Perfluorooctane sulfonate  (PFOS), its salts and precursors - information sheet


Per- and polyfluoroalkyl substances (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 being considered under the Government’s Chemicals Management Plan related to PFAS.

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  • The Government of Canada conducted science-based evaluations of PFOS, its salts, and its precursors to address the potential for harm to Canadians and to the environment. These assessments were completed in 2006.
  • Under the Canadian Environmental Protection Act, 1999 (CEPA 1999), the risk posed by a substance is determined by considering both its hazardous properties (its potential to cause adverse human health or ecological effects) and the amount of exposure there is to people and the environment. A substance may have hazardous properties; however, the risk to human health or to the environment may be low depending upon the level of exposure.
  • The health assessment of PFOS, its salts and its precursors found that PFOS exposures were below levels that would be harmful to human health. However, the ecological assessment concluded that PFOS is entering or may enter the environment at concentrations that are harmful to the environment.

About this substance

  • Perfluorooctane sulfonate, also known as PFOS, is a man-made chemical substance belonging to a large family of compounds known as perfluoroalkyl substances (PFASs).
  • Prior to the announcement of a global voluntary phase-out of the production of PFOS by a major manufacturer beginning in 2000, PFOS was imported into Canada and used primarily in water-, oil-, soil- and grease-repellents for use on paper and packaging, carpets and fabrics, and in fire-fighting foams used to fight fuel-based fires.
  • According to information gathered by the Government and a 2004 industry survey of remaining PFOS uses, only 3,000 kg of PFOS was imported into Canada for use as a surfactant in the chromium electroplating sector.
  • There are no manufacturers or exporters of PFOS in Canada.
  • The assessment was undertaken in response to a public nomination to the Minister of Environment to add these substances to the Priority Substances List. Precursors considered to have the potential to degrade to PFOS were included in the assessment.
  • The ecological assessment focused on PFOS, but also considered its precursors given similar use applications and given that PFOS is the final degradation product of precursors. While the assessment did not consider the additive effects of PFOS and its precursors, it is recognized that the precursors contribute to the ultimate environmental loading of PFOS. Precursors may also play a key role in the long-range transport and subsequent degradation to PFOS in the Canadian Arctic.

Human and ecological exposures

  • Given the historic use patterns, exposure of Canadians to these substances would likely result from contact with, and/or the use of products available to consumers that contain PFOS.
  • Human exposure may also occur from environmental sources (for example, air) as well as food; however, given that environmental data are limited, exposure was assessed using levels of these substances measured in humans (human biomonitoring data).
  • Human biomonitoring is the measurement of substances in blood, urine or breast milk. The presence of a substance in the body does not necessarily mean that it is causing harm. Harmful effects will depend on the levels and the properties of the substances. The information on measured levels in humans is important to estimating exposure to Canadians.
  • At the time of the assessment, globally, PFOS could be released to the environment throughout its lifecycle, from the handling of the chemical to the use and disposal of products which contain it.
  • Exposure of the Canadian environment would likely result from the release, transformation, and movement of PFOS and its precursors in effluents, emissions to air and water from manufacturing sites elsewhere in the world, and releases from wastewater effluents.

Key health and ecological effects (hazard)

  • The critical or important effects considered in the human health assessment of PFOS and its salts included effects on the liver and thymus, as well as effects on blood chemistry.
  • PFOS and its salts are considered to have ecological effects of concern (such as growth, survival, and reproductive effects) due to their persistence and their potential to accumulate in and cause harm to organisms.

Risk assessment outcomes

Screening assessment conclusions

  • As a result of the state of science report for human health, it was found that PFOS, its salts and its precursors are not harmful to human health at the levels of exposure current at the time of the assessment. 
  • However, the Government concluded that PFOS, its salts, and its precursors are entering the environment at levels that are harmful to the environment.

Preventive actions and reducing risk

Related information

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