Ecotoxicological assessment of pesticide mixtures: effects of imidacloprid and propiconazole on Danio rerio and Astyanax lacustris

Despite global efforts to promote sustainable agriculture, the increasing use of pesticides remains a critical concern, particularly in local ecosystems with limited environmental monitoring. This study aimed to evaluate the toxicological effects of the insecticide @Provado (imidacloprid) and the fungicide @Tilt (propiconazole) on two freshwater fish species, Danio rerio (zebrafish) and Astyanax lacustris (lambari). Standard ecotoxicological parameters (EC₅₀, LC₅₀, EC₁₀, NOEC, and LOEC) were determined for each pesticide individually and in combination to assess toxicity and potential additive, synergistic, or antagonistic interactions. Sublethal exposures were conducted to evaluate morphological alterations in D. rerio larvae and biochemical responses in adult A. lacustris, focusing on oxidative stress biomarkers (glutathione-S-transferase-GST, catalase-CAT, malondialdehyde-MDA) in gill and liver tissues. For A. lacustris, LC₅₀ values were 1.1 mg L⁻¹ for Tilt and 5.49 mg L⁻¹ for Provado, with the mixture exhibiting LC₅₀ of 0.35 + 13.7 mg L⁻¹. For D. rerio, the EC₅₀ for Tilt was 1.62 mg L⁻¹ and the EC₁₀ was 0.32 mg L⁻¹. Acute exposure resulted in reduced larval survival and malformations, including yolk sac and pericardial edema. GST activity significantly decreased in gills following exposure to Tilt (6.0 µg L⁻¹) and Provado (1 mg L⁻¹), whereas liver GST activity increased under Tilt exposure. These results demonstrate the significant toxic impacts of these pesticides, emphasizing environmental risks and the complexity of their interactions in aquatic ecosystems, especially where regulatory control is insufficient.