Single and mixtures toxicity of emerging (polystyrene nanoplastic) and persistent (PAHs and PCBs) pollutants and their sub-lethal adverse effects on larval stage zebrafish (Danio rerio)

Persistent organic pollutants (POPs) such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), with emerging contaminants such as nano-microplastics, continue to raise concerns for both wildlife and human health. This study evaluated the sub-lethal effects of environmentally relevant concentrations of single and mixtures of PAHs, PCBs, in co-exposure with polystyrene (PS) nanoplastics during the early life stages of zebrafish (Danio rerio). Larvae (n = 25/treatment) were exposed from 2 to 5 days post-fertilization (dpf) in semi-static renewal conditions in temperature (28 ± 1 °C) controlled aquaria. Mixtures of PAHs and PCBs triggered in vivo cytochrome P450 (CYP450) biotransformation activity, which aligned with increases in mass-specific metabolic (oxygen consumption) rate (MO₂). This elevation in MO₂ suggests a heightened requirement for molecular oxygen, likely supporting CYP450-mediated mono‑oxygenation pathways. Exposure to PS nanoplastics alone (0.1 μm beads at 10 μg/L) did not significantly alter any measured endpoints. In contrast, co-exposure of PS nanoplastics with either phenanthrene (PHE) or PCB 81 produced 70% and 57% increases in MO₂, respectively. Significant reductions in cardiac blood flow were detected in larvae exposed to PCB 18 + PS, PCB 81 + PS, and PCB 105 + PS, indicating that PCBs co-exposure with PS were the primary contributors to the observed cardiovascular impairments rather than PS nanoplastics alone. Collectively, these results emphasize the value of studying multivariate sub-lethal effects of persistent contaminants (PAHs, PCBs) and emerging pollutants such as nanoplastics in various environmentally relevant concentration mixtures to understand contaminant toxicity.