My first reaction is skeptical... several bags a day for several years they say, which is not very specific. But they did then go and measure the amount of the stuff in the air in his home so thats better science. Still I dont think there is enough information there to decide if this was the cause, further testing will be necessary.
I'm not defending the flavoring you understand. I like popcorn! Not too fond of the extra strong smell they add to the microwave variety though. Seems you could have unscented that would then smell like what it is, popcorn and oil and salt
which should be good enough just by itself!
The part that bothers me is that we're taking a chemical that we know causes problems when inhaled in large quantities and we're not talking about just removing it, but about reformulating. So we'll be replacing a danger that we know and that can be mitigated by not working in the plant or eating the stuff for breakfast lunch and dinner every day for years, and instead using something new for which there isn't any data but that might turn out to be just as dangerous if not worse. I'd rather the poison where I know I'm below the dangerous dose, than the new stuff that I have no idea about. But then I have the same problem with that new copper treated lumber I've been using on the deck. I knew how to be safe with the old stuff, no idea how the new stuff will affect things...
Perhaps we could let Orville and the gang know that we like popcorn that is popcorn flavored and perhaps so many non-food smells aren't actually necessary to get us to like their product.