Seventh Circuit Affirms Exclusion of Expert Witnesses in Vinyl Chloride Case

Last week, the Seventh Circuit affirmed a federal district court’s exclusion of plaintiffs’ expert witnesses in an environmental vinyl chloride exposure case. Wood v. Textron, Inc., No. 3:10 CV 87, 2014 U.S. Dist. LEXIS 34938 (N.D. Ind. Mar. 17, 2014); 2014 U.S. Dist. LEXIS 141593, at *11 (N.D. Ind. Oct. 3, 2014), aff’d, Slip op., No. 14-3448, 20125 U.S. App. LEXIS 15076 (7th Cir. Aug. 26, 2015). Plaintiffs, children C.W. and E.W., claimed exposure from Textron’s manufacturing facility in Rochester, Indiana, which released vinyl chloride as a gas that seeped into ground water, and into neighborhood residential water wells. Slip op. at 2-3. Plaintiffs claimed present injuries in the form of “gastrointestinal issues (vomiting, bloody stools), immunological issues, and neurological issues,” as well as future increased risk of cancer. Importantly, the appellate court explicitly approved the trial court’s careful reading of relied upon studies to determine whether they really did support the scientific causal claims made by the expert witnesses. Given the reluctance of some federal district judges to engage with the studies actually cited, this holding is noteworthy.

To support their claims, plaintiffs offered the testimony from three familiar expert witnesses:

(1) Dr. James G. Dahlgren;

(2) Dr. Vera S. Byers; and

(3) Dr. Jill E. Ryer-Powder.

Slip op. at 5. This gaggle offered well-rehearsed but scientifically unsound arguments in place of actual evidence that the children were hurt, or would be afflicted, as a result of their claimed exposures:

(a) extrapolation from high dose animal and human studies;

(b) assertions of children’s heightened vulnerability;

(c) differential etiology;

(d) temporality; and

(e) regulatory exposure limits.

On appeal, a panel of the Seventh Circuit held that the district court had properly conducted “an in-depth review of the relevant studies that the experts relied upon to generate their differential etiology,” and their general causation opinions. Slip op. at 13-14 (distinguishing other Seventh Circuit decisions that reversed district court Rule 702 rulings, and noting that the court below followed Joiner’s lead by analyzing the relied-upon studies to assess analytical gaps and extrapolations). The plaintiffs’ expert witnesses simply failed in analytical gap bridging, and dot connecting.


The Circuit agreed with the district court that the extrapolations asserted were extreme, and that they represented “analytical gaps” too wide to be permitted in a courtroom. Slip op. at 15. The challenged expert witnesses extrapolated between species, between exposure levels, between exposure duration, between exposure circumstances, and between disease outcomes.

The district court faulted Dahlgren for relying upon articles that “fail to establish that [vinyl chloride] at the dose and duration present in this case could cause the problems that the [p]laintiffs have experienced or claim that they are likely to experience.” C.W. v. Textron, 2014 U.S. Dist. LEXIS 34938, at *53, *45 (N.D. Ind. Mar. 17, 2014) (finding that the analytical gap between the cited studies and Dahlgren’s purpose in citing the studies was an unbridged gap, which Dahlgren had failed to explain). Slip op. at 8.

Byers, for instance, cited one study[1] that involved exposure for five years, at an average level that was over 1,000 times higher than the children’s alleged exposure levels, which lasted less than 17 and 7 months, each. Perhaps even more extreme were the plaintiffs’ expert witnesses’ attempted extrapolations from animal studies, which the district court recognized as “too attenuated” from plaintiffs’ case. Slip op. at 14. The Seventh Circuit rejected plaintiffs’ alleged error that the district court had imposed a requirement of “absolute precision,” in holding that the plaintiffs’ expert witnesses’ analytical gaps (and slips) were too wide to be bridged. The Circuit provided a colorful example of a study on laboratory rodents, pressed into service for a long-term carcinogenetic assay, which found no statistically significant increase in tumors fed 0.03 milligrams vinyl chloride per kilogram of bodyweight, (0.03 mg/kg), for 4 to 5 days each week, for 59 weeks, compared to control rodents fed olive oil.[2] Slip op. at 14-15. This exposure level in this study of 0.03 mg/kg was over 10 times the children’s exposure, as estimated by Ryer-Powder. The 59 weeks of study exposure represents the great majority of the rodents’ adult years, which greatly exceeds the children’s exposure was took place over several months of their lives. Slip op. at 15.

The Circuit held that the district court was within its discretion in evaluating the analytical gaps, and that the district court was correct to look at the study details to exercise its role as a gatekeeper under Rule 702. Slip op. at 15-17. The plaintiffs’ expert witnesses failed to explain their extrapolations, which was made their opinions suspect. As the Circuit court noted, there is a methodology by which scientists sometimes attempt to model human risks from animal evidence. Slip op. at 16-17, citing Bernard D. Goldtsein & Mary Sue Henifin, “Reference Guide on Toxicology,” in Federal Manual on Scientific Evidence 646 (3d ed. 2011) (“The mathematical depiction of the process by which an external dose moves through various compartments in the body until it reaches the target organ is often called physiologically based pharmokinetics or toxicokinetics.”). Given the abject failures of plaintiffs’ expert witnesses to explain their leaps of faith, the appellate court had no occasion to explore the limits of risk assessment outside regulatory contexts.

