Toxicological Assessment of Polypropylene Microplastics in Male Nile Tilapia (Oreochromis niloticus): Growth, Hematological, and Histopathological Insights

Polypropylene microplastics (PP-MPs) are widely distributed in aquatic environments and may harm fish through ingestion. Despite growing research on microplastic toxicity, very limited study prevails on the pernicious impacts of waterborne PP-MPs on Nile tilapia. Hence, this study aims to examine the impact of PP-MPs on the growth, hematobiochemical parameters, erythrocytes, and histopathology in male Nile tilapia (Oreochromis niloticus). Juvenile Nile tilapia was exposed to water-borne PP-MPs (0, 0.1, 1, and 10 mg/L) for 28 days in glass aquaria in a chronic semi-static exposure system. Specific growth rate (SGR) was calculated on the basis of established formulas, hematological and biochemical parameters, and histology were assessed using standard laboratory protocols; and subsequently histopathological slides were evaluated microscopically. Weight gain and SGR were reduced significantly, with the highest concentration (10 mg/L) showing the most noticeable decline. A marked decrease in red blood cell (RBC) count, hemoglobin (Hb) levels, and packed cell volume (PCV) was noted. Conversely, white blood cell (WBC) count and blood glucose levels significantly increased, indicating a physiological stress response. Nuclear abnormalities such as blebbed nuclei, karyopyknosis, micronuclei, notched nuclei, and nuclear bridges were observed, indicating potential genotoxic effects. Cellular abnormalities, including fusion, teardrop, twin cells, and spindle-shaped erythrocytes, were noted, reflecting structural deformities in cell morphology. Gill, liver, and intestinal histology exhibited clear deterioration in the highest exposure group (10 mg/L), especially at later sampling times. These findings highlight the detrimental impact of waterborne PP-MPs on fish health, emphasizing the urgent need for further research into their long-term ecological consequences.