Two important issues arise in any asbestos-exposure case. First, was the injured party exposed to the defendant’s product? Second, did that exposure cause the injury in question? See, e.g., Eagle-Picher Indus. v. Balbos, 604 A.2d 445, 460 (Md. 1992). The first question is typically addressed by testimony from the injured party and so-called product-identification witnesses, along with the occasional historian or industrial hygienist. The second question requires expert testimony to answer, and has become the realm of epidemiologists, pathologists, and cell biologists.
To meet their burden of establishing that a particular exposure had a causal relationship with the injury in mesothelioma cases, plaintiffs’ experts have in recent years adopted the position that any and every exposure to asbestos is causative. This theory of causation goes by several names: The “single fiber” theory, “any exposure” theory, and “every exposure” theory are common formulations. Whatever name the expert witness uses, the important feature of the theory is that the expert can and typically does ignore all of the normally salient features of toxic exposures—e.g., dose, duration of exposure, intensity of exposure, and the specific nature of the compound at issue. Instead, the expert merely needs a report (even a hypothetical report) of exposure to opine that that exposure caused (or was a substantial contributing factor toward) the injured party’s mesothelioma. In the opinion of an every exposure expert, exposure equals causation. Period.
Rather than engaging with the question of medical causation, the every-exposure theory exploits the “hands off” approach that some courts take toward expert testimony to trivialize the causation question. In recent years, however, many courts have begun to embrace their gatekeeping role and, realizing the theory’s serious scientific and logical flaws, exclude testimony relying on it.
Disease Causation and Mesothelioma
To understand the scientific flaws in the every-exposure theory, it is first necessary to briefly review the disease in question—mesothelioma—and some important tenets of the scientific disciplines used to uncover disease etiology.
Mesothelioma is a cancer of mesothelial cells, which form protective membranes around several internal organs. Asbestos-related mesothelioma most commonly forms in the outer lining of the lungs, called the pleura, but can more rarely form in sites such as the peritoneum (the lining of the abdominal cavity) or the pericardium (the heart lining). The specific cellular mechanism by which mesothelioma is caused is not yet known, but it is known that exposure to at least certain types of asbestos can cause the disease.
Asbestos, therefore, can be considered a toxic substance. The scientific discipline charged with studying the effects of potentially toxic substances is known as toxicology. A central premise of that discipline is that “the dose makes the poison.” Bernard D. Goldstein & Mary Sue Henifin, Reference Guide on Toxicology, in Manual on Scientific Evidence 401, 403 (Fed. Judicial Ctr. 2d ed. 2000). In other words, the amount of a toxic substance (1) to which a person was exposed and (2) that actually made its way into that person’s system (in other words, the dose) is determinative in the question of whether the exposure caused any particular adverse effect. See David L. Eaton, Scientific Judgment and Toxic Torts—A Primer in Toxicology for Judges and Lawyers, 12 J.L. & Pol’y 5, 11 (2003). The determination of dose rests upon examination of several factors related to the exposure: duration of exposure, intensity of exposure, physical circumstances of exposure, specific toxic chemical involved, and a host of others. See Borg-Warner Corp. v. Flores, 232 S.W.3d 765, 770 (Tex. 2007).
The counterpart to toxicology is the discipline of epidemiology—the study of the “frequency of disease in human populations and the way in which the frequency varies from one population to another.” Richardson v. Richardson-Merrell, Inc., 857 F.2d 823, 826 n.11 (D.C. Cir. 1988). Epidemiology is a complex science that uses a variety of fine statistical and scientific tools to reach its conclusions, most of which are beyond the scope of this article. In very (perhaps overly) simplified terms: To determine whether exposure to a particular substance can be said to create a particular adverse effect, epidemiologists will compare the rates of that adverse effect in the exposed population with that of an unexposed population. See Michael D. Green et al., Reference Guide on Epidemiology, in Manual on Scientific Evidence 333–400 (Fed. Judicial Ctr. 2d ed. 2000). If the rate of the adverse effect in the exposed group is (to a statistically significant degree) higher than that in the unexposed group, the differential suggests that the exposure caused the disease.
