Highlighting the importance of strong expert testimony, the Eleventh Circuit affirmed exclusion of an expert’s testimony where—among other defects—the expert (1) failed to properly assess dose-response, (2) failed to meaningfully rule out alternative causes, and (3) failed to account for background risk. See Williams v. Mosaic Fertilizer, LLC, 889 F.3d 1239, 1245-46 (11th Cir. 2018).

Plaintiff alleged that her pulmonary disease, pulmonary hypertension, allergic reactions, diabetes, and other health conditions were caused or exacerbated by chemicals, dust, and other emissions from a fertilizer plant located three miles from plaintiff’s home. Mosaic moved to exclude plaintiff’s causation expert under Federal Rule of Evidence 702 and Daubert and then moved for summary judgment. Without holding a Daubert hearing, the trial court excluded the testimony and granted Mosaic summary judgment. Plaintiff appealed.

Reviewing for abuse of discretion, the Eleventh Circuit affirmed. First, the court found that plaintiff’s expert never conducted an independent dose response specific to plaintiff, instead relying solely on regulatory standards like EPA’s National Ambient Air Quality Standards. The court chided that it had previously explained the “methodological perils of relying, at face value, on regulatory emissions levels to establish causation.” Namely, regulatory standards are often prophylactic, whereas dose-response calculations identify the exposure levels that actually cause harm. Second, plaintiff’s expert “failed to meaningfully rule out other potential causes” of plaintiff’s conditions and symptoms. “Indeed, one of the studies heavily relied upon by [plaintiff’s expert] determined that environmental factors and emissions by other facilities caused the vast majority of pollution in the area in which [plaintiff] lived.” Third, plaintiff’s expert failed altogether to address background risk in his report or elsewhere.