Terminology

BASIC

PFCs (Perfluorocarbons):

  • “PFCs” has long been defined to mean perfluorocarbons, a family of greenhouse gases regulated by the Kyoto Protocol.
  • Perfluorocarbons contain only carbon and fluorine atoms. 
  • The acronym “PFCs” has been mistakenly used to refer to per- and polyfluoroalkyl substances (PFASs) as well as perfluoroalkyl acids (PFAAs) such as PFOA and PFOS. 

Fluorochemical / Fluorinated Chemical:

  • A general, non-specific term used to describe a universe of organic and inorganic substances that contain at least one fluorine atom.

FluoroTechnology:

  • The use of fluorine chemistry to create any fluorinated product, including fluoropolymers, fluorotelomer-based chemicals, and other fluorochemicals.

Fluoropolymer:

  • Polymers with carbon-only backbone and fluorine directly attached to the backbone of carbon atoms
  • A typical fluoropolymer is PTFE (polytetrafluoroethylene).
  • Typical properties are heat and chemical resistance, non-stick, and unique dielectric properties.
  • Specialty plastic used in applications such as wire and cable coatings; linings for pipes, tanks, and equipment in chemical and pharmaceutical manufacturing; and non-stick cookware.

Fluorotelomer-based Products:

  • Polymeric:
    • Also known as  side-chain fluorinated polymers
    • Fluorinated polymers consisting of non-fluorinated carbon backbones with polyfluoroalkyl side chains
    • Used to treat textiles, carpets, nonwovens and paper to provide water, soil, oil and stain resistance
  • Non-Polymeric:
    • Fluorotelomer-based derivatives, such as fluorinated surfactants used in firefighting foams and as coatings additives
    • Fluorotelomer-based raw materials as feedstock to produce polymeric fluorotelomer-based chemicals

PFOA: 

  • Perfluorooctanoic acid (C7F15COOH)
  • Historically used as a polymerization processing aid in the manufacture of certain fluoropolymers.  Alternatives are in widespread commercial use.
  • Potential degradation product and impurity related to long-chain fluorotelomer-based products and other precursor substances.

PFOS:

  • Perfluorooctane sulfonic acid (C8F17SO3H) or Perfluorooctane sulfonate (C8F17SO3)
  • A fluorosurfactant historically used in etching solutions in the semiconductor industry, as a mist suppressant in metal plating industry and as a surfactant in firefighting foams. PFOS-related polymeric substances were used to provide soil/stain resistance in textiles, carpets and paper. PFOS-related surfactants were widely used in a wide array of consumer and industrial applications.

ADVANCED

Perfluoroalkyl and Polyfluoroalkyl substances (PFASs) 1

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) vary widely in their physical and chemical properties and their health and environmental profiles. Therefore, it is often not accurate to make general statements about the health and environmental impacts of this broad family of chemistry. However, it is possible to differentiate between the health and environmental impacts of long-chain and short-chain perfluoroalkyl substances. As indicated by the U.S. EPA, the short-chain substances are eliminated more rapidly from the body and are less toxic than the long-chain substances. One of the FluoroCouncil’s primary goals is to support a global transition toward short-chain chemistries that limit environmental impacts.

While some PFASs are sold as commercial products, some are manufacturing intermediates used to make commercial products, and some may also occur as unintended by-products from the degradation of polyfluoroalkyl substances.

Long-chain per- and poly-fluoroalkyl substances (PFASs):

  • Perfluorocarboxylic acids (PFCAs) with carbon chain lengths of 8 and higher, including perfluorooctanoic acid (PFOA).
  • PFSAs with carbon chain lengths of 6 and higher, including perfluorohexane sulfonic acid (PFHxS) and perfluorooctane sulfonate (PFOS).
  • Precursors of these substances that may be produced or present in products. A "precursor" means a substance that has been recognized as having the potential to degrade to the above substances, such as long-chain fluorotelomer-based raw materials.
  • Polymeric and non-polymeric fluorotelomer-based chemicals made from long-chain flurorotelomer-based raw materials belong to the class of long-chain PFAS.

Short-chain per- and polyfluoroalkyl substances (PFASs):

  • PFCAs with carbon chain lengths of 7 and lower, including perfluorohexanoic acid (PFHxA)
  • PFSAs with carbon chain lengths of 5 and lower, including PFBS
  • Precursors of these substances that may be produced or present in products. A "precursor" means a substance that has been recognized as having the potential to degrade to the above substances, such as short-chain fluorotelomer-based raw materials.
  • Polymeric and non-polymeric fluorotelomer-based chemicals made from short-chain flurorotelomer-based raw materials belong to the class of short-chain PFAS.

Some sub-categories of perfluoroalkyl substances
(In parentheses is the number of carbon atoms in each molecule of the substance, which influences its performance, health and safety profile.)

  • PFCAs (Perfluorocarboxylic acids):

    Long-Chain:
    Perfluorodecanoic acid (PFDA), (C9F19COOH) | (C10) | Potential breakdown product
    Perfluorononanoic acid (PFNA), (C8F17COOH) | (C9) | Commercial product
    Perfluorooctanoic acid (PFOA), (C7F15COOH) | (C8) | Commercial product

    Short-Chain:
    Perfluoroheptanoic acid (PFHpA), (C6F13COOH) | (C7) | Potential degradation product
    Perfluorohexanoic acid (PFHxA), (C5F11COOH) | (C6) | Potential degradation product
    Perfluoropentanoic acid (PFPeA), (C4F9COOH) | (C5) | Potential degradation product
    Perfluorobutanoic acid (PFBA), (C3F7COOH) | (C4) | Commercial product
       

  • PFSAs (Perfluoroalkane sulfonic acids):

    Long-Chain:
    Perfluorooctane sulfonic acid (PFOS), (C8F17SO3H) | (C8) | Commercial product
    Perfluorohexane sulfonic acid (PFHxS), (C6F13SO3H) | (C6) | Commercial product

    Short-Chain:
    Perfluorobutane sulfonic acid (PFBS), (C4F9SO3H) | (C4) | Commercial product
       

  • PFAIs (Perfluoroalkyl iodides) – Manufacturing intermediates used in the production of fluorotelomer-based products. (Fluorotelomer-based products are not perfluorinated substances – they are polyfluorinated substances, which may degrade in the environment to perfluoroalkyl carboxylic acids.)

    Long-Chain:
    PFAIs (>8 carbons) manufacturing intermediate

    Short-Chain:
    PFBI (perfluorobutyl iodide), (C4F9I) | (C4) | Commercial product
    PFHxI (perfluorohexyl iodide), (C6F13I) | (C6) | Commercial product

Numerous categories of per- and poly-fluoroalkyl chemistry are not addressed here, including perfluoroalkyl ethers and perfluoropolyethers. See the open-access publication cited below for additional information.

Reference

  • Perfluoroalkyl and polyfluoroalkyl substances in the environment: Terminology, classification, and origins. Integrated Environmental Assessment and Management 2011, 7, 513-541.
    http://dx.doi.org/10.1002/ieam.258

1 U.S. EPA uses PFAS to refer to perfluoroalkyl sulfonates.
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