Orange Bulletin.com, "Buttery flavor might be harmful to your health"

          Bronchiolitis obliterans, a severe form of lung disease, causes shortness of breath, coughing and lung destruction. Although the disease is very rare, it has been affecting certain workers at an alarming rate. Workers exposed to the chemical, diacetyl, which imparts butter flavoring to foods and beverages, have been developing bronchiolitis obliterans far above that which would be expected. Concerns began centering on diacetyl after a cluster of bronchilotits obliterans was discovered among workers at a popcorn factory in the Midwest.
          Since that initial cluster, disease has been found among workers at other popcorn making facilities and in individuals who work in the flavoring industry. According to Dr. Richard Kanwal, a National Institute of Health scientist, "The rate of disease is striking ... that's enough to say this exposure is really bad." Diacetyl, which was introduced in the early 1980s, was deemed by the FDA to be a GRAS substance - generally recognized as safe. Since diacetyl was considered a safe substance, no testing needed to be done before it was introduced to the market.
          Veronica Castro, a spokeswoman for the FDA, said there was no evidence that diacetyl was hazardous. Although she admitted that there was no scientific data to support that information, she added, "The bottom line is it is assumed to be safe."
In truth, little is known about diacetyl. Animal studies, however, have documented that severe, often lethal, respiratory damage occurs from inhalation of diacetyl. Researchers are concerned that other industries may be at risk, as well. Diacetyl is used in many food processes to give a buttery flavor to: cookies/snacks, dairy products, beverages, frozen foods and candy/confections. Kanwal said, "If there is butter flavoring, there's almost certainly diacetyl in it."

Learn more about diacetyl butter flavoring dangers and lawsuits.