Microwave popcorn makers across the United States are making some product changes in the wake of concerns about a chemical used as a buttery flavoring.

Diacetyl has reportedly been linked to a rare lung ailment known as bronchiolitis obliterans, or popcorn lung, in employees of popcorn plants.

ConAgra Foods, Inc., General Mills, and American Pop Corn Company make the Orville Redenbacher, Act II, Pop Secret and Jolly Time brands, and say they are working to remove diacetyl from those products.

Indianapolis, Indiana-based Weaver Popcorn Company has already moved to replace the ingredient in its products. On its website, the company is already informing customers that its Pop Weaver product has “no diacetyl flavorings.”

The Weaver Popcorn website states the following:
“Although diacetyl has long been considered safe for use in consumer food products, the flavoring has been cited as a possible source of injury to certain employees of food companies who may have inhaled large dosages of diacetyl while mixing it under unsafe conditions.”