Individual and mixture effects of five agricultural pesticides on zebrafish (Danio rerio) larvae

Abstract

In the present study, we evaluated the individual and mixture toxicities of imidacloprid and other four pesticides (atrazine, chlorpyrifos, butachlor, and λ-cyhalothrin) to the zebrafish (Danio rerio) larvae in order to clarify the interactive effects of pesticides on aquatic organisms. Results from the 96-h semi-static toxicity test indicated that chlorpyrifos, λ-cyhalothrin, and butachlor had the highest toxicities to D. rerio with an LC₅₀ value ranging from 0.28 (0.13∼0.38) to 0.45 (0.31∼0.59) mg AI L^-1, followed by atrazine with an LC₅₀ value of 15.63 (10.71∼25.76) mg AI L^-1, while imidacloprid exhibited the least toxicity to the organisms with an LC₅₀ value of 143.7 (99.98∼221.6) mg AI L^-1. Seven pesticide mixtures (two binary mixtures of imidacloprid + atrazine and imidacloprid + λ-cyhalothrin, two ternary mixtures of imidacloprid + atrazine + λ-cyhalothrin and imidacloprid + butachlor + λ-cyhalothrin, two quaternary mixtures of imidacloprid + atrazine + chlorpyrifos + λ-cyhalothrin and imidacloprid + chlorpyrifos + butachlor + λ-cyhalothrin, and one quinquenary mixture of imidacloprid + atrazine + chlorpyrifos + butachlor + λ-cyhalothrin) exhibited synergistic effects with equitoxic ratio and equivalent concentration on the zebrafish. Our results highlighted that the simultaneous presence of several pesticides in the aquatic environment might lead to increased toxicity, causing serious damage to the aquatic ecosystems compared with their individual toxicities. Therefore, the toxic effects of both individual pesticides and their mixtures should be incorporated into the environmental risk evaluation of pesticides.

Keywords: Aquatic organism; Ecotoxicology; Imidacloprid; Mixture toxicity.