2. The transformation mechanism and eco-toxicity evaluation of butylated hydroxyanisole in environment
Yan Wang, Xiang Li, Xiaomin Sun Ecotoxicol Environ Saf. 2022 Feb;231:113179. doi: 10.1016/j.ecoenv.2022.113179. Epub 2022 Jan 10.
Butylated hydroxyanisole (BHA) is one of important phenolic antioxidants and its fate in the environment has attracted much attention in recent years. In this study, the initial reactions of BHA with OH radicals, including 8 abstraction reactions and 6 addition reactions, were calculated. The lowest energy barrier of 3.20 kcal mol-1 was found from the abstraction reaction on phenolic hydroxyl group. The reaction barriers of addition paths are in the range of 5.48-9.28 kcal mol-1, which are lower than those of the abstraction paths. The reaction rate constants were calculated by using transition state theory, and the rate constants are 8.12 × 107 M-1 s-1and 4.76 × 107 M-1 s-1 for the H-abstraction and OH-addition reactions, respectively. Through the calculation of the subsequent reactions of the abs-H0-TS1 and add-C4-M1 it was found that BHA would be further transformed into 2-tert-Butyl-1,4-benzoquinone (TBQ), tert-butylhydroquinone (TBHQ) etc. in the aqueous phase, and the eco-toxicities of these transformed products of BHA in the aqueous phase were significantly increased comparing with that of the BHA and they are toxic to aquatic organism.
3. Butylated hydroxyanisole: Carcinogenic food additive to be avoided or harmless antioxidant important to protect food supply?
Susan P Felter, Xiaoling Zhang, Chad Thompson Regul Toxicol Pharmacol. 2021 Apr;121:104887. doi: 10.1016/j.yrtph.2021.104887. Epub 2021 Feb 6.
Tumor data from rodent bioassays are used for cancer hazard classification with wide-ranging consequences. This paper presents a case study of the synthetic antioxidant butylated hydroxyanisole (BHA), which IARC classified as Group 2B ("possibly carcinogenic to humans") on the basis of forestomach tumors in rodents following chronic dietary exposure to high levels. IARC later determined that the mechanism by which BHA induces forestomach tumors is not relevant to humans; however, the classification has not been revoked. BHA was listed on California Proposition 65 as a direct consequence of the IARC classification, and there is widespread concern among consumers regarding the safety of BHA driven by the perception that it is a carcinogen. While many regulatory agencies have established safe exposure limits for BHA, the IARC classification and Proposition 65 listing resulted in the addition of BHA to lists of substances banned from children's products and products seeking credentials such as EPA's Safer Choice program, as well as mandatory product labeling. Classifications have consequences that many times pre-empt the ability to conduct an exposure-based risk-based assessment., It is imperative to consider human relevance of both the endpoint and exposure conditions as fundamental to hazard identification.