Children’s Vulnerability

Plaintiffs’ expert witness asserted that children are much more susceptible than adult workers, and even laboratory rats. As is typical in such cases, these expert witnesses had no evidence to support their assertions, and they made no effort even to invoke models that attempted reasonable risk assessments of children’s risk.

Differential Etiology

Dahlgren and Byers both claimed that they reached individual or specific causation conclusions based upon their conduct of a “differential etiology.” The trial and appellate court both faulted them for failing to “rule in” vinyl chloride for plaintiffs’ specific ailments before going about the business of ruling out competing or alternative causes. Slip op. at 6-7; 9-10; 20-21.

The courts also rejected Dahlgren’s claim that he could rule out all potential alternative causes by noting that the children’s treating physicians had failed to identify any cause for their ailments. So after postulating a limited universe of alternative causes of “inheritance, allergy, infection or another poison,” Dahlgren ruled all of them out of the case, because these putative causes “would have been detected by [the appellants’] doctors and treated accordingly.” Slip op. at 7, 18. As the Circuit court saw the matter:

“[T]his approach is not the stuff of science. It is based on faith in his fellow physicians—nothing more. The district court did not abuse its discretion in rejecting it.”

Slip op. at 18. Of course, the court might well have noted that physicians are often concerned exclusively with identifying effective therapy, and have little or nothing to offer on actual causation.

The Seventh Circuit panel did fuss with dicta in the trial court’s opinion that suggested differential etiology “cannot be used to support general causation.” C.W. v. Textron, 2014 U.S. Dist. LEXIS 141593, at *11 (N.D. Ind. Oct. 3, 2014). Elsewhere, the trial court wrote, in a footnote, that “[d]ifferential [etiology] is admissible only insofar as it supports specific causation, which is secondary to general causation … .” Id. at *12 n.3. Curiously the appellate court characterized these statements as “holdings” of the trial court, but disproved their own characterization by affirming the judgment below. The Circuit court countered with its own dicta that

“there may be a case where a rigorous differential etiology is sufficient to help prove, if not prove altogether, both general and specific causation.”

Slip op. at 20 (citing, in turn, improvident dicta from the Second Circuit, in Ruggiero v. Warner-Lambert Co., 424 F.3d 249, 254 (2d Cir. 2005) (“There may be instances where, because of the rigor of differential diagnosis performed, the expert’s training and experience, the type of illness or injury at issue, or some other … circumstance, a differential diagnosis is sufficient to support an expert’s opinion in support of both general and specific causation.”).

Regulatory Pronouncements

Dahlgren based his opinions upon the children’s water supply containing vinyl chloride in excess of regulatory levels set by state and federal agencies, including the U.S. Environmental Protection Agency (E.P.A.). Slip op. at 6. Similarly, Ryer-Powder relied upon exposure levels’ exceeding regulatory permissible limits for her causation opinions. Slip op. at 10.

The district court, with the approval now of the Seventh Circuit would have none of this nonsense. Exceeding governmental regulatory exposure limits does not prove causation. The con-compliance does not help the fact finder without knowing “the specific dangers” that led the agency to set the permissible level, and thus the regulations are not relevant at all without this information. Even with respect to specific causation, the regulatory infraction may be weak or null evidence for causation. Slip op. at 18-19 (citing Cunningham v. Masterwear Corp., 569 F.3d 673, 674–75 (7th Cir. 2009).


Byers and Dahlgren also emphasized that the children’s symptoms began after exposure and abated after removal from exposure. Slip op. at 9, 6-7. Both the trial and appellate courts were duly unimpressed by the post hoc ergo propter hoc argument. Slip op. at 19, citing Ervin v. Johnson & Johnson, 492 F.3d 901, 904-05 (7th Cir. 2007) (“The mere existence of a temporal relationship between taking a medication and the onset of symptoms does not show a sufficient causal relationship.”).

Increased Risk of Cancer

The plaintiffs’ expert witnesses offered opinions about the children’s future risk of cancer that were truly over the top. Dahlgren testified that the children were “highly likely” to develop cancer in the future. Slip op. at 6. Ryer-Powder claimed that the children’s exposures were “sufficient to present an unacceptable risk of cancer in the future.” Slip op. at 10. With no competence evidence to support their claims of present or past injury, these opinions about future cancer were no longer relevant. The Circuit thus missed an opportunity to comment on how meaningless these opinions were. Most people will develop a cancer at some point in their lifetime, and we might all agree that any risk is unacceptable, which is why medical research continues into the causes, prevention, and cure of cancer. An unquantified risk of cancer, however, cannot support an award of damages even if it were a proper item of damages. See, e.g., Sutcliffe v. G.A.F. Corp., 15 Phila. 339, 1986 Phila. Cty. Rptr. LEXIS 22, 1986 WL 501554 (1986). See alsoBack to Baselines – Litigating Increased Risks” (Dec. 21, 2010).

[1] Steven J. Smith, et al., “Molecular Epidemiology of p53 Protein Mutations in Workers Exposed to Vinyl Chloride,” 147 Am. J. Epidemiology 302 (1998) (average level of workers’ exposure was 3,735 parts per million; children were supposedly exposed at 3 ppb). This study looked only at a putative biomarker for angiosarcoma of the liver, not at cancer risk.

[2] Cesare Maltoni, et al., “Carcinogenity Bioassays of Vinyl Chloride Monomer: A Model of Risk Assessment on an Experimental Basis, 41 Envt’l Health Persp. 3 (1981).

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