Investigating the Release and Toxicity of Microplastics/Nanoplastics From Single-Use Plastic Bags to Zebrafish

The environmental degradation of single-use polyethylene (PE) bags poses a growing concern due to the release of microplastics (MPs) and nanoplastics (NPs). This study investigated the fragmentation behaviour of PE bags under simulated environmental conditions (mechanical shear stress, temperature, pH, and ultraviolet [UV] exposure) and evaluated the toxicity of resulting particles using zebrafish (Danio rerio) embryos. Shear stress alone caused up to 30.76% polymer deterioration and released approximately 4.7 × 10³ particles per microliter. The ideal fragmentation occurred at pH 6.5, 50°C, and 1-h UV exposure, whereas minimal release was also observed at pH 6.5, 30°C, and 15-h UV exposure. The MP/NP characterization revealed that MPs/NPs from PE bags were morphologically heterogeneous and chemically distinct from pure PE MPs/NPs, containing additives such as Si, Al, and Ti. Zebrafish exposure studies demonstrated dose-dependent developmental toxicity, including pericardial oedema, spinal curvature, delayed hatching, and mortality up to 93% at the highest particle concentration. Compared to pure PE MPs/NPs, MPs/NPs released from PE bags showed higher toxicity, likely due to chemical degradation products. Hatching rates also declined significantly with increasing particle concentrations. The total ratio of normal zebrafish declined intensely from 60% at the lowest concentration to only 10% at the highest exposure level, confirming a strong concentration-dependent toxic effect. This reduction in healthy larvae, with increase in malformations and mortality, shows the developmental toxicity induced by MPs/NPs. These findings highlight the critical environmental and biological risks of plastic pollution from disposable PE bags and emphasize the need for stricter waste management and regulatory oversight.