Potassium benzoate

Benzene, a carcinogen, can form at very low (ppb) levels in some beverages that contain both benzoate salts (such as sodium or potassium benzoate) and ascorbic acid (vitamin C); heat and light can stimulate this. FDA found the vast majority of beverages had no detectable benzene or levels well below the 5 ppb limit, and the few products above 5 ppb were reformulated or discontinued.

When potassium benzoate is used alongside vitamin C in a drink, tiny amounts of benzene (a carcinogen) can form, especially with heat and light. The FDA found this is rare and that most beverages tested were well within safe limits, with the few exceptions reformulated.