PFAS forever chemicals are now detectable in the blood of virtually every human on Earth. They do not break down. Linked to cancer, immune failure, and hormonal disruption — and the companies that made them knew, for decades, before anyone else did.
In 1999, the United States Centers for Disease Control began testing blood samples from a representative sample of the American population for a class of industrial chemicals that had never been routinely measured in human tissue. They found what the chemical companies manufacturing these substances had suspected, and concealed, for thirty years: PFAS were everywhere. In farmers and office workers. In children and elderly people. In remote rural communities with no industrial activity nearby. In the blood of the general population, without exception.
By the time the CDC's National Health and Nutrition Examination Survey had processed enough samples to publish, the picture was unambiguous. More than 97% of Americans tested had measurable concentrations of at least one per- and polyfluoroalkyl substance in their blood. Similar surveys in Europe and elsewhere produced comparable results. Subsequent testing found PFAS in Arctic polar bears, in Antarctic penguins, in the blood of newborn infants via the placenta, in breast milk. The contamination was not regional. It was not occupational. It was total.
PFAS — per- and polyfluoroalkyl substances — are a family of more than 12,000 synthetic chemicals that share a common structural feature: a backbone of carbon atoms bonded to fluorine. The carbon-fluorine bond is the strongest bond in organic chemistry, with a bond energy of approximately 544 kilojoules per mole. It does not break under normal environmental conditions. It does not break in human metabolism. It does not break in water treatment, soil decomposition, or biological degradation. It simply does not break. This is why the industry gave them a marketing name that has become their epitaph: forever chemicals.
PFAS were first synthesized by 3M in the late 1940s. The flagship product was PFOS — perfluorooctane sulfonic acid — the active ingredient in Scotchgard fabric protector and in aqueous film-forming foam (AFFF), the firefighting foam used on military bases and commercial airports worldwide. DuPont independently developed PFOA — perfluorooctanoic acid — as a processing aid for Teflon non-stick coatings. For five decades, both companies sold these chemicals in enormous volumes while possessing internal research documenting serious health concerns they did not share with regulators, workers, or the public.
The routes of human exposure are effectively impossible to avoid. PFAS leach from food packaging — the grease-resistant coating on fast food wrappers, microwave popcorn bags, and pizza boxes. They are present in the non-stick surfaces of cookware, in water-resistant fabrics, in dental floss, in cosmetics. They enter drinking water from contaminated groundwater near industrial sites, military bases, and landfills. A 2023 study by the United States Geological Survey found PFAS in 45% of US tap water samples from a nationally representative network — including samples from small municipal systems and private wells in areas with no known industrial contamination. The chemicals have dispersed so thoroughly through the environment that exposure is no longer primarily a matter of proximity to a source. It is simply a condition of modern life.
To understand why PFAS are classified as persistent organic pollutants — in the same regulatory category as PCBs and DDT — it helps to understand what makes the carbon-fluorine bond exceptional.
Fluorine is the most electronegative element on the periodic table: it draws electrons toward itself more strongly than any other atom. When fluorine bonds to carbon, it creates an extremely stable, low-energy configuration. The C-F bond energy of 544 kJ/mol compares to approximately 411 kJ/mol for a carbon-hydrogen bond and 339 kJ/mol for a carbon-carbon bond. The fluorine atoms also shield the carbon backbone from chemical attack — their tight electron cloud repels water, oils, and other reactive molecules. This is precisely what makes PFAS so useful industrially: a fluorinated carbon chain resists heat, repels water, resists chemical degradation, and reduces friction. It is also precisely what makes it indestructible in the environment.
Most organic pollutants, given enough time, are broken down by soil bacteria, metabolized by animals, or degraded by UV light. PFAS resist all of these processes. In human blood, the half-life of PFOA — the time it takes for the body to eliminate half of a given dose — is approximately 3.8 years. PFOS has a half-life of around 5 years. These are among the longest half-lives of any environmental chemical in human biology. Even with zero new exposure, a person contaminated with PFAS would carry half of that load seven years later, a quarter of it fourteen years later. Continuous low-level exposure, which is the situation faced by virtually everyone alive, means blood concentrations stabilize rather than declining.
In 2016, the Stockholm Convention — the international treaty governing persistent organic pollutants — listed PFOS and PFOA for global elimination. Most PFAS production in the United States and Europe has shifted to newer "short-chain" PFAS, which are promoted as replacements. Research has found that short-chain PFAS are also persistent, also bioaccumulate in some tissue types, and also show biological activity. The industry transition from long-chain to short-chain PFAS has been described by environmental chemists as "regrettable substitution" — replacing one problematic class with another whose health effects are less studied but not demonstrably safer.
The environmental persistence of PFAS creates a compounding problem. They accumulate in soil and water systems over decades. They bioaccumulate in organisms — concentration increasing at each step up the food chain, so that a predator at the top of a food web carries concentrations of PFAS that are orders of magnitude higher than the water or soil it ultimately derives them from. Polar bears in the High Arctic, thousands of miles from the nearest industrial source, carry PFAS concentrations in their blood that are associated with immune suppression and hormonal disruption in laboratory studies. The contamination of remote wildlife is not a curiosity. It is a measure of how thoroughly these chemicals have distributed themselves through the planetary circulation of air and water.