What epidemiologists do not use to determine causation are “case reports”—anecdotal summaries of particular individuals who have contracted a disease and had a particular exposure. See Reeps v. BMW of N. Am., LLC, No. 100725/08, 2013 N.Y. Misc. LEXIS 2099, at *6–8 (N.Y. Sup. Ct. May 10, 2013). While such case reports may be useful in generating hypotheses about disease etiology that can then be tested using appropriate methods, case reports themselves are simply not useful for making causation determinations. See Wade-Greaux v. Whitehall Lab., 874 F. Supp. 1441, 1453 (D.V.I. 1994) (“Because of individual confounding factors, one cannot draw causation conclusions from such anecdotal data.”).
The Every-Exposure Theory
Contrary to these principles, proponents of the every-exposure theory hold that “each and every exposure to asbestos by a human being who is later afflicted with mesothelioma  contributed to the formation of the disease.” Smith v. Ford Motor Co., No. 2:08-cv-630, 2013 U.S. Dist. LEXIS 7861, at *4 (D. Utah Jan. 18, 2013). Despite the fact that different varieties of asbestos have radically different potencies, and, indeed, there is some debate in the scientific literature regarding whether certain types of asbestos can cause mesothelioma at all, an “every exposure” expert has no need to know the particular type of asbestos involved. See Betz v. Pneumo Abex LLC, 44 A.3d 27, 36 (Pa. 2012). Similarly, the expert need not know the characteristics of the exposure in terms of duration or frequency—as long as those exposures were “more than nothing,” the expert regards them as causative. See Dixon v. Ford Motor Co., 47 A.3d 1038, 1047 (Md. Ct. Spec. App. 2012). In other words, every-exposure experts simply ignore the concept of dose, despite disclaiming that mesothelioma is a dose/response disease.
Next, experts relying on the every-exposure theory routinely conflate the concepts of risk and causation. Even assuming that each individual exposure to asbestos increased the risk of an individual developing mesothelioma, every exposure would not necessarily have actually contributed to the injured party’s mesothelioma. See Betz, 44 A.3d at 48–49. Therefore, every-exposure experts have no hesitation in declaring that very minor exposures are causative, even when an individual has truly massive alternative exposures, and despite the fact that each and every person is exposed to a certain background level of asbestos. See id. at 35–36.
Finally, the every-exposure theory is not based on accepted epidemiological studies. Instead, proponents rely primarily on “case reports, animal studies, and regulatory standards,” along with tenuous downward extrapolation from established epidemiology, to support their hypothesis that every exposure to asbestos contributes to the risk (or, as they would say, the actual causation of) mesothelioma. See id. at 55.
Judicial Treatment of the Theory
The judicial opinion that, to a large degree, started the current wave of decisions excluding testimony based on the every-exposure theory did not actually deal with the question of the admissibility of expert testimony. In Gregg v. V-J Auto Parts Co., 943 A.2d 216 (Pa. 2007), the Pennsylvania Supreme Court held that—despite “every exposure” testimony from experts—a plaintiff could not survive summary judgment when his only exposure to the defendant’s product was de minimis. Along the way, the court criticized the common practice of submitting “expert affidavits attesting that any exposure to asbestos, no matter how minimal, is a substantial contributing factor in asbestos disease,” noting that “we do not believe that it is a viable solution to indulge in a fiction that each and every exposure to asbestos, no matter how minimal in relation to other exposures, implicates a fact issue concerning substantial-factor causation.” See id. at 226–27.
