Bioaccumulation Potential of 4‘‘-epi-(Methylamino)-4‘‘-deoxyavermectin B1a Benzoate (Emamectin Benzoate) in Bluegill Sunfish

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Rapid uptake of [5-3H]MAB1a by bluegill was observed under flow-through aqueous conditions, attaining steady-state concentration by about 21 and 10 days, respectively, in whole fish and viscera. Uptake by fillet was, by comparison, much lower, and steady state was not attained by 28 days. Residue levels on the final exposure day (i.e., day 28) were 90, 40, and 128 μg/kg, respectively, in whole fish, fillet, and viscera. Following 14 days of depuration, these residue levels all declined by about 90%. The steady-state bioconcentration factors for whole fish, fillet, and viscera were 80, 30, and 116, respectively, indicating that emamectin benzoate will neither bioconcentrate in individual aquatic organisms nor biomagnify in the food chain. Analysis of 28-day-exposed fish by HPLC showed that the only significant metabolite was the N-demethylated derivative, comprising about 14% and 9%, respectively, of total residues in fillet and viscera, while parent emamectin benzoate was about 63% and 49%, respectively.