Synergistic impact of nanoplastics and nanopesticides on <i>Artemia salina</i> and toxicity analysis

Polystyrene nanoplastics (PSNPs) when exposed to nanopermethrin (NPER) exacerbate toxicity on <i>Artemia salina</i>. In the environment, NPs act as a vector for other pollutants mainly heavy metals and pesticides. Nanopesticides are efficient compared to their bulk form. The adsorption of NPER on PSNPs was studied systematically and it was found that the binding of NPER is inversely proportional to its concentration. NPER adsorption on PSNPs followed pseudo-first-order kinetics with an adsorption percentage of 1.7%, 3.7%, 7.7%, 15.4%, and 30.8% when PSNPs were incubated with 2 mg L^-1,4 mg L^-1, 8 mg L^-1, 16 mg L^-1, and 32 mg L^-1 of NPER. The adsorption followed the Langmuir isotherm. The increased hydrodynamic size of the NPER/PSNP complex was observed. Different characterization studies were performed for NPER, PSNPs, and their complex using Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray diffraction, and gas chromatography-mass spectrometry. The LC₅₀ value for the NPER/PSNP complex treated with <i>Artemia salina</i> was 3.127 mg L^-1, compared to LC₅₀ NPER which was found to be 4.536 mg L^-1. PSNPs had a lower mortality rate in <i>Artemia salina</i>, where 50% mortality (LC₅₀) was not observed at their working concentration. Both the nanoforms led to morphological changes in <i>Artemia salina</i>. Reactive oxygen species increased to 87.94% for the NPER/PSNP complex, 78.93% for NPER, and 23.65% for PSNPs. Greater amounts of ROS in the cells may have led to SOD degradation. Superoxide dismutase activity for the NPER/PSNP complex was 1.2 U mg^-1, NPER was 1.3 U mg^-1, and PSNPs was 2.1 U mg^-1. A lipid peroxidation study reveals that the melondialdehyde synthesis by NPER/PSNPs complex, NPER and PSNPs were found to be 2.21 nM mg^-1, 1.59 nM mg^-1, and 0.91 nM mg^-1 respectively. Catalase activity in a complex of NPER/PSNPs, NPER, and PSNPs was found to be 1.25 U mg^-1, 0.94 U mg^-1, and 0.49 U mg^-1. This study envisages the individual and combined toxicity of nanopesticides and PSNPs on aquatic organisms. Increased plastic usage and new-age chemicals for agriculture could result in the formation of a PSNPs-NPER complex potentially causing highly toxic effects on aquatic animals, compared to their pristine forms. Therefore, we should also consider the other side of nanotechnology in agriculture.