A research study published in the journal Toxicological Sciences shows that a substance used to flavor popcorn causes a very dangerous lung disease called lymphocytic bronchiolitis.

Tests have proved that diacetyl, the compound that gives popcorn the artificial butter flavor, is harmful to the nose and airways of mice.

Scientists at the National Institute of Environmental Health Sciences (NIEHS) initiated the study after discovering that diacetyl had been involved in causing obliterative bronchiolitis (OB) in humans.

The tests involving mice showed that the mice exposed to diacetyl vapors for three months developed lymphocytic bronchiolitis, which usually leads to OB. Symptoms of OB usually include cough and difficult breathing.

“This is one of the first studies to evaluate the respiratory toxicity of diacetyl at levels relevant to human health. Mice were exposed to diacetyl at concentrations and durations comparable to what may be inhaled at some microwave popcorn packaging plants,” said Daniel L. Morgan, Ph.D., head of the Respiratory Toxicology Group at the NIEHS and co-author of the study, according to Science Daily.

ConAgra Foods Inc and Weaver Popcorn Co Inc, two microwave popcorn makers have recently declared they would stop using diacetyl as an ingredient in their products.

While the risk for popcorn consumers to develop obliterative bronchiolitis is relatively low, a case reported certainly suggests that long-term consumption of butter-flavoured popcorn can lead to the dangerous disease. The case involved a man who ate popcorn twice a day for ten years until he was diagnosed with OB.

The National Toxicology Program plans to continue the research concerning the toxicity of artificial butter flavoring, so it can find methods to protect the workers in popcorn making companies.