Antioxidant: vegetable oil, snack foods, cereals, other fat-containing foods.
This preservative prevents rancidity. It is sometimes used along with similar preservatives, including BHA, BHT, and propyl gallate, with which it has a synergistic effect. (TBHQ is chemically related to BHA and forms when BHA is metabolized by the body.) One benefit of TBHQ over those other preservatives is that it does not cause discoloration in the presence of iron.
In a government study which used a better design than other similar studies, TBHQ increased the incidence of tumors in rats.