A 53-year-old man from Colorado enjoyed eating microwave buttered popcorn so much that he ate large portions daily for ten years – and then developed a rare disease called “popcorn worker’s lung.”

Bronchiolitis obliterans aka popcorn lung is a serious lung condition that can be life-threatening. The only chance of survival in a severe case is a lung transplant.

It was first noted in 2001 in workers at an American plant that manufactured microwavable popcorn. The Colorado man, who reportedly ate two or three bags of microwave extra-butter-flavored popcorn each day for ten years, is the first consumer to develop bronchiolitis obliterans.

Even back then, researchers singled out diacetyl, a chemical ingredient in the buttery flavoring of the popcorn, as the culprit, but not with 100 percent certainty.

Earlier this week, a team of Dutch researchers published a new study in the September issue of the American Journal of Respiratory and Critical Care Medicine, pointing once again to diacetyl as the chemical ingredient most likely to cause bronchiolitis obliterans.

They note however that several other ingredients could also contribute to the development of the disease, such as acetoin and acetyldehyde.

The case of the Colorado man, a furniture salesman, brings more attention to a serious situation. Federal safety experts initially said consumers were not at risk of becoming ill because of the relatively low exposure to buttery-flavor fumes and powders, which actually cause popcorn lung.

After the Colorado man was treated at the National Jewish Medical and Research Center in Denver, doctors there sent letters describing the case to four federal regulatory agencies.

Dr. Cecile Rose, director of the occupational disease clinical programs at the Center, said the man’s symptoms were initially baffling and that the diagnosis he had received was not consistent with his lifestyle and living conditions.

He presented shortness of breath and was overweight, but he did not smoke. Diagnosed with hypersensitivity pneumonitis, an inflammation of the lungs usually caused by chronic exposure to bacteria, mold or dust, the man was exposed to neither factor.

Dr. Rose followed a hunch she had.

“I said to him, ‘This is a very weird question, but bear with me. But are you around a lot of popcorn?’” Dr. Rose asked. “His jaw dropped and he said, ‘How could you possibly know that about me? I am Mr. Popcorn. I love popcorn.’”

He then told Dr. Rose of his decade-long habit of eating large quantities of popcorn daily.

“When he broke open the bags, after the steam came out, he would often inhale the fragrance because he liked it so much,” Dr. Rose said. “That’s heated diacetyl, which we know from the workers’ studies is the highest risk.”

The man’s doctors subsequently measured the levels of diacetyl in his house and found they were similar to those found in microwave popcorn plants.

Dr. Rose asked him to stop eating popcorn and 6 months later, he had lost 50 pounds while his lung function had improved slightly.

“This is not a definitive causal link, but it raises a lot of questions and supports the recommendation that more work needs to be done,” Dr. Rose said.

The Flavor and Extract Manufacturers Association replied on Tuesday by recommending microwave popcorn producers who use diacetyl to reduce the chemical’s concentration in flavors. The association emphasized that the popcorn itself is safe for consumers.