Toxicology of synthetic antioxidants EQ, BHA, BHT and their metabolites retained in the fillet of farmed Atlantic salmon.

Synthetic antioxidants are used as preservatives in fish feed and fish feed ingredients to prevent the auto-oxidation of unsaturated lipids. The market demand for more oily fish flesh has lead to an increased lipid content in fish feed in Norway during la st 30 years, which has consequently resulted in the increased use of antioxidants. The recently finished SYNTOX project funded by NFR and performed by the authors, generated information regarding the pharmacokinetics of dietary EQ and BHT uptake from fish feed into salmon. To our knowledge no similar studies have been performed on BHA. The results of the SYNTOX project exhibited marginal differences between the dispositions of EQ and BHT, which differs from earlier published results. It was demonstrated t hat 16% of dietary EQ could be retained in fillet in the form of at least 14 metabolites. Moreover, our results have shown that under starvation conditions the parent EQ is not excreted from the fillet, as reported in an earlier study, but metabolised fur ther. This indicates that the fillet of commercial salmon likely retain the same metabolites as found in our previous study. The toxicity of these newly described metabolites is not known. Recently, Japanese authorities proposed a maximum residue limit (M RL) for antioxidants in fish. The proposed limit of 1 mg/kg is of no concern if only parent EQ is considered. However, the total EQ content may be considerably above the proposed MRL if the EQ metabolites are taken into account. The knowledge of the toxic ity of antioxidant metabolites retained in the fillet is of value for subsequent risk assessments which form the basis for legislation on antioxidants in fish feed and for establishing maximum levels in fish. All biological material required for the per formance of this project is already collected. The present work will examine the pharmaco-kinetics and -dynamics of metabolites in a mammalian to assess the potential effects on the health of salmon consumers.