tert-Butylhydroquinone

What this is

TBHQ's safety picture is mixed but not a simple toxic-or-allowed split. JECFA established an ADI of 0-0.7 mg/kg body weight, and FDA, EU/Codex and Canada allow TBHQ only under use limits, mainly in fats, oils, or fat-containing categories. JECFA's intake review found best national mean-intake estimates at or below the ADI, while some high-consumer and maximum-use models exceeded it; those models often assumed all eligible foods contained TBHQ at maximum legal levels, which may overestimate real exposure. Long-term NTP feed studies found no evidence of carcinogenic activity in rats or mice, although in vitro chromosome assays produced some positive results. The strongest current policy signal is Japan: Japan's Food Sanitation Act bars undesignated additives from foods sold or imported for sale, and MHLW import-monitoring materials list TBHQ as an undesignated antioxidant additive. A 2025 U.S. federal bill also proposed FDA reassessment of priority food chemicals including TBHQ. The toxicology concern is Limited because concerns are mainly exposure-margin and high-dose animal-study signals, not a confirmed high-risk conclusion at permitted food-use levels. The High concern tier reflects Japan's broad not-permitted treatment rather than evidence that ordinary permitted-use exposure has been shown to cause harm.

Safety Review

The critical endpoints experts review in safety assessments. This is not a prediction of harm.

JECFA set an ADI of 0-0.7 mg/kg body weight for TBHQ, and intake reviews found mean estimates generally at or below the ADI while some high-consumer or maximum-use scenarios exceeded it. NTP long-term feed studies found no evidence of carcinogenic activity in rats or mice, but in vitro CHO chromosome assays were positive with metabolic activation, and high-dose animal studies reported litter, body-weight, estrous-cycle, and sperm-parameter effects. The High concern tier mainly reflects Japan treating TBHQ as an undesignated additive that cannot be used in foods sold or imported for sale, not evidence that ordinary permitted-use exposure has been shown to cause harm.