EDITH H. JONES, Circuit Judge:
Walter Allen died of a brain cancer known as glioblastoma multiforme after having been a maintenance worker at Baton Rouge General Hospital for over 20 years. During that time, he occasionally replaced cylinders containing ethylene oxide ("EtO"), a chemical that has been widely used in this country to sterilize heat and moisture sensitive medical and surgical devices. Allen's widow and son (the "Allens") filed suit against numerous defendants, including American Sterilizer Company, the manufacturer of EtO sterilizers. On motions for judgment as a matter of law, the district court held both that two of the Allens' three expert witnesses were not qualified to render opinions that exposure to EtO caused Allen's fatal cancer and that the opinions of all three experts were inadmissible in federal court for lack of sufficient scientific grounding.
We affirm. Where, as here, no epidemiological study has found a statistically significant link between EtO exposure and human brain cancer; the results of animal studies are inconclusive at best; and there was no evidence of the level of Allen's occupational exposure to EtO, the expert testimony does not exhibit the level of reliability necessary to comport with Federal Rules of Evidence 702 and 703, the Supreme Court's Daubert decision,
This court reviews the judgment as a matter of law on two levels. First we must evaluate the trial court's evidentiary ruling under the manifest error standard, and then, with the record defined, we review de novo the order granting judgment as a matter of law. Christophersen v. Allied-Signal Corp., 939 F.2d 1106, 1109 (5th Cir.1991) (en banc), cert. denied, 503 U.S. 912, 112 S.Ct. 1280, 117 L.Ed.2d 506 (1992). If the trial court has excluded evidence essential to maintain a cause of action, the propriety of summary judgment depends, as here, entirely on the evidentiary ruling. Id.
In Daubert, the Supreme Court meticulously explained the criteria for admitting expert scientific testimony pursuant to Federal Rule of Evidence 702:
Further, the Court held that a trial court has a duty to screen expert testimony for both its relevance and reliability. Id. An expert's opinion must have a "reliable basis in the knowledge and experience of his discipline." Id. at 592, 113 S.Ct. at 2796. Specifically, the court must determine that the reasoning and methodology underlying the testimony is scientifically valid and that the reasoning and methodology can properly be applied to the facts in issue. Id. at 592-93, 113 S.Ct. at 2796.
The Court added that under Rule 703, an expert must base his opinion on facts and data of a type reasonably relied on by experts in the field. Id. at 595, 113 S.Ct. at 2797-98.
Although the trial court wrote a cursory opinion on the admissibility of Allen's expert evidence, the parties developed a considerable record, and the court heard oral argument before rendering a decision that the experts' evidence, testimony and opinions did not satisfy the standards set forth in Daubert or relevant authorities of this Court. Those standards may readily be applied to the evidence before us.
Appellants produced three expert witnesses, Dr. Page, Dr. Kelsey and now — Dr. LaMontagne,
While appellants' experts acknowledge the lack of statistically significant epidemiological evidence, they rely on certain studies as "suggestive" of a link between EtO exposure and brain cancer. "Suggestiveness" is not by the experts' own admission statistical significance, nor did the appellants' experts show why and how mere "suggestiveness" scientifically supports a causal connection; this basis for their scientific opinion must be rejected.
Second, the experts rely on two studies that found brain tumors in F-344 rats exposed to inhaled EtO, and on other animal studies that have found EtO-associated increases in the rodents' various solid and hematopoietic cancers. In Brock, this court noted "the very limited usefulness of animal studies when confronted with questions of toxicity." Brock, 874 F.2d at 313. Brock goes on to outline a number of reasons why studies of the effects of chemicals on animals must be carefully qualified in order to have explanatory potential for human beings. So it is here. Although in these particular studies, F-344 rats contracted brain cancer after being exposed to EtO, Allen's experts concede that the same effect did not occur in mice studies. As an expert for appellee concludes:
Reliance on these animal studies furnishes at best speculative support for appellants' causation theory.
On examination, none of the scientific data on which appellants' experts rely furnishes a scientifically valid basis for the conclusion they would draw. The paucity of epidemiological evidence, the unreliability of animal studies, and the inconclusiveness of cell biology combine to undercut the expert testimony.
We are also unpersuaded that the "weight of the evidence" methodology these experts use is scientifically acceptable for demonstrating a medical link between Allen's EtO exposure and brain cancer. 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. This methodology results from the preventive perspective that the agencies adopt in order to reduce public exposure to harmful substances. 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." Wright v. Willamette Industries, Inc., 91 F.3d 1105, 1107 (8th Cir.1996). In addition, in this case, the public health agencies acted at least partly on the basis of epidemiological studies that showed a relationship between EtO exposure and other kinds of human cancer, so their use of a "weight of the evidence" methodology was grounded in stronger probative evidence than appellants' experts have adduced to show a link between EtO and brain cancer.
Not only is the experts' conclusion at best weakly supported, if not contradicted, by the evidence on which they rely, but they all declined to say that they would subject their findings to the test of peer review for publication. Daubert notes that this is "a component of `good science' in part because it increases the likelihood that substantive flaws in methodology will be detected." Daubert, 509 U.S. at 593, 113 S.Ct. at 2797 (1993). Dr. LaMontagne, in fact, inadvertently described exactly the problem this court faced in evaluating his and appellants' other expert testimony:
Pace Dr. LaMontagne, the goal of Daubert and this court's previous cases has been to bring more rigorous scientific study into the expression of legal opinions offered in court by scientific and medical professionals. In the absence of scientifically valid reasoning, methodology and evidence supporting these experts' opinions, the district court properly excluded them.
An additional ground for excluding the opinions lies in Federal Rule of Evidence 703, which requires that the facts on which the expert relies must be reasonably relied on by other experts in the field. In this case, there is no direct evidence of the level of Allen's exposure to EtO. The Kelsey/LaMontagne opinion relies principally on the affidavit of a coworker and on extrapolations concerning EtO handling at the hospital where Allen worked based on conditions in other hospitals in the 1970's. The experts actually knew more about Allen's exposure to EtO through his smoking a pack of cigarettes a day than they did about his occupational exposure to the chemical. Nevertheless, Dr. Kelsey and Dr. LaMontagne discounted the effect of tobacco, while speculating that the
The other issue on appeal was whether the district court erred in finding that Dr. LaMontagne (who at the time of his expert deposition had not yet obtained his Sc.D.) and Dr. Norbert Page (D.V.M.) were not qualified to testify as experts on the issue of medical causation in this case. We need not decide this issue, as the testimony of all three experts is in any event inadmissible.
For the foregoing reasons, the judgment of the district court is AFFIRMED.