Per- and polyfluoroalkyl substances (PFAS) are man-made chemicals with many fluorine atoms attached to a carbon chain. There are about 7 million PFAS chemicals listed in PubChem.

People started using PFAS widely in 1938 when Teflon was invented. Teflon is a material that resists heat, oil, stains, grease, and water. PFAS are used in many products, including waterproof clothing, yoga pants, carpets, shampoo, phone screens, paint, furniture, adhesives, food packaging, firefighting foam, electrical insulation, and cosmetics.

Some PFAS, like PFOS and PFOA, are harmful to health and the environment. These chemicals stay in the environment for a long time and build up in animals, which are then eaten by humans. PFAS can be found in rain, drinking water, and wastewater. Because there are so many types of PFAS, it is difficult to fully understand their risks to human health and the environment.

Exposure to PFAS has been linked to health problems, including cancer, thyroid disease, lower immunity, and issues with pregnancy and child development. International agreements, like the Stockholm Convention, have regulated PFAS since 2009. Some countries, such as China and the European Union, plan to reduce PFAS use further. However, countries like the United States, Israel, and Malaysia have not agreed to these rules, and the chemical industry has lobbied to keep regulations weak.

Because of health concerns, some companies have stopped selling PFAS or products that contain them. Companies that made PFAS have paid billions of dollars to settle legal claims, such as a $10.3 billion settlement by 3M in 2023 for water contamination. Studies show that companies knew about the health risks of PFAS as early as the 1970s. The cost of cleaning up PFAS pollution, treating related diseases, and monitoring pollution may be as high as $17.5 trillion each year.

In 2023, the PFAS market was worth about $28 billion. Most of these chemicals are made by a few large companies. Sales of PFAS, which cost about $20 per kilogram, generated about $4 billion in yearly profits with 16% profit margins.

Definition

Per- and polyfluoroalkyl substances (PFAS) are man-made chemicals that contain fluorine and carbon atoms connected in specific ways. Different groups have varying ways to define PFAS, which has led to estimates of between 8,000 and 7 million different chemicals in this group. The U.S. Environmental Protection Agency (EPA) lists 14,735 unique PFAS chemicals in its database called DSSTox. Another database, PubChem, lists 7 million PFAS chemicals.

An early definition required PFAS to have at least one part of the molecule called a perfluoroalkyl group, written as −C n F 2 n +1. In 2021, the Organization for Economic Cooperation and Development (OECD) updated its definition, stating that PFAS are chemicals with at least one fully fluorinated carbon atom (a carbon with no hydrogen, chlorine, bromine, or iodine attached) in a methyl or methylene group. This includes chemicals with a perfluorinated methyl group (−CF 3) or a perfluorinated methylene group (−CF 2−).

The EPA defines PFAS in the Drinking Water Contaminant Candidate List 5 as chemicals that contain one of three specific chemical structures:
1. R−CF 2−CF(R')R, where both the −CF 2− and −CF− parts are saturated carbons, and none of the R groups can be hydrogen.
2. R−CF 2−O−CF 2−(R'), where both −CF 2− parts are saturated carbons, and none of the R groups can be hydrogen.
3. CF 3−C−(CF 3)RR', where all carbons are saturated, and none of the R groups can be hydrogen.

Examples of PFAS include:
– Perfluoroalkyl carboxylic acids (PFCAs), such as trifluoroacetic acid (TFA).
– Perfluorosulfonic acids (PFSAs), such as perfluorooctanesulfonic acid (PFOS).
– Precursors to PFCAs, such as fluorotelomers (FTOHs).
– Precursors to PFSAs, such as perfluorobutane sulfonamide (H-FBSA), perfluorooctanesulfonamide (PFOSA), perfluorobutanesulfonyl fluoride (PFOSB), or perfluorooctanesulfonyl fluoride (PFOSF).
– Fluoropolymers, such as polytetrafluoroethylene (PTFE, also known as Teflon).

A summary of these definitions is described in Hammel et al. (2022).

