Spatial Variation of Heavy Metals Content in Bitter Leaf (Vernonia amygdalina) in Port Harcourt and Human Health Risk Assessment

Abstract

Bitter leaf (Vernonia amygdalina) is a vegetable widely consumed in most tropical African countries including Nigeria. This plant possesses phytochemical compounds known to be biologically active, hence termed a medicinal plant. Depending on the quality of soil where it is cultivated, it has the capacity to accumulate varying quantities of heavy metals. This study evaluated the heavy metal content of leaves of Bitter leaf harvested from four locations in Port Harcourt, Rivers State Nigeria, as well as their carcinogenic risk. Dry weights of samples were wet digested and heavy metal content determined by method of AAS. Using the required formulae, the estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI), and total cancer risk (TCR) values were derived. Data was analyzed using GraphPad Prism version 9.02 and P values of ≤0.05 were considered significantly different. Results show Lead content (in mg/kg) for Eagle Island as: 17.4±2.0; Choba as:11.1±0.05; Mgbuoshimini as:15.5±1.5 and Diobu as: 13.4±2. For Mercury (in mg/kg), Eagle Island as: 0.03±0.1; Choba as: 0.01±0.001; Mgbuoshimini as: 0.87±0.03 and Diobu as: 0.06±0.04. Arsenic contents (in mg/kg) are as follows: Eagle Island 9.99±1.2; Choba: 3.2±0.1; Mgbuoshimini: 7.5±1.2 and Diobu: 5.8±0.2. while Cadmium contents (in mg/kg) are as follows: Eagle Island: 6.5±1.5; Choba: 1.12±0.1; Mgbuoshimini: 4.7±0.5 and Diobu: 2.8±0.6. The results obtained for the non-carcinogenic and carcinogenic risks indicated that the locations investigated were relatively unsuitable for growing vegetables like Bitter leaf in view of the health risks associated with ingesting the contaminated Bitter leaf. It is therefore recommended that industrial activities and other common sources of environmental pollution in the four locations studied be thoroughly controlled/monitored in order to reduce pollution levels.