PFAS Dark Matter: Per- and polyfluorinated precursors in soil and water Pat Benvenuto, Heather Lord, Terry Obal, Maxxam Analytics, Mississauga, ON Canada

Do You Know How Much PFAS Is On Your Site? Presentation Outline PFAS Background Chemical and Physical Properties Problem of PFAS Precursor Transformation TOP Assay Experimental Water and Soil Data Method Considerations Provide some background on PFASs. Show some experimental data where the top assay was applied to water and soil samples

PFASs What are PFAS? PFASs are Per- and PolyFluorinated Alkyl Substances. Exclusively anthropogenic. Structures contain a hydrophobic perfluoroalkyl backbone and a hydrophillic end group Include a diverse range of compounds with a variety of chain lengths and end groups Hydrophobic Hydrophillic Perfluorooctanoic acid PFOA Teflon® 8:2 Fluorotelomer sulfonate 8:2 FTS The acronym PFAS stands for For FTS nomenclature - ratio of fluorinated carbons to hydrogenated carbons Mention that chains don’t have to be linear. Branched chain congeners too. Make mention that part of FTS is per and the other is poly (maybe)

Perfluorocarboxylic acids PFAS crash course: Within PFAS, compounds are further organized into classes PFOA is part of the perfluorocarboxylic acids (PFCA) class Structure # of Carbons Name 4 Perfluorobutanoic acid (PFBA) PFCAs Carboxylic Acid 8 Perfluorooctanoic acid (PFOA) 12 Perfluorododecanoic acid (PFDoA) -within that class you see that the end group is conserved. This is the carboxylic acid and the perfluoroalkyl chain varies in length. -PFOA, a well known perfluorinated compound is part of this class.

Perfluorosulfonates PFAS crash course continued… Perfluorosulfonates is another important class PFOS belongs to this class Structure # of Carbons Name 4 Perfluorobutane sulfonate (PFBS) Perfluoro- sulfonates Sulfonate 8 Perfluorooctane sulfonate (PFOS) 10 Perfluorodecane sulfonate (PFDS)

Chemical and physical properties CF bonds are very strong End groups may be reactive and transformed Good stability under heat and chemical stress Low volatility Soluble in water Good surfactants Sorb to a variety of materials Perfluorooctane sulfonate PFOS Scotchguard® -Stress chemical and physical properties for PFASs in the general sense -Reaction at the sulfonate group but little transformation through the perfluoroalkyl chain

Where do they come from? Industrial Uses PFAS are used in a variety of applications because of their chemical and physical properties. These include: Industrial polymers (Teflon® - PFOA) Stain repellants (Scotch Guard® - PFOS) Aqueous film forming foams (AFFF) – fire fighting applications Sources Can be found anywhere at differing (generally lower) concentrations, Areas of elevated concentration and concern are: Airports Run-off from incidents of fire Landfill leachate WWTP effluent -because of their chemical stability, surfactant properties….. Attributes of PFAS - stability, water solubility also reason for them being hazards AFFF is PFOS. Maximum allowable concentration is now regulated. Shift towards polyfluorotelomer sulfonate variants in newer formulations Waste water treatment plant

Toxicology Commercial PFAS detected in humans - possible sources of exposure include drinking water, food and dust/ambient air Persistent Bioaccumulate Toxicity of certain PFASs such as PFOA and PFOS has been observed in some rodent studies Potential for deleterious effects in humans is suspected and is under further study PFOS was added to Annex B of the Stockholm Convention on Persistent Organic Pollutants (POP) in May 2009 The industrial attributes of PFAS (stability, water solubility) are also reason for them being hazards Fluorotelomers were being used in packaging at mac and BK. They were being phased out in early to mid 2000s

Soil Concentration (µg/g) Regulatory status In Canada: Risk management strategies seek to have environmental PFOS concentrations as low as possible, prevent re-introduction to market, and address remaining uses (restrictions, exemptions, BMP etc.) On and after May 29, 2013, manufacture, use, sale, import of PFOS and PFOS-containing products is prohibited in Canada Limit Guidelines:   Drinking Water Soil Concentration (µg/g) Jurisidiction PFAS Concentration (µg/L) Residential Commercial Industrial Canada - Health Canada PFOA 0.2 0.85 1.28 12.1 PFOS 0.6 2.1 3.2 30.5 U.S.A - EPA 0.07 - U.S.A - EPA Region IV 16 6 *When both PFOA and PFOS are present, their combined ratio of measured to screening value should not exceed 1 ** 0.07 µg/L combined when both PFOA and PFOS are present in drinking water Health Canada drinking water/soil screening values/proposed max acceptable concentrations (January 2017), EPA lifetime Health Advisory (2016) for drinking water and EPA emerging contaminants for soil screening value (2014). Effort to reduce/eliminate PFOS and PFOA in Canada and the US, and in some cases compounds that degraded to these PFASs C8 PFASs most abundantly produced according to Houtz and Sedlak and EPA. More data/study of commonly used PFOA and PFOS hence why regulations tend to focus on these compounds. http://healthycanadians.gc.ca/health-system-systeme-sante/consultations/perfluorooctane-sulfonate/document-eng.php Best management practice

