I just bought some microwave popcorn. I got the one that says, "No Diacetyl Added," because the last thing I want is popcorn with extra diacetyl. Yuck! I'm surprised the government hasn't banned it yet.
By the way, uh, what is diacetyl?
Ah, yes, consulting Wikipedia, I find that diacetyl -- also known as "biacetyl" -- is the chemically known to scientists as butanedione. It is a byproduct of fermentation, and, as such, occurs naturally in alcoholic beverages; it is also present in butter, and is therefore used as flavouring in artificial butter products. Apparently, people who work in factories that manufacture artificial butter flavouring can get a nasty lung disease from inhaling this chemical over a period of years.
The only consumer ever to be diagnosed with the same lung disease ate two bags of microwave popcorn per day for ten years; the air in his kitchen had levels of diacetyl comparable to that in factories. I can therefore eat diacetyl-laced popcorn (and other products) in perfect serenity. The funny thing is that this popcorn is the decadent stuff -- butter popcorn, not butter-flavoured -- so I don't know why they would need to add artificial flavouring anyway. But I guess if roast beef needs to have beef flavouring added, butter needs to have butter flavouring added.