The artificial butter flavoring widely suspected of causing a potentially fatal disease known as “popcorn lung” has produced symptoms similar to the disease in mice, according to a study conducted by researchers from the National Institutes of Health’s (NIH) National Institute of Environmental Health Sciences and published in the journal Toxicological Sciences.
Diacetyl is a chemical that naturally occurs in butter and is widely used in artificial butter flavoring. But concerns have been raised that it is responsible for the disease called bronchiolitis obliterans or constrictive bronchiolitis, in which the lungs are wounded and then fill up with fibrous tissue, with potentially fatal consequences. Because the rare disease is unusually common among workers in microwave popcorn factories, it has also been nicknamed popcorn workers’ lung, or simply popcorn lung.
Symptoms of popcorn lung are vague and include a steadily worsening dry cough, wheezing and shortness of breath. There is no known treatment for the disease, which is irreversible, short of a lung transplant.
NIH researchers exposed mice to diacetyl vapors at concentrations similar to those found in popcorn factories. After three weeks, the animals had developed lymphocytic bronchiolitis, a precursor to popcorn lung.
At least one case is suspected of a consumer acquiring popcorn lung. The patient in question inhaled the fumes released by preparing and eating two bags of microwave popcorn every day. In response to that case, the two biggest popcorn makers in the United States, ConAgra and Weaver, announced that they were phasing out diacetyl as an ingredient.
The House of Representatives has passed a bill ordering the Occupational Safety and Health Administration to act to limit workers’ exposure to diacetyl, but the Senate has not yet followed suit.
In Europe, the former Committee of Experts on Flavoring Substances of the Council of Europe ruled diacetyl safe for ingestion, but did not study inhalation risk. But the European Food Safety Authority is revisiting the issue and reviewing diacetyl along with a number of other flavor chemicals.