"Popcorn lung" is a term used to describe bronchiolitis obliterans, a respiratory condition that affects the bronchioles of the lungs. It is caused by inhaling toxic chemicals, such as diacetyl, which was used to flavor microwave popcorn. When inhaled, diacetyl causes inflammation and may lead to permanent scarring in the smallest branches of the airways, which makes breathing difficult. Popcorn lung has no lasting treatment, but there are treatments that manage its symptoms, such as coughing, wheezing, chest pain, and shortness of breath.

It is important to note that while diacetyl was swiftly removed from popcorn products since it could cause this devastating disease among factory workers, it is still found in many e-cigarette flavors. E-cigarettes have many different types of chemicals in them that may be dangerous to lung tissue, and it is thought that the vapor may affect not only the person vaping but also the people around them. However, there have been no confirmed cases of popcorn lung reported in people who use e-cigarettes.