I use Krusteaz all the time, but the bag (I buy it in bags, and I mean the contents of course, not the bag itself) usually doesn't last longer than 6 months. I keep it in the cupboard with the top tightly rolled and clamped shut to keep out weevils, etc.

I can't see anything in the contents that would poison anyone, nor anything that would change into a poison. Could it have been contaminated with something else?

(I've had people get sick looking at my cooking and from the taste, but I go by the old principle "Non-toxic in, non-toxic out.")