Perfluoroalkyl and polyfluoroalkyl substances (PFASs) in the environment: terminology, classification and origins

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1 1 2 Perfluoroalkyl and polyfluoroalkyl substances (PFASs) in the environment: terminology, classification and origins Robert C. Buck, James Franklin, Urs Berger, Jason M. Conder, Ian T. Cousins, Pim de Voogt, Allan Astrup Jensen, Kurunthachalam Kannan, Scott Mabury and Stefan P. J. van Leeuwen Per(poly)fluoroalkyl (PFASs) s Perfluoropolyether (PFPE) Acrylate Urethane Oxetane Non s Acid (PFAA) Perfluorocarbon (PFC) Halide Perfluoroalkyl Aldehyde Fluorotelomerbased Electrochemical Fluorination (ECF)based (Poly) Etherbased Manuscript accepted for publication in Integrated Environmental Assessment and Management (IEAM). A SETAC Journal Background 3 Background 4 The discovery of fluorinated substances such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in the environment has prompted an expansive increase in research and publications on these and related substances. Concomitantly, authors have created new words and acronyms to describe these and like substances. Unfortunately this has resulted in multiple names and acronyms that describe the same substances and broad names to describe a wide array of substances that may in fact not really be like one another. For example, what does the acronym PFC describe?

2 5 6 PFC What does it mean? Nomenclature Matters Perfluorocarbon chemical compound Structural differences make a BIG difference in physical, chemical and biological properties # Carbons: Methane vs. Decane: CF 4 vs. C 10 F 22 # Carbons: F COOH vs. FCF 2 COOH chemical Perfluorocarboxylate Polyfluorocarboxylate Perfluoroalkyl chemical Porto These Fútbol substances Club may be VERY different from one another! substances are NOT all the same, they are very different PFC s are persistent and bioaccumulative Factually correct? No. Confusing? Definitely. The solution is to be clear, specific and descriptive of the substance(s) you are talking about. Do not use indeterminate broad terms. Convinced we need common nomenclature to eliminate confusion? 7 8 Objective To provide an overview of perfluoroalkyl and polyfluoroalkyl substances (PFASs) detected in the environment, wildlife and humans and recommend clear, specific and descriptive terminology, names and acronyms for PFASs. To unify and harmonize communication on PFASs by offering terminology for use by the global scientific, regulatory and industrial communities. Emphasis is placed on longchain perfluoroalkyl acids, substances related to the longchain perfluoroalkyl acids, and substances intended as alternatives to the use of the longchain perfluoroalkyl acids or their precursors.

3 Long chain* vs. Short chain Perfluoroalkyl acids (PFAAs) Long Chain n > 6 PFDS, PFOS, PFHxS Perfluoroalkane sulfonate PFSA C n F 2n+1 SO 3 (H) Short Chain n < 5 PFBS 9 Key Terms Fluorochemical (aka fluorinated chemical / substance) Fluorosurfactant aka Surfactant, Tenside and 10 x > 8 PFDA, PFNA, PFOA Perfluoroalkyl carboxylate PFCA C x F 2x1 O 2 (H) x < 7 PFHxA, PFPeA, PFBA Per and Polyfluoroalkyl (PFASs) Perfluorocarbon (PFC) * As defined by U.S. EPA LongChain Chemicals Action Plan, April 2010 and by OECD A first definition Fluorochemical / Chemical / Synonymous general, nonspecific, broad names for substances containing the element fluorine. Describes a universe of substances with vastly different physical, chemical, and biological properties. Fluorosurfactant Surfactant Tenside synonymous names General, nonspecific, names for a surface active substance which contains fluorinated carbon atoms. Describes a universe of substances with vastly different physical, chemical, and biological properties. Surfactants a general definition (from wikipedia) Are amphiphilic, meaning they contain both hydrophobic groups (their "tails") and hydrophilic groups (their "heads") Reduce surface and interfacial tension

