What Are PFAS Forever Chemicals? Health Risks, Sources, and Exposure

What Are PFAS "Forever Chemicals"?

Per- and polyfluoroalkyl substances, commonly known as PFAS, are a large group of more than 12,000 man-made chemicals that have been manufactured and used in a wide variety of industries since the 1940s. The defining feature of PFAS is the carbon-fluorine bond, one of the strongest bonds in organic chemistry. This extreme chemical stability is precisely why PFAS are called "forever chemicals" by the EPA: they do not naturally break down in the environment or in the human body.^[1]

PFAS are characterized by their remarkable resistance to heat, oil, grease, and water. These properties made them commercially valuable for decades. However, the same characteristics that made them useful in consumer products have made them a persistent environmental and public health crisis. Once PFAS enter the environment or the human body, they accumulate indefinitely.^[1]

The two most extensively studied PFAS are PFOA, historically used by DuPont in manufacturing Teflon nonstick coatings, and PFOS, historically manufactured by 3M and used in the firefighting foam AFFF (aqueous film-forming foam). Both PFOA and PFOS have largely been phased out in the United States, but they persist in the environment, in drinking water, and in the blood of virtually every American tested. Newer replacement PFAS chemicals are now raising their own health concerns.^[2]

Where Do PFAS Come From?

PFAS have been used in an extraordinarily wide range of industrial and consumer applications. The Agency for Toxic Substances and Disease Registry (ATSDR) identifies the following as major sources of PFAS exposure:^[2]

• Aqueous film-forming foam (AFFF): Firefighting foam used extensively at military bases, civilian airports, and by fire training facilities. AFFF is the single largest source of PFAS contamination in drinking water near military installations.
• Nonstick cookware: PFOA was used to manufacture Teflon and similar coatings until 2013, when manufacturers voluntarily phased it out under EPA's PFOA Stewardship Program.
• Food packaging: PFAS are used in grease-resistant food packaging such as microwave popcorn bags, pizza boxes, fast food wrappers, and paper plates.
• Stain-resistant textiles: PFAS-based treatments such as Scotchgard (3M) are used on carpets, upholstery, and clothing to repel water and stains.
• Industrial manufacturing: Semiconductor fabrication, chrome plating, and oil and gas production have historically used PFAS compounds.
• Personal care products: Some waterproof mascaras, foundations, and shampoos contain PFAS as a stabilizer.
• Water-resistant outdoor gear: Gore-Tex and similar materials use PFAS-based durable water repellents (DWRs).

The most significant pathway for human PFAS exposure is contaminated drinking water. The Environmental Working Group's Tap Water Database has documented PFAS contamination at more than 2,800 locations across all 50 states. Communities near military bases and industrial facilities using AFFF are at the highest risk, with some water systems reporting PFAS levels orders of magnitude above the EPA's 2024 health standards.^[3]

Dietary exposure is also significant. PFAS-contaminated water used for irrigation or livestock drinking can transfer these chemicals into the food supply. The FDA has detected PFAS in seafood, leafy green vegetables, and dairy products from contaminated agricultural regions. PFAS from food packaging can migrate into food, particularly when packaging is heated.^[4]

Health Risks of PFAS Exposure

Extensive research has linked PFAS exposure to a range of serious health conditions. ATSDR's comprehensive toxicological profile for PFAS identifies the following health effects as supported by the scientific evidence:^[2]

• Kidney cancer: Studies of workers exposed to PFOA at DuPont facilities and community members near manufacturing sites have shown elevated rates of kidney cancer. PFOA is classified as possibly carcinogenic to humans by the International Agency for Research on Cancer (IARC).
• Testicular cancer: Research on communities near PFOA manufacturing facilities and on PFAS-exposed military personnel has consistently found elevated rates of testicular cancer.
• Thyroid disease and thyroid cancer: PFAS interfere with thyroid hormone production and regulation. Studies have linked PFAS exposure to both hypothyroidism and thyroid cancer.
• High cholesterol (hypercholesterolemia): One of the most consistently observed effects; PFAS appear to interfere with lipid metabolism.
• Ulcerative colitis: Inflammatory bowel disease has been linked to PFAS exposure, particularly PFOA, in community health studies.
• Immune system suppression: PFAS reduce the effectiveness of vaccines and weaken the immune response, particularly in children.
• Pregnancy complications: PFAS exposure during pregnancy is associated with pregnancy-induced hypertension, preeclampsia, and low birth weight.
• Liver damage: PFAS accumulate in the liver and are associated with elevated liver enzymes, non-alcoholic fatty liver disease, and hepatotoxicity.

