Archives of Razi Institute, Vol. 76, No. 5 (2021) 1501-1508 Copyright © 2021 by Razi Vaccine & Serum Research Institute DOI: 10.22092/ari.2021.355622.1705 1. Introduction The development of new materials and technology has resulted in pollution of the air, land, and water as human civilization has progressed. At levels of milligrams or micrograms per kg of environmentally hazardous compounds, natural or man-made compounds, as biological unities, harm plants, animals, and humans (1). Metal melting, mine drainage, other anthropogenic activities and industrial processes, as well as natural ones, such as volcanic eruptions, forest fires, sea-salt sprays, rock erosion, and borne soil particles, distribute inorganic contaminants throughout the environment (2). Heavy metals are among the most dangerous inorganic contaminants due to their toxicity to both terrestrial and aquatic life. Animals require metals, such as Cadmium (Cd), Cobalt (Co), Manganese (Mn), and Zink (Zn), which are involved in cellular metabolism, antioxidant, anti- inflammatory defenses, gene expression, and protein synthesis (3, 4). Heavy metal concentrations in the environment are too excessive and become dangerous to animals and plants. The Cd and Lead (Pb) are primarily stored in the kidneys and liver, although they can be found in high concentrations in the digestive system and spleen (5). Heavy metals are difficult to degrade and continue their presence in the environment Original Article Histopathological Study of Liver and Kidney Tissues in C57 Mice via Chronic Exposure to Cadmium and Zinc Gattea Al-Rikabi, Z 1 , Abbas, A. H 1* , Kadhum Oudah, H 1 , Sajer Nassir, H 1 , Ali, S. A 1 1. Ministry of Sciences and Technology, Environment and Water Directorate, Baghdad, Iraq Received 2 August 2021; Accepted 30 August 2021 Corresponding Author: adn927an@gmail.com Abstract Heavy metals have a wide application in the industrial world, affecting the health and longevity of living organisms. The current study assessed the possible effects of Cadmium (Cd) and Zinc (Zn) on the liver and kidney. Therefore, 150 male and female white mice C57BL were treated in three different groups with 0.685 mg/L CdCl2. 2.5H2O (group 1), and 0.567 mg/L ZnSO4.7H2O (group 2) in drinking water, while the control group only received water for 90 days to investigate how these elements accumulated in the liver/kidney and evaluate the possible histological changes in the liver and kidney. During 90 days, the histopathological consequences of Cd and Zn on the liver and kidneys were recorded. The results pointed out that exposure to heavy metals, such as Cd and Zn, led to organ accumulation of these elements. The histological evaluations demonstrated significant detrimental effects on the liver and kidney. Under the influence of Cd, light microscopic examination revealed significant histological alterations in both organs. In the animals exposed to Cd and Zn, histopathological alterations were observed in the liver, including extensive degeneration, necrosis, depletion, and necrosis of hepatocytes with significant nuclear hypertrophy. When animals are exposed to Cd and Zn, histological alterations in the kidneys include severe vascular degeneration and renal tubule necrosis. In conclusion, heavy metal intoxication has been shown to cause histopathological changes in the liver and kidneys of experimental animal models. Keywords: Heavy metal, Accumulation, Liver, Kidney, Histopathology