Uses

PFAS are used to make fluoropolymers through a process called emulsion polymerization. They are used in products like stain repellents, polishes, paints, and coatings because they resist heat, oil, stains, grease, and water. PFAS were first used when Teflon was invented in 1938. They are found in many products, including waterproof fabrics like nylon and yoga pants, carpets, shampoo, feminine hygiene products, mobile phone screens, wall paint, furniture, adhesives, food packaging, firefighting foam, and the insulation of electrical wires. The cosmetic industry uses PFAS in many cosmetics and personal care products, such as lipstick, eyeliner, mascara, foundation, concealer, lip balm, blush, and nail polish. Pesticides like fluazinam and flufenacet break down to form trifluoroacetic acid.

Fluorinated surfactants, a type of PFAS, have a water-repelling fluorinated "tail" and a water-attracting "head." These surfactants lower the surface tension of water more effectively than similar hydrocarbon surfactants. Fluorosurfactants often gather at the boundaries between different substances. Fluorocarbons repel both oil and water. This happens because fluorine’s strong electronegativity and short bond length reduce the ability of fluorinated molecules to interact with other substances. Fluorosurfactants are more stable than hydrocarbon surfactants because the bond between carbon and fluorine is strong. Perfluorinated surfactants remain in the environment for a long time because of this stability.

Fluorosurfactants like PFOS, PFOA, and perfluorononanoic acid (PFNA) have drawn attention from regulatory agencies due to their long-lasting presence in the environment, their harmful effects, and their widespread presence in people’s blood.

The PFAS market was valued at US$28 billion in 2023. Most PFAS are produced by 12 companies: 3M, AGC Inc., Archroma, Arkema, BASF, Bayer, Chemours, Daikin, Honeywell, Merck Group, Shandong Dongyue Chemical, and Solvay. In 2023, sales of PFAS, which cost about $20 per kilogram, generated $4 billion in annual industry profits with a 16% profit margin.

Environmental effects

In 2022, levels of at least four types of perfluoroalkyl acids (PFAAs) in rainwater worldwide were much higher than the EPA's lifetime drinking water safety limits and similar standards from Denmark, the Netherlands, and the European Union. This led scientists to conclude that the global spread of these chemicals has caused the planet to exceed safe limits for chemical pollution. The most common PFAS found in the environment is Trifluoroacetic acid (TFA). It is found everywhere in the environment, especially in water ecosystems, where its levels are increasing globally.

It was once believed that PFAAs would eventually reach the oceans, where they would mix with water over many years. However, a 2021 study by researchers at Stockholm University found that these chemicals often move from water to air when waves hit land. This process contributes to air pollution and leads to their presence in rain. The researchers noted that this pollution can affect large areas. Soil is also contaminated, and these chemicals have been found in remote places like Antarctica. Contaminated soil can cause higher levels of PFAS in foods such as white rice, coffee, and animals raised on polluted land. In 2024, a global study of 45,000 groundwater samples found that 31% of the samples had PFAS levels that could harm human health. These samples were taken from areas not near known pollution sources.

PFAS contamination has also been found in water wells and other drinking water sources. This contamination is reported in the United States, United Kingdom, Germany, Japan, and Canada, but information about PFAS in developing countries, especially in Africa, is very limited. This lack of data is due to economic and technological challenges in these regions.

Bioaccumulation refers to how pollutants, including PFAS, build up inside living organisms. When this process is studied across entire food webs, it is called biomagnification. This is important because small amounts of pollutants in the environment, such as in seawater or sediments, can quickly become harmful in organisms higher up the food chain, including humans. For example, PFOS and C10–C14 PFCAs can reach levels more than 5,000 times higher in living organisms than in water. PFAS can enter organisms through eating sediment, drinking water, or consuming food. They tend to build up in areas of the body with high protein content, such as the blood and liver, and are also found in other tissues.

