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Response of Rattus norvegicus to Bitumen Leachate Toxicity

Ayandiran TA, Fawole OO, Dahunsi SO and Ogundiran MA

This study investigated the response of Rattus norvegicus to bitumen leachate to evaluate its toxicity in a terrestrial animal model following previous aquatic studies on the environmental impacts of Nigerian bitumen exploration. Adult rats were administered different concentrations (20 to 100%) of bitumen leachate for 30 days before analyses. Fourteen blood plasma clinical–chemical parameters (BCCPs), seven hematological parameters as well as histological changes in organs of exposed animals were studied. The analyses showed that all values for the BCCPs and the hematological parameters are significantly different (P<0.05) from the control values. Concentrations of liver enzymes, Alanine aminotransferase (ALAT), Gamma glutamyltransferase (GGT) and Alkaline phosphatase (ALKP) increased with increasing concentrations of bitumen leachate but were not dose-dependent. In the same vein, counts for Packed cell volume (PCV), White blood cell (WBC), Red blood cell (RBC) and hemoglobin (Hb) all decreased with increasing concentration of toxicants but was not so for differential counts (Neutrophils, Lymphocytes and Eosinophils). Results of histological study revealed several changes ranging from mild to severe lesions in organs of exposed rats. The very pronounced changes include irregularly arranged cardiac muscle fibres (Heart), pronounced inflammation (Spleen), hyperchronic nuclei and degenerated flattened squamous epithelial cells lining the Bowman’s capsule (Kidney), pronounced reduction of Graffian follicle (Ovary) and cellular hypertrophy with severe congestion of the central vein (Liver). Based on these results, important organ functions could be negatively affected by continuous exposure to bitumen leachate which reflects health effects having an overall impact on both animal and human populations.