Heavy metal pollutants in selected organs of African giant rats from three agro-ecological zones of Nigeria: evidence for their role as an environmental specimen bank.

An assessment of the concentration of heavy metals in the liver, brain, kidney, bone, and lungs of African giant rats (AGRs) from three agro-ecological zones of Nigeria having different industrial activities was carried out using atomic absorption spectrophotometer. Twenty adult AGRs from cities in mangrove/freshwater swamp, rainforest, and woodland/tall grass savanna agro-ecological zones of Nigeria were used for this study. AGRs were euthanized, carefully dissected, and the brains, liver, lungs, bone, and kidneys were harvested, digested, and analyzed for concentrations of vanadium (V), lead (Pb), cadmium (Cd), zinc (Zn), selenium (Se), copper (Cu), and iron (Fe). All data generated were evaluated for statistical significance using one-way ANOVA with Tukey's multiple post-test comparison. Results showed the major environmental heavy metal pollutants of the mangrove/freshwater swamp to be vanadium and selenium while those of woodland/tall grass savanna agro-ecological zones were lead, selenium, and zinc. The vanadium concentration was more than twofold higher in the observed tissues of AGR from the mangrove/freshwater swamp, and this may be related to increased exploitation of minerals and the activities of militants in pipeline vandalization in this zone. Interestingly, the highest concentration of this metal was seen in the lungs suggestive of a respiratory route of exposure. Among the potential adverse effects derived from exposure to metals, developmental toxicity is a serious risk. This type of investigation can assist in knowing the level of animal and human exposure to environmental pollutants both in highly industrialized and non-industrialized areas and is more ideal in environmental monitoring. This study therefore suggests AGR as model for ecotoxicological research and environmental specimen banks (ESBs) in this part of Africa.