They are exempt because they have relatively powerful lobbies, I guess. I think it may come down to old BS about protecting corporate trade secrets and stuff.
If I ingest a little corn: 4 hours after consumption: I start to turn darker shades of pink; something akin to a sunburn in nature. I get a brutal headache, a little runny nose, blood pressure shoots up, a sour attitude, little bumps on my temples and arms, bizzare sweating, drier eyes, and muscles in my neck and back tend to tighten up.
day 2: Sore throat, dry lips, intense unquenchable thirst, lack of appetite, headache, muscles. water weight gain.
day 3: Strong appetite that can't be appeased, dry flaky skin and itching on elbows, arms, forehead, and scalp. Headache, muscles.
day 4 : things normalize and I start to shed the water weight gain. Left depressive and listless; sorta like the day after getting over the flu... a total loss of energy, apathy, headache.