This question asks about using corrugated cardboard for mulch. In the comments and the answer there are some questions about glues and inks possibly having "bad stuff" that you might not want in the vegetable garden.
I'm wondering about cereal boxes (this type of cardboard in general). They're printed with glossy inks, which from what I read probably have heavy metals? Does anyone know of literature about what's in these boxes/inks and whether it would be safe for mulching around vegetables?