Children face heightened risks from PFAS exposure because their immune and endocrine systems are still developing. Research has linked childhood PFAS exposure to reduced vaccine response, altered thyroid function, and metabolic disruption. The National Institute of Environmental Health Sciences (NIEHS) is actively funding research to better characterize the developmental effects of PFAS.^[5]

How PFAS Accumulate in the Body

Unlike many toxic chemicals, PFAS are not metabolized by the body. Once ingested or inhaled, certain PFAS bind to proteins in the blood, particularly albumin and lipoproteins, and are transported to organs including the liver, kidneys, and thyroid. Because they are not metabolized, PFAS accumulate with each subsequent exposure in a process called bioaccumulation.^[2]

The biological half-life of PFAS varies by compound. PFOS has an estimated half-life in humans of approximately 5 years; PFOA has a half-life of approximately 3.5 years. This means that even after PFAS exposure ends, these chemicals remain in the body for years or even decades. People with occupational or drinking water exposure to PFAS can carry elevated blood PFAS levels for the rest of their lives.^[2]

National health surveys conducted by the CDC through the National Health and Nutrition Examination Survey (NHANES) have found detectable levels of PFAS in the blood of approximately 97 percent of Americans tested. This near-universal exposure reflects decades of PFAS use in consumer products, industrial processes, and firefighting activities, and the subsequent contamination of air, water, soil, and food supplies.^[6]

Who Is Most at Risk?

While virtually all Americans carry some PFAS in their blood, certain populations face significantly higher exposure levels and associated health risks:

• Residents near military bases: Over 700 military installations have confirmed PFAS contamination in their drinking water, according to the Department of Defense. Communities near these bases, where AFFF was used in training exercises for decades, often have water PFAS levels far exceeding federal health advisories.
• Firefighters: Career firefighters have among the highest occupational PFAS exposures due to direct contact with AFFF during training and response, as well as PFAS off-gassing from burning materials containing flame retardants.
• Workers at PFAS manufacturing facilities: Former DuPont employees at the Washington Works plant in West Virginia and 3M employees at manufacturing facilities have demonstrated significantly elevated PFAS blood levels and corresponding health outcomes.
• Residents of communities with contaminated water: Towns served by water utilities drawing from PFAS-contaminated groundwater or surface water face ongoing exposure.
• Children: Pound-for-pound, children consume more water than adults and are therefore more vulnerable to waterborne PFAS. Infants fed formula reconstituted with contaminated tap water face particularly high exposure.
• Subsistence fishers and farmers: People who fish from or irrigate crops with PFAS-contaminated water may have elevated dietary PFAS exposure.

What the Government Is Doing

In April 2024, the EPA finalized the first-ever federal drinking water standards for PFAS. The Maximum Contaminant Levels (MCLs) set the limit for PFOA at 4 parts per trillion (ppt) and PFOS at 4 ppt, with additional standards for PFNA, PFHxS, HFPO-DA (GenX), and mixtures of PFAS. Water utilities must comply by 2029.^[1]

The EPA estimates that these standards will reduce PFAS exposure for approximately 100 million Americans and prevent thousands of deaths from cancer and other PFAS-related illnesses over the coming decades. Compliance will require many water utilities to install expensive treatment systems, such as granular activated carbon or reverse osmosis filtration.^[1]

Congress passed the PFAS Action Act and included PFAS provisions in the Infrastructure Investment and Jobs Act of 2021, which allocated $10 billion for PFAS remediation in drinking water systems. The Department of Defense has also been required to begin phasing out AFFF and transitioning to fluorine-free firefighting foams at all military installations by 2024.^[4]

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