PFAS: The Forever Problem

How big is the PFAS problem?
 

At this point, it is not surprising to find PFAS in the environment given its widespread use across industries. And although we understand the prevalence of PFAS, we are still learning about the types of toxicity and the effect of different concentrations of PFAS in our water, soil, air, food, and residing in our blood.

The main challenges are in sample preparation because we’re looking for PFAS in so many different matrices. Of course, the dirtier the matrix, the less robust the method. Another major challenge is background contamination that comes from reagents, plastics, and instrument components.

In food and beverage specifically, different food matrices – especially fatty foods – affect analysis, so additional clean up steps are required. In addition to matrices, as detection limit requirements go lower, it will be increasingly hard to identify and quantify the PFAS present in each sample.

Furthermore, recent guidance for EU Reference Laboratories for food and feed recommends parts-per-quadrillion (ppq) detection levels, which is raising concerns from contract and high-throughput laboratories. This contrasts with 70 ppt-level recommended by health advisories in the US and EU water authorities. The challenge is not instrumentation capabilities, but the removal of background contamination in the analysis workflow from solvents, vials, plastics, coatings, and so forth. 

What main methods are used to detect PFAS?
 

The first validated methods in the US were EPA 537, 537.1 and 533. These methods used solid phase extraction (SPE) followed by LC-MS/MS detection and were approved for use with drinking water only. EPA methods tend to favor SPE, which cleans and concentrates samples, providing lower detection limits and more injections without having to reclean any instrumentation. These are working well for the current compound list and the most common detection limits and the relatively clean drinking water matrices they are designed for.

The EPA is in the process of validating a method for non-potable waters, solids, biosolids, and tissues known as EPA 1633. Like the EPA’s methods for drinking water, it uses SPE followed by LC-MS/MS, yet it must meet recovery and lower detection limits for a broader range of PFAS compounds in dirtier matrices. In addition, the method uses additional clean up steps to remove background interferences – and that requires more time and incurs a greater cost.

There are other direct injection methods, such as those developed by the American Society for Test Methods (ASTM) D7979 and D8421, that do not use SPE. In these cases, the lab must decide if they can meet the detection limits with their instrumentation and whether clean-up and preconcentration steps are required.

Are new developments or analytical advances needed to address some of the challenges previously mentioned? 
 

Current methods are based on a limited set of PFAS compounds and more work needs to be done to determine whether unknown PFAS compounds exist in these same samples, especially as the list of PFAS compounds under investigation by the US and EU regulators continues to grow. 

To truly grasp the scale of this PFAS problem – and if the goals is to ultimately make effective regulations – toxicology and prevalence of PFAS in food and drinking water should be considered together, not as separate issues.

I am hopeful regulators will soon validate methods for PFAS detection from serum and urine samples, informing our understanding of the PFAS compounds most commonly found in the human body and that will help provide additional evidence for any regulatory determinations.

Because toxicology data requires much more rigor to implement and must clear a higher threshold to justify government action of some kind, our analytical knowledge tends to run slightly ahead of regulatory determinations.

Overall, how would you characterize the current state of the PFAS detection field?
 

We have recently seen 3M decide to phase out PFAS production and plans to ban over 1000 PFAS compounds are under consideration in EU. Unfortunately, the tough nature of these “forever chemicals” means they’ll be with us and future generations for many, many years – if not centuries. Substitute compounds need to be developed immediately to accelerate the justification for a global PFAS ban.

However, overall I think solid progress is being made in terms of detection; it’s really quite astounding how low we can go!

_{Richard Jack is the Global Market Development Manager for Environmental and Food Markets at Phenomenex. He has spent nearly 20 years in chromatography and mass spectrometry, and worked with a range of global regulatory agencies, including the US Environmental Protection Agency, on water analysis, hydraulic fracturing, and PFAS detection. He received his PhD in biochemistry and anaerobic microbiology from Virginia Tech University.}