Subacute toxic effects of polyvinyl chloride microplastics (PVC-MPs) in juvenile common carp, Cyprinus carpio (Pisces: Cyprinidae)

Pollution of the aquatic environment by microplastics (MPs) is one of the most serious environmental issues worldwide and has raised many concerns about their availability and hazards for aquatic biota. In addition, fish is an important source of protein for humans, hence, the accumulation, and toxic effects of the MPs in fish deserve special attention. This study aims to examine the ingestion, tissue accumulation and toxic effects of polyvinyl chloride microplastics (PVC-MPs) in juvenile common carp.  Fluorescent-tagged PVC-MPs were found in various tissues of fish only after 4-5 days of exposure. The size of MPs showed a significant role in acute toxicity and mortality due to PVC-MPs. 100% mortality were observed after 7 and 10 days exposures to 1000 and 100 µg L-1 class A-PVC-MPs (100>µm) respectively, while 1000 µg L-1 of class A-PVC-MPs (300-1000 µm) killed only 16.6% of fish after ten days. Different grades of tissue damage were found in the gills, gut, and liver of fish in proportion to size, time, and concentration of PVC-MPs. Epithelial detachment, thinning of the bowel wall, and lesions of villi in the gastric wall were the dominant damages in the gastrointestinal tract. Gills also were affected in the form of necrosis, adhesion, and partial fusion of secondary lamellae. Hepatic damages (cellular necrosis and infiltration) were found only due to exposure of fish to class A-PVC-MPs. Altogether, these findings suggest that common carp intake significant levels of environmental microplastics (intentionally or accidentally), which seriously affect fish health and raise significant concerns about marine ecosystem health and seafood safety due to microplastic pollution.