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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)
Summary
Scientists exposed baby zebrafish to common pollutants—like those from car exhaust and old industrial chemicals—both alone and combined with tiny plastic particles (nanoplastics) to see how they affect developing bodies. While nanoplastics alone caused no harm, combining them with these pollutants made things worse: fish had to work harder to process toxins and showed reduced blood flow to the heart. This suggests that in the real world, where we're exposed to plastic pollution alongside other chemicals at the same time, the combined effects on health could be more serious than looking at any single pollutant alone.
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.