Heavy Metal Bioaccumulation, Systemic and Gastric Toxicopathology in Rattus norvegicus Exposed In situ to Municipal Solid Waste Landfill-Derived Contaminants

Landfill sites emit hazardous contaminants that pose significant health risks to exposed populations. This study evaluated metal accumulation, organ weight indices, gastric physiopathology, and tissue alterations in Wistar rats ( Rattus norvegicus ) exposed in situ at Olusosun landfill, Lagos, Nigeria. Male rats (n = 30/point) were exposed at three different points to ambient air and underground water (via drinking) at the landfill for 4-, 8-, 12-, 16-, 20- and 24-week periods. Control rats were housed 17.3 km away in a residential area. Early exposure induced clinical signs of toxicity and heavy metal analysis confirmed elevated lead (Pb), cadmium (Cd), and chromium (Cr) levels in blood and lungs. There was significant (p < 0.05) increases in absolute and relative liver, kidney, and lung weights, and strong positive correlations between exposure duration and absolute organ weights. Gastric indices showed increased absolute stomach weight but decreased relative weight at most exposure periods. There was significant increases in parietal cell (4, 8, and 24 weeks), gastric mucous cell (4 and 24 weeks), and mucus secretion (4 and 24 weeks). Gross and histopathological findings revealed liver cysts, tissue inflammations, cell hyperplasia, necrosis and fibrosis, and gastric mucosal lesions. The observed metal bioaccumulation in blood and lungs, organ hypertrophy and gastric toxicopathology suggest potential health risk of short- and long-term exposure to landfill-derived pollutants. These results underscore the need for stricter landfill management practices, particularly in urban centers, and support the incorporation of biological monitoring models in environmental safety assessments to inform public health interventions.