In a pair of toxic tort cases arising from the Deepwater Horizon oil spill, the Eleventh Circuit held that general causation expert evidence must establish a minimum level of exposure at which crude oil, its dispersants, or their associated chemicals are hazardous to human beings. In re Deepwater Horizon BELO Cases, 2024 WL 4522690 (11th Cir. Oct. 18, 2024).
After the April 2010 explosion of the deep-sea platform Deepwater Horizon, it took thousands of people working for months to clean up millions of barrels of oil that spilled into the Gulf of Mexico. Many clean-up workers and coastal residents sued BP Exploration & Production, Inc. and BP American Production Co., alleging that exposure to crude oil and other chemicals from the spill caused various medical conditions. All personal injury cases were consolidated in the Eastern District of Louisiana as part of the Deepwater Horizon multidistrict litigation. A settlement agreement in 2012 provided personal-injury claimants two avenues of recovery: (1) those diagnosed with a specified condition shortly after the spill could submit a claim against the settlement amount; while (2) those diagnosed with “later-manifested physical conditions” could file separate, individual tort suits against BP, called the “back-end litigation option” in the settlement. Back-end litigation plaintiffs must establish that their exposure to the oil and other substances from the spill or response activities caused their condition. About 500 of these cases alleging a later-manifested condition were transferred to the Northern District of Florida.
In toxic tort cases, where the medical community does not recognize an “agent” as both toxic and capable of causing the alleged injury, plaintiffs must establish both general and specific causation. General causation is about the effect of an agent on the incidence of disease in a group and not about causing any specific individual’s disease. Plaintiffs prove general causation with three kinds of evidence: (1) epidemiological evidence; (2) dose-response relationship; and (3) background risk of disease.
Two plaintiffs in the Northern District of Florida back-end litigation alleged that their clean-up work caused chronic sinusitis. Because the medical community does not widely accept that oil, dispersants, or associated chemicals can cause common conditions like chronic sinusitis, the plaintiffs were required to prove both general and specific causation. Their expert witnesses, however, did not identify the harmful exposure level for crude oil, a dispersant, or the chemicals associated with them. Accordingly, the district court adopted the magistrate judge’s recommendation, excluded the plaintiffs’ expert witness evidence, and granted BP’s motions for summary judgment.
After acknowledging the abuse-of-discretion standard on review of a district court’s decision to exclude or admit expert evidence, the Eleventh Circuit affirmed on appeal in an opinion by Chief Judge William Pryor. The district court did not abuse its discretion by requiring the experts to identify a specific “toxin” and prove the threshold harmful exposure level. The court rejected the plaintiffs’ argument that proving a threshold harmful dose is only relevant to specific causation, concluding based on prior Eleventh Circuit decisions that “whether a harmful level of the toxin exists in the first place” is an essential question under the general-causation framework.
The court also affirmed the district court’s other grounds for excluding the plaintiffs’ expert evidence, including that one expert’s cited studies failed to support her causation opinion and the other disregarded limitations in his cited studies. Accordingly, the court held, “even setting the threshold dose aside—the district court did not abuse its discretion when it excluded their testimony and granted summary judgment to BP.”