4 13 14 (alkyl substances) Aliphatic substances for which all of the hydrogen atoms attached to carbon atoms in the nonfluorinated substance from which they are notionally derived have been replaced by fluorine atoms, except those hydrogen atoms whose substitution would modify the nature of any functional groups present. Examples C 8 F 17 SO 3 C 4 F 9 I (alkyl substances) aliphatic substances for which all hydrogen atoms attached to at least one (but not all) carbons have been replaced by fluorine atoms, in such a manner that they contain the perfluoroalkyl moiety C n F 2n+1 (e.g., C 8 F 17 OH). The general chemical concept of polyfluorination embraces compounds containing scattered multiple fluorine atoms (such as in FCHFCHF OH), as well as grouped ones (such as in CF 3 CF 2 COOH) We consider that only those polyfluorinated substances having at least one perfluoroalkyl moiety C n F 2n+1 belong to the PFAS family. C 6 F Per and Polyfluoroalkyl (PFASs) Origin of the acronym PFAS Highly fluorinated aliphatic substances that contain one or more carbon atoms on which all the hydrogen substituents (present in the nonfluorinated analogs from which they are notionally derived) have been replaced by fluorine atoms, in such a manner that they contain the perfluoroalkyl moiety C n F 2n+1. These compounds are hereafter referred to as the perfluoroalkyl and polyfluoroalkyl substances and denoted by the acronym PFASs Perfluoroalkylated substances aquatic environmental assessment. Rijksinstituut voor Kust en Zee (RIKZ), Environmental and toxicity effects of perfluoroalkylated substances. Rev Environ Contam Toxicol., 2003, 179,

5 Perfluorocarbon (PFC) Perfluorocarbons meaning fully fluorinated hydrocarbons are one of the groups of compounds regulated under the Kyoto Protocol on greenhouse gases, where they are designated in official documents as PFCs. 17 Clear, specific, descriptive nomenclature and acronyms for fluorinated substances is needed and will be enormously useful. 18 A substance derived from a hydrocarbon by replacing all the hydrogen atoms with fluorine atoms. So how do we begin? Perfluorocarbons (PFCs) contain only carbon and fluorine atoms. e.g., ) n F Those PFCs that have a perfluoroalkyl moiety (C n F 2n+1 ) constitute a subset of PFASs. How about we think about two groups, a polymer and a substance that is not a polymer? Per(poly)fluoroalkyl (PFAS) s Perfluoropolyether (PFPE) Acrylate Urethane Oxetane Non s Acid (PFAA) Perfluorocarbon (PFC) Halide Perfluoroalkyl Aldehyde Fluorotelomerbased Electrochemical Fluorination (ECF)based (Poly) Etherbased What is the type of fluorinated polymer? Look at the polymer backbone. Perfluoropolyether (PFPE) Acrylate Urethane Oxetane Is the substance a polymer or not? Sidechain fluorinated 1. What is the atomic composition and chemical structure of the polyfluorinated substance? 2. What commercial manufacturing process does the substance originate from? Non Is the substance perfluorinated? What is the functional group X attached to the perfluorocarbon ) n X? What s X?

6 21 22 Definition Is the substance a polymer or not? Non A general term for a polymer in which one or more of the monomer units contains fluorine Definition A distinct subset of fluorinated polymers What is the type of fluorinated polymer? Look at the polymer backbone. Perfluoropolyether (PFPE) Acrylate that is made from the (co)polymerization of olefinic monomers, at least one of which Urethane Sidechain fluorinated contains fluorine bound to one or both of Oxetane the olefinic carbons, to form a carbononly polymer backbone. 6/21/2011

7 25 26 s Perfluoropolyethers (PFPE) Perfluoropolyether (PFPE) Tetrafluoroethylene (TFE) CF 2 =CF 2 polymers: PTFE, ETFE Vinylidene Fluoride (VDF) =CF 2 : PVDF Vinyl Fluoride (VF) =CHF : PVF Hexafluoropropene (HFP) CF 2 =CFCF 3 : FEP Fluorine bound to the carbon(s) that react to form a carbononly polymer backbone Perfluoropolyethers are a class of fluorinated polymers whose backbone consists of perfluorinated carbon atoms linked by ether bonds. e.g., A proprietary process, involving UVassisted copolymerization of TFE with oxygen obtains this fluorinated backbone. An example: CF 3 (OCF 2 ) m (OCF 2 CF 2 ) n OCF 3 A functionalized perfluoropolyether polymer is: XCF 2 O(CF 2 CF 2 O) m (CF 2 O) n CF 2 X where X is a generic functional group, such as OH 6/21/2011 6/21/ Monomer / Reactant examples s Acrylate Monomer ) 6 OC(O)C(R)= ) 4 SO 2 N(R) OC(O)C(R)= Oxetane Monomer Oxetane monomer from fluorinated alcohol R f OH R f = CF 3, ( ) 2 (CF 2 ) x F (x = 2, 3, 4) Alcohol Reactant ) 6 OH ) 4 SO 2 N(R) OH Acrylate Oxetane Urethane acrylate polymer Acrylate acrylate monomer R f XOC(O)CR= R f = carbon chain that contains fluorinated carbons (e.g., ) n ) X = linking group such as R = H, or alkyl (e.g., )Me, Et, Bu Cl Cl a b c O=C O O=C OC 12 H 25 C 8 F 17 6/21/2011

