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'''PFOS''', or perfluorooctane sulfonate, is a [[perfluorinated compound]]. PFOS is used for its properties that make materials stick and stain resistant. Until 2002, PFOS was a breakdown product of the chemicals used to make [[Scotchgard]] products.<ref>[http://pollutioninpeople.org/toxics/pfcs Perfluorinated Compounds (PFCs)], Pollution in People], Accessed September 24, 2010.</ref> Perfluorinated compounds like PFOS are highly persistent in the environment.