A fellow trial lawyer sent me the story this morning, with the comment “this is going to be the new McDonald’s hot coffee case.” At first blush the case sounds primed to create an urban legend: a $7 million verdict for regularly using the same consumer product millions of us use every day? Let’s dig a little bit deeper.


It’s no secret that exposure to diacetyl, which was used in the butter flavoring of microwave popcorn, can cause a particular type of obstructive lung disease called bronchiolitis obliterans. The National Institute for Occupational Safety and Health (NIOSH) first confirmed that back in 2000, when more than a dozen employees of the Gilster-Mary Lee Corporation’s microwave popcorn plant in Jasper, Missouri, filed workers’ compensation claims alleging their permanent coughing, wheezing, shortness of breath and so on were the result of exposures in the workplace. What NIOSH found was awfully suspicious:

Plant employees had 2.6 times the rates of chronic cough and shortness of breath compared to national data, adjusted for smoking and age group; younger employees who had never smoked had rates about five times higher than expected from national rates. Overall, plant employees had 3.3 times the rate of obstructive spirometry abnormalities compared to national adjusted rates; never smokers had 10.8 times the national expected rate. Worker reports of physician-diagnosed asthma and chronic bronchitis were about twice as frequent as expected from national data, with a 3.3-fold excess of chronic bronchitis in never smokers. Microwave popcorn workers had statistically higher rates of regular trouble breathing and unusual fatigue, compared with workers in two lower exposure groups. Strong exposure-response relationships existed between quartile of estimated cumulative exposures to diacetyl and respirable dust and frequency and degree of airway obstruction.

NIOSH noted that “BBA butter flavoring, which contains diacetyl and many volatile organic compounds, has caused damage to epithelial lining of the rat respiratory system in animal experiments,” and concluded “we believe that butter flavoring vapors in the air caused lung disease in workers at this plant.” NIOSH thought the exposure was so problematic they recommended the company set up an industrial ventilation hood in the “quality control area” – you know, the place where they’re just microwaving popcorn like you and me. The company didn’t remove diacetyl from their butter flavoring until 2007, five years after the NIOSH recommended it.


The problem is so serious there’s a page up on the CDC website for the specific problem of “flavorings-related lung disease.” But that’s for the workers, who were exposed to extraordinary amounts of the chemicals day in and day out in a closed space with inadequate ventilation, often without any sort of protection like respirators. Can eating two bags of popcorn a day for ten years, like Wayne Watson did, really expose someone to enough diacetyl that they develop bronchiolitis obliterans?


We’ve been down this road many times before with the asbestos litigation. Although there’s no medical or scientific doubt that, in theory, a single exposure to asbestos fibers can increase the risk of developing mesothelioma, courts have generally taken a dim view of that “each and every breath” argument, and have required more specific proof from plaintiffs.


And Wayne Watson has that proof: his treating physician, Dr. Cecile Rose, MD, MPH, a published expert and researcher of occupational pulmonary diseases, explained how she reached that conclusion:

Q: What’s the basis for your opinion that his exposure to microwave popcorn is a cause of the lung disease that you diagnosed in him?

A: Well, the basis for that opinion relates mainly to the fact that his lung disease has stabilized with the cessation of use of the product and exposure to the inhalants related with that product. The fact that there was no other causal explanation for his lung condition and the fact that the clinical findings in his lung disease were similar to those that occurred in workers who were exposed to butter flavoring also support that opinion.

The Defendants moved to exclude Dr. Rose’s testimony on Daubert grounds, arguing that her conclusions were not “the product of reliable scientific principles and methods.” The Court denied the Motion; here’s the Court Order, as well as the last-filed briefs of the Plaintiff and the Defendants.


I’ve written before about The Difference Between Scientific Evidence And The Scientific Method. This case puts several issues of law, science, and medicine squarely in focus: on the one hand, it seems that exposure testing within Mr. Watson’s home was unable to show that he’d be exposed to dangerous levels of diacetyl, but on the other hand Mr. Watson has an extraordinarily rare lung disease that can’t be explained any other way except by way of his extensive exposure to microwave popcorn.


There’s nothing frivolous about this case: the plaintiff has a serious disease, one that modern medicine has concluded by the process of elimination had to be caused by his exposure to the microwaved popcorn. The question is more one of legal policy: should we require plaintiffs show more scientific evidence than that? The law on that, at least in the federal Tenth Circuit, is clear. As the Court found in Watson’s case:

[T]he Tenth Circuit has recognized that a medical expert does not always have to cite to published studies on general causation in order to establish causation and, under the right circumstances, a differential diagnosis (i.e., ruling out other possible causes of the condition) may reliably form the basis of an opinion that a particular item caused an injury. Hollander v. Sandoz Pharm. Corp., 289 F.3d 1193, 1211-12 (10th Cir. 2002) (quoting Turner v. Iowa Fire Equip. Co., 229 F.3d 1202, 1209 (8th Cir. 2000)). “The first several victims of a new toxic tort should not be barred from having their day in court simply because the medical literature, which will eventually show the connection between the victims’ condition and the toxic substance, has not yet been completed.” Turner, 229 F.3d at 1209. Dr. Egilman and Dr. Rose have both discussed why they believe that other known causes of bronchiolitis obliterans have been eliminated, leaving Mr. Watson’s exposure to butter flavoring vapors as the most plausible explanation.

Thus, the Daubert challenge was denied, and Dr. Rose was allowed to testify in front of the jury, and the jury was tasked with deciding if plaintiff had adequately proven microwave popcorn caused his lung disease, and the popcorn manufacturer was given the opportunity to point out the absence of any testing, and the fact that there are other potential causes of bronchiolitis obliterans.


Thus, like in the original “hot coffee” case, there’s nothing frivolous about this claim, but there are serious issues worth considering. Should a court rule that, as a matter of law, a doctor’s differential diagnosis about the cause of the rare disease isn’t “reliable” enough science to even let the case go in front of the jury? Or should the jury decide whose scientists and doctors are correct?