A study in a macrotidal estuary in Gironde, France, found that PFOA and PFNA are highly bioaccumulative. PFOS, a long-chain sulfonic acid, was found at the highest levels in fish and birds in northern seas like the Barents Sea and the Canadian Arctic. A global review of studies showed that PFAS levels in organisms generally double with each step up the food chain, though this varies by chemical type. Notably, an industrial replacement chemical called F-53B showed the highest increase in concentration as it moved up the food chain, even more than some older PFAS it was meant to replace.

A 2023 study analyzing 500 fish fillet samples collected in the United States from 2013 to 2015 found that freshwater fish commonly contain high levels of harmful PFAS. Eating a single serving of these fish can significantly increase PFOS levels in the blood.

PFAS accumulation in marine species like fish and shellfish can affect human health. These chemicals are often found in fish and shellfish that people eat, which poses health risks. Studies on how PFAS build up in certain species help determine safe limits for human consumption and identify areas where these limits may be exceeded. This is especially important for communities that eat large amounts of wild fish and shellfish. PFAS contamination has also caused disruptions in food supplies, such as fishing restrictions.

PFAS reach the Arctic through migrating birds that carry these chemicals from polluted areas in the south. While this is less common than pollution from wind and ocean currents, birds act as carriers, spreading toxins. This affects Arctic predators, as the chemicals from birds often enter the food chain directly because birds are prey for many species.

Fluorosurfactants with shorter carbon chains may be less likely to build up in mammals, but they may still harm humans and the environment.

Health effects

PFAS were originally thought to be chemically inert, meaning they did not react with other substances. Early studies of workers exposed to these chemicals found higher levels of PFOS and PFOA in their blood, but no health problems were reported. These levels, measured in workers at a 3M plant, ranged from 0.04 to 10.06 ppm for PFOS and 0.01 to 12.70 ppm for PFOA. These amounts were below levels considered harmful or cancer-causing in animal studies.

Some PFAS remain in the body for more than eight years. They are not broken down but are removed through urine. Because they stay in the body for so long and are found in the environment, PFAS can build up in humans, leading to health issues.

Between 2005 and 2013, three health researchers called the C8 Science Panel studied the health of people in the Mid-Ohio Valley as part of a legal case involving communities near a DuPont plant. They tested the blood of 69,000 people near the plant and found an average PFOA level of 83 ng/mL, compared to 4 ng/mL in the general U.S. population. The panel reported possible links between higher PFOA levels and health problems, including high cholesterol, ulcerative colitis, thyroid disease, testicular cancer, kidney cancer, pregnancy-related high blood pressure, and preeclampsia. The severity of these effects depends on how long and how much someone is exposed to PFAS and their overall health.

Exposure to PFAS increases the risk of high blood pressure and preeclampsia during pregnancy. It is unclear if PFAS also affect other heart-related issues during pregnancy. PFAS can be found in human breast milk, which may pass these chemicals to infants through breastfeeding.

Using personal care products like nail polish, fragrances, makeup, hair dyes, and hair sprays during pregnancy or while breastfeeding is linked to higher PFAS levels in blood and breast milk. For example, women who dyed their hair at least twice during pregnancy had PFOS levels more than one-third higher than those who did not. PFOS is one of the most common and dangerous PFAS compounds.

PFAS, which are endocrine disruptors, are connected to issues with male fertility. A 2023 study by the Icahn School of Medicine at Mount Sinai found that high PFAS exposure was linked to a 40% lower chance of successful pregnancy in women, as well as hormone imbalances and delayed puberty.

Fetuses and children are especially at risk from PFAS exposure. These chemicals are linked to health problems such as low birth weight, early birth, shorter breastfeeding periods, lower-quality breast milk, brain development issues, and reduced effectiveness of childhood vaccines.

A review of studies on PFAS and liver health found evidence that PFOA, PFHxS, and PFNA may cause liver damage in humans.

PFOA is classified as cancer-causing to humans (Group 1) by the International Agency for Research on Cancer (IARC) based on strong evidence from animal studies and human exposure. PFOS is considered possibly cancer-causing (Group 2b) due to strong evidence of mechanisms in humans. More research is needed to fully understand the links between specific PFAS chemicals and certain cancers.

