PFAS, the «forever chemicals»: they are already in everyone's bloodstream

There is a class of molecules first synthesised by humans in the 1940s that, eighty years later, can be found in the blood of practically anyone on the planet who has a sample drawn. The U.S. CDC, through the NHANES programme, has been measuring them in representative population samples since 1999. The figure that emerges every year is uncomfortable: more than 98% of tested Americans have detectable PFAS in their blood. Mean PFOS concentrations have fallen by more than 85% and PFOA by more than 70% since the year 2000, but the presence is essentially universal and, in adolescents, it remains measurable even in those born after the companies stopped making the best-known versions. The relevant question is not whether we carry PFAS in our bodies. It is how they got there, what they do once inside, and why it took seven decades to regulate their entry into tap water.

PFAS are per- and polyfluoroalkyl substances: carbon chains in which some or all carbon-hydrogen bonds have been replaced with carbon-fluorine bonds. That bond, one of the most stable in organic chemistry, is what gives them their valuable industrial properties (water-repellent, stain-resistant, fire-resistant, acid- and grease-resistant) and at the same time earns them the «forever chemicals» nickname: once made, they do not decompose on human timescales.

Under the OECD/UNEP definition published in 2021, the family covers more than 10,000 distinct substances. Industry has been using them since the 1940s and 1950s for waterproofing fabrics, non-stick cookware, fire-fighting foams, fast-food packaging, technical lubricants, paper coatings, inks, paints, waxes and, very prominently, building materials: roofing membranes, carpets, sealants, caulks, adhesives, paints and joinery. The invasion never made the news because their industrial appeal lies precisely in being invisible, odourless and non-volatile in any obvious way. They reach the environment through manufacturing, through wear during the product's service life, and through end-of-life disposal.

Twenty years of accumulated epidemiology have associated PFAS exposure with a wide catalogue: increased total cholesterol, pregnancy-induced hypertension, altered liver function, reduced immune response to childhood vaccines, lower birth weight, increased risk of testicular and kidney cancer, and thyroid disorders. The International Agency for Research on Cancer classified PFOA as a Group 1 carcinogen (carcinogenic to humans) in its 2023 monograph and PFOS as Group 2B (possibly carcinogenic).

The ethical discomfort of the file is not that any of these effects still requires investigation. It is that most of them were documented internally by the manufacturers decades before they became public. Documents disclosed in U.S. court proceedings showed that both DuPont and 3M knew of health effects on their workers in the 1970s and 1980s and continued producing and selling without substantially altering operations.

Vendl and colleagues published in 2024 in Ecological Solutions and Evidence a systematic map of all PFAS research in wildlife available in the scientific literature: more than 200 peer-reviewed studies have detected over 120 distinct PFAS compounds in 625 animal species across all five continents and the oceans. The highest concentrations are recorded in Arctic polar bears, where they are roughly ten times those measured in people living in the same region. The most studied species are common carp (8% of studies), polar bear (6%) and European perch (5%).

In vegetation, PFAS accumulate in contaminated soils, are taken up through roots, concentrate in leaves and fruits and enter the food chain through livestock, freshwater fishing and consumption of vegetables irrigated with affected water. The European Food Safety Authority (EFSA) revised the tolerable weekly intake in 2020 to 4.4 ng/kg of body weight for the sum of PFOA, PFOS, PFNA and PFHxS, a value already regularly exceeded in European dietary surveys through routine consumption of fish and intensively grown produce.

Tracking tools come in three main types. Human blood biomonitoring, led by NHANES since 1999 in the U.S. and replicated by DEMOCOPHES and HBM4EU in Europe, measures what enters and what stays inside. Environmental monitoring tracks presence in waters, soils, sediments and air: in Spain it is run by the Directorate-General for Water of MITECO through the Watch List Vigilance Programme, which in 2023 sampled 23 points in Drinking Water Catchment Zones (ZCAP) analysing 24 distinct PFAS. Epidemiology links exposure to disease through prospective cohorts such as the C8 Health Project in Ohio and West Virginia, which enrolled 69,000 people with contaminated water and followed their health for years.

Prevention advances along two parallel paths: control at the source (regulation of manufacturing and use) and control at the end of the chain (limits on drinking water, food and materials). In 2024 the U.S. EPA set, for the first time, federal Maximum Contaminant Levels (MCLs): 4 ng/L for PFOA and PFOS individually, and 10 ng/L for PFHxS, PFNA and HFPO-DA, plus a Hazard Index of 1 for mixtures. Suppliers have three years to monitor and five to comply. In the EU, the authorities of Denmark, Germany, the Netherlands, Norway and Sweden submitted in January 2023 a universal PFAS restriction proposal under REACH covering more than 10,000 substances; the final decision is expected by the end of 2026. In Spain, Royal Decree 3/2023 obliges water suppliers to analyse four PFAS by 2 January 2024 and meet specific parameters by 2 January 2025.

