What the HAL? Understanding EPA’s new PFAS Health Advisory Levels

On 15-June-2022, the EPA announced Interim Health Advisory Levels (HALs) for PFOS and PFOA (updated), and Final Health Advisory levels for GenX chemicals and PFBS. The PFOS and PFOA numbers were eye-popping!

  • Interim updated HAL for PFOA = 0.004 parts per trillion (ppt)
  • Interim updated HAL for PFOS = 0.02 ppt
  • Final HAL for GenX chemicals = 10 ppt
  • Final HAL for PFBS = 2,000 ppt

The EPA also released an informative frequently asked questions page that provides a lot of information on the rationale, what this announcement means and more.

The first question that came up was on measurement. 4 ppq?? What the HAL? Is that even possible. The short answer is, Yes, But!


Ultratrace labs all over the world routinely measure dioxins (2,3,7,8-TCDD specifically) down to 5 ppq, we take that for granted. These measurements are made on mass spectrometers nowhere as sensitive as what are available today. The mass spectrometer used at SGS AXYS for the dioxin method SGS AXYS ATP 16130 by GC-MS/MS is over 10 times more sensitive than a typical dioxin instrument, and our clean-water reporting limits on this instrument are 2 ppq. This mass spectrometer when used for PFOS/PFOA gives us the raw sensitivity needed if methods are designed similar to dioxin methods, with a high concentration factor going from sample to instrument.


Background, background, background. PFOS/PFOA are still ubiquitous and though our lab has tested down to a factor of 100 below the 4 ppt limit using sequestered rooms and preparation equipment, there’s still a bit more work to do.


If this measurement was truly required down to 4 ppq, it would likely involve a separate workflow from prep to instrument with pre-screening to eliminate any samples with PFAS detected even at low ppt/high ppq levels. Then yes, on a relatively clean water sample, we will get there if we can implement a 1613 type approach. A premium sensitivity instrument may also be required. There are other ways as well, but what I outlined here is based on what has been achieved routinely in other ultratrace methods.

Is this needed now?

Not quite. The EPA’s current measurement needs are much more modest as summarized in the table below from the EPA, based on what will be required for UCMR5:

Chemical Minimum Reporting Level (ppt) Lifetime Health Advisory Level (ppt)
PFOA 4 0.004 (Interim)
PFOS 4 0.02 (Interim)
GenX Chemicals 5 10 (Final)
PFBS 3 2,000 (Final)

However, we expect, given the HALs, for labs to need to go lower with time. We routinely report to a 0.4 ppt for example.

Larger context

It’s important to note that these are interim health advisory levels based strictly on toxicity calculations arising from the most sensitive end-point. As stated by the EPA:

“The most sensitive non-cancer effect and the basis for the interim updated health advisories for PFOA and PFOS is suppression of vaccine response (decreased serum antibody concentrations) in children.”

These HALs are health-based levels, not dependent on what’s achievable from a remediation or measurement standpoint. As the EPA states:

The proposal will include both a non-enforceable Maximum Contaminant Level Goal (MCLG) and an enforceable standard, or Maximum Contaminant Level (MCL) or Treatment Technique.The 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 an adequate margin of safety. The enforceable standard is set as close as feasible to MCLG. EPA considers the ability to measure and treat a contaminant as well as costs and benefits in setting the enforceable standard.

So, there’s lots more work to do before we get to an enforceable MCL, and we expect multiple stakeholders to push back on the health advisory levels as well, and the toxicity tests and assumptions involved.

For more information, please contact us using our webform at Contact Us – SGS AXYS.