Microwave popcorn lung (which I like to call golden buttery lung) is for real. It first started showing up when workers in microwave popcorn factories started to develop breathing problems. The main symptoms are difficulty breathing especially exhaling.
The blame for this disorder is said to be a flavoring agent called Diacetyl which delivers the buttery taste. When vaporized and inhaled, the chemical damages the lungs.
But don't worry it's perfectly safe for consumer consumption. Maybe. Well, not for one guy but I sure it's safe for everyone else.