Per- and polyfluoroalkyl substances have become the defining mass tort of the current era. Litigation involving PFAS contamination of drinking water, occupational exposure, and consumer product exposure has produced a nationwide docket that spans municipal water systems, military bases, industrial sites, and individual product claims. For the plaintiff practitioner building individual PFAS cases, the regulatory terrain and the MDL structure in the District of South Carolina provide the scaffolding for the theory , but the case still rises and falls on specific causation for the individual client.
The EPA 2024 Maximum Contaminant Levels
The Environmental Protection Agency finalized maximum contaminant levels for six PFAS compounds in drinking water on April 10, 2024. The rule set MCLs for PFOA and PFOS at 4.0 parts per trillion each, making them the lowest MCLs for any regulated contaminant in history. It also set MCLs for PFNA, PFHxS, and HFPO-DA (GenX chemicals), and established a combined Hazard Index for mixtures of certain PFAS. Public water systems must achieve compliance by 2029.
These MCLs serve two litigation functions. They establish that regulatory authorities have concluded these substances are harmful at very low concentrations, which supports general causation expert testimony on the health effects of PFAS exposure. They also establish a reference point for contamination levels at which exposure has occurred , a water system that has operated above the MCL for years has been delivering contaminated water to its customers, and the duration and concentration of that exposure is a key input into the specific causation analysis.
The AFFF MDL and Its Scope
The Aqueous Film Forming Foam Multi-District Litigation, MDL No. 2873, is pending before Judge Richard M. Gergel in the District of South Carolina. The MDL consolidates thousands of cases involving PFAS contamination from AFFF, a firefighting foam used extensively by military installations and civilian airports. The litigation includes both municipal water system claims and individual personal injury claims arising from occupational and community exposure.
For individual plaintiffs considering PFAS claims, the MDL's development of general causation science through the bellwether process has generated a body of expert testimony and Daubert rulings that inform individual case development outside the MDL itself. The specific disease associations that have survived Daubert challenges , kidney cancer, testicular cancer, thyroid disease, ulcerative colitis, and high cholesterol , are the diagnoses around which individual cases are most commonly built.
Identifying Defendants in a PFAS Case
The PFAS supply chain runs from chemical manufacturers who produced the PFAS compounds, to formulators who incorporated them into products, to distributors who sold those products, to end users who applied them. At the manufacturer level, 3M, DuPont, and their corporate successors are the primary defendants in AFFF litigation because they manufactured PFOA and PFOS and sold them for use in AFFF formulations.
In cases arising from non-AFFF exposure , drinking water contamination from a manufacturing facility, for example , the defendant is typically the facility operator whose discharge contaminated the source water. In consumer product cases involving PFAS-treated cookware, food packaging, or apparel, the brand, the manufacturer, and potentially the retailer may all be in the chain of liability depending on the state's strict liability rules for product sellers.
Work backward from the plaintiff's exposure history to identify the defendants. Where did the PFAS enter the environment or the product? Who is responsible for that introduction? Who sold the product or maintained the system? Each answer identifies a potential defendant, and the available discovery will be different for each.
The Specific Causation Challenge
General causation , whether PFAS can cause the relevant disease , is established by the regulatory record, the epidemiological literature, and the MDL's expert development. Specific causation , whether this plaintiff's exposure to PFAS caused this plaintiff's disease , is the challenge that determines whether an individual case has merit.
Specific causation in a PFAS case requires quantification of the plaintiff's individual PFAS exposure, comparison of that exposure to dose-response data for the relevant disease, a differential diagnosis that rules out other causes, and an expert opinion tying the exposure to the diagnosis. Blood serum PFAS testing, where the plaintiff's serum levels are documented and compared to population background levels, is the most direct evidence of individual exposure. If serum testing was not done during or shortly after the exposure period, the opportunity may be lost , PFAS compounds have half-lives measured in years, so historical serum values can still be meaningful in long-term cases. For related strategy on managing large-scale toxic tort evidence, see our resources on product liability and updates on emerging settlements in our case law and settlements coverage.
Preserving Serum Evidence and Expert Coordination
In PFAS individual cases, serum PFAS testing is the bridge between general causation science and the specific plaintiff. A client whose blood serum shows elevated PFAS levels compared to population norms has documented, quantified individual exposure. Where serum testing has not been performed, explore whether older blood samples from prior medical workups are available for retrospective testing, or whether the client's documented water use history and proximity to a contaminated source supports an exposure estimation model. Coordinate the toxicologist and the epidemiologist early, because the dose-response relationship between measured PFAS serum levels and the specific diagnosed condition is where specific causation is ultimately argued.