The ingredient 2,3-pentanedione (PD), used to impart the flavor and aroma of butter in microwave popcorn, is a respiratory hazard that can also alter gene expression
in the brain
of rats. Manufacturers started using PD when another butter flavoring, diacetyl, was found to cause bronchiolitis
obliterans, a life-threatening and nonreversible lung disease in workers who inhaled the substance. New research on PD with implications for "popcorn workers' lung" is published in The American Journal of Pathology
and indicates that acute PD exposure has respiratory toxicity which is comparable to diacetyl in laboratory animals.
"Our study demonstrates that PD, like diacetyl, damages airway epithelium in laboratory studies. This finding is important because the damage is believed to be the underlying cause of bronchiolitis obliterans," says lead investigator Ann F. Hubbs, DVM, PhD, DACVP, Health Effects Laboratory Division of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV. "Our study also supports established recommendations that flavorings should be substituted only when there is evidence that the substitute is less toxic than the agent it replaces."
The study included groups of rats exposed for six hours to different concentrations of PD, a comparable concentration of diacetyl, or filtered air. Since the investigators observed signs of delayed toxicity, they exposed additional rats to PD, and further microscopically examined the brains, lungs, and nasal tissues from these rats 0-2 hours, 12-14 hours, and 18-20 hours after exposure. investigators then evaluated changes in gene expression in discrete brain regions.