PFAS Precursor Pool Much larger PFAS compounds – “Precursors” - are often released along with those typically monitored. PFAS precursors are themselves PFAS. Problem: Evidence suggests precursors can be transformed, through biological and environmental processes, to target PFAS of interest such as PFOA Overlooking precursor pool may lead to underestimates of target PFAS of interest Pool of potential precursors is large and generally unknown – PFAS “Dark Matter” What is Needed: A method to estimate the potential magnitude of the precursor pool PFAS Precursor PFOA Natural Processes PFOSA -We have these persistent perfluorinated compounds that are potentially harmful and whose regulatory limits are pretty low. In the current sequence of events… -From a remediation standpoint, not considering pool of precursors may underestimate scale and scope of remediation strategy and also the strategy might alter the PFAS composition at the contaminated site

Total Oxidizable Precursor (TOP) Assay Background Chemical oxidation method developed by Houtz and Sedlak1 Transforms PFAS precursors to perfluorocarboxylic acid (PFCA) end products without affecting target PFAS Accelerated “mimic” of the natural transformation of PFAS precursors How it works Heat and persulfate generate hydroxyl radicals Hydroxyl radicals react with PFAS precursors and break them down to compounds such as PFOA and other carboxylic acid end products Based on laboratory spiking experiments S2O82 Heat OH Persulfate Hydroxyl Radical C8 Precursor C7 PFOA C3-7 PFCAs (1) (2) 1Houtz, E.F. and Sedlak, D.L. (2012). Environ. Sci. Technol., 46, 9342-9349. -One possibility is through the use of the TOP Assay -Point out that natural may be a misnomer and will be discussed later in the presentation. -State that only the precursor is transformed, not the target PFAS -Sulfate radical can react with PFOA, but its formation to OH radical is faster under these conditions -PFSAs are produced from PFAS precursors through microbial and biological process, but under the TOP assay conditions, PFCAs are produced -PFOA not oxidized by OH radical to a high degree

TOP Assay Example Workflow Before TOP Assay PFAS Precursor Quantify targets and precursors Sample - Water - Soil 8:2 Fluorotelomer sulfonate (C10 total, C8 containing F) LC/MS/MS Analysis Oxidation OH ( ) After TOP Assay Quantify targets and precursors Perfluorooctanoic acid (C8) Perfluorohexanoic acid (C6) Reacted Sample LC/MS/MS Analysis Perfluoroheptanoic acid (C7) Perfluorobutanoic acid (C4) -First, quantify PFASs prior to oxidation, make mention that the “before” stream is our PFAS test which we’ve been doing for approximately 1 yr? Second, oxidize sample according to reaction previously mentioned Third, quantify PFASs after oxidation and then compare targets and precursors before and after to estimate magnitude of pool -Before we have precursor and PFBA -After, we have no precursor left, but we now have PFOA, C7, C6 and PFBA from before -Note that all products shorter chain length and PFCAs -So basically we quantify the PFASs before and after oxidation

PFAS Target List Target PFAS and Precursors Pool of PFAS targets and precursors is large. Maxxam monitors 16 target PFAS and 9 precursors Target PFAS (16 total) Perfluorocarboxylic Acids: C4 to C14 Perfluorosulfonates: C4, C6-C8 and C10 Precursors: Perfluorooctane sulfonamide (PFOSA) N-methylperfluorooctane sulfonamide (MeFOSA ) N-ethylperfluorooctane sulfonamide (EtFOSA ) N-methylperfluorooctane sulfonamidoethanol (MeFOSE) N-ethylperfluorooctane sulfonamidoethanol (EtFOSE) N-methylperfluorooctane sulfonamidoacetic acid (MeFOSAA) N-ethylperfluorooctane sulfonamidoacetic acid (EtFOSAA) 6:2 Fluorotelomer sulfonate (6:2FTS) 8:2 Fluorotelomer sulfonate (8:2 FTS) -Pool of targets and precursors is very large. We monitor 16 target PFASs and 9 precursors. These do not include all precursors, just ones of interest

