Toxicity of nanoencapsulated bifenthrin to rainbow trout (Oncorhynchus mykiss)

Abstract

Bifenthrin is an effective pyrethroid pesticide with known detrimental effects on aquatic biota, despite its relative insolubility in water. In this study, we examine the potential mitigation of the toxic effects associated with bifenthrin by using its nanoencapsulated form (nano-bifenthrin). The production of nanoscale materials results in physicochemical properties that vary from those of the conventional form, namely because of the surface area to volume ratio. Therefore, we hypothesized that the nano-bifenthrin would have different physiological effects on and subsequent toxicity to juvenile rainbow trout (Oncorhynchus mykiss). We determined the 96 h LC₅₀ (lethal concentration where 50% mortality occurs) values for conventional bifenthrin (6.2 μg L⁻¹; 95% C.I. (confidence intervals) 4.3–8.1 μg L⁻¹), which were significantly different than the LC₅₀ values for nano-bifenthrin (11.2 μg L⁻¹; 95% C.I. 9.1–13.4 μg L⁻¹). Further examination of xenobiotic transformation was quantified by the EROD assay (a measure of cytochrome P450 induction), with 2–3 fold increases in all treatments compared to the control after 48 and 96 hour (h) exposures. Finally, measurements of gill Na⁺/K⁺ ATPase displayed 2 fold increases in the conventional pesticide treatment only with respect to the control only after 96 hours, while H⁺ type ATPase activity demonstrated significant increases from 1.2 μmol ADP per mg protein in controls to 2.7 μmol ADP per mg protein in conventional bifenthrin treatment only at 96 h. Taken together, these results provide the first evidence that mitigation of bifenthrin toxicity may occur using nano-enabled formulations and may provide a safer alternative for large scale agricultural applications.