The long-awaited fourth draft of US EPA Method 1633 was released in July 2023[i], as the product of a nearly 4-year collaboration between the U.S. Department of Defense (DoD) and the US EPA. A notice in the method provides that its use for Clean Water Act compliance monitoring will not be required until after it has been proposed and promulgated through rulemaking. The US EPA does not anticipate that criteria for landfill leachates, solids (soil), biosolids, and tissue samples will be added until the release of a subsequent draft later in 2023. Further out, a final version of the method will be produced for promulgation. Certainly, the path this method has taken enroute to public release and recommendation for use is unprecedented.

Since the July release, on August 7, 2023, the DoD released a Memorandum[ii]; the crux of which is that for work conducted under DoD contracts and task orders awarded after the signature date, the use of Draft Method 1633 is required for definitive analysis for matrices other than drinking water, and that work must be performed by a DoD-accredited laboratory. This includes per- and polyfluoroalkyl substances (PFAS) testing for regulatory compliance, risk assessment, comparison to a project screening or action level or to confirm absence. Other PFAS methods may only be used for screening to determine the presence or magnitude of PFAS concentration; however, the use of alternative screening methods must be approved by a DoD project representative.

This is an interesting twist in the tortured path PFAS testing for environmental samples has taken over the past 20+ years. It seems we have come to the point where an unproven method; one that has not even been subjected to Proposed Rulemaking, is being required for use to demonstrate regulatory compliance and environmental protection; whereas, fully promulgated and time-tested methods may only be used with prior approval for screening.

How have we come to this point and what does it mean as we move forward in attempting to understand the impacts and implications of the PFAS present in our surroundings?

A brief journey through the history of PFAS testing may shed some light on the subject. Although PFAS have been in commercial and industrial use for decades, it wasn’t until 2001, with the wide availability of liquid chromatography-tandem mass spectrometry (LC-MS/MS) equipment and the publication of the first comprehensive PFAS method using the technology,[iii] that the broader community was able to seek answers to the many questions around PFAS prevalence and relevance. A seminal article from 2004, authored by 21 top international PFAS researchers outlined the many challenges and shortcomings of numerous methods in use at the time and recommended appropriate procedures (Martin et al.).[iv] Subsequently, US EPA Method 537 was published in 2009,[v] which incorporated some of the recommendations from the Martin et al. article, notably solid-phase extraction (SPE) cleanup and internal standard calibration. The method was adopted by numerous commercial laboratories to support the completion of Third Unregulated Contaminant Monitoring Rule (UCMR 3, 2013 to 2015).[vi] This testing highlighted the extent of PFAS presence in public water systems (PWS) across the U.S. and the importance of military fire training areas, aqueous film-forming foam- (AFFF-) certified airports, and wastewater treatment plants as the sources of these impacts.[vii] It also highlighted the need for an improved drinking water testing method and a method for general environmental testing.

The publication of US EPA Method 537 in 2009 spurred many laboratories to modify the method for general environmental sample analysis according to published recommendations from academic and industry laboratories and DoD guidance, along with ASTM D7968-17a[viii] for solids/soils analysis. Although these in-house modified methods had very little resemblance to US EPA Method 537/537.1, they were – and often still are – colloquially referred to as 537.1m (modified) methods.

The year 2019 was a bit of a watershed year in the attempt to bring some consistency to these efforts. The DoD released QSM 5.3 in May, including Table B-15 to codify most of the procedural improvements in the 537.1m methods and standardize quality assurance (QA) criteria. In July 2019, the US EPA released Draft Method 8327[ix], which was tested in surface water, groundwater, and wastewater matrices. It was a bit of a step back; however, as it employed direct-injection (i.e., no SPE cleanup) with external standard calibration and weak branched and linear isomer identification.  Also in July 2019, the U.S. Secretary of Defense created a PFAS Task Force to “manage growing health concerns over releases of these substances and the effects on military installations and their surrounding communities,”[x] and in November of that year, the DoD released a memorandum[xi] stating that US EPA Draft Method 8327 was found to be unsuitable for DoD decision-making needs and that all DoD “Components” are to test media other than drinking water using methods that meet criteria of QSM 5.3 Table B-15. As well, SERDP/ESTCP Project ER19-1409 was initiated in November 2019 for the “Development and Validation of EPA Method 1633 for PFAS.” This was the impetus for the subsequent joint effort by the DoD and US EPA to develop a robust standardized method for PFAS testing in environmental samples – a full 15 years after the framework for such a method had been presented by Martin et al.

