Effect of Polystyrene Microplastic Exposure on Blood Parameters in Mice

Microplastics are emerging environmental contaminants capable of crossing epithelial barriers and circulating systemically, potentially affecting organisms, including humans. This study investigated the hematological and biochemical effects of sub-chronic oral exposure to polystyrene microplastics (PS-MPs) in male Swiss albino mice. Animals received 1 μm PS-MPs in drinking water at 0.01 mg/day for four weeks, followed by a two-week recovery period. Blood samples were collected weekly for hematological and biochemical analysis. PS-MP exposure resulted in an increased number of certain immunocytes after the first week of treatment. The highest values compared with the control group were observed in Week 2, reaching 18.5 ± 4.61 vs. 7.2 ± 1.14; 10.9 ± 2.58 vs. 5.1 ± 1.20; and 5.8 ± 2.35 vs. 2.2 ± 0.69 × 109 cells/L for white blood cells, lymphocytes, and granulocytes, respectively (p < 0.001). A significant increase in platelet count was also observed, becoming evident by Week 6 (725.8 ± 307.96 vs. 470.1 ± 121.87 × 109 cells/L, p < 0.05). The elevated alanine aminotransferase and aspartate aminotransferase activities observed after PS-MP exposure were potentially associated with hepatic pathology, erythrocyte damage, and inflammatory responses. No significant recovery was observed during the period after exposure. These findings demonstrate that sub-chronic oral PS-MP exposure induces inflammatory responses and may disrupt organ function.