The “Dirty Dozen” and “Clean Fifteen” are familiar labels for shoppers trying to reduce exposure to pesticide residues. Each year, the Environmental Working Group (EWG) ranks conventionally grown fruits and vegetables according to residue test results, while identifying produce with comparatively lower levels.
But what do these lists reveal about PFAS in drinking water?
The short answer is less straightforward than a supermarket guide might suggest. The Dirty Dozen is not a PFAS ranking, and the Clean Fifteen does not prove that a food, farm or water supply is free from “forever chemicals”. However, the lists highlight a wider issue: contaminants can move through connected systems, from industrial sites and wastewater to rivers, farmland, food and eventually the human body.
PFAS—per- and polyfluoroalkyl substances—are a large family of manufactured chemicals used for decades in products designed to resist water, oil, stains and heat. Some have been detected in drinking water, food packaging, soil, crops and human blood. Their persistence means that contamination does not simply disappear when a product leaves the factory or when a chemical is phased out.
What are the Dirty Dozen and Clean Fifteen?
EWG’s annual Shopper’s Guide to Pesticides in Produce is based on testing data published by the United States Department of Agriculture (USDA). The Dirty Dozen identifies conventionally grown fruits and vegetables that, in the relevant testing, tend to show pesticide residues more frequently or in greater numbers. The Clean Fifteen identifies produce with fewer detected residues.
The guide is designed to help consumers decide where buying organic may offer the greatest reduction in pesticide exposure. It is not a toxicological ranking, and it does not mean that every item on the Dirty Dozen is unsafe or that every item on the Clean Fifteen is contaminant-free.
That distinction matters when discussing PFAS. Pesticide residue testing and PFAS monitoring are separate activities. A produce sample can meet pesticide standards and still be grown using water affected by PFAS. Conversely, a crop may be exposed to PFAS without that contamination appearing in a routine pesticide test.
In other words, a list created to answer one question—“Which produce carries the most detectable pesticide residues?”—cannot answer another: “Which foods were exposed to PFAS?”
Why PFAS contamination is relevant to food and water
PFAS are often described as “forever chemicals” because many of them break down extremely slowly in the environment. Their chemical structures can make them resistant to heat, water and oil, but those same properties make environmental management difficult.
PFAS can enter water through a range of pathways, including:
- Industrial manufacturing and processing;
- Firefighting foams used at airports, military facilities and training grounds;
- Landfill leachate and contaminated waste;
- Wastewater treatment plants and biosolids applied to land;
- Food and consumer products containing PFAS;
- Stormwater runoff from contaminated sites.
Once present in groundwater or surface water, PFAS can travel beyond the original source. Drinking-water supplies are particularly important because they provide a direct and repeated route of exposure. Water used for irrigation can also introduce contaminants into agricultural soils, although the extent of plant uptake varies substantially between different PFAS, crops, soil types and growing conditions.
Research has shown that shorter-chain PFAS may be more mobile in soil and water, while longer-chain compounds can bind more strongly to soil and organic matter. Some crops may take up PFAS through their roots, but uptake is not uniform. Leafy vegetables, for example, may behave differently from fruiting crops. These differences make broad claims about “safe” and “unsafe” produce scientifically unreliable.
The limits of using a shopping list to understand PFAS
The appeal of the Dirty Dozen and Clean Fifteen is their simplicity. PFAS contamination is not simple.
Several important limitations should be kept in mind:
- PFAS are a chemical class, not a single substance. Thousands of PFAS have been identified, but monitoring commonly focuses on a much smaller group.
- Testing is targeted. If a laboratory does not analyse for a particular PFAS, the result cannot show whether that compound is present.
- Contamination is location-specific. Produce grown in one region may have a very different exposure history from the same crop grown elsewhere.
- Concentrations can change over time. Rainfall, irrigation practices, groundwater movement and remediation work can all affect environmental levels.
- Food and water exposure are connected but not interchangeable. Drinking water may be a major exposure pathway in one community, while food packaging, occupational exposure or contaminated dust may matter more in another.
The absence of a PFAS result in a report should therefore not be interpreted as proof of absence. It may simply indicate that the substance was not included in the test panel or was present below the laboratory’s reporting limit.
What the phrase “15 clean” can—and cannot—tell us
The “Clean Fifteen” label can create an unintended sense of security. A low pesticide-residue result is useful information, but it is not a complete environmental health assessment.
Consider a hypothetical farm located downstream from an industrial facility. Its apples may appear on a low-residue produce list because USDA testing detects few pesticides. Yet the farm’s irrigation water could still contain PFAS. The fruit may not absorb significant quantities, or it may absorb measurable levels depending on the chemical and growing conditions. Without PFAS-specific testing, the pesticide result cannot resolve that question.
The reverse can also happen. A farm may use water with no detectable PFAS, while produce is exposed to pesticide residues through conventional crop protection. Different contaminants require different investigations.