The companies knew. The documents exist, they were eventually produced in litigation, and they describe internal studies from the 1960s and 1970s showing toxicity that was never disclosed. This is not a case of science catching up with industry. It is a case of industry concealing science from everyone else.
The science of PFAS health effects is extensive, still growing, and consistently alarming. The strongest and most replicated associations are with kidney cancer and testicular cancer, thyroid disease, elevated cholesterol, high blood pressure in pregnancy, low birth weight, and suppression of immune response. The evidence for each of these links has been built painstakingly through epidemiological studies of exposed populations, animal experiments, and mechanistic research, over decades — much of it driven by researchers who were working against an active industry disinformation effort.
The C8 Health Project offers the most detailed long-term picture of PFAS exposure and human health. DuPont's Washington Works plant in Parkersburg, West Virginia, had released PFOA into the local water supply for decades. In 2001, after a lawsuit brought by farmer Wilbur Tennant — whose cattle were dying after drinking water from a creek contaminated by DuPont landfill runoff — the company agreed to fund an independent science panel. The C8 Science Panel spent seven years analyzing health data from 69,000 people in the Mid-Ohio Valley. Their conclusions were unambiguous: PFOA exposure had a "probable link" to kidney cancer, testicular cancer, thyroid disease, high cholesterol, ulcerative colitis, and pregnancy-induced hypertension. DuPont's own internal research had reached similar conclusions as early as the 1970s. The company did not disclose these findings.
The immune effects are particularly troubling from a public health perspective. A series of studies led by Philippe Grandjean and colleagues found that PFAS exposure in children suppressed the antibody response to vaccines — including standard childhood vaccinations against diphtheria and tetanus. Children with the highest PFAS exposure produced roughly half the antibody titers of children with the lowest exposure, suggesting that PFAS contamination may be quietly undermining vaccination programmes at a population level. A 2020 study estimated that PFAS exposure may have increased the susceptibility of exposed populations to infectious diseases and reduced the effectiveness of childhood immunisation globally.
The endocrine disruption properties of PFAS connect them directly to other stories in this series. PFAS interfere with oestrogen and testosterone signalling, with thyroid hormone function, and with the hormonal regulation of metabolism. Researchers studying the global decline in sperm count have identified PFAS as one of the candidate endocrine disruptors whose cumulative exposure may be contributing to the trend. The overlap between PFAS contamination, microplastic exposure, and reproductive health outcomes is substantial enough that some researchers now refer to a "chemical cocktail" effect — where the combined burden of multiple endocrine-disrupting substances creates effects that exceed what any single compound would produce alone.
In April 2024, the United States Environmental Protection Agency finalised the first federal drinking water standards for PFAS. The Maximum Contaminant Levels set enforceable limits for PFOA and PFOS at 4 parts per trillion — a limit set at the lowest level that analytical methods can reliably detect, which itself signals something about how seriously the EPA now takes the risk. The rule also set limits for four additional PFAS compounds and a "hazard index" limit for mixtures.
The cost of complying with these limits is staggering. The EPA's own estimate projected that bringing US drinking water systems into compliance would cost approximately $1.5 billion per year, a figure that independent analyses suggest is substantially lower than the actual remediation costs water utilities will face. The Association of Metropolitan Water Agencies estimated total costs for large utilities alone could run to hundreds of billions of dollars over the compliance period. Many of the contaminated water systems are in communities that cannot afford the treatment infrastructure required. The companies that produced these chemicals — 3M agreed to pay $10.3 billion in a settlement with US public water suppliers in 2023, DuPont and Chemours reached a separate $1.18 billion settlement — have contributed less than the full cost of cleanup by any measure.
Remediation of contaminated soil and groundwater is an even larger and less tractable problem. PFAS contamination from military base firefighting foam — the United States Department of Defense has identified more than 700 installations with known or suspected PFAS contamination — has spread into surrounding communities' drinking water supplies across the country. The Pentagon's own estimates for cleaning up PFAS at military sites run into tens of billions of dollars, and the feasibility of complete remediation is uncertain. No proven technology exists to fully extract PFAS from contaminated aquifers at scale. Emerging techniques using electrochemical oxidation and certain mineral substrates show promise in laboratory settings. None are ready to deploy across the hundreds of thousands of contaminated sites that exist in the United States alone, let alone globally.
What makes PFAS distinct from many other environmental contamination stories is the combination of universality, irreversibility, and established corporate foreknowledge. This is not a case of science discovering harm that industry could not have anticipated. The documents produced in litigation establish that both 3M and DuPont conducted internal studies showing the toxicity of their flagship PFAS compounds, classified those studies as confidential, and continued selling the chemicals while opposing regulatory scrutiny. The legal and financial reckoning that has followed — the settlements, the regulatory action, the growing body of personal injury litigation — has been significant. The contamination it was meant to prevent is already complete. Every person reading this article carries these chemicals in their blood, placed there by decisions made before most of them were born. The C-F bond will be there for years to come. The question now is only how thoroughly we understand what it is doing.
© 2026 Lisa Pedrosa · lisapedrosa.com
All articles cited to primary institutional or peer-reviewed sources
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