PFAS 101

What Are Forever Chemicals?

PFAS are a group of over 12,000 man-made chemicals built around a carbon-fluorine bond so strong that nature has no effective way to break it. They were designed to last. They do.

What Are PFAS?

PFAS stands for per- and polyfluoroalkyl substances. The name covers a family of more than 12,000 synthetic chemicals, all sharing one defining feature: a chain of carbon atoms bonded to fluorine. That bond is one of the strongest in organic chemistry. It does not break down in water. It does not break down in soil. It does not break down in your body. That is why scientists call them forever chemicals.

Manufacturers have used PFAS since the 1940s because their properties are useful. They repel water and oil. They withstand extreme heat. They reduce friction. Those same properties make them a serious public health problem once they escape into the environment, which they do constantly.

Key distinction

Not all PFAS are the same. PFOA and PFOS are the two most studied and most regulated. Both are long-chain compounds, meaning they have longer molecular chains that accumulate in the body and break down extremely slowly in the environment. They are the compounds most linked to cancer, thyroid disease, immune suppression, and reproductive harm in the research literature.

But the PFAS family includes thousands of related compounds. When regulators moved against PFOA and PFOS, manufacturers replaced them with shorter-chain alternatives and structurally different compounds. The most common substitutes now in use include:

PFBS, a short-chain replacement for PFOS used in stain-resistant treatments and food packaging coatings.

PFBA, a short-chain replacement for PFOA, used in cookware coatings and food contact materials.

GenX chemicals, developed by Chemours as a replacement for PFOA in industrial applications. GenX compounds have been detected in drinking water near manufacturing facilities and show toxicity in animal studies.

HFPO-DA, the primary GenX compound, is now under EPA review and has prompted state-level action in North Carolina and the Netherlands.

F-53B, a PFOS replacement used extensively in China’s chrome plating industry, now detected in rivers, fish, and human blood samples globally.

The pattern is consistent. A compound gets regulated. A replacement enters the market with less data and less scrutiny. Years pass before research catches up.

PFAS contamination is not a US-only problem. The European Union has taken a broader approach. In 2023, five European nations submitted a proposal to restrict the entire class of PFAS chemicals rather than regulating them one at a time. The EU’s REACH regulation is moving toward a universal PFAS restriction that would cover thousands of compounds simultaneously.

Denmark banned PFAS in food packaging in 2020, ahead of most of the world. Germany, the Netherlands, Norway, and Sweden joined the restriction proposal. The UK maintains its own post-Brexit chemical review process and has signaled alignment with EU PFAS limits.

In the US, regulation has moved compound by compound, which gives manufacturers room to substitute. The EPA’s 2024 drinking water rule set limits for six specific PFAS compounds. It does not cover the full class.

The core problem is the same everywhere. These compounds were designed not to break down. That property does not change based on which country manufactured them or which regulation prompted the reformulation.

The Chemistry

Every PFAS molecule shares a basic structure: a carbon backbone with fluorine atoms attached. Fluorine is the most electronegative element on the periodic table. When it bonds with carbon, it creates a connection with a bond dissociation energy around 544 kJ/mol. By comparison, a carbon-hydrogen bond sits around 413 kJ/mol. That difference is why PFAS resist breakdown so effectively.

Why persistence matters

Most environmental contaminants break down over time through sunlight, microbial activity, or chemical reactions. PFAS resist all three. They accumulate in soil, sediment, surface water, and groundwater over decades. They move through watersheds, travel in dust, and cycle through food chains. Once a site is contaminated, cleanup is extremely difficult and costly.

Bioaccumulation

PFAS bind to proteins in blood and organs, particularly the liver and kidneys. Unlike fat-soluble contaminants, they do not accumulate in fatty tissue — they accumulate in protein-rich tissues. This means conventional detox strategies have no meaningful effect on body burden. The primary way PFAS leave the body is through excretion, a slow process. PFOS has an estimated half-life in the human body of approximately five years. PFOA is somewhat shorter, around three to four years.

What this means for you

Your body burden of PFAS reflects cumulative lifetime exposure. Reducing ongoing exposure matters more than any post-exposure action. The focus should be on source control: filtered water, reduced contact with PFAS-containing products, and awareness of high-exposure occupations and environments.

