Assessment of Heavy Metals Level in Soil and Vegetables Grown in Peri-Urban Farms around Osun State and the Associated Human Health Risk

Farming around urban centres (peri-urban farming) is a major source of fresh crop produce, notably vegetables. However, the limitation of land resources and the associated high level of soil contamination from domestic and industrial pollutants are major concerns for the safety of food materials from peri-urban farms. Thus, this study investigated heavy metals (As, Cd, Cu, Pb and Zn) concentration in soil and vegetable samples (Amaranthus hybridus and Corchorus olitorius) collected from selected peri-urban farms with a view to providing information on the human health risks associated with consumption of peri-urban vegetables.This study showed that the concentration of investigated heavy metals in the soils of peri-urban farms were within the background range for farming set by FAO/WHO (2002) and EU (2006) while appreciable level of these metals were observed in vegetable samples. Arsenic concentration was below detection limit in all samples. Amaranthus showed higher retention capacity for the assayed heavy metals except Cu. Transfer Factor values showed metal uptake by vegetables in the order Cd > Zn > Pb > Cu. The estimated daily intake showed that the highest consumption of Cd, Cu, Pb and Zn were from Amaranthus. The Health risk index showed high values for Cd and Pb but low values for Cu and Zn for both Amaranthus and Corchorus. The results obtained in this study regarding the hazard index indicate that vegetables grown in selected peri-urban farms are not safe for consumption.