Mamsen, Björvang and colleagues published between 2017 and 2019 in Environment International direct measurements of PFAS in human embryonic and fetal organs from first, second and third trimester pregnancies. They found PFOA, PFOS and other perfluorinated compounds in liver, lung, brain and placenta. A meta-analysis published in 2021 quantified placental transfer efficiencies: they range from 36% (PFUnDA, PFDA) to over 100% (some branched FOSA isomers), meaning certain compounds concentrate in the foetus at levels higher than in the mother.

After birth, breastfeeding extends the transfer. Mother-child cohort studies in regions with contaminated water (Ronneby, Sweden) have documented persistently elevated levels in children years after maternal exposure ceased. The operational consequence is unavoidable: a regulatory decision a State takes ten or twenty years to make is biologically inherited by at least one generation.

The paradigmatic case is Parkersburg, West Virginia. In 1999 cattle farmer Wilbur Tennant sued DuPont because his cows were dying near a company landfill. His lawyer, Robert Bilott, uncovered internal documents revealing that DuPont had known about PFOA's effects (internally called C8) on worker health since the 1970s. In 2001 he filed a class-action lawsuit on behalf of approximately 70,000 residents of six water districts, which would grow to 80,000. The verdict and subsequent settlements led to payments exceeding 850 million dollars and, more importantly, funded the C8 Health Project, an epidemiological cohort that linked PFOA exposure to testicular cancer, kidney cancer, ulcerative colitis, pregnancy-induced hypertension and thyroid dysfunction.

3M, the historical PFOS manufacturer, reached in June 2024 a 10.3 billion dollar settlement with U.S. public water systems to fund decontamination. The company also announced it would stop manufacturing PFAS by the end of 2025. Identified beneficiaries over seventy years: the shareholders and the balance sheets of both companies, which grew steadily throughout the period in which they concealed data. Cost shared by everyone: half the world with PFAS in their blood, drinking water to be decontaminated at taxpayer and ratepayer expense.

The Green Science Policy Institute report published in 2021, Building a Better World: Eliminating Unnecessary PFAS in Building Materials, mapped the catalogue. PFAS are present in roofing membranes, exterior and interior paints and coatings, sealants, caulks, adhesives, carpets, office furniture and textile upholstery. Their main industrial function is water and grease repellency, chemical resistance and surface durability. The good news is that PFAS-free commercial alternatives exist for all these categories: modified vegetable oils, natural waxes, silicon-based coatings, standard fluoro-free polymers and untreated fabrics already meet the reasonable performance market.

For the designer the operational tool is the certifications that explicitly veto PFAS. The Living Building Challenge (LBC) Red List, maintained by the International Living Future Institute since 2006, added 5,938 PFAS substances in May 2023 and now exceeds 12,500 entries in its 2024 version, with more than 10,000 PFAS specifically banned. The Declare label by the same body identifies products free of Red List substances. Cradle to Cradle Certified restricts PFAS at its higher tiers through the Material Health module. Specifying products with these labels in construction documents is the closest the sector comes today to guaranteeing PFAS-free.

The «we did not know» argument is closed. DuPont and 3M knew about effects on human health in the 1970s. The EPA set the first federal drinking-water limit in 2024. Fifty years between what the industry knew and what citizens could demand. The European Union still awaits the final decision on the universal restriction proposal expected in 2026. Spain published its Royal Decree in 2023, granting two years of grace to suppliers before they must meet parameters. Meanwhile, PFAS keep entering through the roof, the carpet, the sofa, the paint and the tap, every day, in every home. Inaction is not a technical failure; it is an administrative decision. Let it be known, let it be on record, and let it be named.

1. Calafat, A. M., et al. (2025). Per- and polyfluoroalkyl substances (PFAS) exposure in the U.S. population: NHANES 1999-March 2020. Environmental Research. PMC12082571. PubMed PMID: 39848516.
2. U.S. Environmental Protection Agency. (2024). Final PFAS National Primary Drinking Water Regulation. Federal Register, 89 FR 32532, doc 2024-07773.
3. European Chemicals Agency, Denmark, Germany, Netherlands, Norway and Sweden. (2023). Annex XV restriction proposal — universal PFAS restriction. ECHA. Updated background document August 2025.
4. Spanish Royal Decree 3/2023, of 10 January, on technical and sanitary criteria for the quality of water for human consumption. BOE No. 9, 11 January 2023.
5. Mamsen, L. S., Björvang, R. D., Mucs, D., Vinnars, M. T., Papadogiannakis, N., Lindh, C. H., Andersen, C. Y., & Damdimopoulou, P. (2019). Concentrations of perfluoroalkyl substances (PFASs) in human embryonic and fetal organs from first, second, and third trimester pregnancies. Environment International, 124, 482-492. DOI: 10.1016/j.envint.2019.01.010
6. Vendl, C., et al. (2024). Profiling research on PFAS in wildlife: Systematic evidence map and bibliometric analysis. Ecological Solutions and Evidence, 5(1), e12292. DOI: 10.1002/2688-8319.12292
7. Green Science Policy Institute. (2021). Building a Better World: Eliminating Unnecessary PFAS in Building Materials. Berkeley, California.
8. International Living Future Institute. (2024). Living Building Challenge Red List 2024 Update. Seattle, Washington.