Although diacetyl has been used for decades as a flavoring agent to impart a buttery odor and taste to coffee, flour, chocolate, tobacco, cooking oils, popcorn and other snack foods (NIEHS 2007; NTP 2005; NTP 2007), concerns have been raised regarding reported respiratory disorders in certain food and flavorings manufacturing workers. Specifically, over the past ten years, some scientists at the National Institute for Occupational Safety and Health (NIOSH) have investigated numerous microwave popcorn and flavoring production facilities and they have concluded that diacetyl may be contributing to or causing severe respiratory disorders, including the rare disease bronchiolitis obliterans (referred to by some as “popcorn lung”), in highly exposed workers. Due to worker health concerns, possible insurance coverage issues, and anticipated difficulties in meeting proposed workplace standards, diacetyl has largely been phased out in the food/flavoring industries and replaced by 2,3-pentanedione and other chemicals.