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This section is for: Recent Developments
The section is from a Focused Issue Brief on: Assessing Scientific Causation Claims in PFAS Exposure Litigation
The primary research jurisdiction is: United States of America
Recent Developments
Recent Case and Litigation Developments
The AFFF multidistrict litigation landscape underwent substantial restructuring during 2024 as major defendants reached final settlements with public water systems, fundamentally altering which claims and scientific causation theories remain actively contested. The U.S. District Court for the District of South Carolina entered a series of final approval orders that collectively resolved most water provider contamination claims against the largest AFFF manufacturers.
In February 2024, the MDL court granted final approval to the DuPont, Chemours, and Corteva public water system class settlement. Final approval of 3M’s nationwide PWS settlement followed in March 2024. The court entered additional major defendant resolutions throughout the year, with final approval orders for both the Tyco Fire Products/Chemguard PWS settlement and the BASF PWS settlement in November 2024. Each settlement established specific frameworks for which contamination claims are released versus retained, effectively channeling remaining PFAS litigation toward personal injury claims, non-class property damage cases, and disputes involving non-settling defendants.
With water contamination liability largely resolved for major defendants, the scientific focus shifts to proving bodily injury causation.
Exposure reconstruction, dose-response relationships, and specific causation methodologies face more demanding evidentiary standards than the presence-of-contamination theories that supported PWS settlements. The court continued structuring expert discovery and Daubert motion practice in the remaining tracks. In May 2024, the MDL court issued a case management order setting deadlines for Daubert motions in the Telomer Water Provider track, signaling where scientific and expert admissibility battles are expected to concentrate. The court anticipates Rule 702 challenges to focus initially on the telomer manufacturer cases rather than the personal injury bellwether track, though secondary reporting suggests personal injury bellwether timing has been adjusted with trial dates vacated as of August 2025.
Outside the federal MDL, PFAS contamination litigation proceeded to trial in state court. New Jersey’s site-focused contamination case against DuPont and Chemours began trial proceedings in May 2025, representing one of the first major PFAS contamination trials to reach the merits phase. Site-specific trials generate court rulings on exposure reconstruction, fate and transport modeling, and toxicological causation that frequently inform expert strategies in subsequent cases. The New Jersey proceedings carry particular relevance for practitioners handling similar contamination scenarios.
Evidentiary and Expert Witness Developments (Daubert / Rule 702)
The Eastern District of North Carolina’s Cape Fear PFAS contamination litigation produced the most significant expert admissibility ruling during this period. The court issued a comprehensive order addressing multiple expert challenges in September 2025. The court granted a motion to exclude DeWitt’s 2024 expert report and testimony under Rule 702, focusing specifically on the expert’s failure to adequately engage with conflicting literature when offering broad PFAS toxicity and safety opinions.
PFAS toxicology experts must provide methodologically rigorous engagement with the full scientific literature, including contrary findings, to survive Rule 702 challenges.
The DeWitt exclusion order provides concrete guidance on how courts evaluate PFAS toxicology experts’ methodological rigor. The court emphasized that experts offering sweeping conclusions about PFAS health effects must demonstrate sufficient engagement with contrary evidence and conflicting studies rather than selectively citing supportive literature. This ruling establishes a precedent for challenging PFAS toxicology experts who fail to address contradictory epidemiological or toxicological findings in their causation opinions. Courts will scrutinize whether expert methodologies meet reliability standards when the underlying scientific literature contains significant uncertainties.
The AFFF MDL court has structured Daubert motion practice across multiple tracks, with expert admissibility challenges scheduled for different case categories at different times. The May 2024 case management order setting Daubert deadlines in the Telomer Water Provider track indicates the court expects scientific admissibility battles to proceed in staged fashion rather than comprehensive challenges across all case types simultaneously. This sequencing allows practitioners to observe how the court treats specific expert methodologies and causation theories before those approaches are tested in other tracks.
Secondary reporting suggests that personal injury bellwether cases have experienced scheduling adjustments, with at least one kidney cancer trial setting vacated in August 2025. While the specific reasons for the postponement require verification from primary docket sources, trial delays typically indicate ongoing expert discovery disputes or Daubert motion activity that may affect the timing of when general causation and specific causation expert challenges are definitively resolved.
