Comparative study on the ecotoxicity of nanoformulated and conventional emamectin benzoate to Raphidocelis...

The potential risks of nanopesticides to aquatic ecosystems are still unclear. This study compares the toxicological effects and mechanisms of emamectin benzoate (EMB) in a nanoformulated microemulsion (ME, 3.02 nm) with conventional formulations, emulsifiable concentrate (EC, 2435 nm) and technical material (TC, 232 nm), on Raphidocelis subcapitata. The results demonstrated that the toxicity of ME was 0.0916 times that of EC and 1.68 times that of TC. At sublethal concentrations, ME did not significantly affect the photosynthetic pigment content, but scanning electron microscopy identified notable surface folding and damage on algal cells. ROS levels in ME-exposed algae were 1.29-1.93 times higher than in the control, with changes in the antioxidant enzyme activities. No significant differences were observed between the ME adjuvant group and the control, whereas EC toxicity was primarily attributed to its adjuvant. Metabolomics analysis demonstrated that ME, EC, and TC significantly affected 6, 11, and 10 metabolic pathways, respectively. EC and TC mainly affected the TCA cycle and amino acid metabolism, leading to widespread metabolic disruption. Whereas ME mainly disturbed CoA biosynthesis and carbon metabolism, suggesting a potential risk to R. subcapitata. These findings suggest that ME offers a lower ecological risk than conventional formulations and could be a more environmentally friendly alternative for pest control.