In a nuanced and intelligently written opinion that gives new life to key defense arguments opposing class treatment of medical monitoring claims, a federal judge in West Virginia has rejected certification of a class of persons allegedly exposed to perfluorooctanoic acid (PFOA) in their drinking water, Rhodes v. E. I. du Pont De Nemours and Co., 2008 WL 4414720 (S.D.W.Va., 09/30/08).

Too often, courts pay mere lip service to the requirement that plaintiffs establish the propriety of class treatment for each of their causes of action. Refreshingly, the judge in Rhodes observed that of plaintiffs' six causes of action (including trespass and negligence), only one had been significantly addressed in the class certification briefing: medical monitoring. Consequently, the court found that the plaintiffs had not met their burden as to the five other causes of action.

The court then focused on the commonality requirement of Rule 23 and its updated and more stringent requirement, cohesiveness, "The plaintiff must offer evidence that commonly proves the elements of a medical monitoring claim for each proposed class member."

This requirement, applied to plaintiffs' key expert proofs – risk assessment and general epidemiology – resulted in the failure of the plaintiffs' case.

The court found that classwide exposure risk assessment has two serious flaws. First, it "does not demonstrate that any extra level above the 'safe' level are significantly harmful." Second, it does not demonstrate that each class member has a significantly increased risk. Indeed, "risk assessment is of limited utility in a toxic tort case" because it does not provide information about actual risk or causation. However interesting and important risk assessments may be from a precautionary, public health perspective, they do not provide the certainty required by tort law.

The epidemiology evidence offered by the plaintiffs suffered from similar inadequacies. Although that evidence may show that PFOA "generally causes some diseases," it does not show that class members' exposures caused a significantly increased risk of disease for each member of the class.

It is the general theme of the court's opinion that is most instructive and important to practitioners: There is a world of difference between what may be wise to do from a public health perspective and what is required for class certification. Indeed, the court stated that plaintiffs had presented "compelling evidence" that exposure to PFOA may be harmful to human health. That is not proof, however, of specific causation or the common injury required for class cohesiveness and class certification.