Regulatory and Agency Developments
EPA implemented the most significant PFAS regulatory framework in agency history during 2024, establishing enforceable drinking water standards that provide new benchmarks for exposure and contamination arguments in litigation. In April 2024, EPA finalized the National Primary Drinking Water Regulation for PFAS, setting maximum contaminant levels for six PFAS compounds: individual MCLs for PFOA and PFOS, plus MCLs for PFNA, PFHxS, and HFPO-DA (GenX chemicals), along with a Hazard Index approach for evaluating PFAS mixtures that includes PFBS in the mixture framework.
EPA issued a final rule in April 2024 designating PFOA and PFOS as CERCLA hazardous substances, fundamentally altering the legal framework for contamination liability and cleanup obligations. The CERCLA designation triggers federal release reporting requirements and expands Superfund cost-recovery mechanisms, driving additional site investigations that generate new exposure data and shift litigation strategies around contamination source responsibility. EPA also published final human health toxicity assessments for PFOA and PFOS in April 2024, providing updated hazard identification, dose-response analysis, and quantitative toxicity values including reference doses and cancer slope factors. These assessments serve as foundational materials in PFAS causation disputes, though they also provide targets for expert challenges when parties dispute EPA’s hazard characterization or dose-response methodologies.
Regulatory momentum shifted significantly in 2025 when EPA announced plans to modify the 2024 drinking water standards.
In May 2025, EPA indicated it would maintain strict limits for PFOA and PFOS while reconsidering or rescinding standards for other PFAS including GenX chemicals and mixture provisions, and extending compliance timelines for water systems. This proposed rollback creates uncertainty about which regulatory standards courts will treat as settled scientific and policy positions, particularly for non-PFOA/PFOS PFAS compounds and mixture evaluation approaches.
FDA completed a voluntary phase-out of PFAS grease-proofing agents in paper food packaging, announcing in February 2024 that these substances are no longer sold into the U.S. market. FDA subsequently issued notices in January 2025 that 35 PFAS food contact notifications are no longer effective, formally clarifying the authorization status of various food-contact applications. These actions help define current versus historical exposure scenarios in product liability contexts. ATSDR updated its clinician guidance materials in November 2024, providing healthcare practitioners with updated information on PFAS health effects and pathophysiology. The updated guidance frequently appears in litigation as evidence of medical and scientific consensus regarding which health outcomes are associated with PFAS exposure versus those that remain uncertain or unsupported.
Emerging Scientific Literature
Several significant studies published since January 2024 directly address health outcomes commonly pleaded in PFAS litigation, providing updated scientific foundations for causation arguments. A systematic review and meta-analysis published in Toxicology Letters in 2024 synthesized human studies evaluating PFAS exposure and thyroid cancer risk, concluding that PFAS exposure represents a potential risk factor for thyroid cancer while acknowledging the typical limitations of observational studies including exposure assessment variability and confounding control.
A 2025 meta-analysis specifically evaluating serum PFOA levels and kidney cancer risk reported that evidence for increased kidney cancer risk appears limited, with any association being small and not statistically significant based on current biomonitoring studies.
This meta-analysis directly challenges kidney cancer causation theories that have been prominent in AFFF personal injury litigation and will likely feature in Daubert briefing as defendants seek to undermine general causation for kidney cancer claims. The thyroid cancer meta-analysis provides updated quantitative synthesis directly relevant to thyroid cancer causation claims in AFFF litigation. Practitioners should evaluate the heterogeneity among included studies and the quality of exposure assessment methodologies before relying on the meta-analysis conclusions, as these factors affect both the strength of general causation arguments and potential expert challenges.
A nested case-control study published in Clinical Gastroenterology and Hepatology in 2024 evaluated prediagnostic serum PFAS concentrations in relation to inflammatory bowel disease development, including ulcerative colitis, using a military cohort framework. The study design using prediagnostic samples addresses temporal relationship concerns that often arise in PFAS exposure studies, making it particularly relevant for ulcerative colitis causation arguments. The mixture analysis approach also provides methodological examples for evaluating combined PFAS exposures.
Additional meta-analytical work published in 2024 assessed associations between multiple PFAS compounds and thyroid hormone levels, examining TSH, T3, and T4 endpoints that are frequently cited as mechanistic bridges in PFAS causation theories. While the bibliographic record confirms publication in Science of the Total Environment, full-text review would be necessary to evaluate effect sizes, heterogeneity measures, and confounder adjustment that determine litigation utility.
