Tracking an occupational hazard down the food manufacturing chain: Flavorings-induced bronchiolitis obliterans in popcorn consumers

Respiratory exposure to diacetyl (2,3-butanedione) used in butter flavorings has caused lung disease, including bronchiolitis obliterans (BO), in both flavorings workers and downstream popcorn manufacturers. Historically, occupational respiratory toxins (e.g. asbestos, isocyanates) have displayed a pattern of disease emergence that begins with raw material producers, moving to downstream manufacturing workers and finally emerging in end-product consumers. Our objective is to assess whether this historical pattern of disease emergence manifests among populations exposed to diacetyl and butter flavorings. We evaluate potential exposures to consumers and compare them with worker exposures. We examine industry marketing campaigns that encourage inhalation of off-gassed chemicals, and the current practice of replacing diacetyl with undisclosed, untested and highly toxic substitutes. We present five cases of lung disease among medium to heavy consumers of microwave popcorn. Each case's clinical presentation, radiologic and pathologic findings are consistent with a BO diagnosis. Occupational and exposure histories are reviewed and other possible causes of BO ruled out. Lung biopsies confirm the presence of obliterative fibrosis of the bronchioles in all five cases. These findings provide strong evidence that flavorings-induced disease is not limited to an occupational context and that popcorn consumers are at risk of severe lung disease. This pattern of disease emergence mirrors those previously seen with other respiratory toxins. It further calls into question the reliability of industry claims about the safety of consumer products whose manufacture causes disease in workers, particularly when the safe level of exposure to the causative agent is unknown or understudied.