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The Takeaway

A likely roadmap exists to understanding how PFAS litigation[1] (which is predicted to eventually affect nearly all businesses) may evolve: the Aqueous Film Forming Foams (AFFF) Multi-District Litigation (MDL) in the United States District Court of South Carolina.

Given the likely impact of PFAS litigation, prudent businesses and industries would be well served to monitor and understand the case management orders, scientific evidence, expert testimony, and notable settlements and judgments unfolding in that litigation.

Introduction

Since 2018, more than 10,000 PFAS cases have been added to the Aqueous Film Forming Foams (AFFF) Multi-District Litigation (MDL).This vast proceeding includes civil actions alleging injuries from PFAS-containing AFFF and the alleged contamination that these foams can cause in local ground and drinking water.[2] So far, the settlements within the AFFF MDL have reached eye-popping levels: nearly $15 billion has already received final approval, and hundreds of millions of more dollars were granted preliminary approval in 2024.

The AFFF MDL generally involves three categories of cases:

1. plaintiffs who claim personal injury from exposure to PFAS
2. actions filed by states’ attorneys general based upon harm to natural resources and PFAS cleanup costs
3. public water suppliers seeking drinking water testing and remediation costs

Personal Injury Cases in the MDL

A certain type of personal injury case within the AFFF MDL is particularly important: bellwether cases. In multi-district mass-tort litigation in general, a bellwether case is a lawsuit designated to go to trial that will be used as a guide for adjudicating similarly supported future claims of the same nature.[3] To be designated a “bellwether,” a case should allege facts similar to and in common with many other cases within the MDL. An overarching goal of a bellwether trial is for attorneys to gain an understanding of how jurors conceptualize the unique issues found in cases comprising an MDL.[4]

Defining bellwether cases. In mass torts, designating a bellwether case can be challenging because the facts related to exposure, injury, and damages vary. PFAS exposure claims are no different. Plaintiffs have alleged dozens of diseases arising from exposure to PFAS and claimed the exposure came from a variety of products and numerous occupations.[5] Unlike other mass tort cases, however, no purported “signature diseases” have been associated with PFAS exposure. (Think asbestos and mesothelioma.) Nonetheless, the AFFF MDL has associated the following conditions with PFAS exposure: kidney cancer, testicular cancer, ulcerative colitis, hypothyroidism, thyroid cancer, and liver cancer.[6] Thus, a diagnosis of one of these diseases may be grounds for a case to be designated as a bellwether one.

Science and medicine’s role. Peer-reviewed studies, science, and medicine play a critical role in determining what conditions may be associated with PFAS exposure. As has been done in other MDL proceedings,[7] the presiding judge has ordered a Science Day. (In the AFFF MDL, it’s now June 6, 2025). Representatives from the plaintiff and defense bars will exchange theories and present experts, providing a succinct opportunity to learn what science currently supports each side’s position. It may also help the presiding judge delineate between well-supported studies and theories from so-called “junk science,” as well as assist in determining cases that may be designated as bellwether material.

Experts’ role. A plaintiff can’t show causation without expert testimony. Therefore, experts will play a key role in AFFF MDL cases, not only on Science Day but also during any subsequent trials. But unlike many mass tort proceedings alleging exposure to purportedly toxic substances, there is no stable of PFAS experts ready to testify.[8] Nevertheless, because of the large variety of products[9] in numerous industries that purportedly cause diseases associated with PFAS exposure, successfully defending a PFAS lawsuit will hinge, in part, on retaining experts who can artfully refute theories of causation.

Evidentiary rule challenges. It also follows that those expert opinions and the science upon which they’re based will likely create Federal Rules of Evidence 702 challenges. This testing of the strength of expert testimony will create the base upon which rests the theories and science that prove or disprove causation of injuries from PFAS exposure.

Other Cases in the MDL

A number of PFAS MDL matters involve public water systems.

Plaintiffs allege that companies or other entities contaminated public water supplies with PFAS. Therefore, the following types of entities may expect to be targets of future environmental actions and lawsuits: industrial sites, manufacturing facilities, construction sites, and other entities near community water supplies who now or previously may have used PFAS in their businesses or had it on their sites. Those observing this litigation project that initial PFAS settlements for these types of claims will surpass tobacco settlement values from the 1990s[10] and may achieve values typically associated with oils spills and emissions scandals.

Although statutory compliance will likely play a fundamental role in defending PFAS public water system claims, the regulation of PFAS in public water systems is in its infancy. [11] [12]  Considering the role that water systems play in communities, it’s understandable that states may vigorously pursue adequate compensation for remedying a purported longstanding presence of PFAS in public water systems. However, early settlements suggest it may be difficult to calculate clean-up costs associated with removing high concentrations of PFAS substances from sophisticated water systems.[13] It will be important to monitor for notable settlements reached, judgments entered, and other significant developments between parties litigating in the AFFF MDL.

Why it All Matters

PFAS litigation is widely anticipated to grow into one of the largest areas of litigation in the United States. With nuclear verdicts on the rise across the U.S., there’s great risk of significant PFAS judgments. Like the proverbial canary in the coal mine, the PFAS AFFF MDL litigation is a warning to businesses to stay aware of developments and trends in PFAS litigation.

HeplerBroom has created resources to help businesses navigate PFAS litigation. (See our articles on basic PFAS concepts and considerations, regulatory updates, and tips for preparing a PFAS defense strategy.) We’re also committed to expanding these resources as crucial developments happen.

[1] For a summary of the basic concepts of PFAS litigation (what PFAS chemicals are, where they may be found, what medical conditions may be caused by them, and who’s suing whom for purported PFAS exposure), see Part 1 of this series.

[2] Aqueous Film-Forming Foams (AFFF) Products Liability LitigationMDL No. 2873 (last accessed 4/5/2025).

[3] Bellwether Trials in Multidistrict Litigation (last accessed 4/5/2025).  

[4] Id.

[5] My Mom Would Say That, When it Comes to PFAS, the Judicial Panel on Multi District Litigation's Eyes Were Bigger Than its Stomach! (last accessed 4/5/2025).  

[6] Initially, there was only one bellwether process in the AFFF MDL, which extended to only kidney cancer, testicular cancer, thyroid disease, and ulcerative colitis. In early 2024, a second bellwether process was established to extend to liver and thyroid cancer.

[7] See, e.g., Attorneys and Experts Come Together for “Science Day” in Taxotere Hair Loss MDL (last accessed 4/5/2025).

[8] Unlike PFAS matters, plaintiff and defense bars in asbestos litigation each rely upon a finite number of widely known experts to support claims in many jurisdictions. Expert retention may become quite similar in the PFAS context, depending on how many diseases can successfully be tied to PFAS exposure under Daubert/Frye principles.

[9] For example, food packaging or athletic clothing as compared to firefighting foam.

[10] ‘Forever Chemical’ Lawsuits Could Ultimately Eclipse the Big Tobacco Settlement (last accessed 4/5/2025.

[11] While the country’s PFAS regulatory scheme is only beginning, and some statutes may not be used in private enforcement actions, the U.S. EPA only recently released national standards for PFAS in drinking water. See, e.g., Per- and Polyfluoroalkyl Substances (PFAS) Final PFAS National Primary Drinking Water Regulation (last accessed 4/5/2025.

[12] AWWA Releases Updated National PFAS Cost Estimate (last accessed 4/5/2025).

[13] Groundbreaking Study Shows Unaffordable Costs of PFAS Cleanup from Wastewater (last accessed 4/5/2025).