"Popcorn lung" is a colloquial way to refer to bronchiolitis obliterans, an incurable condition that scars the lungs, causes cough and inhibits breathing, says MedicineNet. Bronchiolitis obliterans gained the nickname after several workers were diagnosed with the disease as a result of working in a Missouri microwave popcorn factory.
Popcorn lung is caused by inhaling fumes of diacetyl, a chemical used to create a buttery taste, says the Boston Globe. Hundreds of popcorn factory workers were affected by the disease, and one consumer developed popcorn lung after eating multiple bags of microwavable popcorn each day for years. In 2007, the four largest manufacturers of microwavable popcorn removed diacetyl from the ingredients, reducing the risk to both workers and consumers.