What Causes Popcorn Lung?
The chemical that gave this condition its nickname is diacetyl. After workers at a factory that packaged microwave popcorn were found to have bronchiolitis obliterans more often than other people, some companies stopped using diacetyl as a flavoring. But it's still used in some electronic cigarette flavors in the US. Many e-cigarette makers state they aren't using this chemical in their products and its use in e-cigarettes is banned in Europe.

Another common cause is acetaldehyde, a chemical found in the smoke from marijuana and some electronic cigarettes. Acetaldehyde also can damage the lining of your mouth, throat, and stomach.