If you’ve heard the term “forever chemicals” in the news, you’ve heard about PFAS. Per- and polyfluoroalkyl substances are a family of thousands of synthetic chemicals that have been manufactured and used since the 1940s — and they’ve spread so broadly through the environment that they’re now detectable in the blood of nearly all Americans.
In 2024, the EPA finalized the first-ever federal limits for PFAS in drinking water. Here’s what you need to know about where these chemicals come from, what they do to the body, and how to protect yourself.
What Are PFAS?
PFAS stands for per- and polyfluoroalkyl substances. The name describes the chemistry: these are carbon-based compounds in which fluorine atoms are attached to carbon chains. The carbon-fluorine bond is one of the strongest in organic chemistry, which is what makes PFAS so stable — and so persistent.
There are more than 12,000 individual PFAS compounds. They were developed because their chemical stability and ability to repel both water and oil made them extraordinarily useful for industrial and consumer applications. They don’t break down under heat, don’t react with other chemicals, and resist degradation by sunlight, water, or soil microbes.
That stability is exactly the problem. In the environment, PFAS accumulate in water and soil essentially indefinitely. In the human body, they resist metabolism and are excreted extremely slowly — with half-lives in the bloodstream measured in years. “Forever chemicals” is not a metaphor; it is an accurate description of their environmental and biological behavior.
The two most studied PFAS compounds are:
- PFOA (perfluorooctanoic acid): Used in the manufacture of Teflon (non-stick coatings) and other fluoropolymers. Phased out of US production by 2015 under EPA pressure.
- PFOS (perfluorooctane sulfonate): Used in Scotchgard (fabric and carpet protectors) and military firefighting foam. 3M voluntarily phased out production in 2002.
Though production of PFOA and PFOS has largely moved offshore or shifted to shorter-chain substitutes, their legacy contamination persists in soil, groundwater, and the blood of people exposed decades ago.
Where PFAS Come From
PFAS contamination in drinking water has multiple sources, some local and point-specific, others diffuse and widespread.
Firefighting Foam (AFFF)
Aqueous film-forming foam (AFFF) is the most significant point source of PFAS contamination near drinking water supplies. AFFF was used for decades at military bases, civilian airports, and industrial fire training facilities. When the foam is applied — or when it leaches from improperly managed stockpiles — PFAS saturate the soil and migrate into groundwater.
Many of the most severely contaminated drinking water sources in the US are located near military installations. The Department of Defense has identified hundreds of sites with PFAS contamination related to AFFF use. Bases including Peterson Air Force Base in Colorado, Pease Air National Guard Base in New Hampshire, and dozens of others have contributed to contaminated community water supplies.
Industrial Manufacturing and Discharge
Facilities that manufacture or use PFAS in industrial processes — including semiconductor fabrication, chrome plating, and various chemical manufacturing operations — have historically discharged PFAS into waterways. The Chemours plant on the Cape Fear River in North Carolina contaminated drinking water for hundreds of thousands of residents with GenX (a PFOA replacement) for years before the contamination was publicly disclosed.
Consumer Products and Diffuse Sources
Non-stick cookware, stain-resistant carpet and upholstery treatments, waterproof clothing (including outdoor gear treated with durable water repellent, or DWR), grease-resistant food packaging (fast-food wrappers, microwave popcorn bags, pizza boxes), and dental floss (some brands) have all been identified as sources of PFAS exposure. These products contribute more to dietary and dust exposure than to drinking water contamination directly, but PFAS from consumer products can enter wastewater treatment systems and — because conventional treatment does not remove PFAS — can end up in biosolids spread as agricultural fertilizer or discharged into waterways.
Health Effects
The health effects of PFAS exposure are an active area of research, and the science has evolved significantly over the past decade as long-term epidemiological data has accumulated.
The most thoroughly studied compounds are PFOA and PFOS, primarily because they were produced at highest volumes and persisted in exposed populations long enough for health outcomes to be tracked. Key findings include:
Cancer: PFOA is classified as a possible-to-probable human carcinogen. Studies of workers at PFOA manufacturing facilities and communities near them found elevated rates of kidney cancer and testicular cancer. The International Agency for Research on Cancer (IARC) classified PFOA as a Group 1 human carcinogen (definite cause) in 2023. PFOS has been associated with bladder and kidney cancers in some studies.
Thyroid disease: PFAS appear to interfere with thyroid hormone metabolism. Studies have found associations between PFAS exposure and both hypothyroidism and hyperthyroidism, as well as altered thyroid hormone levels in children.
Immune system effects: This is one of the most consistently documented effects of PFAS. Studies of children exposed to PFAS through drinking water in the Faroe Islands and the US found that higher PFAS blood levels were associated with reduced antibody responses to vaccines — meaning vaccinated children with higher PFAS exposure had less protection. The EPA cited immune effects as a key driver of the low MCL levels set in the 2024 rule.
Reproductive and developmental effects: PFAS have been linked to preeclampsia, reduced birth weight, altered infant immune development, and reduced fertility in both men and women.
Cardiovascular effects: Elevated blood cholesterol (particularly high LDL cholesterol) has been consistently associated with PFAS exposure across multiple populations.
Liver effects: PFAS alter liver enzyme levels and are associated with non-alcoholic fatty liver disease in animal studies and some human research.
How Widespread Is PFAS Contamination?
