cigarette fluids from 36 different manufacturers, 69.2% contained diacetal (2,3-butanedione).
This flavorant (butter-like flavor), while approved safe for ingestion (i.e., US FDA, Generally
Recognized as Safe) is recognized as a respiratory irritant and has been implicated in the
development of bronchiolitis obliterans, an irreversible respiratory disease, also called “popcorn
lung disease” [15].