Basic Information about Per- and Polyfluoroalkyl Substances (PFASs)

Includes Information on Perfluorooctanoic Acid (PFOA), Perfluorooctyl Sulfonate (PFOS), and All Other PFASs, and on PFCs

Basic Information

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What are perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS) and other perfluoroalkyl substances (PFASs)?

Per- and polyfluoroalkyl substances (together, PFASs) are a class of man-made chemicals. They are not found naturally in the environment.  PFOA and PFOS have been the most extensively produced and studied of these chemicals.  Both chemicals are very persistent in the environment and in the human body.

Molecules in all PFASs chemicals contain carbon and fluorine atoms; some PFASs also include oxygen, hydrogen, sulfur and/or nitrogen atoms. One characteristic that differentiates molecules of one PFASs from those of another is the chain length, or the number of carbon atoms, in the molecule. For example, PFOA has eight carbon atoms, which is why it is sometimes referred to as C8.

Scientists sometimes study PFASs as a group because of potential similarities in their chemical properties and their toxicity. Some studies compare one PFAS chemical to another to understand the relationship between the chemical's chain length and its toxicity. Scientists are also investigating:

  • how the toxicity of one PFAS is similar or different to that of other PFASs, and
  • toxicologically, what all PFASs have in common.

Related: What are PFCs and How Do They Relate to PFASs?

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What are PFASs used for?

PFASs have been widely used to make products more stain-resistant, waterproof and/or nonstick. For example, PFASs have been used in the manufacture of products that:

  • keep food from sticking to cookware,
  • make upholstered furniture, carpets and clothing resistant to soil, stains and water,
  • make shoes, clothes and mattresses more waterproof,
  • keep food packaging from sticking to food, and
  • help fight fires at airfields and other places where petroleum-product-based fires are a risk.

Because they help reduce friction, they are also used by a variety of other industries such as aerospace, automotive, construction, and electronics factories or businesses.

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Where are PFASs made?

  • Certain PFAS chemicals, including PFOA and PFOS, are no longer manufactured in the United States as a result of voluntary phaseouts and the PFOA Stewardship Program, with a few exceptions for limited industrial uses.  As part of the Stewardship Program, eight major chemical manufacturers committed to eliminate by 2015:
    • the use of PFOA and PFOA-related chemicals in their products, and
    • PFOA and PFOA-related chemical emissions from their facilities.
    All companies have indicated that they have met the PFOA Stewardship Program goals. Learn more about the PFOA stewardship program.
  • Although PFOA and PFOS are no longer manufactured in the U.S., they are still produced in other locations around the globe, and they may continue to be imported into the United States in consumer goods such as carpets, leather and apparel, textiles, paper and packaging, coatings, and rubber and plastics.

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How widespread are these chemicals in the environment?

PFOA, PFOS and other PFASs are widespread around the globe, primarily due to their manufacturing, processing and use here in the U.S. and internationally.   They are widespread in part because they are persistent in the environment – that is, they do not break down when exposed to air, water or sunlight. As a result, people may become exposed to PFASs manufactured months or years in the past.

Due to their persistence, PFASs can travel long distances through the air; monitoring in the Arctic has shown levels of PFASs in air, water, and living things.  As a result, people may become exposed to low levels of PFASs manufactured or emitted from production facilities thousands of miles away.

Because these chemicals have been used in an array of consumer products, most people have been exposed to them.  Studies have found PFOS and PFOA in blood samples of humans and wildlife nationwide. Using data from CDC's 2003–2004 National Health and Nutrition Examination Survey (NHANES), scientists detected PFASs in over 98% of the thousands of blood samples collected during the survey.   In more recent years, blood sampling data indicate that exposures are declining in the U.S. population, most likely due to the decline in U.S. manufacturing resulting from the PFOA Stewardship Program

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How People are Exposed

How are people exposed to PFAS chemicals?

  • People can be exposed to low levels of PFASs through food, which can become contaminated with PFASs through:
    • contaminated soil and water used to grow the food,
    • food packaging, and
    • equipment used to process food. 
  • People can also be exposed to PFAS chemicals if they are released during the normal use, biodegradation or disposal of consumer products that contain PFASs present in commercially-treated products to make them stain- and water-repellent and/or to confer nonstick properties. These goods include carpets, leather and apparel, textiles, paper and packaging materials.
  • People who work at PFAS production facilities, or facilities that manufacture goods made with PFASs, may be exposed in certain occupational settings or through contaminated air.
  • Drinking water can be a source of exposure in communities where these chemicals have contaminated water supplies. Such contamination is typically localized and associated with a specific facility, for example,
    • an industrial facility where these chemicals were produced or used to manufacture other products, or
    • an oil refinery, airfield or other location at which they were used for firefighting. 

    PFOA and PFOS have been found in a number of drinking water systems due to localized contamination.  You can view more information about exposures to PFOS and PFOA through drinking water on our Drinking Water Health Advisories for PFOA and PFOS page.

  • Few scientific studies have evaluated exposures or related human health effects from inhalation of PFASs or skin exposure to PFASs.

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What steps should I take if I have reason to believe that I have been exposed to unsafe levels?

If you live in an area where the food or water is contaminated with levels of PFOA, PFOS or another PFAS that exceed health advisory levels, you should contact your state health department to see what steps they recommend. Recommendations will depend on the level, length and source(s) of contamination. Recommendations may include:

  • not drinking water from the public water supply,
  • not cooking with water from the public water supply, and/or
  • testing private wells.

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Health Effects

Why can exposure to these chemicals be a potential health concern?

Exposures to PFAS chemicals are known to have a number of adverse effects in laboratory animals and humans.

If humans or other animals ingestHelpingestionThe act of swallowing something through eating, drinking, or mouthing objects. A hazardous substance can enter the body this way. PFASs (by eating or drinking food or water than contain PFASs), the PFASs are readily absorbed, and can accumulate in the body. PFASs stay in the human body for long periods of time. As a result, as people get exposed to PFASs from different sources over time, the level of PFASs in their bodies may increase to the point where they suffer from adverse health effects.

Studies indicate that PFOA and PFOS can cause reproductive and developmental, liver and kidney, and immunological effects in laboratory animals.  Both chemicals have caused tumors in animal studies. The most consistent findings from human epidemiology studies are increased cholesterol levels among exposed populations, with more limited findings related to low infant birth weights, effects on the immune system, cancer for PFOA, and thyroid hormone disruption for PFOS.

Is cancer a concern?

The risk for cancer is characterized as suggestive for both PFOA and PFOS based on the animal data. Human epidemiology studies of a community identified an increased risk for kidney and testicular cancer in people who were highly exposed to PFOA. Chronic exposure to PFOA has been shown to lead to the development of testicular, pancreatic, and liver cancers in animals. Chronic exposure to PFOS has been shown to lead to liver tumors in animals.

What non-cancer health concerns are associated with PFASs?

Peer-reviewed studies of the effects of PFASs on laboratory animals (monkeys, rats and mice) and epidemiologicalHelpepidemiologyStudy of the distribution of disease, or other health-related states and events in human populations, as related to age, sex, occupation, ethnicity, and economic status in order to identify and alleviate health problems and promote better health. studies of human populations that have been exposed to PFASs indicate that exposure to PFOA and PFOS over certain levels may result in adverse health effects, including:

  • changes in cholesterol,
  • developmental effects to fetuses during pregnancy or to breastfed infants (e.g., low birth weight),
  • liver effects (e.g., tissue damage),
  • immune effects (e.g., depressed antibody production in response to vaccination), and
  • thyroid effects.

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Related Information from Other Sources

From EPA

From Other Governmental Organizations

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