Mind the Gaps: Unreliable Expert Testimony Dooms Plaintiff's Toxic Exposure Suit in Airline Uniform Case

In Zurbriggen v. Twin Hill Acquisition Co., the Northern District of Illinois granted summary judgment in favor of defendants American Airlines and Twin Hill, a uniform manufacturer, holding that airline employees alleging toxic exposure from chemically treated uniforms failed to present scientifically reliable expert testimony on causation. The decision highlights the rigorous evidentiary standards in toxic tort litigation, where the admissibility of expert testimony often determines the outcome and reaffirms the critical gatekeeping role of Daubert and Rule 702 in preventing jurors from filling scientific gaps with speculation.

American Airlines contracted with Twin Hill to manufacture a new line of uniforms for more than 60,000 employees. A pre-launch wear test yielded early complaints of skin irritation and similar symptoms, prompting American to retain Intertek Scientific & Regulatory Consultancy to assess the uniforms for potentially harmful chemicals. Intertek’s initial testing identified two potential sensitizers and several irritants but emphasized that these were common fragrance ingredients and appeared only in garments that had already been worn, suggesting contamination by the user rather than by the manufacturing process. Importantly, Intertek did not measure the concentration of these substances, noting whether harm could occur depended heavily on concentration.

A second round of testing several months later resulted in similar conclusions. Nonetheless, American proceeded with the uniform rollout the following year. Complaints from employees escalated almost immediately. Two flight attendant unions encouraged broad reporting of adverse reactions “regardless of whether [employees] had experienced a reaction.” One month later, American allowed employees to revert to older uniforms or choose alternatives and commissioned a third round of Intertek testing along with a health evaluation by the National Institute for Occupational Safety and Health (NIOSH).

The third Intertek analysis, conducted the following month, expanded its scope: it tested new, worn, and unworn Twin Hill uniforms, previous Twin Hill uniforms, and random off-the-rack garments. While various potential irritants and sensitizers were found across all categories, no single chemical appeared in every Twin Hill uniform. Eight chemicals were unique to Twin Hill, but Intertek concluded that they were unlikely to cause sensitization at the levels detected. NIOSH similarly concluded that while it was “possible” that textile chemicals had contributed to some reactions, testing failed to identify any single chemical responsible. NIOSH also found that exposure by mere proximity, without direct skin contact, was unlikely to cause symptoms. American ultimately terminated its contract with Twin Hill, and litigation followed.

Procedural History

Plaintiff flight attendant filed a federal class action in the Northern District of Illinois asserting claims for strict and negligent product liability, battery, and intentional infliction of emotional distress. Plaintiffs later amended their complaint twice, ultimately dropping all unintentional tort claims against American and narrowing their focus to battery and intentional infliction of emotional distress against all defendants, and product liability claims against Twin Hill.

During discovery, plaintiffs disclosed three experts, two of whom addressed causation: Dr. Carson, a physician and toxicologist, and Dr. Hauser, a textile chemist. Both experts concluded that the chemicals detected in the Twin Hill uniforms caused the plaintiffs’ symptoms.

Key Issues

American and Twin Hill filed motions for summary judgment under two main premises. First, defendants argued summary judgment was warranted because the plaintiffs could not convince a reasonable jury that they were exposed to Twin Hill uniforms with harmful defects. Second, defendants argue that no reasonable jury could reach that finding because plaintiffs failed to provide admissible expert testimony on that subject, and that, even if admissible, the plaintiffs’ experts cannot establish that their particular uniforms were defective based on the evidence.

Under Daubert and Rule 702, expert opinions must be grounded in sufficient facts, rely on sound methodology, and reflect a reliable application of that methodology to the facts of the case. Both Dr. Carson and Dr. Hauser fell short of these standards. Neither expert offered any accepted biological theory for how Twin Hill uniforms caused the plaintiff’s symptoms, declining to specify the exact chemical or set of chemicals responsible, dosage, or any associated environmental factors that may affect reaction. They failed to conduct any independent testing, relying almost exclusively on Intertek’s findings without addressing critical gaps for a lay jury to find causation. Dr. Carson opined that any level of exposure to the detected chemicals was harmful. However, both the court and the Seventh Circuit have rejected “any exposure” theories as unscientific unless supported by robust data, which was not provided here. Experts must establish a threshold dose at which a substance becomes harmful and demonstrate that the plaintiff was exposed to at least that amount. Courts expect experts to do more than repackage third-party findings. Experts must apply reliable methods and ground their opinions in specific, testable data.

To bolster his opinion and lack of reliable scientific support, Dr. Carson claimed to have invoked the “Bradford Hill criteria,” a methodology used to evaluate whether a statistical association supports a causal relationship. But as the court explained, the Bradford Hill framework begins with identifying an existing statistically significant association; it does not create one. Dr. Carson failed to establish such an association and instead relied on anecdotal complaints from American employees to infer causation without even specifying the specific chemical or set of chemicals responsible for the symptoms. This backward application undermined the reliability of his analysis. Courts have repeatedly held that Bradford Hill is not a shortcut around insufficient epidemiological data.

Finally, the court faulted plaintiffs’ experts for failing to rule out alternative explanations for plaintiffs’ symptoms. Experts must affirmatively eliminate other plausible causes, particularly when medical records or broader garment testing (like Intertek’s) raise competing possibilities. Dr. Carson failed to address potential external sources of contamination suggested by Intertek, nor did he account for alternative explanations hinted in the plaintiff’s medical records.

The court granted the defendants’ motion for summary judgment in full, finding that the plaintiffs failed to prove by a preponderance of the evidence that they were exposed to harmful defects in the Twin Hill uniforms that caused their symptoms. Employee complaints were unreliable and inconsistent, the Intertek testing provided limited insight into the source, characteristics, toxicity levels, or specific chemicals responsible for the symptoms, and both Dr. Carson and Dr. Hauser failed to fill these critical evidentiary gaps. As a result, the plaintiffs could not meet their burden.

Conclusion