Acute toxic effects of polyurethane microplastics on adult Zebra fish (Danio rerio)

 Microplastics (MPs) have become an emerging environmental contaminant and there are increasing concerns about potentially toxic effects on living organisms. This study is aimed to determine uptake, tissue accumulation, and toxic effects of polyurethane microplastics (PUR-MPs) on zebra fish. 

 The zebra fish were exposed to different concentrations of PURs-MPs of different sizes for 10 days. Mortality and behavioral changes were monitored. Ingestion and tissue accumulation of PUR-MPs were studied by fluorescent tagging of PUR-MPs. Pathological damages of tissues were investigated with hematoxylin-eosin staining. 

 Microsize PUR-MPs can be ingested by zebra fish and fluorescent-tagged PUR-MPs were found in gills and gastrointestinal (GI) tract of fish after 10 days of exposure. A significant negative correlation was found between fluorescence intensity in fish tissues and size of PUR-MPs. Gills, GI tract, and liver were the most affected tissues by PUR-MP toxicity. GI damages included epithelial detachment, thinning of the bowel wall, congestive inflammation, epithelial damage, and lesions of villi in the gastric wall. Necrosis, adhesion, and partial fusion of secondary lamellae were the dominant pathological damages in the gills. Liver also was affected by cellular necrosis, infiltration, and lipid droplets. 

 Exposure of zebra fish to PUR-MPs leads to ingestion of these particles by fish and significant increase in fish mortality and tissue damages. Particle size and MP concentration were the key determinant factors in PUR-MP toxicity. The results of the present study provide novel insights into environmental toxicity of PUR-MPs and toxic effect of PUR-MPs in aquatic organisms.