Causation in Toxic Torts: Burdens of Proof, Standards of Persuasion, and Statistical Evidence

Abstract

Toxic torts 1 present major challenges to tort law and the judicial system. 2 Causation requirements pose one such challenge.Proving the cause of injuries that remain latent for years, are associated with diverse risk factors, and occur at background levels even without any apparent cause, 3 1.Adhering to the tradition that a footnote appear within the first clause of any Note, I here attempt to define "toxic tort."A functional description, stating characteristics common to most such cases, suffices for the purposes of this Note.Typically, a toxic tort case involves an alleged personal injury and related harm resulting from exposure to a toxic substance-usually a chemical, but perhaps a biological or radiological agent.Generally, in toxic torts: (1) the injury is neither traumatic nor an acute toxic response, but results from genetic or biochemical disruption; (2) exposure is typically, though not necessarily, chronic and repeated; (3) injury manifests itself after a latency period.Well-known toxic tort cases, in this sense, include: vaginal clear cell adenomas allegedly caused by maternal exposure to diethylstilbestrol (DES); asbestos workers' claims for various lung diseases; Vietnam veterans' claims that they were injured by exposure to dioxin-contaminated Agent Orange.Increasingly, claims based on exposure to hazardous wastes are being reported.See, e.g., Pereira v. Dow Chem.Co., 129 Cal.App.3d 865, 181 Cal.Rptr.364 (1982) (employe exposed to epoxies and organic solvents suffered kidney failure); Johnson v. Tipton, 103 Ill.App.3d 291, 431 N.E.2d 464 (1982) (farm's well polluted by metals and phenols from neighbor's dump).Cases stemming from the swine flu vaccine program are an unusual but significant example.See infra notes 55, 64. 2. Various problems unique to toxic torts, not discussed in this Note, have been considered elsewhere.See, e.g., Estep & Van Dyke, Radiation Injuries: Statute of Limitations Inadequacies in Tort Cases, 62 MicH.L. REV.753 (1964) (latency causing bar of claims by laches); Locks, Asbestos-Related Disease Litigation: Can the Beast Be Tamed?, 28 VILL.L. REV.