A Brief History of PFAS

PFAS did not appear by accident. They were deliberately engineered, aggressively marketed, and produced at enormous scale for decades before their risks became undeniable.

1938

Scientists at DuPont accidentally discover polytetrafluoroethylene (PTFE), later sold as Teflon. The first commercial PFAS.

1950s

3M develops PFOS-based Scotchgard for stain resistance on carpets and textiles. PFAS production scales up significantly.

1960s–70s

The U.S. military adopts aqueous film forming foam (AFFF) containing PFOS for fighting jet fuel fires. Widespread use at military bases begins contaminating surrounding communities.

1998

3M internal documents show the company knew about PFAS contamination in human blood since the 1970s. A whistleblower surfaces evidence that DuPont knew about PFOA contamination in West Virginia drinking water.

2000

3M voluntarily phases out PFOS production under EPA pressure. The company had been manufacturing PFOS for nearly 40 years.

2005

EPA fines DuPont $16.5 million for concealing information about PFOA health risks near its Washington Works plant in Parkersburg, WV. At the time, the largest civil penalty in EPA history.

2015–2016

Contamination at military bases in multiple states makes national news. EWG publishes a contamination database showing PFAS in water systems across the country.

2023

3M agrees to a settlement of up to $12.5 billion to resolve PFAS water contamination claims by public water utilities. One of the largest environmental settlements in U.S. history.

April 2024

EPA finalizes the first-ever national drinking water standards for six PFAS, setting an MCL of 4 parts per trillion for PFOA and PFOS. Compliance deadline extended to 2031.

How You Are Exposed

PFAS did not appear by accident. They were deliberately engineered, aggressively marketed, and produced at enormous scale for decades before their risks became undeniable.

Drinking Water

The most direct exposure route for most people. Over 200 million Americans may have PFAS in their tap water. Contamination is highest near military bases, industrial facilities, and airports.

Food Packaging

Grease-resistant coatings on fast food wrappers, microwave popcorn bags, pizza boxes, and takeout containers leach PFAS into food, especially when heated.

Cookware

Non-stick pans coated with PTFE (Teflon) release PFAS when scratched or overheated above 500°F. Worn or damaged pans pose greater risk.

Contaminated Fish

Eating fish from contaminated waterways is a significant pathway near military bases and industrial sites. Some states issue fish consumption advisories.

Personal Care Products

Some dental floss, cosmetics, and shampoos contain PFAS as coatings or film-forming agents. Skin absorption adds to cumulative exposure.

House Dust

Carpeting, upholstery, and stain-treated fabrics shed PFAS into indoor dust. Young children with frequent hand-to-mouth contact face elevated exposure this way.

Occupational

Firefighters using AFFF foam, semiconductor workers, and textile workers face elevated exposure levels well above the general population.

Air Near Facilities

Communities near PFAS manufacturing plants, landfills with PFAS waste, or wastewater treatment facilities face airborne exposure from off-gassing and biosolid spreading.

Health Effects

The strongest evidence links PFAS exposure to several serious conditions. The data comes from occupational studies of workers at manufacturing plants, community studies near contamination sites, and animal studies. PFOA and PFOS are the most studied. Research on the broader family is growing but less complete.

Important context

Dose, duration, and life stage all matter. Exposures during pregnancy, infancy, and early childhood carry higher risk. Workers with decades of high occupational exposure show the strongest disease associations. Most consumer exposures are lower but cumulative over a lifetime.

Kidney Cancer

Studies of workers at PFAS manufacturing plants show elevated kidney cancer rates. EPA classifies PFOA as a human carcinogen based on this evidence.

Thyroid Disease

PFAS interfere with thyroid hormone binding and production. Studies link higher blood PFAS levels to hypothyroidism and thyroid cancer.

Immune Suppression

Children with higher prenatal PFAS exposure show reduced antibody responses to vaccines, suggesting impaired immune development.

High Cholesterol

One of the most consistent findings across studies. PFAS exposure correlates with elevated total cholesterol and LDL cholesterol levels.

Liver Disease

PFAS accumulate in the liver and alter lipid metabolism. Human data show elevated liver enzymes in exposed populations.

Pregnancy Complications

Higher PFAS levels associate with preeclampsia, gestational diabetes, and reduced birth weight in multiple population studies.

Testicular Cancer

Communities near contaminated water supplies show elevated testicular cancer rates. Occupational data from 3M plant workers support the association.

