Popcorn lung: A form of bronchiolitis obliterans, a severe obstructive lung disease, first described in workers who mix and package flavored microwave-popcorn or are involved in other flavoring manufacturing. The syndrome has also been observed in people who consumed microwaved popcorn in large quantities. “Popcorn lung” is due to chronic exposure to a chemical that is used in making artificial butter flavoring. The chemical is diacetyl (2,3-butanedione). High levels of diacetyl damage cells lining the respiratory tract. Moreover, in 2015 the offending chemical, diacetyl, was found to be present in flavored e-cigarettes, leading to a potential risk for lung disease from this type of exposure. Signs and symptoms of "popcorn lung" are primarily cough and shortness of breath. The symptoms may develop slowly over time and can become disabling. Other possible symptoms are fevers, night sweats, and weight loss.
Allen et al. "Flavoring Chemicals in E-Cigarettes: Diacetyl, 2,3-Pentanedione, and Acetoin in a Sample of 51 Products, Including Fruit-, Candy-, and Cocktail-Flavored E-Cigarettes." Environ Health Perspect; DOI:10.1289/ehp.1510185