A number of courts since Gregg have taken the issue head-on, and many have subsequently excluded causation opinions based on the every-exposure theory. Chronicling the full development of the law in this area is beyond the scope of this article, but legal commenters have assembled several excellent analyses of the law in this area. See, e.g., William L. Anderson et al., The “Any Exposure” Theory Round II—Court Review of Minimal Exposure Expert Testimony in Asbestos and Toxic Tort Litigation Since 2008, 22 Kan. J.L. & Pub. Pol’y 1 (2012); Mark A. Behrens & William L. Anderson, The “Any Exposure” Theory: An Unsound Basis for Asbestos Causation and Expert Testimony, 37 Sw. U. L. Rev. 479 (2008); David E. Bernstein, Getting to Causation in Toxic Tort Cases, 74 Brook. L. Rev. 51 (2008).
Recent judicial criticism of the every-exposure theory has generally proceeded along one of three axes. The first, and perhaps most obvious, are cases holding that the every-exposure theory does not provide the basis for a scientific or reliable methodology for developing a causation opinion. See, e.g., Betz, 44 A.3d at 57–58. In other words, courts may not permit experts to ignore the rigors of the scientific discipline dedicated to making causation determinations—epidemiology—in favor of making tenuous inferences from case reports. See, e.g., Butler v. Union Carbide Corp., 712 S.E.2d 537, 555 (Ga. Ct. App. 2011).
The next type of judicial disapproval of every-exposure testimony comes in the form of a recognition that testimony based on the theory can and essentially does ignore the underlying facts of the case. See, e.g., Smith, 2013 U.S. Dist. LEXIS 7861, at *7–10. As discussed above, testimony based on the every-exposure theory ignores the concept of dose in its entirety and does not attempt to quantify the amount or nature of the injured party’s exposure. See, e.g., Dixon, 47 A.3d at 1048. Every-exposure experts also disclaim the need to rule out the causative role of alternative potential exposures. Courts are coming to the realization, however, that “[j]ust because we cannot rule anything out does not mean we can rule everything in.” Smith, 2013 U.S. Dist. LEXIS 7861, at *8. Indeed, Texas courts have gone so far as to require quantification of the amount of exposure, along with expert testimony establishing that the amount of exposure quantified is sufficient to cause mesothelioma. See, e.g., Hearn v. Snapka, No. 13-11-00332-CV, 2012 Tex. App. LEXIS 10788, at *19–20 (Tex. App. Corpus Christi Dec. 28, 2012).
Finally, some courts have reached the conclusion that testimony based on the every-exposure theory is simply unhelpful to the jury in making causation determinations, particularly when that testimony does not include some sort of measurement of the increased risk caused by the particular exposure in question. See, e.g., Dixon, 47 A.3d at 1050–51. Simply testifying that a given exposure potentially increased an individual’s risk of mesothelioma—without any explanation of to what degree the risk was increased, or what facts are used to establish the increased risk—does not provide a juror with sufficient information to determine whether the exposure was actually causative of the injured party’s mesothelioma. See id. While based on a somewhat vague standard, criticism of the every-exposure theory based on its lack of helpfulness to the fact finder aptly crystallizes the problems with the theory: Rather than assist the jury with making an honest assessment of the causation issues in an asbestos case, the theory is designed simply to provide plaintiffs with a mechanism for avoiding summary adjudication of their claims. See Butler, 712 S.E.2d at 554–55.
Consideration of the every-exposure theory reveals it to be the worst of result-oriented science. As courts across the country have begun to realize, the purported scientific basis for the theory is illusory, and it is simply unhelpful to jurors in attempting to ascertain whether a particular exposure to asbestos caused (or contributed to) the formation of the injured party’s mesothelioma. See Bernstein, supra, at 60 (“[T]he cases [discussing the every exposure theory] reflect judicial recognition that courts have a gate keeping obligation to keep ‘junk science’ out of the courtroom.”). Indeed, given the trend in the case law, it appears that the every-exposure theory may soon be consigned to the same dust bin of “scientific” opinion testimony as monomania and phrenology.
Keywords: mass torts litigation, asbestos, every exposure, any exposure, single fiber, mesothelioma
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