PFAS are bad because they don’t break down in the environment, accumulate in your body over years, and are linked to serious health problems including cancer, immune suppression, thyroid disruption, and high cholesterol. Nearly all people in the United States have detectable levels of PFAS in their blood, making this one of the most widespread chemical exposures in modern life.
Why PFAS Don’t Break Down
PFAS stands for per- and polyfluoroalkyl substances, a group of thousands of synthetic chemicals built around carbon-fluorine bonds. The carbon-fluorine bond is one of the strongest chemical bonds known, which is part of the reason these compounds earned the nickname “forever chemicals.” But the persistence problem goes deeper than bond strength alone.
The real issue is biological. Microorganisms in soil and water have never encountered anything like PFAS in nature, so they haven’t evolved the enzymatic machinery to break them down. To degrade a single molecule of PFOA (one of the most common PFAS), a microbe would need to simultaneously transport the chemical into its cell, express the right enzymes, cleave multiple carbon-fluorine bonds, and survive the release of 15 fluoride ions, which are highly toxic to cells. That combination of biological functions doesn’t exist in any known natural organism. So PFAS persist in water, soil, and living tissue essentially indefinitely.
How Long PFAS Stay in Your Body
Once PFAS enter your bloodstream, they bind to proteins and recirculate rather than being quickly filtered out. The estimated half-life for PFOA in humans is 2 to 10 years. For PFOS, the other most-studied variety, it’s 3 to 27 years. That means if you stopped all PFAS exposure today, it could take decades for your body to clear even half of what’s already there. With ongoing exposure from water, food, and household products, levels tend to stay elevated or climb over time.
Cancer and Cholesterol
The health effects of PFAS exposure span multiple organ systems. The strongest evidence ties PFOA exposure to kidney cancer and testicular cancer. PFOA, PFOS, and several related compounds are also associated with increased cholesterol levels, which raises long-term cardiovascular risk. Changes in liver enzymes, a marker of liver stress, have been linked to PFOA, PFOS, and PFHxS exposure. In the liver, PFAS can activate resident immune cells called Kupffer cells, triggering inflammation and cell proliferation that may promote liver cancer.
Weakened Immune Response
Some of the most concerning evidence involves the immune system, particularly in children. The strongest finding is that PFAS exposure reduces the body’s ability to produce antibodies after vaccination. Children exposed to higher levels of PFAS, especially through tetanus and diphtheria vaccines, show measurably weaker immune responses. This isn’t just a laboratory observation. Animal studies confirm the same pattern, and epidemiological data links PFAS exposure to higher rates of respiratory and gastrointestinal infections in children, particularly those exposed in the womb.
PFAS exposure may also worsen pre-existing asthma and allergic reactions in the lungs. The picture that emerges is of a chemical class that suppresses the parts of the immune system you need (like antibody production) while potentially amplifying the parts you don’t (like allergic inflammation).
Thyroid and Hormone Disruption
Your thyroid gland produces hormones that regulate metabolism, energy, and development. PFAS interfere with this process at a molecular level. Mid- to long-chain PFAS physically alter the protein structures involved in making thyroid hormones, blocking the production of thyroxine (T4). Some PFAS compounds, particularly the sulfonic varieties like PFOS, inhibit the protein that transports iodide into thyroid cells, a critical first step in hormone production. The result is disrupted thyroid function, which can affect everything from weight regulation to cognitive development, especially in pregnant women and young children.
Risks During Pregnancy and Early Development
Prenatal PFAS exposure has been associated with reduced birth weight and altered growth patterns in early childhood. In one study, children born to mothers with the highest PFOA levels had BMI scores roughly a third of a standard deviation lower than those born to mothers with the lowest levels through age two. PFOA and PFOS exposure during pregnancy is also linked to pregnancy-induced hypertension and preeclampsia, a dangerous condition involving high blood pressure that can threaten both mother and baby.
At the cellular level, PFAS suppress the production of inflammatory proteins in placental cells that are necessary for establishing proper blood flow between the placenta and the uterine lining. This helps explain why fetal growth can be affected even at relatively low exposure levels.
Where PFAS Exposure Comes From
Contaminated drinking water is the most significant source for communities near factories, military bases, airports, wastewater treatment plants, and landfills. These are sites where PFAS were manufactured, used in firefighting foam, or concentrated through waste processing. Farms where sewage sludge was used as fertilizer are another hotspot.
Beyond water, PFAS show up in a wide range of everyday products:
- Food packaging: grease-resistant paper, fast food containers, pizza boxes, popcorn bags, candy wrappers
- Textiles: stain-resistant carpets, upholstery, water-resistant clothing
- Personal care products: shampoo, dental floss, nail polish, eye makeup
- Household products: cleaning products, paints, varnishes, sealants
You absorb PFAS by drinking contaminated water, eating food that contacted PFAS-containing packaging, and even ingesting household dust from treated fabrics and carpets.
EPA Drinking Water Limits
The EPA now limits PFOA and PFOS in public drinking water to 4 parts per trillion each. To put that in perspective, one part per trillion is roughly equivalent to a single drop of water in 20 Olympic swimming pools. Three other PFAS compounds (PFNA, PFHxS, and GenX) are capped at 10 parts per trillion. When two or more of these chemicals appear together, their combined effect is evaluated using a hazard index. These limits reflect how toxic PFAS are at extraordinarily small concentrations.
Reducing Your Exposure
The most effective step is filtering your drinking water. Three types of home filtration systems have been shown to greatly reduce PFAS levels: granular activated carbon filters, ion exchange systems, and reverse osmosis systems. Reverse osmosis is typically the most thorough, forcing water through a multi-stage filtration process that physically separates contaminants. Granular activated carbon filters trap PFAS in tiny pores as water passes through. Both work, but only if you replace filters on the manufacturer’s recommended schedule. An old, saturated filter won’t remove much of anything.
When shopping for a filter, look for certification under NSF/ANSI 53 (for carbon and ion exchange filters) or NSF/ANSI 58 (for reverse osmosis systems). These certifications specifically verify PFAS reduction. Beyond water filtration, you can limit exposure by avoiding grease-resistant food packaging when possible, choosing untreated fabrics for furniture and carpets, and checking personal care products for PFAS-related ingredients.