Heavy Metals Contamination and Potential Human Health Risk via Consumption of Vegetables from Selected Communities in ONELGA, Rivers State, Nigeria

Background: Anthropogenic activities such as excessive oil exploration, automobile emissions with agricultural activities, etc tend to elevate the concentrations of heavy metals in the soil. These metals are accumulated by plant roots, thereby resulting to heavy metal contamination of such plants.

Objectives: This study evaluated the concentration of heavy metals namely: Lead (Pb), Cadmium (Cd), Nickel (Ni), Arsenic (As), Iron (Fe), and Copper (Cu) in edible vegetables from selected communities in Ogba/Egbema/Ndoni Local Government Area (ONELGA), Rivers State, Nigeria, and the concentrations of these metals were used to assess the human health risk posed to the consumers of the edible vegetables.

Materials and Methods: Sixteen different vegetable samples comprising Vernonia amygdalina, Talinum triangulare, Abelmoschus esculentus and Telfairia occidentalis were digested and analyzed for heavy metals using Flame Atomic Absorption Spectrophotometer (F-AAS). Results obtained from this study were used to estimate the human health risk of these heavy metals.

Results: The results showed that the concentrations of Pb, Cd, Ni, As, Fe, and Cu ranged from 0.168-4.908; 0.364-2.977; 2.780-10.241; 0.157-2.633; 61.589-101.520 and 12.029-46.540 mg/kg, respectively. The concentrations of Pb, Cd, Ni and As in some of the analyzed vegetable samples exceeded the permissible limit as recommended by WHO/FAO, EC/CODEX and NAFDAC respectively. The concentration of Fe and Cu were below the permissible limit as recommended by WHO/FAO. The Estimated Daily Intake (EDI) of Pb and Cd exceeded the permissible tolerable daily intake of metals (TDI) but fall within the upper tolerable daily intake (UTDI) recommended by Institute of medicine, FDA, also Ni, Fe, and Cu fall within the recommended TDI and the UTDI. The EDI values of As exceeded the recommended TDI and the UTDI. The Target Hazard Quotient (THQ) and Hazard Index (HI) values of Pb, Cd, Cu and Ni were greater than 1. The Life Cancer Risk (LCR) of Pb were within the range of permissible predicted lifetime risks for carcinogens as recommended by US EPA.

Conclusion: The result from the present study indicate that the exposed population may be at risk of Pb, Cd, Ni and Cu toxicity.