The U. S. Court of Appeals for the 5th Circuit affirmed a lower court decision, agreeing that the plaintiff did not have adequate proof that gasoline exposure could cause leukemia. In Burst v. Shell, the 5th Circuit made clear that courts must insist on rigorous proof in order to link chemical exposure to disease.
General Causation and Specific Causation
In exposure cases, courts generally require two steps to establish causation. First, plaintiffs must establish general causation, by showing that the type of exposures that the plaintiff encountered could result in the disease contracted by the plaintiff. Second, plaintiffs must establish specific causation, by showing that the disease suffered by the plaintiff was indeed caused by the particular exposure, as opposed to other potential causes.
Failure to “Connect the Dots” between Benzene Literature and Gasoline Exposure was a Failure to Establish General Causation
In Burst, the trial court determined that the plaintiff could not establish that gasoline exposure could cause leukemia. In attempting to establish general causation, the plaintiff’s experts identified scientific literature that benzene causes leukemia. The plaintiff’s experts then attempted to correlate the benzene exposure literature to the estimated benzene exposure of the plaintiff, who had worked in gasoline service stations for much of his life.
In essence, the trial court held and the 5th Circuit affirmed that the plaintiff’s experts failed to “connect the dots” between the benzene literature and the possible exposure of the plaintiff to benzene from gasoline. The 5th Circuit noted that the literature relied upon by the plaintiff was for benzene exposure causing leukemia. None of the literature apparently dealt specifically with gasoline exposure causing leukemia. The plaintiff argued that gasoline contains benzene, and made some attempts to estimate the plaintiff’s benzene exposure based on the benzene concentration of the gasoline. However, the trial court held, and the 5th Circuit affirmed, that the variation in benzene concentrations in gasoline, along with poor evidence to establish the actual concentrations in the gasoline handled by plaintiff, precluded any proof of general causation between gasoline and leukemia.
For example, the 5th Circuit noted that the plaintiff’s experts assumed an average concentration of 2% benzene, even though the evidence was that some gasoline handled by the plaintiff had less than 1% and others had up to 4% benzene. The variation in benzene concentration and the absence of a reliable estimate of the plaintiff’s benzene exposure prevented the plaintiff’s experts from establishing a general causation link between gasoline and leukemia.
Courts Require Rigorous Proof to Link Disease to Exposure
This case is another example of the ongoing rigor that courts require in order to link a disease to exposure. A reliable exposure estimate is a necessary step to establishing general causation. Without accurate exposure estimates, plaintiffs will have a very difficult time linking any exposure to the medical literature, and thus will be unable to establish general causation.