Aquaculture Research. 2020;00:1–8. wileyonlinelibrary.com/journal/are | 1 © 2020 John Wiley & Sons Ltd 1 | INTRODUCTION Butyl hydroxytoluene (BHT) chemically referred to as 2,6-di-tert-bu- tyl-p-cresol or 2,6-di-tert-butyl-1-4 methyl phenol is one of the most extensively used synthetic phenolic antioxidant in foods, mainly con- taining fats and oils, packaging materials and cosmetics by arresting the chain reaction in the oxidation of other molecules which results in increasing shelf-life of the products (Lanigan & Yamarik, 2002; Parke & Lewis, 1992; Yang et al., 2018). Among various synthetic phenolic antioxidant, butylated hydroxytoluene (BHT) is most commonly used in foodstuff with maximum allowable addition amount of 200 mg/Kg in food, beverages or oil products regulated by the U.S. Food and Drug Administration (FDA), the European Union (EU) and CODEX STANDARD (Freitas & Fatibello-Filho, 2010; Yang et al., 2018; Zhou, Li, Lv, Hu, & Jia, 2015). However, the compound is carried over from feed to farmed fish (Bohne, Lundebye, & Hamre, 2008). BHT is cur- rently authorized in feed for all animal species with a maximum con- centration of 150 mg/kg feed, alone or in combination with another authorized synthetic antioxidant (Lundebye, Hove, Måge, Bohne, & Hamre, 2010). Earlier studies suggested that BHT could exert endo- crine-disrupting effects, including weak estrogenic activity, the Received: 23 January 2020 | Revised: 18 May 2020 | Accepted: 20 May 2020 DOI: 10.1111/are.14732 ORIGINAL ARTICLE Toxicity of a synthetic phenolic antioxidant, butyl hydroxytoluene (BHT), in vertebrate model zebrafish embryo (Danio rerio ) Raktim Sarmah 1 | Sarada Kanta Bhagabati 1 | Rajdeep Dutta 1 | Dipanka Nath 1 | Hemanta Pokhrel 1 | Lawonu P. Mudoi 1 | Nishi Sarmah 1 | Jiten Sarma 2 | Abdul M. Ahmed 1 | Rupam Jyoti Nath 1 | Lucy Ingtipi 3 | Kedolhouse Kuotsu 1 1 Department of Aquatic Environment Management, College of Fisheries, Assam Agricultural University, Nagaon, India 2 Department of Fisheries Resource Management, College of Fisheries, Assam Agricultural University, Nagaon, India 3 Department of Aquaculture, College of Fisheries, Assam Agricultural University, Nagaon, India Correspondence Raktim Sarmah, Department of Aquatic Environment Management, College of Fisheries, Assam Agricultural University. Email: rx93@mail.com Abstract The synthetic antioxidant 3,5-di-tert-butyl-4-hydroxytoluene (BHT) is widely used as an additive in the food, cosmetic and plastic industries to increase the tenability of food and plastic for the past 70 years. BHT is degraded to 3,5-di-test -butyl-4-hydroxy- benzaldehyde (BHT-CHO) in mammals, as well as in the natural environment such as in river and water. The average daily intake of BHT for human being is estimated to be 0.3 mg/kg body weight. Even though it is considered safe for human at authorized level, but its ubiquitous presence in the aquatic environment and the controversial toxicological data are of great concern for human as well as aquatic life. The experi- mental findings of zebrafish embryo toxicity test (ZFET) showed that the acute toxicity of 96-hr (LC 50 ) exposure during the embryogenic stage was found to be 4.388 mg/L and the effective concentration (EC 50 ) was 1.375 mg/L. The reduce heart rate from the sublethal concentrations indicates the chemical to be cardiotoxic but a further review is to be needed. The Teratogenic Index (TI) calculated to be 3.19, which implies the compound may be a potential teratogen in aquatic life. The findings obtained in this study will stretch more evidence regarding developmental toxicity of BHT, which will be of much importance in further risk assessment of ecotoxicological studies. KEYWORDS BHT, embryotoxicity, teratogenicity, zebrafish