Per- and polyfluoroalkyl substances, commonly known as PFAS, are a group of man-made chemicals used since the 1940s in products ranging from nonstick cookware and waterproof clothing to firefighting foam and industrial coatings. They are called “forever chemicals” because they do not break down in the environment. Over decades, these compounds have leached into groundwater, rivers, and public water supplies across the country. When a community discovers PFAS in its drinking water, the question quickly becomes not just how to clean it up, but who will be held legally responsible for the contamination, the health harms, and the cost of remediation.

Environmental liability for contaminated drinking water sources typically falls under several legal theories. The most common are negligence, strict liability, nuisance, and product liability. Negligence requires showing that a company or government entity failed to act with reasonable care when handling, storing, or disposing of PFAS-containing materials. Plaintiffs must prove that the defendant knew or should have known the chemicals could migrate into water supplies and did nothing to prevent it. Strict liability, by contrast, does not require proof of carelessness. In many states, activities that involve ultrahazardous substances—and PFAS are increasingly treated as such—make the responsible party liable for any harm caused, regardless of precautions. Nuisance law covers interference with the use and enjoyment of property, which includes having contaminated well water or being unable to sell a home because of pollution. Product liability targets the manufacturers of PFAS-based products, arguing that the chemicals were defectively designed because they posed unreasonable risks that the manufacturers knew about but hid from the public.

The most high-profile PFAS liability cases have been brought against chemical giants like 3M, DuPont, and Chemours. In recent years, these companies have reached multi-billion-dollar settlements with water utilities and states. For example, in 2023, 3M agreed to pay more than $10 billion to compensate public water systems for PFAS contamination. DuPont and its spinoffs settled a separate class action for over $1 billion. These settlements do not admit wrongdoing, but they reflect the enormous financial exposure these companies face. The money is meant to fund filtration systems, alternative water supplies, and health monitoring. However, individual residents who have developed illnesses linked to PFAS—such as kidney cancer, thyroid disease, or ulcerative colitis—have often had a harder road. Many of their personal injury claims have been consolidated into multidistrict litigation, where thousands of plaintiffs seek compensation for medical monitoring and damages. Courts are still wrestling with the scientific evidence connecting PFAS to specific diseases, which is a major hurdle for proving causation.

Another layer of liability involves the entities that used PFAS, particularly fire departments, airports, military bases, and industrial sites. Aqueous film-forming foam used for firefighting has been a major source of groundwater contamination around training facilities and crash sites. The federal government, as the owner or operator of many military bases, has been sued under the Resource Conservation and Recovery Act and the Comprehensive Environmental Response, Compensation, and Liability Act—commonly known as Superfund. The Environmental Protection Agency has proposed listing certain PFAS as hazardous substances under Superfund, which would allow the government to force polluters to pay for cleanup and to sue for natural resource damages. If that rule becomes final, liability will extend backward in time and across any party that contributed to the contamination, including waste haulers, landfills, and even property owners who allowed PFAS to be used on their land.

Private landowners and small businesses can also be dragged into liability. A farmer who spread biosolids from a wastewater treatment plant as fertilizer may find that the sludge contained PFAS from upstream industrial sources. That farmer could be held liable under state or federal laws for contaminating groundwater, even if they had no knowledge of the chemicals. The strict nature of environmental liability means that innocence is rarely a defense. Proving that someone else was the original source may reduce the farmer’s share of cleanup costs, but it does not eliminate their legal obligation to address the contamination on their property.

One of the biggest challenges in PFAS liability cases is the sheer number of potential defendants and the difficulty of tracing the specific chemical to a specific source. PFAS are ubiquitous. They are found in rainwater, in the blood of nearly every American, and in countless consumer products. When a water supply tests above the new federal maximum contaminant levels, the utility cannot always pinpoint which factory, fire training site, or landfill caused the problem. This has led to a wave of contribution lawsuits, where water utilities sue every possible industrial customer in their service area, hoping to spread the cost among dozens of parties. The legal fees alone can bankrupt smaller municipalities.

Meanwhile, insurance coverage for PFAS claims is a battleground of its own. Liability insurers are denying coverage on grounds that PFAS contamination is a gradual pollution event excluded under standard commercial general liability policies. Policyholders, including cities and manufacturers, are taking insurers to court, arguing that the releases were sudden and accidental or that the pollution exclusion does not apply because PFAS were not known to be hazardous at the time. These coverage disputes can take years to resolve, leaving contaminated communities without the funds needed for immediate treatment.

The bottom line for anyone dealing with contaminated drinking water is that the liability landscape is shifting rapidly. Federal rulemaking, court decisions, and scientific studies are redefining who can be sued and what they must pay. If you suspect PFAS in your water, you need to act quickly because statutes of limitations vary by state and type of claim. Do not assume the chemical company or the government will step up without a fight. Legal liability exists, but it is rarely automatic, and the burden of proof rests on the injured party. The only certainty is that the cleanup of forever chemicals will be a long and expensive process, and the question of who foots the bill will be settled one lawsuit at a time.