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Fluorotelomer

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Fluorotelomers are fluorocarbon-based oligomers, or telomers, synthesized by telomerization.[1] Some fluorotelomers and fluorotelomer-based compounds are a source of environmentally persistent perfluorinated carboxylic acids such as PFOA and PFNA, while others are under extended investigation.

Types

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There are many broad categories of fluorotelomers:[2][3][4]

Production

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In the radical telomerization of fluorotelomer molecules, a variety of fluorinated alkenes can serve as unsaturated taxogens including tetrafluoroethylene, vinylidene fluoride, chlorotrifluoroethylene, and hexafluoropropene. However, many fluorotelomers, such as fluorotelomer alcohols, are fluorocarbon-based because they are synthesized from tetrafluoroethylene. In addition to alcohols, synthetic products include fluorotelomer iodides, olefins, and acrylate monomer.[5] Polymerized acrylate from iodide and alcohol monomers represent >80% of the global manufacture and use of fluorotelomer-based products.[5]

General (simplified) synthetis route of fluorotelomer-based urethane side-chain fluorinated polymers (SCFPs)[6]

Applications

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Fluorotelomers are used in fire-fighting foams, grease-resistant food packaging, leather protectants and stain-resistant carpeting, textiles, anti-fogging sprays and wipes.[7] Fluorotelomers are applied to food contact papers for their lipophobicity, making paper resistant to absorbing oil from fatty foods.[8] Fluorotelomer coatings are used in microwave popcorn bags, fast food wrappers, candy wrappers, and pizza box liners.[9][2]

Environmental and health concerns

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Fluorotelomers that contain PFOA precursors can be metabolized into, and degrade to, PFOA,[10][11] a persistent global contaminant found in people in the low-parts per billion range.[12] Toxicologists estimate microwave popcorn, because of the high heat and coated bag, could account for about 20% of the PFOA levels measured in an individual consuming 10 bags a year if 1% of the fluorotelomers are metabolized to PFOA.[13]

PFOA is also formed as an unintended byproduct in the production of fluorotelomers,[14] and is thus present in finished goods treated with fluorotelomers, including those intended for food contact. In a U.S. Food and Drug Administration (USFDA) study, fluorotelomer-based paper coatings (which can be applied to food contact paper in the concentration range of 0.4%) were found to contain 88,000–160,000 parts per billion PFOA, while microwave popcorn bags contained 6–290 parts per billion PFOA.[8]

Industry and government actions

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In 2002 Burger King stopped using fluorotelomer coated boxes.[15]

After more than a year of negotiating with "telomer makers Asahi Glass, Clariant, Daikin America, and DuPont to perform degradation studies on 13 of their products", the U.S. Environmental Protection Agency (USEPA) and companies were not able to agree on terms.[16] Thus, in late June 2004 the USEPA announced it would perform the degradation studies itself, with an expected time to complete the studies of 1 year.[16] However, in a December 2005 deal with the USEPA over alleged withholdings, DuPont agreed to test nine of its fluorotelomer-based products' potential to break down into PFOA by 27 December 2008.[17] Yet, in late December 2008, the USEPA and DuPont filed a joint motion stating that DuPont needed additional time[17] to purify the products.[7] USEPA lawyers extended the deadline by three years, to 27 December 2011, in the last month of the Bush administration.[17]

In 2009 a 546-day USEPA study was published that estimated a degradation half-life for a fluorotelomer-based polymer in the range of 10–17 years.[18] This estimate was much shorter than the half-life estimated by a DuPont study.[19] Given this discrepancy, the USEPA undertook an extensive effort to develop methods for testing the degradation rate of commercial fluorotelomer-based polymers.[20] The USEPA then carried out studies with two DuPont polymers in four soils and water using these methods. These new studies reported half-life ranges for these commercial fluorotelomer-based polymers of 33 to 112 years, roughly consistent with EPA's 2009 estimate.[10][11]

