What Are PFAS? Definition, Sources, and Health Risks

What products in your home contain these dangerous "forever chemicals"?

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PFAS are a group of thousands of lab-created chemicals in the per- and polyfluoroalkyl group. These organic compounds have been around for decades and have been used around the world for different manufacturing processes. They are made of a chain of carbon and fluorine atoms, which is one of the strongest chemical bonds possible. Known by the ominous nickname “forever chemicals,” PFAS do not break down and disappear in the environment the way many chemicals do. Because of this, they can last a long time in the soil and water. They eventually make their way into humans, where they have been linked to a variety of adverse health effects.


One of the most common members of the PFAS family is perfluorooctanoic acid (PFOA), a chemical that was used to produce polytetrafluoroethylene (PTFE), also known as Teflon. First discovered at a DuPont Laboratory in 1938, PTFE was initially used by the U.S. military for the isolation and purification of uranium-235 during the top-secret Manhattan Project. It’s been used as a coating for cookware, fabrics, surgical implants, and chemical containers because of its non-stick nature and water repellent properties. It also acts as a good insulator, which makes it useful in the manufacture of medical devices and semiconductors.

PTFE itself is still used in these products, but PFOA has not been on its ingredient list since 2002, when manufacturers began using a new process that no longer required it. Other companies, however, continued using PFOA until 2006 when the EPA asked eight major companies to work to eliminate PFOA production and use by the end of 2015. Under this stewardship program, the companies agreed to halt the use of PFOA. As of 2016, all eight had stopped producing and using the chemical. But even though companies in the U.S. have phased out PFOA, international manufacturers continue to use it. Those products can still be imported to the U.S. and sold to consumers. The EPA has proposed regulations for imported products that contain PFOA, but regulations aren’t currently in place. In addition, since these are "forever chemicals," the contamination caused by earlier usage of PFOA still remains in the environment.

The same resistant properties that made PFOA so useful in products like fire fighting foam and for industrial processes is the reason it does not break down in the environment. Researchers at The Ohio State University and the EPA found evidence that PFOA from a manufacturing facility in West Virginia had spread through the air and had accumulated in the soil and water in areas far away from the plant. PFOA’s persistence is the reason that people are still drinking contaminated water years after it was phased out by manufacturers. In fact, the EPA believes that most people are exposed to PFOA through their water supply, contaminated foods, or by coming into contact with products like carpet, furniture, clothing, food packaging, and cookware that contain it. The CDC found that a majority of the more than 2,000 participants in a nationwide study had PFOA in their blood serum. They concluded that PFOA exposure is widespread in the U.S., although data show that between 1999 and 2014, PFOA levels in blood serum have decreased by over 60%.

While the levels of PFOA in humans are decreasing, the health effects of the persistent chemical continue to linger. One study by a team of researchers at the University of California, Johns Hopkins University, and the EPA, found that increased exposure to PFOA during human fetal development was associated with a decrease in birth weight. Other studies have indicated that PFOA exposure through contaminated drinking water may result in negative health outcomes like cancer, liver tissue damage, thyroid problems, and harm to the immune system.

Even though studies on the health effects of PFOA are ongoing, the EPA established a health advisory for PFOA in drinking water to protect the public from concentrations high enough to cause health problems. The current maximum limit of PFOA in water is 70 parts per trillion (ppt), and the EPA announced plans to begin regulating PFOA in drinking water under the Safe Drinking Water Act.


Firefighters extinguish a fire. Lifeguards with fire hoses in smoke and fire.
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Perfluorooctane sulfonic acid (PFOS) was first produced in the 1940s, and by the 1950s it was being used to make stain- and water-resistant products as an ingredient in 3M’s Scotchguard. It quickly became an important component of aqueous film forming foam (AFFF), also known as firefighting foam. PFOS is highly stable because of its strong carbon-fluorine bonds. It does not break down in the environment or when it gets into living organisms. It also bioaccumulates, which means it builds up in living organisms. As it makes its way up the food chain, the amount of PFOS within each level increases exponentially. The organisms at the top of the food chain tend to have the highest amounts of PFOS in their blood and tissue.

PFOS was used widely until 2001, when the United Nations introduced a treaty known as the Stockholm Convention on Persistent Organic Pollutants (POPs). The goal of the treaty was to reduce or altogether halt the production and use of POPs. While the initial treaty did not include PFOS, an amendment was added in 2009 that included the chemical because of its ability to persist in the environment no matter what the condition.

In 2006, the EPA asked companies responsible for PFOS to eliminate its production and use. All of the companies had phased out PFOS in their factories by 2016. However, international manufacturers continue to use it, and production of PFOS has increased since then due to the lack of supply from the U.S. Products containing PFOS are still imported and sold in the U.S., though the EPA has proposed—but not yet implemented—regulations for imported products that contain PFOS.

Like PFOA, PFOS presence is enduring and has been found in surface water and in wastewater effluent. Sewage sludge and sediment also commonly contain detectable levels of PFOS. People that lived near facilities that used or produced PFOS or worked in those facilities had higher blood serum levels of PFOS than those who were not associated in any way with PFOS manufacturing. There is some evidence to suggest that PFOS exposure is associated with high cholesterol and developmental and reproductive abnormalities, and may even cause thyroid hormone disruption. 

