PFAS: Last Week Tonight with John Oliver

John Oliver discusses PFAS — a class of chemicals linked to an array of health issues — and why their widespread use isn’t as magical as it may seem.


Per- and polyfluoroalkyl substances (PFASs) are synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. As such, they contain at least one perfluoroalkyl moiety, –CnF2n–. According to the Organisation for Economic Co-operation and Development (OECD):

PFASs are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e. with a few noted exceptions, any chemical with at least a perfluorinated methyl group (–CF3) or a perfluorinated methylene group (–CF2–) is a PFAS.

According to the OECD, there are at least 4730 different PFASs with at least three perfluorinated carbon atoms.[4] A U.S. Environmental Protection Agency (EPA) toxicity database, DSSTox, even lists 8163 PFASs. A subgroup, the fluorosurfactants or fluorinated surfactants, have a fluorinated “tail” and a hydrophilic “head” and are thus surfactants. They are more effective at reducing the surface tension of water than comparable hydrocarbon surfactants. They include the perfluorosulfonic acids such as the perfluorooctanesulfonic acid (PFOS) and the perfluorocarboxylic acids such as the perfluorooctanoic acid (PFOA).

PFOS, PFOA and other PFASs are known to persist in the environment and are commonly described as persistent organic pollutants, also known as “forever chemicals”. Residues have been detected in humans and wildlife,[6] with health concerns resulting in litigation. In 2021 Maine became the first US state to ban these compounds in all products by 2030, except in instances deemed “currently unavoidable”.

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