July 23, 2019 Articles

Are Public Health Agency Positions on Pathogenicity Relevant in Toxic Tort Litigation?

Appellate review of the recent Roundup verdicts will be an opportunity for California appellate courts to address the relevance and admissibility of such opinions by IARC.

By W. Clay Massey

The Monsanto Roundup litigation has brought renewed attention to the use and admissibility of statements by government agencies and nongovernmental organizations on a substance’s pathogenicity at trial. The plaintiffs have used the position of the International Agency for Research on Cancer (IARC) that glyphosate (the active ingredient in Roundup) is “probably carcinogenic to humans” as key evidence of Roundup’s alleged causal connection to the plaintiffs’ non-Hodgkin’s lymphoma (IARC Monograph on Glyphosate). This evidence has helped the plaintiffs obtain multiple exorbitant verdicts in California, the latest exceeding $2 billion.

The outcomes of those cases illustrate the power of such public health positions at trial. The perceived stature and objectiveness of agencies and organizations such as IARC, the World Health Organization (WHO), the Occupational Safety and Health Administration (OSHA), the National Institute for Occupational Safety and Health (NIOSH), the Environmental Protection Agency (EPA), and the Food and Drug Administration (FDA) can carry great weight with jurors. Thus, in toxic tort cases, their positions concerning the ability of a substance to cause a disease can have a substantial influence on jurors’ findings of causation, impressions concerning the parties’ overall credibility, and consideration of opinions offered by experts testifying in the courtroom.

But are those agencies’ positions relevant? And should they be allowed at trial?

The proximate cause question a jury must decide in a toxic tort case is whether exposure to an alleged toxic substance more likely than not caused a plaintiff to develop a particular disease. That question requires expert testimony at trial establishing the causal connection to a reasonable degree of medical or scientific certainty (or probability, depending on the applicable state substantive law) in compliance with the relevance and reliability requirements of Federal Rule of Evidence 702. E.g., In re Paoli R.R. Yard PCB Litig., 35 F.3d 717, 751 (3d Cir. 1994); Allison v. McGhan Med. Corp., 184 F.3d 1300, 1320 (11th Cir. 1999); Fed. R. Evid. 702(b).

The type of risk assessment regulatory agencies and nongovernmental organizations perform is different from that required in expert analysis of causation performed in a toxic tort case. As explained by the Fifth Circuit,

Regulatory and advisory bodies such as IARC, OSHA and EPA utilize a “weight of the evidence” method to assess the carcinogenicity of various substances in human beings and suggest or make prophylactic rules governing human exposure. . . . The agencies’ threshold of proof is reasonably lower than that appropriate in tort law, which “traditionally make[s] more particularized inquiries into cause and effect” and requires a plaintiff to prove “that it is more likely than not that another individual has caused him or her harm.”

Allen v. Pa. Eng’g Corp., 102 F.3d 194, 198 (5th Cir. 1996); see also Indus. Union Dep’t v. Am. Petroleum Inst., 448 U.S. 607, 656 (1980) (“OSHA is not required to support its finding that a significant risk exists with anything approaching scientific certainty” and “is free to use conservative assumptions in interpreting the data with respect to carcinogens, risking error on the side of overprotection, rather than underprotection.”).

Their methodology for classifying a substance as carcinogenic “results from the preventive perspective that the agencies adopt.” Mitchell v. Gencorp., Inc., 165 F.3d 778, 783 n.3 (10th Cir. 1999). Accordingly, they “may pay heed to any evidence that points to a need for caution,” and apply “a much lower standard than that which is demanded by a court of law.” McClain v. Metabolife Int’l, Inc., 401 F.3d 1233, 1249, 1250 (11th Cir. 2005).

For example, IARC will classify a substance as “probably carcinogenic to humans” based on (1) in vivo animal experiments and (2) studies concerning humans (i.e., epidemiology, case reports, case series) for which “chance, bias or confounding could not be ruled out with reasonable confidence.” IARC Monographs on the Evaluation of Carcinogenic Risk to Humans: Preamble 19, 22 (emphasis added). IARC acknowledges that not “all agents that cause cancer in experimental animals also cause cancer in humans.” Therefore, it recognizes that a finding of “sufficient evidence of carcinogenicity” in experimental animals means only that it is “biologically plausible” that a substance can cause cancer in humans “in some circumstances.” Id. at 2, 12. Nevertheless, IARC will consider substances for which its working group finds evidence of carcinogenicity in animal studies to pose a carcinogenic hazard to humans unless other scientific information shows otherwise. Id. at 12.

That is different from the causation determination in toxic tort litigation, which requires a showing of causal probability based on a reliable scientific methodology, and for which courts have recognized the “very limited usefulness of animal studies. . . .” Allen, 102 F.3d at 197; accord Lynch v. Merrell-National Labs., 830 F.2d 1190, 1194 (1st Cir. 1987) (“Studies of this sort, singly or in combination, do not have the capability of proving causation in human beings in the absence of any confirmatory epidemiological data.”); see also Paoli Yard, 35 F.3d at 743 (“[I]n order for animal studies to be admissible to prove causation in humans, there must be good grounds to extrapolate from animals to humans. . . .”); Turpin v. Merrell Dow Pharm., 959 F.2d 1349, 1360 (6th Cir. 1992) (animal studies not admissible due to analytical gap between the reactions in rats to the doses given and causation in humans).

The positions of these agencies and organizations are opinions based on their review of the published scientific literature or interpretation of laboratory experiments. Therefore, they are subject not only to Rule 402’s relevance requirement but also to Rule 702’s admissibility standards. One of those standards is that the opinion must “help the trier of fact to understand the evidence or determine a fact in issue.” E.g., Fed. R. Evid. 702. This helpfulness or “fit” standard “requires a valid scientific connection to the pertinent inquiry as a precondition to admissibility.” Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579, 591 (1993). That inquiry in a toxic tort case is whether, based on the application of a reliable scientific methodology, it is more likely than not exposure to a substance caused a disease in a plaintiff. As federal courts of appeals have found, the risk assessments government agencies and nongovernmental organizations perform are not the same inquiry. Although their positions may be scientifically valid for the prophylactic public health purpose they serve, the Supreme Court has explained that “scientific validity for one purpose is not necessarily scientific validity for other, unrelated purposes.” Id. at 591.

Moreover, federal appellate courts have held that expert testimony that does not establish causation to a reasonable degree of medical or scientific certainty (or probability) does not help the jury determine the issue of causation. E.g., Schudel v. Gen. Elec. Co., 35 F. App’x 481, 484 (9th Cir. 2002); Allison, 184 F.3d at 1320. Out-of-court opinions by government agencies and nongovernmental organizations that similarly do not establish a causal connection to that standard would appear to face the same relevance problem for that additional reason.

Appellate review of the recent Roundup verdicts will be an opportunity for California appellate courts to address the relevance and admissibility of such opinions by IARC. And courts in other jurisdictions where more than 13,000 Roundup cases against Monsanto are pending also will have to address the issue as cases proceed to trial and through the appellate courts. The outcome will have a substantial impact on not only Monsanto’s Roundup litigation but toxic tort trials involving such evidence more generally.

W. Clay Massey is a partner with Alston & Bird LLP in Atlanta, Georgia.


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