This antioxidant — butylated hydroxyanisole (320) — is typically found in margarine and spreads, salad dressings, walnuts and pecans, and instant mashed potato.
It’s listed as "possibly carcinogenic to humans" by WHO’s International Agency for Research on Cancer, and some studies have demonstrated that it causes cancer in rats, mice and hamsters.
But these cancers are controversial because they occur in the forestomach, an organ that humans don’t have.
While it’s considered safe at the low level of use permitted, BHA can be replaced in foods by safer chemicals (such as vitamin E), safer processes or simply left out. Check labels if you want to avoid it.