Products Liability Law Daily Unreliability of experts’ causation testimony upheld, warranting judgment for ConocoPhillips in benzene exposure case
Wednesday, April 11, 2018

Unreliability of experts’ causation testimony upheld, warranting judgment for ConocoPhillips in benzene exposure case

By Susan Lasser, J.D.

In an individual’s action against oil and gas producer ConocoPhillips Company alleging that her childhood exposure to the company’s benzene emissions from one of its refineries caused her to develop leukemia, a federal district court in Oklahoma did not abuse its discretion in excluding her expert testimony on causation and in granting summary judgment in favor of the company, the U.S. Court of Appeals for the Tenth Circuit held, affirming the lower court’s decision. In particular, the appellate court found that the lower court did not err in finding that the differential diagnosis by one of the ailing woman’s experts lacked reliability and required exclusion. Without such expert causation testimony, she could not create a genuine issue of material fact on causation because of the length of time between her exposure to benzene and the onset of her disease (Hall v. Conoco Inc., April 10, 2018, Bacharach, R.).

As a child, the individual lived near a ConocoPhillips Company refinery in Oklahoma. Approximately twenty years later, she developed a form of leukemia known as acute myeloid leukemia with inversion 16 (AML). She filed suit against Conoco Inc., ConocoPhillips Company, and Phillips 66 Company (collectively, ConocoPhillips) on theories of negligence, negligence per se, and strict liability, claiming that her illness had been caused by her early exposure to the refinery’s emissions of benzene. At trial, the woman tried to prove the link through three expert witnesses—an air modeler, an oncologist, and an epidemiologist. The air modeler created an air model to estimate benzene concentrations near where the woman had lived, and based on the modeler’s estimates, the oncologist calculated her cumulative exposure to benzene and used this calculation to opine that benzene exposure had caused her leukemia. The epidemiologist offered a similar opinion.

ConocoPhillips moved for the exclusion of opinion testimony by certain of the ailing woman’s experts, including the oncologist and the epidemiologist. In addition, ConocoPhillips requested summary judgment on the issue of causation. The trial court granted the motion to exclude the experts’ testimony; and absent their testimony, the court also granted summary judgment favoring ConocoPhillips because the woman had failed to present sufficient evidence linking her disease to benzene exposure.

Exclusion of expert testimony. The Tenth Circuit rejected the individual’s challenge to the exclusion of the expert testimony by the oncologist and the epidemiologist. The oncologist had rendered a differential diagnosis—first ruling in benzene, smoking, and idiopathic causes (i.e., a disease or condition of unknown cause) as potential triggers of the woman’s leukemia. He then ruled out smoking as a potential cause, leading him to conclude that benzene exposure had caused the individual’s leukemia. He did not expressly rule out the possibility of idiopathic causes, however. While the trial court assumed that a differential diagnosis could provide an appropriate methodology, it determined that the oncologist’s differential diagnosis was unreliable, in part because he failed to justify ruling in benzene causation or ruling out idiopathic causes of the woman’s disease. In the Tenth Circuit’s assessment, the trial court’s reasoning fell within that court’s discretion.

As did the lower court, the Tenth Circuit assumed that benzene emissions can cause AML. The ailing woman still needed to show that the benzene emissions actually had caused her disease. She relied on the oncologist’s quantification of the exposure to benzene. For this, he relied on the work of another expert who had constructed an air model to estimate the highest hourly average concentration of benzene. With this estimate, the oncologist quantified the cumulative exposure to benzene based on how long the woman had lived near the refinery. The result led the oncologist to rule in benzene as a potential cause of the plaintiff’s leukemia.

However, the district court found two errors in the oncologist’s methodology. First, the court ruled that the oncologist could not reliably use the highest hourly average emission level to calculate the woman’s cumulative exposure to benzene because the air modeler admitted that he was not qualified to decide which figure to use in assessing the impact of benzene emissions on human health. The air modeler conceded that the selection of the benzene concentration level near the woman’s home was best left to an oncologist like the other expert. The expert oncologist, for his part, acknowledged that he had not independently chosen which figure to use, but had admittedly relied on the air modeler’s expertise to select the relevant figure. The oncologist testified that he had called the air modeler, who provided assurance that the highest hourly average-emission level was the metric used in the industry. The appellate court stated that the trial court "could reasonably consider this assurance an inadequate safeguard of reliability." Both experts, having denied responsibility for choosing the value used, left the district court reasonably to conclude that the reliability of the oncologist’s calculation/conclusion was inadequate. Thus, the court of appeals concluded that the district court acted within its discretion in questioning the reliability of the oncologist’s use of the highest hourly average emission level.

