Comparative study of heavy metal content of Manihot esculenta tubers and soil in Rivers State, Nigeria: Effect on histology of kidney and liver of Wistar rats

There is a concern that Manihot esculenta Crantz (Euphorbiaceae) grown in Rivers State, Nigeria may be contaminated with heavy metals due to industrial activities with likely risk to human health. This study determined the heavy metal contents in the soil and tubers of M. esculenta and potential health risks in Wistar rats. Tubers harvested from different farms in Rumuji, Omoku and Gokhana areas of the state with their corresponding soil samples were combined and analyzed for heavy metals such as Pb, Cd, Hg, Cr, As and Ni. The control group rats received normal feed while test groups were fed with 30g of blended tubers from the locations respectively for 28 days. The liver and the kidneys were harvested for histopathological examination. Nickel, Pb, and Cr were present in the three locations while Cd and As were not found in Rumuji and Omoku but were present in Gokhana with a concentration of (0.01 ± 0.00 and 0.01±0.00 mg/kg) respectively. Bioconcentration factor was >1 for Pb and Cr in Rumuji. Liver histopathology showed fatty degeneration while the kidney tissues exhibited occluded Bowman’s capsule space. Heavy metals concentrations were within permissible limits although histological findings indicated some degree of hepatotoxicity and nephrotoxicity.