I used to work in kitchens. I guarantee it's from the gloves they make you wear. It was more prevalent in meats like chicken because they make you wear gloves more when you're handling the meat. Fat from the meat makes the gloves stiff. The chemical they're talking about is the chemical that makes the plastic in the gloves pliable. So the fats you're working with are probably leaching the chemicals out of the gloves into the food. I don't think Mcdonalds is intentionally putting toxic chemicals in your food. I don't think there's some guy at the Mcdonalds commissary walking around dropping vials of poison into the meat. This is more easily explained by ignorance than malice.