Rhonda Williams sued Mosaic Fertilizer, claiming that her lung diseases and other health conditions were related to toxic substances emitted by Mosaic’s plant. Mosaic made a Daubert motion to exclude the expert testimony that linked Williams’ health problems to Mosaic’s emissions. A federal district court granted the motion and the Court of Appeals for the Eleventh Circuit affirmed its decision on appeal.

Williams’ Claim

Williams has lived her whole life in Tampa, about three miles from a Mosaic factory. She alleged that Mosaic uses a number of toxic chemicals in its manufacturing process. She further alleged that Mosaic produces toxic emissions, including arsenic, cadmium, chromium, lead, manganese, nickel, phosphorous, and zinc.

Government agencies have found that sulfur dioxide in their air near Mosaic’s plant exceeded national and state standards. Measurements of particulate matter (inhalable particles that are 10 micrometers or smaller) exceeded the national standard in Williams’ neighborhood. Particulate matter is a respiratory irritant.

Williams’ lung-related health problems included pulmonary hypertension, obstructive pulmonary disease, asthma, and lower lung scarring. She also attributed her fatigue, abdominal pain, and diabetes to the pollutants or to the side effects of treating her lung conditions.

Expert Evidence

To prove that her health conditions were caused by Mosaic’s pollution, Williams relied on the expert opinion of Dr. Franklin Mink, a toxicologist. Dr. Mink opined that Williams had been exposed to a lifetime of pollutants and hazardous materials generated from Mosaic’s operations, including mining, processing, storage, transportation, and waste handling. Mink also concluded that Williams developed adverse health effects from her exposure to those pollutants and materials, and from the therapeutic agents used to treat those diseases.

Dr. Mink appended a list of sources to his report that included environmental studies and regulatory documents. However, he did not make specific references in his report to the cited sources that supported each of his conclusions. One lesson to learn from this case is that experts should carefully cite the specific sources they rely upon in support of each fact or opinion stated in an expert report.

In granting Mosaic’s Daubert motion, the trial court concluded that Dr. Mink failed to address “the hallmark of the science of toxic torts — the dose-response relationship.” The dose-response relationship is a means of proving that a toxic substance caused a particular health outcome by demonstrating that increasing exposure to the substance correlates with an increased risk that the outcome will occur.

The trial court also faulted Dr. Mink’s methodology because he:

• “unjustifiably” relied on regulatory standards to determine the dose that would cause harm to health;
• inferred facts from studies that contradicted his conclusions;
• failed to consider background risks for Williams’ conditions;
• failed to rule out other potential causes for Williams’ conditions; and
• speculated about Williams’ exposure to the toxic substances.

Since the court deemed Dr. Mink’s methodology to be unreliable, the court concluded that his opinions were inadmissible.

Causation Standards

Without deciding whether Williams failed to prove general causation (in other words, to prove that the pollutants emitted by Mosaic are capable of causing the harmful health conditions from which Williams suffered), the Court of Appeals for the Eleventh Circuit agreed that Williams failed to demonstrate specific causation. To establish that her health conditions actually were caused by Mosaic’s toxic discharges, Williams needed to establish a level of exposure that was necessary to produce those effects, and to prove that Williams was exposed to that level. The court concluded that her expert’s failure to do so was fatal to her proof of specific causation.

Dr. Mink did not independently measure the level of pollutants in Williams’ environment, but relied on academic studies measuring the ambient concentration of air pollutants in Williams’ neighborhood. He also relied on Environmental Protection Agency (EPA) air quality standards to determine the threshold exposure to those pollutants that could produce Williams’ health problems.

The court of appeals concluded that Dr. Mink’s analysis was “methodologically problematic,” in part because one of the studies upon which he relied concluded that the concentration of pollutants emitted by fertilizer plants in the Tampa Bay area was below the level that would present a health risk to the public. Dr. Mink explained that he relied on the study’s data, not on its conclusions, but the court of appeals held that Dr. Mink never “clearly explained” until after his opinion was deemed inadmissible why he disagreed with the study authors’ conclusions.

Unfortunately, the appellate opinion does not tell the reader what explanation Dr. Mink gave that prompted the district court’s ruling, making it impossible for the reader to evaluate the clarity of that explanation. Nor does the opinion explain why Dr. Mink was less qualified to draw opinions from the data than the authors of the study.

The court also faulted Dr. Mink for relying on EPA standards to establish causation. The court noted that regulatory standards are protective, in that they might build in a “cushion” to protect sensitive people from exposures that would not adversely affect most people. According to the court, relying on EPA standards is a poor methodology because the standards, unlike the dose-response relationship, cannot predict how many people will be affected by a particular level of contamination.

The court rejected the argument that the EPA standards are, in fact, based on the dose-response relationship. The court noted that EPA cautions that its data cannot predict future risk with precision. Yet the burden in a civil case is not to prove facts with precision, but to prove that they are more likely than not true. While the court stated that it does not require experts to produce “precise numbers,” it faulted the expert’s methodology because the methodology was not based on precise numbers.

Toxic tort cases have become monstrously difficult to prove because appellate courts have set the bar for expert testimony so high that, without investing huge sums of money to establish precise dose-response relationships, experts are unable to use the “exacting” methodologies that industry-friendly judges believe Daubert requires. The unfortunate result is that jurors never get a chance to apply the less-than-exacting civil burden of proof to decide whether a company’s pollution probably caused a plaintiff’s injury. Whether that’s good or bad depends on how judges and legislators balance a company’s interest in being shielded from judgments against society’s interest in compensating victims of toxic torts.

Other Potential Causes of Harm

Finally, the court faulted Dr. Mink for failing to rule out other potential causes of Williams’ health conditions, such as “obesity, allergies, lifestyle, exposure to secondhand smoke, or possible genetic predisposition.” Dr. Mink testified that the probability of those factors causing Williams’ health condition was low.  The court faulted that testimony because it was unsupported by “probability studies.” That complaint arguably goes to Dr. Mink’s credibility. If Dr. Mink was testifying based on his knowledge and experience, whether he can cite supportive probability studies is an issue that could be explored on cross-examination to attack his credibility.

Credibility is generally for the jury to determine. While the court held that “[t]he law does not require the District Court to take [the expert] at his word,” the law does allow juries to do so by assigning credibility determinations to juries rather than judges. In addition, the district court declined to hold a Daubert hearing and thus gave Dr. Mink no opportunity to discuss probability studies that he did not mention (and apparently was not asked about) during his deposition.

Different courts view the elusive border between credibility and the “reasonableness” of testimony in very different ways. This case is a further example of the importance of having experts prepare reports that document every single fact upon which the expert relies in forming an opinion, even if the fact seems blindingly obvious to the expert.