TOP Assay: Application and Results

Product Conversion (%) Product Conversion (%) Product Conversion (%) TOP Assay Results Individual precursor oxidation Known amount of an individual precursor was spiked in water and taken through the TOP assay Detected breakdown products were expressed as a molar percentage relative to the spiked amount N-methylperfluorooctane sulfonamidoacetic acid (MeFOSAA) 6:2 Fluorotelomer sulfonate (6:2 FTS) 8:2 Fluorotelomer sulfonate (8:2 FTS) 6:2 FTS Precursor Breakdown Product(s) Product Conversion (%) Perfluorobutanoic acid (C4) 25 Perfluoropentanoic acid (C5) 29 Perfluorohexanoic acid (C6) 20 Perfluoroheptanoic acid (C7) 2 6:2 FtS 1   Sum 77 8:2 FTS Precursor Breakdown Product(s) Product Conversion (%) Perfluorobutanoic acid (C4) 12 Perfluoropentanoic acid (C5) 17 Perfluorohexanoic acid (C6) 20 Perfluoroheptanoic acid (C7) 22 Perfluorooctanoic acid (C8) Perfluorononanoic acid (C9) 2 8:2 FtS 1   sum 91 MeFOSAA Precursor Breakdown Product(s) Product Conversion (%) Perfluorooctanoic acid (C8) 92   Sum Recall that perfluorocarboxylic acids have the following structure where n = 3 – 13 for the target PFAS -This is a controlled experiment that demonstrates what the TOP assay does to precursors -all breakdown products are PFCAs, identity of precursor in terms of dictating breakdown products formed ex PFOA, overlap of certain breakdown products amongst precursors -Some unconverted precursor for FTSs, but very little -note that PFOA not a product of 6:2 FTS, one of several in 8:2 FTS and the only/major product in MeFOSAA -If we were considering a hypothetical sample whereby only 8:2 FTS and MeFOSSA were detected, you can see that considerable PFOA could be formed through natural processes. This is the problem of PFAS precursor transformation -remaining mass balance resides in compounds not captured by the target list of 16 target PFASs and 9 precursors

TOP Assay Results Groundwater Sample Precursors Carboxylic acids Sulfonates -applying the TOP assay to a water sample -again we monitor the target PFASs and precursors before and after the TOP Assay -see that precursors fall to below detection limits after oxidation. Then we have increases in…. -not much (not 1.5X) change in the heptane and octane sulfonates (STATE THAT PFOS is still part of this sample, just scaling). But we do have an increase in the butane and hexane sulfonate. This is likely coming from a unknown precursor. -It is tempting to attribute increases in targets to just one compound, 6:2 FTS in this case (we know this precursor generates C4, C5 and C6). However the scenario is more complicated. Is it a contributor to C4-6, certainly, is it the main contributor, cannot tell with this kind of data representation. More data manipulation would be necessary to try and answer this question. Answering this question may not be possible with just one simple measurement. So while we get useful information about the magnitude of the pool and the effects on target compounds, TOP assay cannot really tell you main cause of increases because of the PFAS dark matter. Could be more precursors present than just the ones we’re looking for.

TOP Assay Results Soil Sample No literature precedent for TOP assay on soils. Method had to be developed by Maxxam. Two different methods to extract PFASs from soils were evaluated Slurry method does not separate soil and solvent whereas extract method does TOP assay performed for both extraction methods -looking at TOP Assay in soil…. -for slurry soil and solvent analyzed together and for extract only the solvent extract is analyzed -we see increases in……after the TOP assay. Carboxylic acids Sulfonates

TOP Assay Results Soil Sample continued… Observations: (Carboxylic acid) (Sulfonate) (Carboxylic acid) (Sulfonate) Observations: No precursors detected – PFAS dark matter Slurry and extract results comparable Extract method appears to generate slightly more target PFAS on average -This is all still from the same sample -if you noticed, of the precursors we monitor, none were detected. So the increases are likely coming from unknown precursors – that PFAS dark matter -we’re also seeing increases in sulfonates, suggesting that there may be sulfonate precursors being oxidized -Extract method slightly more recovery than slurry method -Overall, comparable trends to what was seen for water sample. (Sulfonate)

Considerations Items to note Method is limited to compounds that are oxidizable by the TOP Assay – the precursor pool may be underestimated if not all precursors are transformed/oxidized. Not all of the PFAS that are produced during the TOP assay necessarily originate from only the 9 precursors that are monitored – pool of precursors is large. Similarly, there could be numerous target PFAS that are produced beyond the 16 that are currently monitored. It is unknown if all precursors are fully oxidized by the TOP assay. Not certain how representative the TOP assay is of the transformations that would occur naturally. Variable site conditions, e.g. soil chemistry, oxidation state? Timescale? -this is why “natural” was put in quotation marks. Since we don’t know how closely TOP assay matches natural conversion -originating – this is what I was speaking about earlier in trying to trace the increases in target PFASs to a few precursors -its also difficult to determine cause and effect. For instance, end products can be share breakdown products as shown in the precursor experiment. And the data we report really isn’t meant to be interpreted that way.

Conclusions What the TOP Assay offers Quick and simple method of PFAS oxidation performed on soil and water. Report provides concentrations of 25 PFAS before and after oxidation as well as the magnitude of the change. Estimate of magnitude of target PFAS increase that could occur at a contaminated site. Potential indication of which precursors are being oxidized. Assay will become more informative as more PFAS targets and precursors of concern are added to the analysis list.

ACKNOWLEDGEMENTS Christopher Atkinson Sin Chii Chia Dany Marqass Consuelo Perez Adam Robinson