Studies show that higher PFOS levels in humans are linked to higher total and LDL cholesterol levels. This suggests changes in how the body processes fats and may involve pathways different from those in rodents.

PFOS and PFOA can change immune and inflammatory responses in humans and animals. As PFOA levels rise, levels of IgA, IgE (in females), and C-reactive protein decrease, while antinuclear antibodies increase. These changes may lead to immune system issues, such as autoimmunity. One possible explanation is a shift toward anti-inflammatory cells in the gut, which allows certain bacteria to grow. This can increase hydrogen sulfide levels, harming the gut lining and reducing nutrient production.

Low thyroid function is the most common thyroid issue linked to PFAS exposure. PFAS reduce thyroid peroxidase, which lowers the production of thyroid hormones. Other possible causes include changes in thyroid hormone signaling, metabolism, and the function of hormone receptors. A complex relationship with thyroid hormone activity has also been observed, suggesting a strong impact on how the body uses thyroid hormones outside the brain.

Responses to knowledge of harmful effects

Because of health issues, several companies have stopped selling or said they will stop selling PFAS or products that contain them. These companies include W. L. Gore & Associates (maker of Gore-Tex), Patagonia, REI, H&M, and 3M. Some companies might move production to countries like Thailand and India, where there are fewer rules.

Since the 1970s, DuPont and 3M knew that PFAS was "very harmful if inhaled and somewhat harmful if eaten." Companies used methods to influence science and rules, such as hiding research that showed problems and changing public discussions. In 2018, during the first year of Donald Trump’s presidency, White House staff and the EPA pressured the U.S. Agency for Toxic Substances and Disease Registry to hide a study that showed PFAS was more dangerous than previously thought.

Costs from cleaning up polluted soil and water, treating diseases linked to PFAS, and monitoring pollution may reach $17.5 trillion each year, according to ChemSec. PFAS has been the subject of many lawsuits worldwide. In the United States, settlements from PFAS pollution claims reached $18 billion by 2024. In 2023, Sweden’s Supreme Court set a legal example by giving money to people who received drinking water contaminated with PFAS.

Canada has set rules for safe drinking water levels for PFOS and PFOA. The European Union is creating a plan to stop using PFAS in products that are not necessary. The United Nations listed PFOS, PFOA, PFHxS, long-chain PFCAs, and related chemicals as dangerous substances under the Stockholm Convention on Persistent Organic Pollutants between 2009 and 2025.

The United States Environmental Protection Agency has created guidelines for safe drinking water levels for PFOA and PFOS, but these are not legally required. In 2021, Maine became the first U.S. state to ban these compounds in all products by 2030. By October 2020, states like California, Connecticut, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Vermont, and Wisconsin had legally required drinking water standards for two to six types of PFAS.

However, some major producers and users, such as the United States, Israel, and Malaysia, have not agreed to rules to reduce PFAS use. The chemical industry has tried to get governments to weaken rules. For example, in the United States, laws meant to regulate PFAS in cosmetics, food packaging, and textiles did not pass in Congress in 2022.

In 2026, the UK tested for PFAS more often as part of a plan to address the substances, which have raised environmental and health concerns. The government says it wants to follow EU rules more closely by 2029, as the EU aims to stop all unnecessary uses of PFAS.

Occupational exposure

Occupational exposure to PFAS happens in many industries because these chemicals are used in products and during industrial processes. PFAS are used in more than 200 ways across industries like electronics, plastics, food, textiles, and construction. Workers may be exposed to PFAS at factories that make them or at other facilities that use them, such as in chrome plating. People who handle PFAS-containing products, like those who install carpets with PFAS coatings, apply ski wax with PFAS, or use PFAS-based firefighting foam, may also be exposed.

Workers exposed to PFAS through their jobs often have higher levels of PFAS in their blood than the general public. While most people are exposed to PFAS through food and water, workers may be exposed through accidental swallowing, breathing in fumes, or skin contact in workplaces where PFAS become airborne.