References

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  1. ^ Lehmler, HJ (March 2005). "Synthesis of environmentally relevant fluorinated surfactants—a review". Chemosphere. 58 (11): 1471–96. Bibcode:2005Chmsp..58.1471L. doi:10.1016/j.chemosphere.2004.11.078. PMID 15694468.
  2. ^ a b Oladipo, Gloria (5 January 2022). "High levels of toxic 'forever chemicals' found in anti-fogging sprays and wipes". The Guardian. Retrieved 5 January 2022.
  3. ^ van Hees, Patrick. "Analysis of the unknown pool of PFAS: Total Oxidizable Precursors (TOP), PFOS Precursor (PreFOS) and Telomer Degradation" (PDF). Eurofins. Retrieved 5 January 2022.
  4. ^ Herkert, Nicholas J.; Kassotis, Christopher D.; Zhang, Sharon; Han, Yuling; Pulikkal, Vivek Francis; Sun, Mei; Ferguson, P. Lee; Stapleton, Heather M. (5 January 2022). "Characterization of Per- and Polyfluorinated Alkyl Substances Present in Commercial Anti-fog Products and Their In Vitro Adipogenic Activity". Environmental Science & Technology. 56 (2): 1162–1173. Bibcode:2022EnST...56.1162H. doi:10.1021/acs.est.1c06990. PMC 8908479. PMID 34985261.
  5. ^ a b Prevedouros K, Cousins IT, Buck RC, Korzeniowski SH (January 2006). "Sources, fate and transport of perfluorocarboxylates". Environ Sci Technol. 40 (1): 32–44. Bibcode:2006EnST...40...32P. doi:10.1021/es0512475. PMID 16433330.
  6. ^ Synthesis Report on Understanding Side-Chain Fluorinated Polymers and Their Life Cycle (PDF). OECD. 2022.
  7. ^ a b Eder, Andrew (10 February 2009). "DuPont gets more time to test PFOA". Delaware Online.
  8. ^ a b Begley TH, White K, Honigfort P, Twaroski ML, Neches R, Walker RA (October 2005). "Perfluorochemicals: potential sources of and migration from food packaging". Food Addit Contam. 22 (10): 1023–31. doi:10.1080/02652030500183474. PMID 16227186. S2CID 44370267.
  9. ^ Weise, Elizabeth (16 November 2005). "Engineer: DuPont hid facts about paper coating". USA Today. Retrieved 19 September 2008.
  10. ^ a b Washington JW, Jenkins TM, Rankin K, Naile JE (2015). "Decades-Scale Degradation of Commercial, Side-Chain, Fluorotelomer-based Polymers in Soils & Water". Environ. Sci. Technol. 49 (2): 915–923. Bibcode:2015EnST...49..915W. doi:10.1021/es504347u. PMID 25426868.
  11. ^ a b Washington JW, Jenkins TM (2015). "Abiotic hydrolysis of fluorotelomer polymers as a source of perfluorocarboxylates at the global scale". Environ. Sci. Technol. 49 (24): 14129–14135. doi:10.1021/acs.est.5b03686. PMID 26526296.
  12. ^ Houde M, Martin JW, Letcher RJ, Solomon KR, Muir DC (June 2006). "Biological monitoring of polyfluoroalkyl substances: A review". Environ. Sci. Technol. 40 (11): 3463–73. Bibcode:2006EnST...40.3463H. doi:10.1021/es052580b. PMID 16786681.
  13. ^ Renner, Rebecca (January 2006). "It's in the microwave popcorn, not the Teflon pan". Environ Sci Technol. 40 (1): 4. Bibcode:2006EnST...40....4R. doi:10.1021/es062599u.
  14. ^ "Information on PFOA". DuPont. Archived from the original on 24 May 2009. Retrieved 14 February 2009.
  15. ^ Sanford Lewis. "The Shareholder’s Right To Know More - 2007 Update: DuPont’s Market and Liability Exposures Continue from PFOA and Related Issues"[permanent dead link] DuPont Shareholders For Fair Value, April 2007. (Accessed September 10, 2008).
  16. ^ a b Cheryl Hogue (July 2004). "Fluorotelomers to the test: Unable to strike deal with industry, EPA to study degradation of chemicals". Chemical & Engineering News. 82 (27): 6. doi:10.1021/cen-v082n027.p006.
  17. ^ a b c Ward, Jr., Ken (7 February 2009). "Bush EPA gave DuPont more time on key PFOA tests". The Charleston Gazette. Archived from the original on 16 July 2011. Retrieved 20 February 2009.
  18. ^ Washington JW, Ellington J, Jenkins TM, Evans JJ, Yoo H, Hafner SC (September 2009). "Degradability of an acrylate-linked, fluorotelomer polymer in soil". Environ. Sci. Technol. 43 (17): 6617–23. Bibcode:2009EnST...43.6617W. doi:10.1021/es9002668. PMID 19764226.
  19. ^ Renner R (September 2009). "Perfluoropolymer degrades in decades, study estimates". Environ. Sci. Technol. 43 (17): 6445. Bibcode:2009EnST...43.6445R. doi:10.1021/es9021238. PMID 19764197.
  20. ^ Washington JW, Naile JE, Jenkins TM, Lynch DG (2014). "Characterizing fluorotelomer & polyfluoroalkyl substances in new & aged fluorotelomer-based polymers for degradation studies with GC/MS & LC/MS/MS". Environ. Sci. Technol. 48 (10): 5762–69. doi:10.1021/es500373b. PMID 24749955.
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