Finally, at the end of a very busy year in the PFAS world, the US EPA released Method 533.[xii] This Method included many of the procedural advances incorporated in the 537.1m methods and has proven to be robust for the determination of 25 PFAS commonly found in drinking water. In summary, by the end of 2019, there were two approved US EPA methods for drinking water testing, one being significantly more advanced than the other, and the environmental monitoring industry in the U.S. had reached a degree of standardization for PFAS environmental testing as it related to DoD installations. However, the method of choice, while colloquially referred to as a modification of the older drinking water method, included procedures that had much more in common with the newer US EPA Method 533.

The next step in this strange journey came in August of 2021, with the release of the first draft of US EPA Method 1633.[xiii] The DoD then released QSM 5.4 in October 2021, including the new Table B-24 with US EPA Draft Method 1633 QA requirements for reporting under DoD acceptance criteria, and in December, a second Memorandum[xiv] updating the provisions of the 2019 Memorandum and including a directive that all new contracts and task orders after December 31, 2021, would require the use of US EPA Draft Method 1633 for PFAS analysis in matrices other than drinking water. In laboratories across the continent, the race was on to set the method up and apply for accreditation.

As mentioned at the outset, US EPA Method 1633 Draft 4 was published in July 2023 and is finalized for wastewater, surface water, and groundwater. A final version containing data for the other matrices is pending. Of note, seven of the 40 PFAS compounds determined by this method are recognized as “poor performers,” despite the fact that they generally perform well in many of the 537.1m methods. This brings us back to the latest twist in this strange journey: the August 7, 2023 publication of the third DoD Memorandum,² requiring the use of US EPA Draft Method 1633 for all definitive analysis of PFAS in matrices other than drinking water, as it pertains to DoD Contracts or Task Orders. The US EPA is also recommending use of this method in general. While very little of this journey to an industry standardized method for PFAS environmental testing could be defined as ‘normal,’ this latest twist gives more than a little pause for thought.

• The DoD is requiring the use of a method that has yet to undergo even Proposed Rulemaking, which hasn’t yet been finalized for several important matrices – soil and landfill leachate – to meet requirements under various laws (g., CERCLA, CWA and RCRA).
• For DoD sites, approved US EPA methods may only be used for screening, and then only with prior approval.
• Despite its good performance track-record, US EPA Method 533 cannot be used for definitive analysis for pristine water samples on DoD sites.
• Despite its poor performance for seven PFAS precursor compounds, US EPA Method 1633 is required for reporting these compounds for regulatory compliance, risk assessment, comparison to a project screening or action level or to confirm absence.
• is explicitly recommending use of a method that has not been formally approved.

It also raises questions around the impacts of implementation of these recommendations and directives. Suffice it to say, demand for US EPA Method 1633 is set to increase exponentially. At the same time, the industry has become accustomed to the price points and turn-around times commercial laboratories have been able to provide with their “537.1m” methods.

• Will laboratories be able to build out capacity fast enough to meet the demand?
• Will suppliers be able to keep up with demand for standards, reagents and consumables?
• Will laboratories need to resort to increased detection limits to manage demand amid limited availability of consumables free of background?
• How will laboratories handle the seven PFAS precursors that frequently fail Table B24 criteria with this method?
• How will laboratories respond given the extra expense and complexity inherent with Method 1633? Will laboratories be looking for enhancements and efficiencies in their processes to meet these expectations while retaining required margins?
• Will laboratories actually be compliant with Method 1633 once these competing priorities balance out?

The industry has been wishing for a robust standardized method for environmental PFAS testing for nearly two decades now. With Method 1633, have we opened the door to a new and brighter future or are we looking into Pandora’s box? Perhaps we should be careful what we wish for!