According to Yoga Dork and Food Babe, the answer is Azodicarbonamide, a rubbery substance used in shoe bottoms, yoga mats and the McRib sandwich. This chemical is banned in every country except the United States and Canada. This is no surprise because the United States is notorious for allowing the use of chemicals that other countries have banned. This chemical is so bad that when a truck crashed dumping the chemical on a Chicago highway in 2001, everyone within a half mile radius had to be evacuated! Subway said that it is removing the chemical from the bread but they have not released a date. If they will put this chemical in their food, think of what else may be in there.