Very widespread. A 2023 USGS study tested tap water from 716 locations across the US and found PFAS in approximately 45% of samples. This included both regulated public water systems and private wells. Private wells were contaminated at a slightly lower rate than public supplies, but many well owners are unaware of any PFAS risk because private wells are not subject to federal drinking water regulations.
The EPA estimates that up to 100 million Americans may be drinking water with PFAS levels that exceed the new 2024 standards. Contamination is particularly elevated near military installations, industrial sites, and in communities with older firefighting foam training facilities.
The EPA’s 2024 PFAS Drinking Water Rule
In April 2024, the EPA finalized the National Primary Drinking Water Regulation (NPDWR) for PFAS — the most significant expansion of federal drinking water standards in decades.
Individual MCLs:
- PFOA: 4 parts per trillion (ppt)
- PFOS: 4 ppt
- PFNA (perfluorononanoic acid): 10 ppt
- PFHxS (perfluorohexane sulfonate): 10 ppt
- HFPO-DA (GenX): 10 ppt
Hazard index for mixtures: The rule also establishes a hazard index of 1.0 for combinations of PFNA, PFHxS, HFPO-DA, and PFBS — recognizing that PFAS compounds may act additively.
The MCLs of 4 ppt for PFOA and PFOS are set at the minimum reporting level — essentially the lowest level reliably measurable with current technology. This reflects the EPA’s assessment that even very low PFAS levels pose health risks, particularly for immune effects in children.
Compliance timeline: Public water systems have until 2027 to complete initial monitoring and assess whether they exceed the new limits, and until 2029 to install treatment systems and achieve compliance. This means that many water systems may currently exceed the new standards — and are not yet required to treat them.
How to Know If Your Water Is Affected
PFAS are not part of standard water testing, and many utilities have not yet completed comprehensive PFAS monitoring. Here’s how to find out what’s in your water:
Check your Consumer Confidence Report (CCR): Utilities are required to send annual CCRs to customers by July 1. If your utility has tested for PFAS, results will appear there. However, testing for PFAS in CCRs became more common only in recent years — older reports may not include it.
Contact your water utility directly: Ask whether your utility has tested for PFAS and request the most recent results. Under the Safe Drinking Water Act, utilities must provide water quality information to customers upon request.
Check EPA and state databases: EPA’s UCMR5 (Unregulated Contaminant Monitoring Rule) required larger water systems to test for 29 PFAS compounds between 2023 and 2025. Results are publicly available through EPA’s Safe Drinking Water Information System (SDWIS) and are increasingly integrated into state water quality portals.
Private wells: If you rely on a private well, you are responsible for your own testing. Private wells are not monitored under federal or state drinking water programs. Testing for a PFAS panel through a certified laboratory typically costs $150–400 depending on the number of compounds tested. The USGS finding that ~45% of tap water samples contained PFAS underscores that well owners in affected regions face real risk.
Filtering PFAS From Drinking Water
If PFAS are detected in your water — or if you want precautionary protection — water filtration is the most practical option. Not all filters remove PFAS effectively.
Reverse osmosis (RO): The most effective technology for PFAS removal. Point-of-use RO systems installed under the sink or as countertop units remove 90–99% of PFOA, PFOS, and other long-chain PFAS. RO systems also remove many other contaminants. Downsides: requires installation, produces wastewater (typically 3–4 gallons of rejected water per gallon of treated water), and reduces flow rate. Look for NSF/ANSI P473 certification, which specifically covers PFOA and PFOS reduction.
Granular activated carbon (GAC): GAC filtration can reduce PFAS concentrations, particularly longer-chain compounds like PFOA and PFOS. It is less effective at removing shorter-chain PFAS and does not achieve the removal rates of reverse osmosis. Many municipal treatment systems that need to address PFAS use large-scale GAC systems; for home use, under-sink GAC filters with NSF P473 certification provide meaningful protection. Standard pitcher filters (like basic Brita) typically use GAC but are not all certified for PFAS — check the specific model.
Ion exchange (IX): Strong anion exchange resins can effectively remove PFAS and are increasingly used at the utility scale. Some point-of-use ion exchange filters are available for home use.
Pitcher filters: Performance varies widely by brand and model. Some pitcher filter models from Brita, ZeroWater, and others have obtained NSF P473 certification for PFOA and PFOS. Do not assume a pitcher filter removes PFAS unless the specific model is certified. Check NSF International’s database at nsf.org.
What doesn’t work: Standard water softeners, carbon block filters not certified for PFAS, and boiling water do not remove PFAS. Boiling actually concentrates them.
What You Can Do Now
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Find out if your utility has tested for PFAS. Request your most recent water quality report and ask specifically about PFAS testing results.
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Check EPA’s UCMR5 data if your system is large enough to have been required to test. EPA’s SDWIS database is publicly searchable.
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If PFAS are detected above 4 ppt, consider installing a reverse osmosis system at the kitchen tap — especially if you have children, are pregnant, or are formula-feeding an infant.
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If your utility exceeds the new MCLs, they are required under the 2029 compliance deadline to address it. You can contact your utility to ask about their compliance plan.
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If you have a private well, arrange PFAS testing through a state-certified laboratory, particularly if you are located near a military base, airport, industrial facility, or agricultural land where biosolids may have been applied.
The 2024 EPA rule is a significant step, but the compliance timeline means many Americans will continue drinking PFAS-contaminated water for years. Knowing your exposure level and taking appropriate filtration steps is the most direct action available to individual households.