Systematic reviews published through 2024 and early 2025 have evaluated PFAS exposure in relation to broader cancer endpoints including colorectal cancer, with at least one review in Environment International covering literature through December 2024. These reviews provide broader carcinogenicity context that may support or undermine general causation frameworks depending on their conclusions regarding strength of evidence and biological plausibility. The National Academies issued updated clinical guidance on PFAS exposure assessment and clinical follow-up that is being disseminated for clinical practice in 2025. This guidance document frequently appears in medical monitoring and personal injury contexts as evidence of appropriate clinical responses to PFAS exposure, though practitioners should verify they are citing the current edition and understand any updates to the recommendations.
Industry and Practice Developments
The cascade of major AFFF manufacturer settlements with public water systems represents the most significant industry development, fundamentally altering the liability landscape for PFAS contamination claims. The sequence of final approvals for settlements by 3M, DuPont/Chemours/Corteva, Tyco, and BASF during 2024 resolved most water provider contamination claims against the largest AFFF manufacturers, shifting remaining litigation focus toward non-settling defendants and other claim categories. These settlements establish payment frameworks that extend over multiple years, with companies like BASF publicly announcing settlement structures and timing in May 2024.
The FDA-led phase-out of PFAS in food packaging represents a significant industry practice shift that affects consumer exposure arguments in product liability contexts. The February 2024 completion of voluntary phase-out for PFAS grease-proofing agents in paper food packaging, followed by formal FDA notices affecting 35 food contact notifications in January 2025, narrows certain exposure vectors over time. These changes help define which consumer exposure pathways are current versus historical, affecting expert assumptions about ongoing PFAS sources and cumulative exposure modeling.
State-level settlements have begun emerging outside the federal MDL framework, with Reuters reporting an $875 million settlement between Chemours/DuPont/Corteva and New Jersey in August 2025 to resolve environmental claims including PFAS. Separate reporting indicates a $450 million PFAS settlement between 3M and New Jersey subject to public comment and court approval as of May 2025. While these settlement amounts require verification from official consent orders, the pattern suggests additional state-by-state resolutions that may affect discovery availability and internal document production in ongoing cases.
Major manufacturers have resolved most water contamination exposure claims through class action settlements while maintaining exposure to personal injury and product liability claims that require individualized causation proof.
This shift concentrates remaining litigation on claim types that face higher evidentiary burdens and more demanding expert qualification requirements. The narrowing of authorized PFAS uses in consumer products also affects exposure reconstruction arguments and alternative source analyses in ongoing cases.
What Has Changed in Practice
The PFAS litigation landscape has undergone fundamental restructuring since January 2024. The most significant change is the resolution of major water contamination claims through class settlements while personal injury and product liability cases proceed toward individualized proof requirements. This shift means practitioners now focus primarily on bodily injury causation rather than environmental contamination presence, requiring more sophisticated toxicological and epidemiological expert foundations.
The DeWitt expert exclusion in September 2025 has materially altered the evidentiary landscape by establishing concrete standards for PFAS toxicology expert methodology. Courts now require experts to demonstrate rigorous engagement with conflicting literature when offering broad PFAS health effect opinions, rather than accepting selective citation of supportive studies. Successful expert preparation must address scientific uncertainties and contrary findings comprehensively.
EPA’s 2024 regulatory framework created new benchmarks for exposure and contamination arguments, but the agency’s announced plans to roll back portions of the drinking water rule in 2025 have introduced uncertainty about which regulatory standards courts will treat as settled scientific authority. The regulatory volatility particularly affects arguments involving non-PFOA/PFOS compounds and mixture evaluation methodologies.
The emerging scientific literature presents mixed implications for causation arguments.
The 2025 kidney cancer meta-analysis appears to undermine general causation for that frequently-pleaded endpoint while thyroid cancer and inflammatory bowel disease studies provide updated evidence that may support those theories. Practitioners must now account for more recent quantitative syntheses that challenge some causation assumptions while supporting others.
Industry practice changes, particularly the phase-out of PFAS in food packaging and the concentration of litigation around personal injury rather than environmental contamination claims, have narrowed certain exposure scenarios while focusing remaining disputes on claim types with higher evidentiary burdens. The result is a litigation environment that demands stronger scientific foundations for causation arguments and more methodologically rigorous expert witness preparation.
Research current as of February 2026. This section reflects developments identified through targeted web searches from January 2024 to present and should be verified against primary sources before reliance.