Lead investigator Ann F. Hubbs of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, in Morgantown, W.Va., said the ingredient 2,3-pentanedione, 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.
Food manufacturers started using pentanedione when another butter flavoring, diacetyl, was found to cause bronchiolitis obliterans -- a life-threatening and non-reversible lung disease in workers who inhaled the substance, Hubbs said.
The study, published in The American Journal of Pathology, said acute pentanedione exposure had respiratory toxicity comparable to diacetyl in laboratory animals.
"Our study demonstrates that pentanedione, 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," Hubbs said in a statement. "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 involved rats exposed for 6 hours to different concentrations of pentanedione, a comparable concentration of diacetyl, or filtered air. The researchers microscopically examined the brains, lungs and nasal tissues up to 20 hours after exposure.
"In 2007, ConAgra Foods removed added diacetyl from our microwave popcorn and replaced it with a new butter flavoring that has no added diacetyl and no pentanedione," a spokeswoman for ConAgra told UPI. "We made this change to address any consumer concerns and also to further ensure a safe work environment for the employees working in our popcorn facilities."