Secondly, the lower court found that the oncologist’s calculation was based on mistakes involving the extent of the woman’s exposure to benzene, including his assumption that she had lived near the refinery for eight years when it only had been about four years. The error meant that his estimate of the cumulative exposure was roughly double what it should have been. The Tenth Circuit concluded that in light of these errors and inconsistencies, the district court could reasonably question the reliability of the oncologist’s opinion ruling in benzene exposure as a potential cause of the woman’s cancer.

Moreover, even if benzene could be ruled in as a potential cause, the oncologist’s differential diagnosis would have depended on his ability to rule out less plausible causes of the ailing woman’s illness and the lower court determined that the doctor failed to rule out idiopathic causes, which the lower court required for a reliable differential diagnosis. According to the appellate court, this conclusion fell within the trial court’s discretion. Because idiopathy accounts for more than half of AML cases, a differential diagnosis could be considered inherently unreliable without ruling out idiopathic causes, the appeals court said.

The Tenth Circuit held that the trial court justifiably could view the oncologist’s differential diagnosis as unreliable because of his failure to: (1) justify ruling in benzene; or (2) rule out idiopathic causes. Thus, the district court did not abuse its discretion in excluding the oncologist’s opinion based on his differential diagnosis.

The lower court additionally excluded the epidemiologist’s opinion testimony linking benzene to the woman’s disease because the epidemiologist, who also conducted a differential diagnosis and opined that benzene had caused the plaintiff’s leukemia, failed to address adequately the issue of exposure. The ailing woman did not challenge the trial court’s rationale, precluding reversal of the testimony’s reversal on appeal. Thus, the Tenth Circuit affirmed the exclusion of this expert’s testimony.

Summary judgment. To avoid summary judgment on the issue of causation, both expert testimony and a quantification of the woman’s exposure to benzene was required. Without the proffered testimony by the oncologist and the epidemiologist, however, the court of appeals ruled that she lacked both the required expert testimony and a way to quantify her exposure to benzene emissions. Therefore, the district court did not err in granting summary judgment favoring ConocoPhillips on causation.

The ailing woman challenged the lower court’s conclusion that without the experts’ testimony, she lacked the required evidence linking her disease to benzene emissions. She argued that the circumstantial evidence—including the presence of hydrocarbon leaks and odors in her neighborhood, groundwater contamination, a high benzene reading near her home, and Environmental Protection Agency estimates showing increased risk from the refinery—was enough to avoid summary judgment. However, the appellate court found that this circumstantial evidence failed to create a genuine issue of material fact on causation because of the need for: (1) expert testimony on the link between her disease and benzene exposure; and (2) quantification of the individual’s exposure to benzene.

Expert testimony was required on causation beyond circumstantial evidence because of the length of time between her exposure to benzene emissions and the onset of her illness. Oklahoma law generally requires expert testimony for complex issues of medical causation. While there is an exception for the common knowledge or experience of laypersons that is "is extensive enough to recognize or infer negligence from the facts … with reasonable certainty," the trial court reasonably could conclude that the long-term carcinogenic effects of benzene exposure was outside the realm of a layperson’s common experience, and required expert testimony. Thus, the Tenth Circuit concluded that in light of the need for expert testimony on the effects of benzene exposure, the woman could not avoid summary judgment by relying solely on circumstantial evidence linking her disease to benzene emissions.

Further, the appellate court noted that when causation involves a link between a disease and exposure to a toxin, the exposure ordinarily must be quantified. The woman’s theory required not only expert testimony but also quantification of her exposure to benzene. The court of appeals rejected her contention that she did not need to quantify her exposure.

The case is No. 17-6086.

Attorneys: Jason Bjorn Aamodt (Aamodt Law Firm) for Samantha Hall. Katherine D. Mackillop (Norton Rose Fulbright) for Conoco Inc., ConocoPhillips Co. and Phillips 66 Co.

Companies: Conoco Inc.; ConocoPhillips Co.; Phillips 66 Co.

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