A family of synthetic compounds prized for shrugging off water, grease, and heat has left a chemical signature inside almost everyone. National biomonitoring surveys in the United States have found detectable levels of these substances in the blood of the overwhelming majority of people tested. Because the chemistry that makes them useful also makes them nearly indestructible, they have earned a blunt nickname: forever chemicals.
The formal name is per- and polyfluoroalkyl substances, usually shortened to PFAS. There are thousands of individual compounds in the group, and they have been manufactured since the mid-20th century for everything from nonstick cookware to firefighting foam. The reason they now circulate in human blood is that they do not readily break down in the environment or in the body.
What makes them so persistent
The defining feature of PFAS is the carbon-fluorine bond, one of the strongest bonds in organic chemistry. That bond is what gives coatings their slick, stain-resistant, water-repellent qualities, and it is also what makes the molecules almost impervious to the natural processes that degrade most pollutants. The overview compiled in the reference entry on per- and polyfluoroalkyl substances notes that this durability is precisely why they accumulate rather than disappear.
Once released, PFAS move through soil into groundwater, ride into rivers and drinking-water systems, and settle in the tissues of fish and wildlife. They resist heat, so incineration does not reliably destroy them. They resist water, so ordinary treatment does not always remove them. The result is a class of chemicals engineered to endure, spreading through the same systems that supply food and water.
How they end up in the bloodstream
People are exposed through several routes at once. Drinking water contaminated by industrial discharge or firefighting foam is a major one, particularly near manufacturing plants, airports, and military bases where the foam was used for decades. Food is another, whether from packaging that contains the chemicals or from crops and animals raised in contaminated areas. Household dust, certain cosmetics, and treated fabrics add smaller contributions.
Because the compounds are so stable, they linger in the body for years rather than being flushed out quickly. Some of the more studied PFAS have half-lives in humans measured in years, meaning it can take that long for the body to clear even half of a given amount. That slow elimination is why repeated small exposures build into the near-universal blood levels that surveys keep finding.
The health questions
Research has linked higher PFAS exposure to a range of health effects, though the strength of the evidence varies from one outcome to the next. Studies have associated certain PFAS with elevated cholesterol, changes in liver enzymes, reduced response to some vaccines, effects on thyroid function, lower infant birth weights, and, for some compounds, an increased risk of kidney and testicular cancer. Public health agencies including the federal toxicology and disease registry have emphasized that the science is still developing and that different compounds carry different risks.
An important nuance is that PFAS is not one substance but thousands, and most have never been individually studied. The best-characterized are older compounds that manufacturers have phased out in many countries. Newer replacements were introduced partly because they leave the body faster, but questions remain about whether they are meaningfully safer over the long term.
Regulation and cleanup
Governments have moved, unevenly, to rein in the chemicals. Some jurisdictions have set enforceable limits for specific PFAS in drinking water, pushing utilities to install filtration capable of capturing the molecules. Others have restricted or banned particular uses, such as in food packaging or consumer textiles. Cleanup of contaminated sites is technically difficult and expensive, in part because the same persistence that spread the chemicals also resists efforts to destroy them.
Filtration technologies such as activated carbon and reverse osmosis can reduce PFAS in water, and researchers are developing methods to break the stubborn carbon-fluorine bond, but scaling those solutions to entire water systems is a slow and costly undertaking. Meanwhile, production of some PFAS continues for uses that industry considers essential, from medical devices to semiconductor manufacturing, which complicates any push toward a full phase-out.
Living with a persistent problem
For individuals, the exposure is largely out of personal control, since it flows through water and food supplies rather than a single avoidable product. Where local water is known to be contaminated, certified home filters can lower intake. Beyond that, the problem is structural: chemicals designed never to break down are now embedded in the environment, and removing them is a generational project rather than a quick fix.
The broader takeaway is that the very properties that made these compounds commercially valuable are what turned them into a lasting contaminant. Their near-universal presence in human blood is a direct consequence of decades of use combined with a molecular stability that resists cleanup. Addressing it will require both curbing new releases and confronting the vast reservoir already in circulation, a task that will define environmental chemistry for years to come.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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