurately report) is also included in the table for reference.

Chemical Minimum Reporting Limit (ppt) 2016 EPA Health Advisory Level (ppt) 2022 EPA HAL (ppt)
PFOA 4 70 (individual and combined) 0.004 (Interim)
PFOS 4 0.02 (Interim)
GenX Chemicals 5 NA 10 (Final)
PFBS 3 NA 2,000 (Final)
ppt = parts per trillion (nanograms per liter)

Interpreting the HA Values:

  • PFOA/PFOS HAs are interim levels; associated health effects assessments for each chemical are in draft form
  • GenX/PFBS HAs are final levels
  • Any detection of PFOA/PFOS can be inferred as an exceedance of the interim HAs
  • It’s confusing to impose criteria that cannot be measured; with the ubiquitous nature of PFAS and the potential for cross-contamination, it is currently impossible to measure PFOA and PFOS down to these low levels
  • It’s confusing to impose criteria that cannot be achieved by current specialized waste treatment technologies
  • The 21 states listed below that adopted, use or plan to use the previous EPA HA of 70 parts per trillion (ppt) for PFOA and PFOS may have to determine if they will implement the new levels; however, since these are interim values, that shift may be premature:
    • Alabama, Alaska, Arizona, Colorado, Delaware, Florida, Idaho, Iowa, Kansas, Kentucky, Missouri, Montana, Nebraska, New Mexico, Ohio, Pennsylvania, Rhode Island, Tennessee, Virginia, West Virginia, Wyoming

Why are the PFOA/PFOS Values So Low?

There are three main input factors that contribute to the derivation of the interim HAs:

  1. The noncancer Reference Dose (RfD) – the toxicity value that establishes the “safe level” for ingestion of a contaminant
  2. The Relative Source Contribution (RSC) – the portion of an individual’s total exposure to a contaminant that is attributed to drinking water ingestion
  3. Body Weight-Adjusted Drinking Water intake (DWI-BW) – exposure factor for the liters of water an individual consumes per day normalized to body weight

For both PFOA and PFOS:

  • RSC = assumed 20% of exposure is through drinking water (80% other sources)
  • RfD = derived from the epidemiological study showing decreased serum antibody concentration in children (suppression of vaccine response)
  • DWI-BW = a standard USEPA exposure factor that was based on the receptor (5-year-old) in the epidemiological study used to derive the RfD

While the RSC and the DWI-BW are standard values that are generally viewed as reasonable, the derivation of the RfD is subject to criticism with only a single epidemiological study as the basis. One of the many recommendations from the SAB in their April 2022 release of its review of the PFOS/PFOA toxicity assessment, was that the EPA should consider multiple human and animal studies for various endpoints to provide convergent evidence that is more reliable than a single study or health endpoint.

Additional Information

  • With the release of the interim HAs, EPA also released $1 billion in grant funding (part of President Biden’s Bipartisan Infrastructure Law) for general technical assistance, water quality testing, contractor training and installation of treatment technologies to help reduce PFAS in drinking water in small or disadvantaged communities facing disproportionate PFAS impacts
  • A cancer-based toxicity value (cancer slope factor [CSF]) will be developed for PFOA as part of the NPDWR
  • The proposed NPDWRs for PFOA/PFOS are anticipated to be released in fall 2022 with finalization in fall 2023
  • The current HALs do not incorporate the SAB’s most recent recommendations
  • According to the EPA PFAS HA webinar on June 23, 2022, if the EPA revises the HAs, they do not anticipate the new levels to exceed the Method Detection Limit (MDL) for PFOA/PFOS

Don’t Panic: Key Considerations

  • EPA’s release of unattainable chemical values is not unprecedented; in 2000, the EPA proposed an arsenic MCL that needed to be reassessed, then was eventually doubled, due to a national debate surrounding the science and costs associated with the ruling
  • Before the EPA can finalize the HAs and subsequently the Maximum Contaminant Level (MCL) for PFOA/PFOS, they will have to address the Science Advisory Board’s (SAB’s) numerous suggestions
  • EPA reassures that these HAs are subject to change and also acknowledges that the interim values may be updated or removed altogether
  • A proposed impending MCL will consider both the science (toxicity and treatment technology) and the economics and will likely be higher than the HAs

In the meantime, calming public concern and addressing public confusion will be at the top of state and municipality agendas.

For more information on managing PFAS at your facility and public outreach efforts, please contact:

Emily Larson, Environmental Risk Assessor

Elizabeth Denly, ASQ CMQ/OE Vice President, PFAS Initiative Leader & Chemistry Director

Catriona V. Smith, R.E.M. Vice President

Emily Larson

Emily Larson has more than 10 years of experience modeling the bioaccumulation of semivolatile compounds and metals in ecological systems, modeling exposure to human and ecological receptors, and preparing human health and ecological risk assessments. She has experience conducting risk assessments with emerging contaminants, specifically per-and polyfluoroalkyl substances (PFAS). In addition, she serves as a technical expert on PFAS within the intermountain region for TRC. She has experience with Superfund (CERCLA) as well as several state-led programs specifically in the Inter Mountain West and Pacific Northwest regions. Emily has worked with several clients in both the private and the public (state and federal) sector. She can be reached at

Elizabeth Denly

Elizabeth Denly serves as TRC’s Vice President, PFAS Initiative Leader. She is also the Quality Assurance & Chemistry Director, responsible for the creation and implementation of the Quality Management Plan and standard operating procedures (SOPs) for field sampling and documentation protocols. Ms. Denly also leads Quality Coordinator networks, which are responsible for the development and communication of quality initiatives within the organization. She is a chemist with 29 years of consulting experience encompassing field and laboratory analyses and audits, QA/QC, data validation, and consulting for regulatory agencies.

Ms. Denly is a leader in ITRC’s PFAS and TPH Risk Work Groups and in TRC’s Center of Research & Expertise (CORE) Emerging Contaminants Team and received the ITRC’s Industry Member of the Year Award in 2017. She is currently focusing on PFAS, specifically the nomenclature, chemistry, sampling procedures, QA/QC, and laboratory analytical methodologies, and has a significant role in educating clients, attorneys, and regulators about PFAS.

As a senior QA specialist at TRC, Ms. Denly is responsible for providing QA/QC oversight in support of a variety of environmental investigations and remediation programs including risk-based soil cleanups, ambient air monitoring, and human health and ecological risk assessments. In this role, she has directed the preparation of QAPPs, coordination with the laboratory, selection of the appropriate analytical methodologies to achieve the desired remedial standards, oversight and performance of the data validation process, and determination of the usability of the data and achievement of data objectives. Ms. Denly has provided this oversight under different regulatory programs.
Read more on Ms. Denly’s bio page. Please contact her at

Catriona Smith

Catriona (Cat) Smith has over 30 years of professional experience in the interpretation and application of regulations for industrial facilities relating to compliance, remediation and negotiations with regulatory agencies. Her clients include upstream and downstream oil and gas, chem-pharma, petrochem, manufacturing and federal, state, and local governments. Ms. Smith is a Vice President and Environmental Sector Market Director for TRC, with nationwide responsibilities to manage our clients’ PFAS challenges, support and grow our Oil and Gas clients and bring multi-disciplinary solutions to their complex projects. Contact Cat at

Looking for effective solutions to your problems?

Turn to the experts at TRC.

By clicking "Accept", you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Read our Privacy Policy.