The Basic Science: What Makes PFAS "Forever Chemicals"?

PFAS are defined by one critical feature: an extremely strong carbon-fluorine (C-F) bond. This is one of the strongest bonds in organic chemistry. It gives PFAS their remarkable properties — heat resistance, water repellency, oil resistance, and chemical stability — that made them so useful in industrial and consumer applications since the 1940s.

That same indestructibility is what makes PFAS so dangerous. Unlike most organic compounds, PFAS do not break down through natural environmental processes — not through ultraviolet light from the sun, not through biodegradation by bacteria, not through normal water treatment. They persist in soil, groundwater, surface water, and the human body for decades.

Key Fact: PFAS were found in the blood of 97% of Americans tested in a 2007 National Health and Nutrition Examination Survey (NHANES), demonstrating near-universal exposure of the U.S. population.

The PFAS Family: PFOA, PFOS, GenX and More

The PFAS family includes over 12,000 distinct compounds. The most studied and most litigated are:

PFOA (Perfluorooctanoic Acid)

Also called "C8" (for its 8-carbon chain), PFOA was used by DuPont for over 50 years in the manufacture of Teflon (polytetrafluoroethylene, or PTFE) nonstick coatings. It was also used in food packaging, carpet treatment, and waterproof fabrics. The EPA classifies PFOA as a probable human carcinogen, specifically for kidney cancer and testicular cancer. DuPont's own internal research dating to the 1960s showed PFOA caused health effects in laboratory animals — but the company continued using it for decades.

PFOS (Perfluorooctane Sulfonic Acid)

PFOS was 3M's flagship PFAS compound, used in Scotchgard fabric and upholstery protector and as the key ingredient in AFFF (aqueous film-forming foam) firefighting foam. 3M's own research in the 1970s showed PFOS was accumulating in human blood globally — including in the blood of their own employees and the general public who had no direct contact with their products. 3M voluntarily phased out PFOS production in 2002 under EPA pressure, but the chemical remains in the environment indefinitely.

GenX Chemicals (HFPO-DA)

After PFOA was phased out under a 2006 EPA stewardship agreement, DuPont's spinoff company Chemours began using GenX chemicals as a replacement at its Fayetteville Works plant in North Carolina. GenX was discharged into the Cape Fear River, contaminating drinking water for communities in the Wilmington, NC area. GenX exhibits similar persistence and toxicity to PFOA, raising serious questions about whether it is truly a safer alternative or simply a delayed liability.

Short-Chain PFAS: PFBS, PFHxS, PFNA, PFHpA

When long-chain PFAS like PFOA and PFOS were phased out, manufacturers introduced "short-chain" PFAS alternatives with 6 or fewer carbons, marketed as safer. Growing scientific evidence shows that short-chain PFAS are also persistent, bioaccumulative to varying degrees, and potentially toxic — they simply haven't been studied as long.

How PFAS Get Into Drinking Water

PFAS contaminate water supplies through several pathways:

  • Industrial discharge: Facilities that manufacture or use PFAS discharge them into wastewater, which enters rivers and groundwater. This is how DuPont contaminated the Ohio River near Parkersburg, WV for decades.
  • AFFF firefighting foam: When AFFF is applied — in military fire training, airport crash rescue, or industrial fire suppression — PFAS leaches through soil into groundwater. This has contaminated drinking water near hundreds of U.S. military installations.
  • Sewage sludge (biosolids): PFAS accumulates in sewage treatment plants and concentrates in the resulting biosolids, which are applied to agricultural fields as fertilizer — leaching PFAS into soil and groundwater.
  • Landfill leachate: Consumer products containing PFAS end up in landfills, where water percolating through the waste picks up PFAS and can contaminate surrounding groundwater.
  • Industrial sites: Textile mills (particularly in North Carolina and Georgia), paper mills, and semiconductor manufacturers have released PFAS into local waterways.

The EPA's UCMR 5 monitoring program, which required testing of large water systems between 2023 and 2025, found PFAS contamination in water systems serving millions of Americans. In April 2024, the EPA finalized the first-ever Maximum Contaminant Levels (MCLs) for PFAS — setting enforceable limits of 4 parts per trillion for PFOA and PFOS.

PFAS and the Human Body: Bioaccumulation

Unlike many toxins that are metabolized and excreted, PFAS bind to proteins in the blood and accumulate in organs — particularly the liver, kidney, and thyroid. They cross the placenta and are found in breast milk, meaning exposure begins before birth and continues through infancy.

The biological half-life (time for the body to eliminate half the dose) of long-chain PFAS is measured in years — not hours or days. PFOA has an estimated half-life of 3–5 years in humans. PFOS has a half-life of approximately 5 years. This means that even after PFAS exposure stops, the chemical continues to affect the body for years.

The History of PFAS: A Cover-Up Decades in the Making

The story of PFAS is largely a story of corporate concealment:

  • 1950s–1960s: 3M and DuPont begin manufacturing PFAS at scale. Early animal studies raise health concerns that are not disclosed publicly.
  • 1976: 3M's internal blood monitoring program finds PFOS in the blood of 3M workers and the general public. The company does not disclose this to regulators.
  • 1980s–1990s: DuPont's health registry documents elevated rates of rare diseases in communities near its Parkersburg, WV plant. The company conducts a secret study — the "C8 Medical Surveillance Program" — but suppresses the results.
  • 2001: West Virginia attorney Robert Bilott (later profiled in the film "Dark Waters") files the first major PFAS lawsuit against DuPont on behalf of Parkersburg residents.
  • 2005: EPA fines DuPont $16.5 million for withholding health data on PFOA — the largest administrative penalty in EPA history at the time.
  • 2006: EPA launches the PFOA Stewardship Program, pressuring manufacturers to phase out PFOA by 2015.
  • 2017: DuPont settles with ~3,550 Ohio and West Virginia plaintiffs for $671 million.
  • 2023: 3M and DuPont/Chemours reach landmark settlements with U.S. water utilities totaling over $11 billion.
  • 2024: EPA finalizes first-ever PFAS MCLs for drinking water.

Regulatory Status of PFAS

The U.S. regulatory response to PFAS has accelerated significantly in recent years:

  • EPA MCLs (April 2024): Maximum Contaminant Levels of 4 ppt for PFOA and PFOS; 10 ppt for PFHxS, PFNA, and HFPO-DA (GenX); and a combined limit for mixtures. Water systems have until 2029 to comply.
  • PFAS Hazardous Substance Designation (2024): EPA designated PFOA and PFOS as CERCLA hazardous substances, triggering Superfund cleanup authority at contaminated sites.
  • NDAA 2020: Congress banned the procurement of AFFF containing PFAS by the Department of Defense and required military transition to PFAS-free foam alternatives.
  • State action: Multiple states have enacted PFAS standards stricter than federal limits, including Michigan, Vermont, Massachusetts, and New Hampshire.
How PFAS Gets Into Your Drinking Water →