Tert-Butylhydroquinone

The European Food Safety Authority (EFSA) and the United States Food and Drug Administration (FDA)^[4] have evaluated TBHQ and determined that it is safe to consume at the concentration allowed in foods.^[5] The FDA^[6] and European Union^[5] both set an upper limit of 0.02% (200mg/kg) of the oil or fat content in foods. It has not been approved in Japan, hence import of food containing TBHQ for selling is not allowed in Japan as of 2007.^[7]

At very high doses, it has some negative health effects on lab animals, such as producing precursors to stomach tumors and damage to DNA.^[8] A number of studies have shown that prolonged exposure to very high doses of TBHQ may be carcinogenic,^[9] especially for stomach tumors.^[10] Other studies, however, have shown opposite effects including inhibition against HCA-induced carcinogenesis (by depression of metabolic activation) for TBHQ and other phenolic antioxidants (TBHQ was one of several, and not the most potent)^[11] and reduction of nitrosamine-induced carcinogenesis (likely due to phase II enzyme induction via Nrf2).^[12] The EFSA considers TBHQ to be noncarcinogenic.^[5] A 1986 review of scientific literature concerning the toxicity of TBHQ determined that a wide margin of safety exists between the levels of intake by humans and the doses that produce adverse effects in animal studies.^[13]

In addition, TBHQ has been identified by high-throughput screening as having potential immunotoxic effects in 2021.^[14] It was previously reported in 2014 that TBHQ enhances allergy response in mice by promoting Th2 cells through Nrf2.^[15]

Experiments on its genotoxicity at high doses are inconsistent. Its oxidized form TBBQ may be responsible for some toxic effects. There exists a wide margin of safety between food-additive doses and doses used in studies.^[12]

There have been reports of vision disturbances in individuals exposed to this chemical.^[16]