I just checked my regular butter substitute. (I prefer to use the real stuff when I can.)
Anyway, it’s ICBINB. I don’t see this ingredient listed. Is it a requirement, I wonder?
There are some butter flavorings that have diacetyl (DA) in them. It may be hard to find them by looking at ingredients because they list “artificial flavorings” rather than the specific artificial flavoring.
This PDF is from a study done by the Seattle Post Intelligencer in 2007:
http://nutrimenti.simplicissimus.it/files/2008/03/diacetylproducts2.pdf
(The Seattle P-I no longer has this file in its archives. Google found it on an Italian server.)
It isn’t only popcorn most man made oils are harmful. Use real oil Olive and coconut oil or real butter not margarine. I wrote an article on this
Is Your Cooking Oil Healthy?
http://coconutcreamcare.com/2012/06/27/is-your-cooking-oil-healthy/