8 29 30 Oxetane s Oxetane Ringopening polymerization of a fluorinated oxetane How to determine nomenclature an Overview Is the substance a polymer or not? Non Non Perfluoroalkyl (PFAS) Non s Is the substance perfluorinated? Acid (PFAA) Fluorotelomer Based Perfluorocarbon (PFC) Halide Perfluoroalkyl Aldehyde Electrochemical Fluorination (ECF) Based (Poly) Ether Based

9 33 Perfluoroalkyl Acid PFAA 34 What is the functional group X attached to the perfluoroalkyl chain C n F 2n+1 X? A substance that contains a perfluoroalkyl (C n F 2n+1 ) moiety directly bound to an acid functionality, e.g., carboxylate, sulfonate, sulfinate, phosphonate, phosphinate. What s X? X = F Perfluorocarbon PFAAs may be used commercially as their salts, e.g. ammonium, sodium and potassium salts. X = C, P, or S oxidized Perfluoroalkyl Acid X = I, Cl, Br Perfluoroalkyl Halide X bound to the perfluoroalkyl chain is Carbon (C) Carboxylate Sulfur (S) Sulfinate, Sulfonate X = CHO Perfluoroalkyl Aldehyde Phosphorous (P) Phosphinate, Phosphonate Alkyl Acids (X = Carbon, C) Carbon (C) general nomenclature CO 2 Carboxylate PFCA perfluoroalkyl carboxylate (anion) e.g., CO 2 PFOA perfluorooctanoate Note: if specifically discriminating the protonated and anionic forms, please be clear; for example, PFO is used for the anionic form and PFOA for the protonated acid form. If not descriminating between the two forms, PFOA is used. CO 2 H Carboxylic Acid PFCA perfluoroalkyl carboxylic acid e.g., CO 2 H PFOA perfluorooctanoic acid CO 2 F Acid Fluoride PAF perfluoroalkanoyl fluoride e.g., CO 2 F POF perfluorooctanoyl fluoride 35 Alkyl Acids (X= Sulfur, S) general nomenclature Sulfur (S) SO 2 Sulfinate PFSIA perfluoroalkane sulfinate (anion) SO 2 H Sulfinic Acid PFSIA perfluoroalkane sulfinic acid e.g., SO 2 PFOSI perfluorooctane sulfinate SO 2 F Sulfonyl Fluoride PASF perfluoroalkane sulfonyl fluoride e.g., SO 3 F POSF perfluorooctane sulfonyl fluoride SO 3 Sulfonate PFSA perfluoroalkane sulfonate (anion) SO 3 H Sulfonic Acid PFSA perfluoroalkane sulfonic acid e.g., SO 3 PFOS perfluorooctane sulfonate 36

10 37 38 Alkyl Acids (X = Phosphorus, P) Phosphorus (P) Perfluorocarbon PFC Perfluorocarbon (PFC) RPO 3 Phosphonate (anion) PFPA perfluoroalkyl phosphonic acids RPO 3 H 2 Phosphonic acid PFPA e.g., PO 2 3 C8PFPA perfluorooctyl phosphonate RR PO 2 Phosphinate (anion) PFPIA perfluoroalkyl phosphinic acids RR PO 2 H Phosphinic acid PFPIA e.g., [ ] 2 PO 2 C8/C8PFPIA Perfluoroalkyl Acid PFAA Carboxylic Acid PFCA Sulfinic Acid PFSIA Sulfonic Acid PFSA Phosphonic Acid PFPA Phosphinic Acid PFPIA Acid (PFAA) bisperfluorooctyl phosphinate R and R are perfluoroalkyl moieties, C n F 2n+1 Perfluoroalkyl Halide Iodide, Bromide, Chloride Aldehyde PFAL Halide Perfluoroalkyl Aldehyde Non Is the substance perfluorinated? 1. What is the atomic composition and chemical structure of the polyfluorinated substance? 2. What commercial manufacturing process does the substance originate from? Fluorotelomer Based Electrochemical Fluorination (ECF) Based (Poly) Ether Based

