"He really liked microwave popcorn. He made two or three bags every day for 10 years," said William Allstetter, a spokesman for National Jewish Medical and Research Center in Denver where the man's respiratory illness was diagnosed.

"He told us he liked the smell of popcorn, so he would open and inhale from freshly popped bags," Allstetter said. And the patient said he did this for a decade.

There are no warnings from federal regulators, nor is there medical advice on how consumers should treat news of the rare, life-threatening disease, bronchiolitis obliterans, also known as popcorn lung.

The popcorn flavoring contains the chemical diacetyl, which has been linked to lung damage in workers inhaling its fumes in food manufacturing plants. The chemical is a naturally occurring compound that gives butter its flavor and is also found in cheese and even wine, according to the National Institute of Occupational Safety and Health.

It's been approved by the Food and Drug Administration as a flavor ingredient, but hundreds of workers have sued flavoring makers in recent years for lung damage.

Dr. David Weissman, head of NIOSH's division of respiratory diseases, said the key difference between homes and the factories where popcorn lung has been found is in the level of exposure to diacetyl. For example, he said, sickened workers at a Joplin, Mo., popcorn factory popped hundreds of bags a day, not just one or two.

The first case of lung damage from a home popcorn maker came to light Tuesday in a recent letter to federal regulators from Dr. Cecile Rose, a lung specialist at National Jewish.

On Wednesday, the nation's largest microwave popcorn maker, ConAgra, said it would stop using diacetyl within a year out of concern for its workers — not because of risks to consumers. ConAgra makes Act II and Orville Redenbacher brands.

Meanwhile, Rose is not making changes in her own home.

"She said she's still letting her kids pop the occasional bag," Allstetter said. "They're not big popcorn consumers, but she's not making any changes because of this case."