Comparative toxicity of zinc oxide nanoparticles and zinc salts in male mice: Hematological, biochemical, and histopathological impacts

The aim of this study was to investigate the toxicity of zinc oxide nanoparticles (ZnO NPs) compared to different zinc salts (ZnSO₄, Zn(NO₃)₂, and ZnCl₂) in male mice. For this purpose, 45 male mice were divided into five groups of nine (one control group). Mice were exposed to ZnO NPs and various zinc salts for 28 days, while the control group remained unexposed. After the exposure period, the mice were euthanized, and hematological, biochemical, enzymatic, and histopathological changes were recorded. Most hematological (RBC, WBC, Hb, Ht counts), biochemical (cholesterol, triglyceride, glucose, total protein, and albumin), and enzymatic parameters alkaline phosphatase (ALP), aspartate transaminase (AST), alanine aminotransferase (ALT) were significantly different in exposed mice compared to the control group (p < 0.05). The number of erythrocytes in mice exposed to ZnCl₂ for 28 days (7.84 ± 1.41 × 10⁶ mm³) was significantly lower than in the control group (10.11 ± 1.14 ×10⁶ mm³) (p < 0.05). Additionally, mice exposed to ZnCl₂ had significantly lower white blood cell (WBC) counts, hemoglobin (Hb), and hematocrit (Ht) levels than the control group (p < 0.05). Zn-exposed mice developed deformed erythrocytes, including dacrocytes, keratocytes, and ovalocytes, likely due to cytogenetically damaged RBC precursors. ZnO NPs and its various salts caused degeneration in hepatocytes, thickening and inflammatory cell infiltration in the renal capsule, congestion in the blood vessels of the lungs, and swelling of goblet cells in the intestine. Adding to the wealth of literature on the toxicity of ZnO NPs and zinc salts, especially ZnCl₂, our study highlights the ecotoxicity of these compounds in mice. Effective and timely measures should be taken to reduce the use of ZnO NPs and its various salts worldwide.