PFAS are often called “forever chemicals” because many of them persist in the environment for years—or even decades—without breaking down naturally. They can move through soil and groundwater, enter drinking-water supplies and accumulate in people and wildlife. The name may sound dramatic, but it reflects a real chemical challenge: once PFAS are released, removing them is difficult, expensive and rarely complete.
These substances are now found in water, food packaging, household dust, consumer products and human blood. Their widespread use has helped make modern products more resistant to water, grease, stains and heat. However, the same chemical properties that make PFAS useful also make them unusually persistent.
Understanding what PFAS are, how they reach drinking water and what scientists know about their health effects is essential for households, water suppliers and policymakers alike.
What are PFAS?
PFAS stands for per- and polyfluoroalkyl substances. It refers to a large family of manufactured chemicals—numbering in the thousands—rather than one single compound. Well-known examples include perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), two substances that have been widely studied and increasingly restricted.
PFAS have been used commercially since the mid-20th century. Their applications include:
- Non-stick cookware and stain-resistant treatments
- Waterproof clothing, carpets and outdoor equipment
- Grease-resistant food packaging, including some takeaway containers
- Cosmetics and personal-care products
- Industrial processes and metal plating
- Aqueous film-forming foams used to fight certain types of fires
The defining feature of many PFAS is a chain of carbon atoms bonded to fluorine. The carbon–fluorine bond is one of the strongest in organic chemistry. It resists heat, water, oil and chemical reactions—useful qualities in a frying pan or protective coating, but problematic once these compounds enter the wider environment.
Not every PFAS behaves in exactly the same way. Some are long-chain compounds that can remain in the body for years. Others are shorter-chain alternatives that may leave the bloodstream more quickly, but can travel more easily through soil and water. Replacing one PFAS with another does not automatically remove the environmental risk.
Why are PFAS called “forever chemicals”?
The phrase does not mean that every PFAS molecule literally lasts forever. It refers to their exceptional resistance to natural degradation. Sunlight, bacteria, water and ordinary environmental processes often cannot break these chemicals down effectively.
PFAS can therefore persist in rivers, groundwater, sediments and soils. Some may also be transported over long distances. A release at an industrial site or airport can affect water supplies far beyond the original location, particularly when contamination reaches an underground aquifer.
There is another complication: some larger PFAS can break down into smaller, highly persistent PFAS. This means that stopping the use of one named chemical may not immediately eliminate contamination. Existing pollution can continue to move through the environment, while precursor compounds slowly transform into substances that are more difficult to remove.
In practical terms, “forever” is a warning about persistence and prevention. Once PFAS enter a water system, treating the contamination is generally more challenging than preventing the release in the first place.
How do PFAS enter drinking water?
PFAS can reach drinking-water sources through industrial discharges, landfill leachate, wastewater, firefighting-foam use and contaminated runoff. Airports, military bases, manufacturing facilities, textile plants and sites where firefighting foams were used have all been associated with PFAS contamination in different countries.
Wastewater treatment plants are not designed specifically to destroy PFAS. They may remove some compounds from the water, but PFAS can remain in treated effluent or become concentrated in sewage sludge. If sludge is applied to agricultural land, contaminants may later migrate into soil and groundwater.
Landfills can also act as long-term sources. PFAS-containing consumer products placed in landfill sites may release chemicals into leachate. Unless that leachate is treated using suitable technology, PFAS can enter nearby watercourses or aquifers.
Private wells may require particular attention. Unlike public water supplies, they are not always routinely monitored for a wide range of emerging contaminants. A well located near an industrial area, airport, landfill or firefighting-training site may face a higher risk, even if the water looks, smells and tastes completely normal.
That last point matters: PFAS contamination cannot be identified by sight or taste. Testing is the only reliable way to determine whether these chemicals are present.
What are the health concerns?
People can be exposed to PFAS through contaminated drinking water, food, consumer products and indoor dust. For many communities, drinking water can be an important source, particularly when contamination levels are elevated and exposure continues over a long period.
Research into PFAS health effects is ongoing, and the evidence differs between individual chemicals. However, studies in humans and laboratory animals have associated exposure to certain PFAS with a range of potential effects, including:
- Changes in cholesterol levels
- Reduced antibody response to some vaccinations
- Effects on liver function
- Impacts on thyroid and other hormone-regulated systems
- Pregnancy-related effects, including changes in birth weight
- Developmental and immune-system concerns
- Increased risk of certain cancers for some well-studied compounds
The International Agency for Research on Cancer classified PFOA as carcinogenic to humans in 2023 and PFOS as possibly carcinogenic to humans. These classifications reflect the available evidence and do not mean that every person exposed to these compounds will develop cancer. Risk depends on factors such as the chemical involved, concentration, duration of exposure and individual susceptibility.