GenX and Other PFAS

PFOA and PFOS were the two most widely used types of PFAS chemicals, but they’re not the only chemicals of concern. One of the newest types of PFAS is GenX, the trade name for the process used to make certain nonstick coatings without using PFOA. GenX technology primarily uses HFPO dimer acid and ammonium salt, but it’s possible that these chemicals aren’t any better than the ones they replaced. They have been found in drinking water, air emissions, rainwater, and groundwater.

Residents of Wilmington, North Carolina, learned of the presence of GenX in their drinking water in 2017 after the North Carolina Department of Health and Human Services and the North Carolina Department of Environmental Quality started investigating the release of chemicals from the Chemours company. The facility, located on the Cape Fear River upstream of Wilmington, had been dumping GenX into the river since 2009. The Chemours company had been disposing of other PFAS chemicals like PFOA since 1980. During its investigation into the illegal dumping, the State of North Carolina collected blood samples from residents around the Cape Fear River and found 10 different PFAS present. Four of the PFAS compounds were unique to the Chemours facility upstream.

The National Institute for Environmental Health Sciences estimates that there are over 4,700 different kinds of PFAS chemicals, a number that is expected to grow as the industry invents new PFAS formulations. In an international consensus statement known as the Zurich Statement, scientists and policymakers agreed that instead of trying to determine the health and environmental effects of each individual chemical within the PFAS family, research moving forward should be focused on PFAS as a whole and what can be done about it. Because there has been so little research done on a majority of PFAS, there are many unknowns about the possible health and environmental damage these chemicals could be doing. And while PFOA and PFAS have been regulated on some levels, the rest of the PFAS chemicals have no limits on their use and exposure to humans and the environment.

List of the Most Common PFAS

  • Perfluorooctanoic acid (PFOA): Used in nonstick products.
  • Perfluorooctanesulfonic acid (PFOS): Used for water- and stain-proofing fabrics, fire-fighting foam.
  • Perfluoropropanoic acid (PFPA): Chemical reagent.
  • Carboxylic acids and their anions and salts (GenX): Processing aid for fluoropolymers.
  • 3H-Perfluoro-3-[(3-methoxy-propoxy) propanoic acid], ammonium salt (ADONA): Production of fluoropolymers.
  • Perfluorobutanesulfonic acid (PFBS): Industrial surfactant.
  • Sulfluramid: Pesticide.
  • 8:2 Fluorotelomer alcohol (8:2 FTOH): Stain-resistance.
  • 6:2 Fluorotelomer sulfonic acid (6:2 FTSA): Fire-fighting foam.
  • Hydro-EVE acid: By-product of Nafion manufacture.

PFAS in Water

The EPA claims that PFAS in drinking water is typically localized and usually the result of contamination from a specific facility that was known to have used or manufactured the chemicals. PFAS can contaminate surface water and well water. The EPA does not, however, say what they mean by localized. And because drinking water is often pulled from surface water at several points along a river system, it’s possible that drinking water far from the source of contamination can contain significant amounts of PFAS. This was the case for GenX in North Carolina, where the Chemours company dumped the chemical into the Cape Fear River at Fayetteville and it was found in a major drinking water supply nearly 100 miles away.

Drinking contaminated water is one of the most common ways people are exposed to PFAS. When ingested, PFAS is absorbed into the blood and tissue and can accumulate over time. Because it stays in the body for such a long time, extended exposure to PFAS can cause it to build up in the body to levels that may negatively affect health.

While the health risks of exposure for humans are still not completely clear, researchers are working to discover all of the adverse health effects caused by PFAS. Most of the studies of the effects of PFAS have been done on laboratory animals. But studies done on humans exposed to PFAS have also shown possible links between chemical exposure and health. One of the suspected health effects of PFAS is hormone disruption. Researchers at Harvard University found that patients with higher baseline levels of PFAS in their blood plasma gained more weight back after dieting than those with lower levels of PFAS. Another study linked PFOS and PFOA to decreased average birth weight in babies born to patients with the chemicals in their blood.

What Can We Do?

Protecting yourself from PFAS can be difficult, but there are some steps you can take to reduce your exposure. Purchasing a drinking water filter is one way that consumers can protect themselves from PFAS. A study out of Duke University found that under-sink dual-stage and reverse osmosis water filters removed nearly all of the PFAS that was present in the unfiltered drinking water. Less expensive filtration options also worked to remove at least some of the PFAS in the water.

The FDA still allows the use of PFAS in what they call “food contact substances” such as non-stick cookware and food packaging. It has determined that there is “reasonable certainty” that the PFAS in these products will not harm people. By avoiding fast-food wrappers, microwave popcorn bags, paperboard containers, and non-stick cookware, you can reduce your chances of PFAS exposure. 

PFAS may also be in clothing and other products, so reading labels for chemicals used to treat fabrics for water or stain resistance may help you avoid exposure, although most PFAS exposure happens through ingestion and not the absorption of the chemicals through your skin. As more information comes out about the effects of PFAS on human health, it’s likely that more consumer-friendly regulations will be put in place to help people avoid PFAS in their daily lives.  

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