PFAS Are in the Blood of 97% of Americans — Here's What the Research Actually Says

There is a class of synthetic chemicals in your blood right now that were not there a century ago, that your body cannot break down, and that will still be measurable in your tissues years from now even if you stopped all exposure today. They are in your non-stick pan, your fast food packaging, your waterproof jacket, your tap water in many cities — joining the [heavy metals](/blog/your-body-is-full-of-heavy-metals) that are already accumulating in virtually everyone, and the blood of 97% of Americans tested by the CDC. They are called PFAS — per- and polyfluoroalkyl substances — and the research on what they do inside the body is not reassuring.

PFAS are a class of more than 12,000 synthetic chemicals characterized by chains of carbon-fluorine bonds — the strongest bond in organic chemistry. This chemical stability is what makes them useful industrially: they repel water, oil, and heat, which is why they appear in non-stick cookware (Teflon), stain-resistant fabrics and carpets, food packaging including microwave popcorn bags and fast food wrappers, firefighting foam (AFFF), and countless industrial applications. It is also why they accumulate. The carbon-fluorine bond does not break down in soil, water, or biological tissue under normal environmental conditions. PFAS that enter the environment or the body persist essentially indefinitely — hence 'forever chemicals.'

The National Health and Nutrition Examination Survey (NHANES), conducted by the CDC, has measured PFAS levels in representative samples of the US population since 1999. The most recent data found detectable levels of at least one PFAS in the blood of approximately 97% of Americans tested. The most studied compounds — PFOA and PFOS, which have been phased out of US production but persist in the environment — are detectable in virtually everyone tested, including newborns, reflecting both ongoing exposure from legacy contamination and transfer across the placenta and through breast milk.

What the Research Links PFAS To

PFAS research has accelerated significantly in the past decade. The associations documented in human epidemiological studies — most of which are observational and therefore subject to confounding — include: thyroid disruption (PFAS interfere with thyroid hormone transport and metabolism), immune suppression — compounding the [vitamin D deficiency](/blog/the-sunscreen-vitamin-d-tradeoff) that already affects 40% of Americans — (reduced vaccine antibody responses in children with higher PFAS exposure), altered lipid metabolism (higher LDL cholesterol and total cholesterol), kidney and testicular cancer (for which the evidence is strongest and has contributed to regulatory action), reduced fertility in both men and women, disruption of the [gut microbiome](/blog/antibiotics-and-your-gut-microbiome), and developmental effects in children exposed in utero including lower birth weight and altered immune development.

The immune suppression finding is particularly well-documented. A 2020 study in Nature Medicine followed children in the Faroe Islands — where PFAS exposure was tracked from birth — and measured antibody responses to childhood vaccines at age 5 and 7. Children with higher PFAS blood levels at ages 5 and 7 showed significantly lower antibody titers to diphtheria and tetanus vaccines, with a doubling of PFAS concentration associated with approximately 20-50% reduction in antibody concentration. The authors estimated that some children with the highest exposures may have fallen below the threshold for protective immunity.

Where Exposure Comes From

PFAS exposure occurs through multiple routes simultaneously. Drinking water contamination is a significant source in many areas — particularly near military bases where AFFF firefighting foam was used, and near industrial facilities. The Environmental Working Group's tap water database has identified detectable PFAS in water systems serving hundreds of millions of Americans. Food is another major route: PFAS migrate from packaging into food (particularly fatty foods and those cooked at high temperatures), and are found in many processed foods — adding chemical contamination on top of the [declining nutrient density](/blog/food-is-less-nutritious-than-it-used-to-be) of the modern food supply, fish from contaminated waterways, and some agricultural produce irrigated with contaminated water.

Non-stick cookware is a contested exposure source. The specific compound originally used in Teflon (PFOA) has been phased out of production in the US, replaced by newer PFAS compounds whose long-term health effects are less studied. At normal cooking temperatures, non-stick pans release minimal PFAS into food. At high temperatures (above approximately 260°C/500°F) or when scratched, degradation and release increase. Stainless steel and cast iron cookware avoid this exposure pathway entirely.

What the Research Doesn't Establish

The majority of human PFAS health research is observational — it documents associations between PFAS blood levels and health outcomes, but cannot definitively establish causation in the way that randomized controlled trials can. PFAS exposure is correlated with other environmental and socioeconomic factors that independently affect health. The dose-response relationships for many health outcomes are not fully characterized, and the health effects of the newer PFAS compounds replacing phased-out ones are substantially less studied.

What the evidence does support — and what regulatory bodies including the EPA and IARC have concluded — is that PFOA and PFOS in particular are probable or possible human carcinogens, that the immune effects in children are among the most concerning and best-documented findings, and that reducing ongoing exposure is prudent given the persistence of these compounds and the accumulating evidence of harm.

What You Can't Unsee

PFAS are not a future risk. They are present in the blood of virtually every person alive today — the result of decades of industrial use of compounds whose persistence in biology was not adequately considered before deployment at global scale. They cannot be eliminated from the body quickly, and the exposures that are accumulating in children today will persist into their adulthood — potentially [altering gene expression](/blog/your-lifestyle-changes-your-gene-expression) across their lifetime. The practical steps that reduce ongoing exposure — filtered drinking water, reduced use of non-stick cookware at high heat, minimizing processed food in PFAS-containing packaging, and supporting the [lymphatic drainage system](/blog/your-lymphatic-system-the-forgotten-drainage-network) through regular movement — do not reverse existing body burden, but they do slow the ongoing accumulation that extends that burden further.