Toxic Tort and Environmental Litigation: Court of Appeals Revisits and Clarifies Causation Requirements for Expert Opinions

Causation is the crux of any toxic tort litigation. The Court of Appeals’ recent decision in Cornell v. 360 West 51st Street Realty, LLC, No. 16 (N.Y. Mar. 27, 2014) underscores that principle and revisits the causation analysis that the Court set forth in 2006 in Parker v. Mobil Oil Corporation, 7 N.Y.3d 434.

The Parker Case involved personal injury claims for benzene exposure. There, the Court explained the requirements for an expert opinion to establish causation: (1) proof of a plaintiff’s exposure to a particular toxin, (2) proof that the toxin is capable of causing the particular illness alleged ("general causation"), and (3) proof that the plaintiff was exposed to a sufficient amount of the toxin to cause the illness involved ("specific causation"). The Parker Court held that an expert need not precisely quantify the exposure level or use the "dose-response" relationship in order to prove specific causation, so long as the scientific community generally accepts whatever methods the expert does use to prove the amount of the plaintiff’s exposure was sufficient to cause the illness.

Last week, the Court applied this three-part causation test for the first time to a toxic mold case. In the Cornell case, the plaintiff, Brenda Cornell, argued that she suffered from various ailments including severe headaches, fatigue, difficulty breathing, and rashes as a result of exposure to mold spores in her former apartment. Plaintiff claimed the mold entered her apartment as a result of the defendant-landlord’s basement cleanup project, which allegedly churned up settled mold spores. After discovery, Defendant moved for summary judgment on the ground that Plaintiff failed to prove that indoor mold exposure can cause illness or that she had been exposed to enough mold to cause her specific ailments. The defense expert, a clinical immunologist, even noted that rather than having elevated mold levels, the levels measured in Plaintiff’s former apartment were at expected rates, average for a home setting. In response, Plaintiff’s expert, a doctor of environmental and occupational medicine specializing in mold-related illness, opined that indoor mold could cause illnesses and the scientific community generally accepted that principle.

In its analysis of the general and specific causation requirements, the Court focused on the evidence the parties presented. Ultimately, the Court rejected Plaintiff’s theory of general causation after the defense established the theory’s lack of general acceptance in the scientific community. Defendant offered proof that the three types of mold exposure accepted by the scientific community to cause human illness did not include the method of exposure that Plaintiff alleged. The burden then shifted to Plaintiff who failed to raise a triable issue of fact since the evidence she offered established only an association or linkage between mold exposure and illness, not causation.

On this issue, the Court of Appeals agreed with the principle decided by Fraser v. 301-52 Townhouse Corporation, 57 A.D.3d 416 (1st Dep’t 2008), a case referenced heavily by the courts below involving similar facts and issues and which the Court of Appeals discussed at length in its own opinion. As was held in Fraser, the Court concluded that the generally accepted principle in the scientific community is that causation is not synonymous with association; therefore, proof of one is not proof of the other. Accordingly, since Plaintiff only offered evidence of an association or linkage between indoor mold exposure and illness, she failed to establish general causation.

Importantly, the Court expressly left the door open to future plaintiffs bringing personal injury claims based on indoor mold exposure, acknowledging that scientific findings are in flux and that someone in the future could conceivably come forward with enough proof to establish a causal relationship between indoor mold exposure and the types of illnesses alleged. The Court underscored that its ruling on lack of general causation hinged on the scientific evidence in the record before the trial court when the case initially began.

The Court of Appeals further stated that Plaintiff failed to prove specific causation for her claims. The Court clarified its earlier holding in Parker that a showing of specific causation does not require precise quantification of a plaintiff’s exposure level or proof of the "dose-response" relationship. The Court explained that while "‘an exact numerical value’ is not required to make a showing of specific causation," a plaintiff still must quantify his exposure to some degree and establish that the exposure was sufficient to cause the ailment alleged.

Plaintiff in Cornell failed to meet her burden to demonstrate specific causation. Except for vaguely describing the mold as a mixture of "atypical microbial contaminants," Plaintiff’s expert neglected to identify the specific disease-causing toxins to which Plaintiff allegedly had been exposed. Furthermore, he made no quantification whatsoever of her exposure level to this mixture, nor did he refute the defense expert’s statement that the mold levels in the apartment were those expected of and average for any home when compared to sampling studies. Finally, while the Court acknowledged that differential diagnosis is a generally accepted methodology which courts can consider, it alone is not enough to establish a plaintiff has been exposed to a sufficient quantity of a toxin to prove specific causation.

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