Professional ski wax technicians are more strongly exposed to PFAS than other groups. They handle PFAS-based glide wax used on skis, which is heated during application. This process releases fumes and particles into the air, making ski waxing the activity with the highest PFAS air concentrations reported so far.

Workers at factories that produce PFAS or use them in manufacturing may be exposed in the workplace. Many studies about PFAS exposure and health effects began in the 1940s with research on workers at fluorochemical production plants in the U.S. and Europe. Between the 1940s and 2000s, thousands of workers participated in studies that helped scientists understand how PFAS enter the body, how the body handles them, and their health effects.

The first study to report higher fluorine levels in the blood of fluorochemical workers was published in 1980. It showed that breathing in PFAS fumes could be a way workers are exposed. Workers at these plants often have higher levels of PFOA and PFOS in their blood than the general public. Blood PFOA levels in these workers are usually below 20,000 ng/mL but have reached as high as 100,000 ng/mL. In contrast, non-exposed people had average levels of 4.9 ng/mL. Workers who handle PFAS directly have higher blood PFAS levels than those with less contact. These levels often drop when direct contact stops. Over time, PFOA and PFOS levels in workers have decreased due to better workplace safety, more protective equipment, and the stoppage of these chemicals in production. Studies in China continue to examine PFAS exposure in manufacturing workers.

PFAS are used in Class B firefighting foam because they resist water and oil and stay stable at high temperatures.

Research on PFAS exposure in firefighters is still developing but often limited by small study groups. A 2011 study found higher levels of PFHxS in firefighters compared to others in their region, with other PFAS also elevated but not statistically significant. A 2014 study in Finland found PFHxS and PFNA levels in firefighters’ blood increased after training sessions, but the small sample size prevented statistical analysis. A 2015 study in Australia linked higher PFOS and PFHxS levels in firefighters to longer years of exposure to firefighting foam.

Firefighters and military members have higher PFAS exposure than the general public, partly because PFAS is used in firefighting and in protective gear. States like Washington and Colorado have taken steps to limit the use of Class B firefighting foam for training.

The September 11 attacks released toxic chemicals, including PFAS, from materials like stain-resistant coatings. First responders were exposed to PFOA, PFNA, and PFHxS through smoke and dust. Health tests showed many had breathing issues, such as coughing and wheezing. Smoke-exposed responders had higher PFAS levels than those exposed to dust.

To reduce risks, strategies like monitoring exposure, regular blood tests, and using PFAS-free alternatives—such as fluorine-free firefighting foam and plant-based ski wax—are recommended.

Remediation

Many technologies are used to treat drinking water, groundwater, industrial wastewater, surface water, and other sources like landfill leachate. These include:

• Sorption (such as granular activated carbon, biochar, and ion exchange resins)
• Membrane filtration (like reverse osmosis and nanofiltration)
• Foam fractionation
• Precipitation, flocculation, and coagulation
• Supercritical water oxidation
• Photodegradation

Private and public organizations use one or more of these methods to clean up contaminated sites in the United States and other countries.

The Interstate Technology and Regulatory Council (ITRC) has studied ex-situ and in-situ treatment methods for water polluted with PFAS. These methods are grouped into three categories: field-implemented, limited application, and developing technologies. They fall into three types: separation, concentration, and destruction.

Foam fractionation uses air bubbles to collect PFAS molecules. The hydrophobic tails of long-chain PFAS attach to the air bubbles, rise to the water surface, and form foam that can be collected and concentrated. This method is based on traditional techniques used by industries to remove contaminants. It avoids using solid materials, reduces waste, and creates a highly concentrated liquid that can be treated further. Field tests show this method is simple and cost-effective for treating complex PFAS-contaminated water.

High-temperature incineration of sewage sludge lowers the levels of perfluorinated compounds.

Supercritical water oxidation is a method that destroys 99% of PFAS in water. During this process, oxidizing agents are added to PFAS-contaminated water, and the liquid is heated above 374°C (critical temperature) at a pressure of over 220 bars. In this supercritical state, PFAS dissolves more easily.