11 Fluorotelomer A process technology used to manufacture fluorinated substances where a perfluoroalkyl iodide (e.g., pentafluoroethyl iodide, C 2 F 5 I, telogen) is reacted with tetrafluoroethylene (TFE, CF 2 =CF 2, taxogen) to yield even carbonnumbered perfluoroalkyl iodides. Note: telomere is a biology term and should not be used or confused with the term telomer ) 2 I CF 2 =CF 2 (Tetrafluoroethylene, TFE) ) n I Perfluoroalkyl Iodide ) n I Fluorotelomer Iodide ) n OH Fluorotelomer Alcohol Telomerization 41 Nomenclature for degradation products from Fluorotelomer substances A:B designation A = number of fluorinated carbons B = number of nonfluorinated carbons Examples ) 7 CO 2 H 7:3 Acid CO 2 H 8:2 Acid ) 7 CF=CHCO 2 H 8:2 Unsaturated Acid ) 7 CH(OH)CH 3 7:2 secondary alcohol Electrochemical Fluorination (ECF) Ether Based 44 A process technology used to manufacture fluorinated substances where an organic raw material is dissolved in hydrogen fluoride and electrolyzed, resulting in the replacement of hydrogens with fluorine. The freeradical nature of the process leads to rearrangement resulting in a product mixture of linear and branched isomers of multiple carbon chain lengths. H( ) n SH H( ) n SO 2 F HF, e ) n SO 2 F PASF ) n SO 2 N(R)(R ) Electrochemical Fluorination Perfluoroalkane sulfonamido substances Polyfluoroalkyl (poly)ether carboxylic acids processing aids E.g., CF 3 OCF 2 CF 2 CF 2 OCHFCF 2 COOH Polyfluoroalkyl polyether carboxylate

12 45 46 Chemical Structure Question Conclusion (CF 2 OH or Non? Non Let s work through a few examples OH? No. The substance has a perfluoroalkyl chain,, but all hydrogen on carbons are not replaced with fluorine. OH Process Origin? Perfluoroalkyl chain with an ethylene spacer ( ). Fluorotelomer origin. Fluorotelomer origin OH Functionality. Alcohol Fluorotelomer Alcohol (FTOH) OH Eight fluorinated carbons, two nonfluorinated carbons, therefore 8:2. 8:2 Fluorotelomer Alcohol (8:2 FTOH) Chemical Structure Question Conclusion Chemical Structure a b c Question Conclusion ) 4 SO 2 NH 2 Cl Cl O=C O O=C OC 12H 25 or Non? or Non? Non C 8F 17 ) 4 SO 2 NH 2? Yes. All hydrogens on all four carbons are replaced with fluorine. Perfluorobutyl.? No. The polymer backbone contains no fluorine bound to carbon. ) 4 SO 2 NH 2 ) 4 SO 2 NH 2 ) 4 SO 2 NH 2 Perfluoroalkyl Acid (PFAA)? No. Has no acid functionality. Process Origin? Perfluoroalkyl chain with a sulfone, SO 2, spacer. Electrochemical fluorination (ECF) origin. Functionality. Sulfonamide ECF origin Perfluorobutanesulfo namide (FBSA) Sidechain fluorinated? Yes. Type? Acrylate. Sidechain fluorinated polymer Sidechain fluorinated acrylate polymer

13 49 50 Perfluoroalkyl and polyfluoroalkyl substances (PFASs) in the environment: terminology, classification and origins Robert C. Buck, James Franklin, Urs Berger, Jason M. Conder, Ian T. Cousins, Pim de Voogt, Allan Astrup Jensen, Kurunthachalam Kannan, Scott Mabury and Stefan P. J. van Leeuwen Supplemental Data 42 families and subfamilies of PFASs and. 268 selected individual compounds, providing recommended names and acronyms, and structural formulas, as well as CAS registry numbers. Summary: Use of clear, specific, descriptive nomenclature and acronyms for fluorinated substances will be enormously useful. Let s agree and use the proposed Nomenclature and Acronyms going forward. Manuscript accepted for publication in Integrated Environmental Assessment and Management (IEAM). A SETAC Journal Per(poly)fluoroalkyl (PFAS) s Perfluoropolyether (PFPE) Acrylate Urethane Oxetane Non s Acid (PFAA) Perfluorocarbon (PFC) Halide Perfluoroalkyl Aldehyde Fluorotelomerbased Electrochemical Fluorination (ECF)based (Poly) Etherbased Thank You : ) Questions welcomed