Toxic substances list: perfluorooctane sulfonate (PFOS), its salts and precursors

Perfluorooctane sulfonate (PFOS), its salts and its precursors are industrial chemicals that belong to the broad class of per- and polyfluoroalkyl substances (PFAS). PFAS are a class of over 4,700 human-made substances. In April 2021, the Government of Canada indicated that it is considering activities that would address PFAS as a class. Visit the PFAS web page for the latest information on publications and actions taken under the Government's Chemicals Management Plan related to PFAS.

PFOS, its salts and precursors are fluorochemicals that contain carbon atoms that are completely saturated by fluorine. It is the strength of the carbon-fluorine bonds that contributes to the extreme stability and unique properties of these perfluorinated chemicals. PFOS is a compound with a chain length containing eight perfluorinated carbon atoms (C8) bonded to a sulfonate anion moiety (SO₃^-).

PFOS, its salts and precursors were primarily used as a surfactant in the metal plating industry and in aqueous film-forming foam (AFFF) used in firefighting, specifically fuel fires. They have water, oil, dirt and grease repellant properties and were historically used in a wide variety of surface treatments for textiles, upholstery, leather, carpet and packaging. They were also used in electrical and electronic equipment such as semi-conductors.

For more information on these substances, please visit the Chemical Substances website and the Chemicals at a glance information sheet for PFOS, its salts and precursors.