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According to a recent study from Harvard University, the US EPA, and NIEHS, traditional targeted analysis techniques poorly characterize the PFAS composition of contemporary PFAS-based firefighting foams, know as aqueous film-forming foams (AFFF).  Using the EPA 533 PFAS drinking water method for the analyte list, the researchers found that targeted mass spectrometry methods accounted for <1% of organic fluorine content.  This is important because it demonstrates that targeted analysis methods miss nearly all the PFAS compounds in modern AFFF mixtures, thus underestimating the risk to human health and the environment.

In the second episode of PFAS Fireside chats, the lead author, Bridger Ruyle, joined me to discuss the study’s main findings and implications.  Bridger is a PhD student in Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Science.        

The study examined both legacy and modern commercial AFFF mixtures.  AFFF are used to combat petroleum-based fires by creating a barrier between the fire and air, and they are they used extensively at airports and by the military around the globe. 

If targeted analytical methods don’t adequately capture all the PFAS compounds in a sample, how did the researchers know what they were missing?  First, the researchers used techniques such as “extractable organofluorine (EOF)” to quantify the total potential PFAS compounds in the AFFF mixtures.  That is how they showed their targeted methods were missing a substantial portion of the PFAS.  Next, they used high-resolution accurate mass spectrometry to identify the unknown PFAS. 

So, what’s in these modern AFFF mixtures?  It turns out that >90% of the PFAS compounds are 6:2 fluorotelomer-based compounds.  While the exact fate of these isn’t well understood, they could potentially degrade to very persistent PFAS compounds, several of which are covered by various state and federal regulations.

The study focused on commercial AFFF mixtures, but what does it look like in the real-world environment where AFFF releases have impacted the surface and groundwater?  Bridger and his colleagues addressed that question in a follow-up paper, and perhaps we will talk about it in a future episode of PFAS Fireside chats.

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