Heavy Metal Contamination of Selected Vegetables from Crude Oil and Non Crude Oil-Producing States in Nigeria: A Comparative Study

Abstract

The aim of this study was to investigate and compare the heavy metal (HM) concentrations of selected vegetables harvested from crude oil-producing Rivers State and non-oil-producing Enugu State in Nigeria. Four vegetables;Telfaria occidentialis, Talinum triangulare, Ocimium gratissimum, and Murraya koenigii,were obtained from local farms in local government areas (LGAs) selected, each from the 3 senatorial zones in each state.The chemical analysis in mg/100g of the heavy metals (HMs) was conducted using standard methods. There mean values varied in the order: lead (Pb) > cadmium (Cd) > mercury (Hg) in mg/100g. Vegetable samples harvested from Rivers State had the highest toxicity level for both Pb (0.19 to 0.34) and Hg (0.01 to 0.03), while samples harvested from Enugu State had the highest toxicity level for Cd (0.07 to 0.25). The mean Pb contents forOcimium gratissimum(0.27) andTalinum triangulare(0.26), harvested from Rivers States were significantly (p < 0.05) higher than their counterparts harvested from Enugu State (0.19 and 0.21, respectively). Mercury had the least mean value than Pb and Cd in all the locations. All the vegetables from all the localities in this study had toxic levels of HM much above the FAO/WHO acceptable limits; 0.03 mg/100g for Pb, and 0.02 mg/100g for Cd in foods and 0.0001 mg/100g for Hg in mineral water. It can therefore be said that the public health importance for increased consumption of fruits and vegetables may equally mean increased HM consumption and bioaccumulation for the population in Rivers and Enugu States.