What are Per and polyfluorinated alkyl substances (PFAS)?
Per and polyfluorinated alkyl substances (PFAS) are a group of over 4,500 widely used, synthetic chemicals, that accumulate over time in the environment and in the human body. The most widely used, and most well-known PFAS, are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). They are used in a wide variety of consumer products, some examples include; non-stick metal coatings for cooking pans, stain resistant coatings on carpets and textiles, paper food packaging, firefighting foams, lubricants, and personal care products such as eye makeup.
Figure 1 Perfluorooctanoic Acid (PFOA)
Perfluorooctane sulfonic acid (PFOS)
How to identify a PFAS? Per and polyfluoroalkyl substances (PFASs) are a family of synthetic chemicals that contain one or more Carbon atoms whereby all the Hydrogen substituents (present in the non- fluorinated analogues from which they are notionally derived) have been replaced by Fluoride atoms, in such a way that they contain the perfluoroalkyl moiety (CnF2n+1–). [4] The polyfluoroalkyl compounds have some H atoms left and not all are replaced with fluorine. There are also “ultra-short- chain” PFAS. [10]. Due to the high electronegativity of fluoride, the C-F structure is one of the strongest chemical bonds in organic chemistry. This means that compounds which contain this bond, do not easily degrade and are therefore extremely persistent and accumulative. This is one of the reasons that PFAS are sometimes referred to as “Forever Chemicals”. PFAS are also frequently described as “long-chain” or “short-chain”. The Organisation for Economic Co-operation and Development (OECD 2011, [5]) defines “long-chain” PFAS as: • Perfluoroalkyl carboxylic acids with eight carbons and greater (with seven or more perfluorinated carbons) • Perfluoroalkane sulfonates with six carbons and greater (with six or more perfluorinated carbons). In contrast, “Short-chain” PFAS refers to: • Perfluoroalkyl carboxylic acids with seven carbons and less (with six or less perfluorinated carbons) • Perfluoroalkane sulfonates with five carbons and less (with five or less perfluorinated carbons). 3
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