What is Perfluorooctane Sulfonate (PFOS)?
PFOS is part of a larger group of chemicals called per- and polyfluoroalkyl substances (PFAS). These chemicals have unique properties that make them useful in many industries, commercial products, and personal products. PFOS is very stable in the environment and hard to breakdown. PFOS also moves easily through groundwater. PFOS is of particular concern because it can accumulate up the food chain in aquatic systems and can lead to high concentrations in predatory fish consumed by anglers. PFOS was phased out of use in the United States in 2002, but because it does not break down it is still found in water, air, and soil. However, the level of PFOS in people’s bodies has fallen more than 85% since its production and use stopped.
How can I be exposed to PFOS?
Before it was discontinued, PFOS was used in firefighting foam, many industries, and in a variety of consumer products. It has been used in food packaging, clothing, upholstery, and carpeting due to its ability to make materials water, oil, and stain resistant. Now that it has been phased out of use, people are mostly exposed to PFOS through contaminated food and water. PFOS can be found in the air, water, and soil due to release from factories producing and using the chemical including discharge from firefighting foam and PFOS-containing water from wastewater treatment plants. Because many of these discharges contaminated surface water, PFOS can be found in certain species of fish in some waterways. Eating too many contaminated fish could increase PFOS exposure. PFOS can also move into groundwater, so communities near factories or airports that used PFOS in the past might also have higher levels of PFOS in their drinking water.
How can PFOS affect my health?
Evidence suggests associations between increases in exposure to PFOS and increased cholesterol or changes in liver enzymes. Exposure can also lower response to some vaccines. It can cause pregnancy-induced hypertension (high blood pressure) and preeclampsia, and a decrease in birth weight.
How likely is PFOS to cause cancer?
Animal studies have found that PFOS can cause cancer in the liver, pancreas, testes, and thyroid. However, studies do not show clearly if PFOS causes cancer in humans.
The International Agency for Research on Cancer (IARC) has classified PFOS as possibly carcinogenic (cancer causing) to humans. In a human health toxicity assessment for PFOS, EPA determined that it is “likely to be carcinogenic to humans”.
How can I reduce exposure to PFOS?
Follow fish consumption advisories to reduce exposure to PFOS. People with private wells should consider testing their well water for PFOS, especially if they are near an area with known PFOS contamination, an airport, military base, or industrial area. PFOS is not typically included in well water testing, so most wells have not been tested for PFOS.
Has the federal government made recommendations to protect human health?
In 2024, the EPA announced a new maximum contaminant level (MCL) of 4 parts per trillion for PFOS in drinking water. The MCL indicates how much PFOS can be in water and still be considered safe.
Where can I get more information about PFOS?
ATSDR Webpage: https://www.atsdr.cdc.gov/pfas/index.html last accessed June 2025
EPA Technical Fact Sheet PFOS: ffrrofactsheet_contaminants_pfos_pfoa_11-20-17_508_0.pdf last accessed June 2025
This fact sheet was made possible by a cooperative agreement [program # CDC-RFA-TS-23-0001] from the Agency for Toxic Substances and Disease Registry (ATSDR). Its contents are solely the responsibility of the Virginia Department of Health, toxicology program and do not necessarily represent the official views of the ATSDR, or the U.S. Department of Health and Human Services.