Determination of Heavy Metal Levels of some Cereals and Vegetables sold in Eke-Awka Market Awka, Anambra State, Nigeria

Abstract

A field survey was conducted to investigate heavy metals present in three vegetables (cucumber, cabbage and carrot) and three cereals (rice, maize and millet) from Eke Awka market, Awka, Anambra State, Nigeria and also evaluate possible health risks to local population through food chain transfer. Atomic Absorption Spectrophotometer (AAS) was used to estimate the levels of Cadmium (Cd), Lead (Pb), Cobalt (Co), Chromium (Cr), Nickel (Ni) and Iron (Fe) in the vegetables and cereals. The levels of the metals obtained in mgkg^-1 were as follows: Cucumber: Pb (0.126), Cd (0.084), Cr (0.032), Ni (0.080), Co(0.016) and Fe (0.985). Cabbage: Pb (0), Cd (0.140), Cr (0.144), Ni (0.142), Co (0.032) and Fe (0.360). Carrot: Pb (0.026), Cd (0.004), Cr (0.024), Ni (0.248), Co (0.188) and Fe (0.445). Maize: Pb (0.100), Cd (0.022), Cr (0.012), Ni (0.192), Co (0.046) and Fe (0.590). Local rice: Pb (0.082), Cd (0.020), Cr (0.014), Ni (0.202), Co (0.042) and Fe (0.405). Imported rice: Pb (0.012), Cd (0.006), Cr (0), Ni (0.042), Co (0.008) and Fe (0.365). Millet: Pb (0.080), Cd (0.028), Cr (0.038), Ni (0.038), Co (0.022) and Fe (0.320). The estimated daily oral intake of the metals (DIM) for the vegetables and cereals were analyzed. Pb was in all samples except cabbage and carrot; Cd was in all samples except carrot; Ni was in all samples except cucumber; and Co was in carrot, local rice and millet were all higher than their corresponding reference dosage (RfD₀). Hazard quotient (HQ) and hazard index (HI) were all less than one except for local rice. These results showed that in all, only local rice posed heavy metal health risks in a long term. Balanced diet and continual monitoring of food crops were recommended to help check heavy metal intake.

Keywords: Vegetables, Cereals, Heavy Metals, Ingestion, Potentially toxic element, Daily Intake, Hazard Quotient, Hazard Index