Omaha, Neb. ? Four of the nation’s biggest microwave popcorn makers are working to remove a flavoring chemical from their products linked to a lung ailment in popcorn plant workers while reassuring consumers about the safety of the snack.

Several of the companies discussed their plans Wednesday, a day after a leading lung research hospital warned that consumers also could be in danger from the buttery flavoring diacetyl.

The three companies that sell Orville Redenbacher, Act II, Pop Secret and Jolly Time microwave popcorn said they planned to change the recipes for their butter-flavored microwave popcorn to remove diacetyl.

The chemical diacetyl has been linked to cases of bronchiolitis obliterans, a rare life-threatening disease often called popcorn lung.

ConAgra Foods Inc., General Mills Inc. and the American Pop Corn Co. all promised to make the change because of safety concerns. Together those companies accounted for more than 80 percent of the market for microwave popcorn over the past 12 months, according to the research firm Information Resources Inc.

ConAgra spokeswoman Stephanie Childs said the change will not affect its popular stovetop popcorn, Jiffy Pop, because it contains natural butter instead of the threatening chemical.

Last week, another popcorn manufacturer, Weaver Popcorn Co. of Indianapolis, said it would replace the butter flavoring ingredient because of consumer concern.

The popcorn makers said consumers worried about diacetyl can buy varieties of microwave popcorn that are not butter flavored because those products don’t contain diacetyl.

Diacetyl occurs naturally in foods such as butter, cheese and fruits, and the FDA has approved its use as a flavor ingredient.