This is why environmental scientists avoid treating one testing programme as a substitute for another. A clean pesticide report is not a clean-water certificate. It is one piece of evidence in a much larger picture.
PFAS in drinking water: the regulatory picture
In the United States, the Environmental Protection Agency (EPA) finalised a national drinking-water regulation in 2024 covering six PFAS: PFOA, PFOS, PFHxS, PFNA and GenX chemicals, along with mixtures of these compounds. The rule established maximum contaminant levels for PFOA and PFOS and a hazard-index approach for certain mixtures.
The regulation is significant because it creates enforceable federal requirements for public water systems. However, implementation requires monitoring, laboratory capacity, treatment investment and public communication. The presence of a federal standard does not mean that every private well is regularly tested or treated.
Private well owners face a particular challenge. Unlike public water systems, private wells are generally not subject to the same routine regulatory monitoring. Testing may be especially important for properties near airports, military bases, industrial facilities, landfills, wastewater sites or areas where firefighting foam has been used.
In the United Kingdom, PFAS regulation and monitoring operate through a different framework. Drinking-water suppliers monitor certain PFAS and must meet regulatory requirements, while guidance and standards continue to develop as scientific understanding improves. Consumers concerned about local exposure should consult their water supplier, the Drinking Water Inspectorate or relevant environmental authorities.
Regulatory limits are important, but they are not a guarantee that exposure is zero. They are designed around available evidence, technical feasibility and public-health risk assessment. As analytical methods improve, regulators may detect more compounds and revise monitoring priorities.
How PFAS reach drinking-water supplies
PFAS contamination is often described as a local problem, but water can carry pollutants across administrative boundaries. A release into soil may migrate into groundwater. A contaminated river may serve as a source for drinking-water treatment. Wastewater discharges may contain PFAS from household and industrial products.
Conventional drinking-water treatment is not always designed to remove PFAS. Processes such as coagulation, sedimentation and filtration can be effective for many contaminants, but they may provide limited removal for dissolved PFAS.
The technologies most commonly discussed for PFAS treatment include:
- Granular activated carbon: often effective, particularly for longer-chain PFAS, although performance depends on water chemistry, contact time and filter management.
- Ion-exchange resins: can remove a broad range of PFAS but require careful handling and disposal of spent media.
- Reverse osmosis: capable of high removal rates, but energy-intensive and associated with a concentrated waste stream.
- Destructive treatment technologies: emerging approaches aim to break PFAS down rather than transfer them into another waste material, but many remain at pilot or early commercial stages.
Treatment is only part of the solution. Preventing releases, identifying sources and monitoring vulnerable communities are equally important. Otherwise, water utilities are left paying to remove chemicals that should never have entered the water cycle.
What consumers can do
There is no need to panic over a produce list. The most useful response is to ask more precise questions.
- Check whether your drinking water provider publishes PFAS monitoring results.
- If you use a private well, consider PFAS testing when there is a potential nearby source.
- Use laboratories accredited for PFAS analysis and ask which compounds and reporting limits are included.
- Do not assume that a basic carbon jug removes all PFAS. Check the product’s independent certification and performance claims.
- Follow manufacturer instructions and replace filters on schedule. A saturated filter may perform poorly.
- Reduce unnecessary contact with products marketed as stain-resistant, grease-resistant or waterproof when safer alternatives are available.
- Wash fresh produce under running water to remove soil and surface residues, while recognising that washing will not remove PFAS taken up internally by a plant.
For households with confirmed contamination, bottled water may provide a temporary option, but it is not an ideal long-term public-health strategy. It can be expensive, generates plastic waste and does not address the contaminated source. Community-wide treatment and source control are more durable solutions.
The larger lesson behind the lists
The Dirty Dozen and Clean Fifteen are useful reminders that food choices are influenced by environmental conditions. Their limitations are just as instructive. No single ranking can capture the full range of chemical exposures in modern life.
PFAS in drinking water demonstrate why environmental monitoring must follow contaminants across systems rather than examining each sector in isolation. Water quality, agriculture, food production, waste management and public health are connected. A chemical released in one place can become a water issue somewhere else—and potentially a food issue after that.
So, is the “Clean Fifteen” free from PFAS? Not necessarily. Is the “Dirty Dozen” a list of PFAS-contaminated food? No. What the comparison really reveals is the need to match the test to the question.
Pesticide testing can inform pesticide exposure. PFAS testing can inform PFAS exposure. Neither can stand in for the other. For consumers, communities and regulators, that distinction is more valuable than any catchy shopping label.
Sources and further reading
- US Environmental Protection Agency, PFAS National Primary Drinking Water Regulation.
- US Environmental Protection Agency, Contaminant Candidate List 5.
- US Department of Agriculture, Pesticide Data Program Annual Summary.
- Environmental Working Group, Shopper’s Guide to Pesticides in Produce.
- Agency for Toxic Substances and Disease Registry, Toxicological Profile for Perfluoroalkyls.
- UK Drinking Water Inspectorate, guidance and information on PFAS in drinking water.