Fact sheet: Perfluorooctane sulfonic acid (Under Review)

From: Public Services and Procurement Canada

Warning

The information contained in this factsheet may be outdated as it is currently under review. For the most up to date information about PFAS, visit: https://www.canada.ca/en/health-canada/services/chemical-substances/other-chemical-substances-interest/per-polyfluoroalkyl-substances.html.

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.

General information

CAS number: 1763-23-1
Molecular formula: C₈F₁₇SO₃H
Formula weight: 500.1 g/mol
Family: Perfluorinated compounds (PFC)

Properties (at room temperature where applicable)

Compound properties list
Parameter	Value	Comment
Melting/boiling point	N/A / 133 °C	Solid
Relative density	1.8 g/cm³	Sinks in water. Applies to PFOA, no data available for PFOS.
Vapour pressure	6 x 10^-3 mm Hg	Not volatile
Vapour density	0	N/A
Solubility in water	550 mg/L	Moderately soluble
Henry's law constant	3.4 x 10^-9 atm·m³/mol	No volatilization when dissolved. Applies to PFOS potassium salt. No data available for PFOS.
log K_oc (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).