Hormone Disruption

PFAS act as endocrine disruptors, interfering with estrogen and androgen signaling. Reproductive effects have been documented in both sexes.

At-risk populations

Pregnant women, infants, and young children face the highest risk because PFAS transfer through the placenta and through breast milk. People living near military bases, airports, or industrial PFAS sites carry higher body burdens. Firefighters represent one of the most heavily exposed occupational groups in the U.S.

Current Regulation

Federal regulation of PFAS in drinking water arrived slowly. For decades, the EPA monitored PFAS without setting enforceable limits. That changed in April 2024 with the first national drinking water standards.

Chemical

MCL

MCLG

Status as of February 2026

PFOA

4 ppt

Zero

In effect. Compliance deadline extended to 2031.

PFOS

4 ppt

Zero

In effect. Compliance deadline extended to 2031.

PFNA

10 ppt

10 ppt

Under litigation. EPA sought to rescind; D.C. Circuit denied in January 2026.

PFHxS

10 ppt

10 ppt

Under litigation. Same status as PFNA.

HFPO-DA (GenX)

10 ppt

10 ppt

Under litigation. Same status as PFNA.

PFAS Mixture (HI)

HI = 1.0

1.0

Under litigation. Applies to mixtures of PFNA, PFHxS, GenX, and PFBS.

4 ppt is 4 micrograms per liter of water. One part per trillion is equivalent to one drop of ink in 20 Olympic-size swimming pools. These are extraordinarily low concentrations, which reflects the EPA’s determination that no safe level of PFOA or PFOS exposure exists.

Private wells are not covered

The federal MCLs apply only to public water systems serving 25 or more people. Approximately 43 million Americans rely on private wells, which are not subject to federal testing or treatment requirements. If you use a private well, testing is your responsibility.

How to Remove PFAS from Water

Three proven treatment technologies remove PFAS from drinking water. All three are available for home use. The right choice depends on your budget, the specific PFAS present, and your water volume needs.

Technology

PFAS Removal

Certification

Notes

Reverse Osmosis (RO)

Up to 94%

NSF/ANSI 58

Most effective residential option. Removes PFOA, PFOS, and most other PFAS. Requires periodic membrane replacement every 1 to 2 years.

Activated Carbon (GAC)

Moderate to high

NSF/ANSI 53

Effective for long-chain PFAS. Less effective for short-chain compounds. Pitcher filters with certified carbon media reduce PFAS significantly.

Ion Exchange (AIX)

High, including short-chain

NSF/ANSI 58

Highly effective across PFAS types. More common in municipal systems. Point-of-use residential units available at higher cost.

Bottom line for consumers


An NSF/ANSI Standard 58 certified under-sink reverse osmosis system is the most reliable option for removing PFAS at the point of use. Verify certification directly with NSF International at nsf.org. Not all filters marketed as “PFAS-removing” have been independently verified.

What You Can Do Now

Eliminating all PFAS exposure is not realistic for most people. Reducing meaningful exposure sources is. Start with the highest-impact actions first.

1

Check your water. Request your water system’s Consumer Confidence Report (CCR), required to be published annually. Search the EWG Tap Water Database at ewg.org/tapwater for your zip code.

2

Filter if necessary. If your water shows PFAS above the MCLs, install a certified RO or activated carbon filter at your primary drinking and cooking source. Boiling water does not remove PFAS.

3

Reduce product exposure. Replace worn non-stick cookware. Avoid reheating food in fast food packaging. Choose PFAS-free personal care products where options exist. See our Safe Products Guide for guidance by category.

4

Know your risk factors. If you live near a military base, airport, chemical plant, or landfill, your risk of water contamination is higher. If you are pregnant or have young children, reducing PFAS exposure is more urgent.

5

Stay informed. PFAS regulation is evolving rapidly. Compliance deadlines, litigation over the contested MCLs, and state-level rules all affect what protections are in place. See our Legal and Regulatory page for current status.

ForeverChemicals.info provides educational information for general consumers. Nothing on this site constitutes legal, medical, or environmental consulting advice. Data sourced from EPA, ATSDR, EWG, and peer-reviewed research. Some links on this page are affiliate links. We earn a commission if you purchase through them, at no cost to you. We only recommend products with verified third-party certifications. Last updated February 2026.