Fact sheet: Perfluorooctane sulfonic acid

From: Public Services and Procurement Canada

Discover a list of a contaminant's important chemical properties, how it will react in the environment, main sources of contamination related, and a brief overview of health and safety issues.

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General information

CAS number


Molecular formula


Formula weight

500.1 g/mol


Perfluorinated compounds (PFC)

Properties (at room temperature where applicable)

Compound properties list
Melting/boiling pointN/A / 133 °CSolid
Relative density1.8 g/cm3Sinks in water. Applies to PFOA, no data available for PFOS.
Vapour pressure6 x 10-3 mm HgNot volatile
Vapour density0N/A
Solubility in water550 mg/LModerately soluble
Henry's law constant3.4 x 10-9 atm·m3/molNo volatilization when dissolved. Applies to PFOS potassium salt. No data available for PFOS.
log Koc (Depending on soil or sediment characteristics)2.5 - 3.0*Moderate adsorption to organic matter

Environmental behaviour

PFOS is part of a family of compounds that are persistent and that bioaccumulate in the environment. PFOS exists as an anion, an acid or as various salts and polymers. As PFOS is a strong acid, the anionic PFOS form is expected to predominate at normal environmental conditions (example, near neutral pH). It has both hydrophobic and hydrophilic functionalities and, as such, it acts as a surfactant. It is characterized by a moderate solubility (an increase in salt content of a solution decreases its solubility) and is non-volatile.

In the environment, PFOS is found in solution or adsorbed onto particles. Following a liquid spill or release, this compound will partly adsorb to sediments, soil and sludge or migrate into a waterway where it can be transported over long distances because of its solubility and persistence. Depending on the nature of soils, PFOS will migrate more or less rapidly in groundwater; the resulting plumes can be relatively large in size.

Health and safety

PFOS should be handled with care as it is toxic.

Principal resources

PFOS has been manufactured for more than 50 years but it has never been manufactured in Canada. PFOS and its precursor perfluorooctane sulfonyl fluoride (POSF)-based chemicals were produced through the Simons electrochemical fluorination (ECF) method in the United States until 2001, date on which the major global producer began a voluntary phase-out of its production. This phase-out in the United States was completed in 2002. In 2003, China began a large-scale PFOS production.

In Canada, the manufacture, import, sale, offer for sale and use of PFOS or of products containing PFOS, unless incidentally present, is prohibited with certain exemptions (example, aqueous film forming foams (AFFF) used for firefighting, aviation hydraulic fluids under certain conditions, some products used in photographic or photolithographic process).


Agency for Toxic Substances and Disease (ATSDR). 2009. Draft Toxicological Profile for Perfluoroalkyls. U.S. Department of Health and Human Services, Public Health Service, Georgia, USA.(PDF, 11.09MB) (Viewed online March 2015).

Brooke, D., Footitt, A. and Nwaogu, T.A. (2004). Environmental risk evaluation report: Perfluorooctanesulphonate (PFOS). Research Contractor: Building Research Establishment Ltd, Risk and Policy Analysts Ltd. Report produced by the Environment Agency´s Science Group.(PDF, 1.76MB) (Viewed online March 2015).

European Food Safety Authority (EFSA). 2008. Perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and their salts. Scientific Opinion of the Panel on Contaminants in the Food chain (Question No EFSA-Q-2004-163). Adopted on 21 February 2008. The EFSA Journal, 653: 1-131.(PDF, 590KB) (Viewed online March 2015).

Environment Canada. 2013. Ecological Screening Assessment Report on Perfluorooctane Sulfonate, Its Salts and Its Precursors that Contain the C8F17SO2 or C8F17SO3, or C8F17SO2N Moiety. (Viewed online March 2015).

Government of Canada. 2008. Perfluorooctane Sulfonate and its Salts and Certain Other Compounds Regulation, SOR/2008-178. Canada Gazette Part II(PDF, 65KB). (Viewed online March 2015).

Hazardous Substances Data Bank (HSDB). 2011. Perfluorooctane sulfonic acid. (Viewed online March 2015).

Organisation for Economic Co-Operation and Development (OECD). 2002. Co-operation on existing chemicals hazard assessment of perfluorooctane sulfonate (PFOS) and its salts. ENV/JM/RD(2002)17/FINAL. Environment Directorate. Joint Meeting of the Chemical Committee and the Working Party on Chemicals, Pesticides and Biotechnology. (PDF, 1.46MB) (Viewed online March 2015).

United States Environmental Protection Agency (U.S. EPA). 2014. Emerging contaminants - Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). Emerging Contaminant fact Sheet – PFOS and PFOA. (Viewed online March 2015).

Zareitalabad, P., Siemens, J., Hamer, M. and Amelung, W. 2013. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in surface waters, sediments, soils and wastewater - A review on concentrations and distribution coefficients. Chemosphere, 91(6): 725-732.(PDF, 706KB) (Viewed online March 2015).