Oh, McRib, you've done it again! +Mike Chmiel, this one's for you:

"...it's still a little disconcerting to know that, for example, azodicarbonamide, a flour-bleaching agent that is most commonly used in the manufacture of foamed plastics like in gym mats and the soles of shoes, is found in the McRib bun. The compound is banned in Europe and Australia as a food additive."
Shared publicly