by Grant Lobdell
PFAS is an acronym for a group of man-made per- and polyfluoroalkyl substances. While a lot of attention has been given to a couple of molecules within this group such as PFOA (perfluorooctanoic acid, Figure 1) and PFOS (perfluorooctanesulfonic acid, Figure 2), this group of substances consists of thousands of known molecules.
What do all PFAS chemicals have in common?
All PFAS molecules contain a carbon to fluorine bond. This is one of the strongest chemical bonds known to man which made PFAS molecules very stable over long periods of time. For a company looking for an edge in a market, the use of these chemicals could result in a longer-lasting product which would be a huge advantage over the competition. Because PFAS molecules were also found to be excellent surfactants, that is they lower the surface tension between two liquids, they became prevalent for applications where a reduction in surface tension was needed. For example, a frying pan coated with a PFAS chemical would save a consumer countless hours of scrubbing pans over several years if properly maintained.
However, a problem arises whenever chemicals end up where they were not originally intended to be. PFAS chemicals drained or leaked into water supplies, will eventually lead to their accumulation in the bloodstreams of living creatures. One of the properties that made these chemicals so great in various applications, their incredibly stable nature, becomes a problem in the body. Neither the body nor mother nature appears to have a mechanism currently capable of breaking down and/or removing these molecules effectively. While these molecules are great surfactants, they do not appear to serve any beneficial function in living creatures. In fact, several studies have been published suggesting these molecules can have a negative impact on health.
PFAS and Firefighting Foam
PFAS molecules are synonymous with firefighting foam. Their ability to lower the surface tension of a firefighting foam solution gave rise to an extra layer of protection: the film formation. No longer did foams work simply by smothering a fire with a foam blanket. They were also able to produce a thin layer of PFAS solution that would sit on top of the fuel and between the foam blanket due to its low surface tension. These foams were named Aqueous Film Forming Foams (AFFF) after this feature. Fluorochemicals were also added to protein-based foams to make film-forming fluoroprotein and fluoroprotein foams. The addition of fluorochemical surfactants improved firefighting effectiveness and quickly became synonymous with long-lasting, quality foam.
As is the case with much in life, there are pros and cons to this new technology. While AFFF, FFFP, and fluoroproteins did perform better in most cases than its fluorine-free counterparts of the day, it rather easily introduced PFAS into the water supply as the foam solution was allowed to drain into storm and sewer drains for years. As a result, while it may be true that most of the PFAS molecules ever made may have been used in applications other than firefighting foam, the foam industry has been under quite a bit of scrutiny due to the nature of their application.
Upon the discovery of the negatives of PFAS, several foam manufactures did act. 3M ultimately decided to quit manufacturing firefighting foam in the early 2000s. Other manufacturers, under the belief that the larger PFAS molecules, that is those PFAS molecules containing eight or more carbons, were the only issue, started to turn to smaller PFAS alternatives. Foam formulations that featured fluorosurfactants with primarily 6 carbons (dubbed C6 by the industry) vs 8 carbons (dubbed C8 by the industry) have been the norm for some time. It should be noted that while manufacturers have only really pushed the advertisement of pure C6 formulations in the last few years, the formulations for quite some time were C6 based with just trace amounts of C8 coming from impurities in the manufacturing process which have now been resolved.
Because increasing regulations are focused on PFAS in general and not just the larger, C8 PFAS molecules, the firefighting foam industry is increasingly developing and evaluating fluorine-free alternatives. While protein-based foams are a fluorine-free alternative that have been around for quite some time, the industry desires to produce a synthetic foam of equal or greater performance than the current fluorinated foams. Only time will tell if such aspirations are possible. In applications where foams featuring PFAS are still allowed due to performance concerns over the current fluorine-free alternatives, proper containment and disposal are advised.
Testing for PFAS in Firefighting Foam
Remember that the term PFAS is an acronym for a group of thousands of chemicals. Asking a laboratory to not only find one needle in a haystack but thousands can be quite the task. As such, most testing to date has been done with a most wanted approach. That is, the laboratory looks for and reports only on a few of the more common molecules such as PFOS and PFOA. Today, most laboratories may typically look for around 20 or 30 different PFAS molecules using analytical techniques called high performance liquid chromatography (HPLC) and mass spectroscopy (MS). The Environmental Protection Agency (EPA) Method 537 Determination of Selected Perfluorinated Alkyl Acids in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS) is a water testing standard that calls for such analytical techniques. Where a standard exists of a PFAS molecule, a laboratory using HPLC/MS may be able to find and quantify that molecule. In fact, HPLC/MS techniques have become so advanced over the years that laboratories may be able to report low part per trillion (ppt) levels of concentration although the repeatability of such tests should always be considered. To illustrate how little 1 ppt is, think of this: 1 ppt is equivalent to just 1 second in 31,709 years.
Looking for just 20-30 of potentially thousands of molecules, unfortunately, does not give the whole picture in terms of PFAS concentration. As a result, a new analytical approach is starting to be adopted by the industry. Using a combination of combustion ion chromatography (CIC) and ion chromatography (IC), a laboratory can determine the amount of fluorine bound to carbon contained in a sample (dubbed organic fluorine by the industry). By looking for just fluorine, a laboratory can get a sense of the PFAS concentration in general. The drawback of this approach is that the analysis will not be able to report any concentration of specific PFAS molecules. In a world where money is no object, one would do both: quantify the most wanted PFAS molecules and then look to see if the fluorine from those molecules account for the vast majority of the fluorine found in the sample. If the fluorine contained in the PFAS molecules identified is much less than the fluorine found, then the laboratory hasn’t found the majority of the PFAS molecules in the sample yet. Some PFAS regulations are starting to be set simply based on total fluorine instead of by individual PFAS molecules. For example, Clean Production Action’s eco-label certification, GreenScreen CertifiedTM, defines a PFAS free foam as having < 1 ppm total organic fluorine as measured by combustion ion chromatography.
If you have any questions regarding this article, please contact Dyne Fire Protection Labs at lab@dyneusa.com or (800) 632-2304.
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