What are the toxicological effects of mixing nanoplastics with a nanopesticide on Daphnia magna and Aliivibrio fischeri?

Nanotechnology has enhanced the efficiency of pesticides such as nanoatrazine (nATZ), but it also raises concerns regarding potential toxicity to non-target organisms, particularly in aquatic environments already threatened by increasing nanoplastic pollution. This study assessed the individual and combined effects of nATZ and polystyrene nanoplastics (PSNP) on the freshwater microcrustacean Daphnia magna and the marine bacterium Aliivibrio fischeri. Acute tests with D. magna evaluated lethality and interactions in mixture scenarios. Chronic exposure over 21 days examined lethality, reproduction, growth, and swimming behavior. For acute and chronic exposures, reactive oxygen species (ROS) and the activity of antioxidant enzymes, including superoxide dismutase (SOD), glutathione S-transferase (GST), and glutathione peroxidase (GPx), were evaluated. Tests with A. fischeri measured changes in bacterial bioluminescence in response to contamination. Acute toxicity tests with D. magna indicated lowest observed effect concentration (LOEC) values of 4 mg l for nATZ, 130.7 mg l for PSNP, and 1.15 + 65.4 mg l for the mixture, with predominantly synergistic responses under the Abbott reference model. Chronic exposure led to growth inhibition in D. magna at concentrations as low as 0.0228 mg l for nATZ and 0.98 mg l for PSNP, with reproductive effects appearing at even lower concentrations. Both contaminants increased ROS production, and their combination further amplified this response. GST activity increased, whereas SOD and GPx remained at basal levels. For A. fischeri, the toxicity of the nATZ + PSNP mixture (EC= 0.53 + 37.79 mg l) resembled that of PSNP alone (EC= 34.10 mg l), suggesting a dominant PSNP effect. These findings highlight the complexity of interactions between emerging contaminants.