A team from Michigan State University and Fraunhofer developed a method using boron-doped diamond electrodes to break PFAS molecular bonds through electrochemical oxidation, eliminating contaminants and producing clean water.

Acidimicrobium sp. strain A6 has been shown to break down PFAS and PFOS. Microbes can degrade unsaturated PFAS more easily than saturated ones. Commercial dechlorination cultures like KB1 can break down unsaturated PFAS but not saturated ones. If other nutrients are available, microbes may prefer those over PFAS.

Researchers at the University of Missouri demonstrated that activated carbon can degrade PFAS at lower temperatures (300°C) than previously required (700°C).

Perfluoroalkyl carboxylic acids (PFCAs) can be mineralized by heating them in a polar aprotic solvent like dimethyl sulfoxide mixed with water and sodium hydroxide at 80–120°C. This process removes the carboxylic acid group, creating perfluoroanions that break down into salts like sodium fluoride. This method does not work on perfluorosulfonic acids like PFOS. A 2022 study showed that C-F bonds in PFAS can break down into YF₃ or YF₆ clusters. Another study described PFAS breakdown using metal-organic frameworks (MOFs).

Constructed wetlands are planted, saturated areas designed to mimic natural processes for managing waste or stormwater. Contaminants are removed through plant uptake, adherence to substrates, microbial degradation, and UV exposure. Recent research has explored using wetlands to treat PFAS-contaminated wastewater, stormwater, and landfill leachate. Granular activated carbon has the highest removal rate as a substrate, while biochar is a low-cost, environmentally friendly alternative. Mixtures of magnetite and quartz sand are preferred in some cases. Wetland performance depends on hydraulic loading rate and retention time. Plants with high root surface area, high protein content, and slow natural degradation are effective for PFAS uptake. Examples include Eichhornia (Pontederia) crassipes, Cyperus alternifolius, and Ceratophyllum demersum. Removal typically involves harvesting mature plants.

Biodegradation of PFAS is limited by the strong C-F bonds in these molecules. Acidimicrobium bacterium A6 has shown the ability to detoxify water. Rhizobacter Burkholderia, Nirosomans Nitrospia, and Opitutus can remove fluorine atoms from PFAS in iron mineral-based wetlands. Adding a 1:2 gravel-magnetite mix can improve wetlands’ ability to break down PFAS. Some fungi have degraded PFAS in laboratory experiments. A major concern with using wetlands for PFAS treatment is the risk of exposing wildlife to high concentrations of contaminants. Machine learning models have shown effectiveness in predicting PFAS removal when chemical-specific data is limited.

Analytical methods

Analytical methods for PFAS analysis are divided into two main types: targeted analysis and non-targeted analysis. Targeted analysis usually uses liquid chromatography–mass spectrometry (LC-MS) instruments. EPA Method 537.1 is currently approved for testing drinking water and includes 18 PFAS compounds. EPA Method 1633 is being reviewed for use in wastewater, surface water, groundwater, soil, biosolids, sediment, landfill leachate, and fish tissue for 40 PFAS compounds. Many laboratories in the United States are already using this method. Fast flow SPE has been developed as an improved version of Method 1633A to reduce the time needed for analysis and lower the Method Detection Limit (MDL). Regulatory limits for PFOA and PFOS set by the US EPA (4 parts-per-trillion) depend on the ability of testing methods to detect very low concentrations of these chemicals.

Non-targeted analysis includes methods such as total organic fluorine (TOF), which can be measured using combustion ion chromatography (CIC). Other methods include total oxidizable precursor assay and other techniques under development. For testing adsorbable organic fluorine (AOF) in water samples, the standards EPA Method 1621 and ISO 18127 were created. Both standards use combustion ion chromatography for analysis.

Detection technology using amplifying fluorescent polymers (AFPs) is gaining attention as a fast and highly sensitive method for on-site testing. This method has the potential to replace traditional mass spectrometry techniques.

In popular culture

• The Devil We Know (2018): a film that explains the health risks of PFAS.
• Dark Waters (2019): a thriller film that shows how a company defended itself against claims related to PFAS and DuPont.