PFAS are a group of man-made chemicals that have become one of the most persistent environmental contamination concerns in the world. They have been detected in drinking water, rivers, groundwater, soil, food packaging, household products and human blood. But what does “PFAS” actually mean, and why are scientists, regulators and water companies so concerned?
PFAS stands for per- and polyfluoroalkyl substances. The term describes thousands of fluorinated chemicals with a shared feature: carbon atoms bonded to fluorine. This chemical structure gives PFAS exceptional resistance to heat, water, oil and chemical reactions. Those properties made them useful in manufacturing—but also make many of them extremely difficult to remove from the environment.
Some PFAS can remain in water and soil for years or decades. For this reason, they are often called “forever chemicals”. The phrase is useful for raising awareness, although it is not a scientific classification: PFAS do not all behave identically, and some can break down more quickly than others. The wider concern is that many PFAS are highly persistent and can travel far from their original source.
What are PFAS used for?
PFAS have been used since the mid-20th century in products designed to resist water, grease, stains or high temperatures. Their applications have included industrial processes, firefighting foams, electronics, textiles, cosmetics and food-contact materials.
Common examples include:
- Firefighting foams used at airports, military sites, oil facilities and training grounds
- Water-resistant outdoor clothing, carpets and upholstery
- Grease-resistant food packaging and takeaway containers
- Non-stick cookware and industrial coatings
- Some cosmetics, dental products and personal-care items
- Manufacturing processes involving semiconductors, metal plating and surface treatments
Two of the best-known PFAS are perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Their use has been restricted or phased out in many countries because of concerns about persistence, bioaccumulation and toxicity. However, replacing one PFAS with another does not automatically eliminate the risk. Some shorter-chain or newer alternatives may be less likely to accumulate in the human body, but they can be more mobile in water and are still being studied.
Why are PFAS called “forever chemicals”?
The carbon–fluorine bond is among the strongest chemical bonds in organic chemistry. As a result, many PFAS resist heat, sunlight, biological activity and ordinary wastewater treatment. They do not simply disappear when a product is thrown away or when contaminated water passes through a conventional treatment plant.
Persistence is only part of the issue. PFAS can also move through groundwater and surface water. A spill or discharge at one location may therefore affect wells, rivers or reservoirs some distance away. In addition, some PFAS can transform into other PFAS in the environment, making contamination more complicated than a single chemical release.
The term “PFAS” covers a very large family of substances. Their properties vary according to chain length, functional groups and molecular structure. Some bind more strongly to soil, while others remain dissolved in water and travel readily through aquifers. This is why testing for only one or two chemicals may provide an incomplete picture of contamination.
How do PFAS enter drinking water?
PFAS can reach water supplies through both industrial and everyday pathways. The most heavily contaminated sites are often associated with facilities where PFAS were manufactured, used or disposed of.
Important sources include:
- Firefighting foam releases at airports, defence sites and emergency training areas
- Industrial discharges and waste from chemical, textile or metal-processing facilities
- Landfill leachate, where PFAS migrate from discarded consumer and industrial products
- Wastewater treatment works, which are not generally designed to destroy PFAS
- Contaminated soil and groundwater near manufacturing or fire-training sites
- Urban runoff carrying chemicals from treated materials and waste
Wastewater treatment can reduce some contaminants, but standard biological treatment is not designed to remove PFAS reliably. In some cases, PFAS leave the treatment process in the effluent; in others, they become concentrated in sewage sludge or biosolids. This can transfer the problem from one environmental compartment to another rather than eliminating it.
Private wells are particularly important to consider. Unlike public water supplies, private wells may not be routinely monitored for a broad range of emerging contaminants. A household located near an airport, industrial facility, landfill or former firefighting training area may need specialist testing to assess its exposure.
What are the health risks of PFAS?
Research has linked exposure to certain PFAS with a range of possible health effects. The strength of evidence differs between individual chemicals and outcomes, and scientists continue to investigate newer compounds. Still, the evidence for concern is substantial, particularly for long-chain PFAS such as PFOA and PFOS.
Studies and assessments from organisations including the World Health Organization (WHO), the UK Health Security Agency (UKHSA), the European Food Safety Authority (EFSA) and the US Environmental Protection Agency (EPA) have examined potential associations with:
- Changes in the immune system, including reduced antibody responses to some vaccinations
- Increased cholesterol levels
- Effects on liver function
- Developmental and reproductive effects
- Changes in fetal growth and birth weight
- Possible effects on thyroid function and metabolism
- Increased risk of certain cancers for specific PFAS, particularly PFOA
These findings do not mean that every person exposed to PFAS will develop an illness. Health outcomes depend on factors such as the chemical involved, dose, duration of exposure, age, genetics and other environmental influences. The scientific concern arises because exposure is widespread and may occur over long periods, often without an obvious taste, smell or colour in the water.
Children and developing fetuses may be more vulnerable to certain chemical exposures because their bodies and immune systems are still developing. This does not mean that families should panic, but it does underline the importance of preventing contamination and following reliable public-health advice.
How common is PFAS exposure?
PFAS exposure is widespread. People may encounter these chemicals through food, household dust, consumer products and drinking water. In biomonitoring studies, PFAS have been detected in the blood of populations across Europe and North America.
