PFAS are a family of thousands of synthetic chemicals built around chains of carbon and fluorine atoms. The carbon-fluorine bond is one of the strongest in organic chemistry, which means these compounds don’t fully break down in the environment or in the human body. That persistence earned them the nickname “forever chemicals.” Nearly all people in the United States have detectable levels of PFAS in their blood.
Why They Don’t Break Down
Every PFAS molecule contains a chain of carbon atoms with fluorine atoms attached. Fluorine grips carbon more tightly than almost any other element, creating a bond that resists heat, water, oil, and biological processes. This is exactly what made PFAS useful to manufacturers: a coating that repels grease on a pizza box works because the chemistry is extraordinarily stable. But that same stability means the chemicals persist in soil, groundwater, and living tissue for years or decades.
In the human body, different PFAS compounds take different amounts of time to clear. Long-chain varieties like PFOS have an estimated half-life of about 2.9 years, meaning it takes nearly three years for your body to eliminate just half of what’s circulating. Shorter-chain replacements leave faster, but even the quickest take many weeks. No PFAS compound is eliminated rapidly.
Where PFAS Show Up in Daily Life
PFAS were first developed in the mid-20th century and quickly spread into an enormous range of products. Their ability to repel water, oil, and stains made them attractive across industries. You’ll find them in nonstick cookware, stain-resistant carpets and upholstery, water-repellent outdoor clothing, ski and boat waxes, surface sealants, and cleaning products. They’ve been used in food packaging like pizza boxes, fast food wrappers, French fry cartons, and microwave popcorn bags. Personal care products, including shampoo, moisturizers, makeup, and nail polish, have also contained PFAS.
One of the largest historical uses was in firefighting foam, known as AFFF, designed to smother large fuel fires at airports, refineries, and military bases. These foams saturated the ground at training sites and crash locations, creating some of the most heavily contaminated areas in the country.
Some states have started banning specific uses. Washington state, for example, now prohibits the sale of new PFAS-containing food packaging, cosmetics, and textile furnishings like sofas and curtains.
How People Are Exposed
The primary route of exposure is ingestion, mainly through food and water. In communities near contaminated sites, drinking water can be the dominant source. But food is a broad category of exposure on its own: meat, dairy, and vegetables grown near places where PFAS were manufactured or used can carry the chemicals, as can fish caught from contaminated water. Grease-resistant food packaging transfers small amounts into the food it touches.
Household dust is another pathway. PFAS-containing products like carpets, upholstery, and treated fabrics shed residue that settles as dust, which you can swallow or inhale. For most people, though, breathing in PFAS is not a major route of exposure because the chemicals aren’t volatile. The exception is workplace settings where people handle PFAS-containing materials and breathe in associated dust or fumes. PFAS also cross the placenta, meaning exposure begins before birth.
Health Effects Linked to PFAS
The health concern with PFAS isn’t usually a single dramatic event. It’s chronic, low-level exposure over years that gradually shifts the body’s chemistry. The strongest and most consistent finding is that PFAS raise cholesterol. Both cross-sectional and long-term studies in adults and children show that PFAS exposure increases total cholesterol and LDL (“bad”) cholesterol, including levels high enough to meet the clinical definition of high cholesterol. A review of population and toxicity data concluded that abnormal cholesterol is the strongest metabolic outcome of PFAS exposure.
Thyroid disruption is another well-documented effect. PFAS alter thyroid hormone levels and may contribute to autoimmune thyroid conditions. Women in the highest quarter of PFOA exposure were roughly twice as likely to report clinical hypothyroid disease compared to those with lower levels, based on national survey data. Effects appear to differ by sex: women show more hyperthyroid outcomes, men more hypothyroid ones. Children may be particularly sensitive.
Cancer risk has also emerged as a concern, especially for kidney cancer. A large longitudinal study of over 32,000 people living near a PFAS-contaminated water supply found increased rates of kidney cancer. A review of six published studies found long-chain PFAS exposure associated with kidney cancer or kidney cancer mortality, with elevated risks across all of them. Evidence for testicular cancer has also accumulated, though the data is less extensive.
Immune and Developmental Effects
Beyond cholesterol, thyroid, and cancer, PFAS exposure has been linked to reduced vaccine effectiveness in children, pregnancy complications including preeclampsia, and lower birth weight. These effects are still being studied, but they contribute to the growing consensus that PFAS are a significant public health problem at exposure levels once considered safe.
Legacy Chemicals vs. Newer Replacements
The two most widely known PFAS are PFOA and PFOS, both long-chain compounds with eight carbon atoms. These were the workhorses of the PFAS world for decades and are by far the most studied. After evidence of their persistence and toxicity mounted, U.S. manufacturers phased them out and replaced them with shorter-chain alternatives.
GenX is one of the most prominent replacements. It has six carbon atoms instead of eight and is used in manufacturing the same types of nonstick and water-resistant products that PFOA enabled. The logic was that shorter chains would leave the body faster and cause less harm. That’s partly true: shorter-chain PFAS do clear faster, with some having half-lives measured in weeks rather than years. But “faster” is relative. Even the shortest-chain compounds studied still take weeks to months to eliminate, and emerging research suggests they carry their own health risks. Replacing one persistent chemical with a slightly less persistent one hasn’t solved the problem.
3M, one of the largest PFAS manufacturers in history, announced in late 2022 that it would exit all PFAS manufacturing and discontinue the use of PFAS across its product portfolio by the end of 2025. This includes fluoropolymers, fluorinated fluids, and PFAS-based additives.
Drinking Water Standards
In April 2024, the EPA finalized the first-ever national drinking water standard for PFAS. The limits are strict. PFOA and PFOS each have a maximum contaminant level of 4 parts per trillion. To put that in perspective, one part per trillion is roughly equivalent to a single drop of water in 20 Olympic-sized swimming pools. Three other PFAS compounds, including GenX, have limits set at 10 parts per trillion. For mixtures of certain PFAS appearing together in water, the EPA established a hazard index that accounts for the combined effect of multiple compounds.
Public water systems will need to test for these chemicals and reduce levels that exceed the limits. Compliance timelines give utilities several years to install treatment systems where needed.
Reducing Your Exposure
If your drinking water comes from a public system, it will eventually be tested and treated under the new federal rules. If you’re on a private well, especially near military bases, airports, industrial sites, or firefighting training areas, testing your water is the most important step you can take.
For home filtration, granular activated carbon filters are the most widely used and studied option. Research estimates that 76 to 87% of PFAS compounds can be cost-effectively removed by activated carbon. Reverse osmosis systems are also effective. Simple pitcher filters with activated carbon can reduce some PFAS, but performance varies by brand and by which specific PFAS are present. Shorter-chain compounds like PFBA, with their smaller molecular size, are harder to capture with any filter.
Beyond water, you can reduce exposure by choosing PFAS-free cookware, avoiding stain-resistant fabric treatments when possible, and minimizing use of grease-resistant food packaging. If you use water- or stain-repellent sprays on furniture or clothing, look for products labeled PFAS-free and use them as sparingly as possible. Keeping household dust levels down through regular cleaning also helps, since dust from treated carpets and upholstery is a meaningful exposure route.