Microwave popcorn gives off a toxic, lung-damaging gas when cooked. You might be reassured to learn that the buttery flavor in microwave popcorn typically comes from a chemical actually found in butter, but you shouldn’t be. This chemical, called diacetyl, is so toxic that it commonly destroys the lungs of workers in microwave popcorn factories, afflicting them with the crippling and irreversible disease known as bronchiolitis obliterans. Bronchiolitis obliterans is so rare outside of this context that it has become more commonly known as “popcorn lung,” after the primary cause of the disease.
Regulators and health professionals have known of this risk for decades, but always assumed that it would only affect people breathing in especially high concentrations in factory settings. Then in 2007, a man who regularly ate two bags of microwave popcorn every day was diagnosedwith popcorn lung, proving that diacetyl enters the air and lungs when microwave popcorn is cooked. Anxious to reassure consumers, most microwave popcorn companies phased out diacetyl—only to replace it with chemicals that have the exact same effects.