Drinking water is not always the largest source of exposure for every individual. However, it can become a significant source when contamination is present because water is consumed regularly and used in cooking. Exposure can also be higher in communities located near known or suspected contamination sites.
PFAS are often present at extremely low concentrations, commonly measured in parts per trillion. To put that into perspective, one part per trillion is roughly equivalent to one second in about 31,700 years. This comparison illustrates how small the concentrations can be—not that such levels are automatically harmless. Advanced analytical instruments can detect PFAS at very low levels, while health-based limits are designed to manage risk at similarly small concentrations.
Why are PFAS difficult to regulate?
Regulation is challenging because there are thousands of PFAS, but toxicological data are available for only a fraction of them. Regulators must decide whether to control chemicals individually, group them together or focus on particular uses and sources.
An individual-chemical approach may miss less-studied PFAS that share similar properties. A group approach can provide broader protection, but it must account for meaningful differences in toxicity, persistence and mobility. Regulators also have to consider the technical feasibility and cost of testing and removing these compounds from water.
In the UK, PFAS management involves drinking-water standards, environmental permitting, chemical controls and monitoring guidance. The Drinking Water Inspectorate has set requirements for certain PFAS parameters in public water supplies, while the UK Environment Agency and other bodies address pollution sources and environmental risks. Requirements can change as new evidence becomes available, so local guidance remains important.
Across Europe, the EU Drinking Water Directive includes limits for PFAS groups. In the United States, the EPA has introduced legally enforceable drinking-water limits for PFOA and PFOS under its national regulatory framework. These measures reflect a wider shift: regulators are moving from reacting to individual contamination incidents towards controlling PFAS as a broader class.
How are PFAS detected in water?
PFAS testing requires specialist laboratory methods. Samples must be collected carefully because PFAS may be present in sampling equipment, tubing, clothing treatments or packaging. Laboratories typically use advanced techniques such as liquid chromatography combined with tandem mass spectrometry.
A water test may target a defined list of PFAS, often including PFOA, PFOS and other commonly monitored compounds. However, a result showing “not detected” does not mean that no PFAS are present. It means that the chemicals included in the test were below the laboratory’s reporting limits.
For a meaningful assessment, ask:
- Which PFAS compounds were tested?
- What were the laboratory detection or reporting limits?
- Was the sample taken from the raw source water or treated drinking water?
- Was the laboratory accredited for PFAS analysis?
- How does the result compare with current national guidance?
One test is also only a snapshot. PFAS concentrations can vary with rainfall, groundwater movement, industrial activity and changes in treatment. Where contamination is suspected, repeated sampling and source investigation may be necessary.
Can PFAS be removed from drinking water?
Yes, certain treatment technologies can reduce PFAS concentrations, but performance depends on the chemical, the water chemistry, the filter design and maintenance. No single technology should be treated as a universal solution.
The main treatment options include:
- Granular activated carbon: effective for many long-chain PFAS when properly designed and maintained. Filters require replacement or regeneration before they become saturated.
- Ion exchange: uses specialised resins to capture PFAS and can perform well across a range of compounds, although the spent resin requires controlled management.
- Reverse osmosis: uses a membrane to remove a broad range of contaminants, including many PFAS. It can produce a concentrated waste stream and may require more energy and maintenance.
- High-pressure membrane systems: useful in larger treatment plants, but their effectiveness depends on membrane selection and operating conditions.
- Destructive technologies: advanced methods aim to break PFAS molecules apart rather than transfer them into another waste stream. These approaches are developing and are not yet suitable for every water-treatment application.
Boiling water does not remove PFAS. In fact, because some water evaporates while the chemicals remain, boiling could slightly increase their concentration. Ordinary jug filters may also provide little or inconsistent protection unless they are specifically certified and maintained for PFAS reduction.
What can households and communities do?
If PFAS contamination is suspected, the first step is to obtain information from the local water supplier, council, environmental regulator or public-health authority. Avoid relying on social-media claims or unverified “detox” products. A certified laboratory test is more useful than a general water-quality kit that does not include PFAS analysis.
Households using private wells should consider testing if they are close to a known source, such as an airport, industrial site, landfill or fire-training area. If treatment is installed, choose equipment supported by independent performance data and follow the manufacturer’s replacement schedule. A filter that has reached capacity may stop protecting the household effectively.
At community level, prevention is more effective than attempting to clean up contamination after it spreads. This means controlling industrial releases, managing firefighting foams responsibly, monitoring vulnerable water sources and developing safer alternatives for uses where PFAS are not essential.
The wider challenge: reducing PFAS at the source
Water treatment is important, but it should not become the only response. Removing PFAS from drinking water can be expensive, energy-intensive and technically complex. It may also create concentrated waste that needs further treatment.
The most effective long-term strategy is to reduce unnecessary PFAS use, improve product transparency, prevent releases and apply the precautionary principle where evidence indicates persistent environmental harm. Manufacturers, regulators, water companies and consumers all have a role to play.
PFAS are not a single chemical and contamination is not a single problem. Understanding the terminology is the starting point: knowing what PFAS means helps people interpret test results, ask better questions and identify practical steps to protect water quality. The science is evolving, but one message is already clear—persistent chemicals require persistent attention.