PFAS are also unusual because they can remain in the human body. Some compounds bind to blood proteins and can have biological half-lives measured in years. Repeated, low-level exposure may therefore contribute to a gradual accumulation, even when each individual exposure appears small.
Scientists continue to study newer and less-researched PFAS. A lack of evidence is not the same as proof of safety. With thousands of related substances in circulation, assessing every compound individually is slow and technically demanding.
How much PFAS is safe in drinking water?
There is no single worldwide limit for PFAS. Drinking-water standards differ between jurisdictions and are being updated as scientific evidence develops.
In the United States, the Environmental Protection Agency introduced legally enforceable limits in 2024 for PFOA and PFOS, along with limits for several other PFAS and mixtures. The European Union Drinking Water Directive sets a limit for “PFAS Total” and a separate limit for the sum of specified PFAS. The UK has historically used a risk-based approach and guidance values, with regulation and monitoring evolving as more evidence becomes available.
These differences can be confusing. A concentration considered acceptable under one framework may exceed a limit used elsewhere. Regulators must account for toxicology, analytical capability, treatment costs and the practical realities of monitoring thousands of compounds.
For residents, the most useful step is to check information from the local water supplier or environmental regulator. Public water-quality reports may include PFAS monitoring, but coverage is not uniform. If you use a private well, arrange testing through an accredited laboratory, especially if the well is near a known or suspected source.
Can PFAS be removed from drinking water?
Yes—several treatment methods can reduce PFAS concentrations, although no single technology is suitable for every situation. Performance depends on the specific chemicals present, their concentrations, water chemistry, flow rate and maintenance practices.
Common treatment approaches include:
- Granular activated carbon: Activated carbon can adsorb many long-chain PFAS, particularly when filters are correctly sized and replaced before they become saturated. Shorter-chain PFAS may be more difficult to capture.
- Ion-exchange resins: These materials attract charged PFAS molecules and can be highly effective. They require careful management and disposal once exhausted.
- Reverse osmosis: Reverse-osmosis membranes can remove a broad range of PFAS, along with many other dissolved contaminants. The process uses energy and produces a concentrated waste stream that must be handled responsibly.
- Advanced destruction technologies: Researchers are developing methods that aim to break PFAS down rather than simply transfer them into spent carbon, resin or concentrate. These approaches include electrochemical treatment, supercritical water oxidation and specialised chemical processes, but many remain at pilot or early commercial stages.
Boiling water is not an effective PFAS treatment. In fact, boiling can reduce the volume of water while leaving the PFAS behind, potentially increasing the concentration. Standard jug filters may also provide little or no protection unless the product has been independently tested and specifically certified for PFAS reduction.
When choosing a home filter, look for clear performance claims, independent certification and instructions covering the relevant PFAS compounds. A filter is only effective if it is installed correctly and replaced on schedule. An exhausted cartridge is not a long-term solution—it is simply a container holding contaminants that may eventually pass through.
What can households do to reduce exposure?
Individuals cannot solve the PFAS problem through shopping choices alone, but practical steps can reduce avoidable exposure and help identify risks:
- Check your water supplier’s latest PFAS or emerging-contaminant reports.
- Test private-well water through an accredited laboratory if contamination is possible.
- Use a certified treatment system when testing confirms PFAS in drinking water.
- Replace filters according to the manufacturer’s schedule.
- Avoid using damaged or overheated non-stick cookware, and consider alternatives such as stainless steel or cast iron.
- Reduce unnecessary use of stain-resistant treatments and grease-resistant packaging.
- Follow local advice after a known industrial, landfill or firefighting-foam release.
It is important not to panic. PFAS exposure is widespread, but risk reduction is possible. People who are pregnant, immunocompromised or concerned about a specific exposure should discuss their circumstances with a healthcare professional rather than relying on general online advice.
Why regulation and monitoring matter
PFAS contamination is not only a household filtration issue. It is also a manufacturing, waste-management and public-health challenge. Treating a contaminated water supply can require years of monitoring and substantial public investment. Preventing releases, identifying sources and applying the “polluter pays” principle are therefore central to effective policy.
Better monitoring is equally important. Testing has traditionally focused on a small number of well-known PFAS, while newer compounds and transformation products may remain undetected. Advances in analytical chemistry are helping researchers measure more substances at lower concentrations, but laboratories still face challenges because PFAS occur at extremely low levels and can be introduced accidentally during sampling.
The most effective response combines source control, transparent reporting, targeted testing and reliable treatment. “Forever chemicals” may be persistent, but public-health decisions do not have to remain stuck in the past. With stronger regulation, improved technologies and informed communities, PFAS exposure in drinking water can be reduced—and future contamination can be prevented.
Sources for further reading: United States Environmental Protection Agency, European Environment Agency, UK Drinking Water Inspectorate, World Health Organization and International Agency for Research on Cancer.