Determination of Heavy Metals in Green Leafy Vegetables along Roadsides by Lagos-Badagry Expressway in Lagos, Nigeria

Abstract

Heavy metals being natural components of the earth’s crust, cannot be degraded or destroyed. They are ubiquitous, so enter the human body through food, water and air, which in high concentrations in biological systems result in human diseases and disorders. Vegetable samples which included leaves of lettuce, spinach and pumpkin were collected from three wayside farms namely; Abule Ado, Abule Oshun and Oluti. A total of 36 samples were collected for the assessment of the heavy metal contents in the vegetables, which included lead (Pb), Zinc (Zn), Cadmium (Cd) and Chromium (Cr) using Flame Atomic Absorption Spectrophotometer (Buck Scientific 210 VGP model) in mg/kg. The average concentration of Pb, Zn, Cd and Cr in lettuce were 29.70, 25.85, 1.6 and 16.54 respectively. The mean concentration of Pb, Zn, Cd and Cr in spinach leaves were 28.84, 38. 43, 0.66 and 19.57 while the average concentration of Pb, Zn, Cd and Cr in pumpkin were 22.98, 38. 70, 0.70 and 29.70 mg/kg respectively. Lettuce had the highest concentration of Pb, while pumpkin had the least Pb concentration. Pumpkin had the highest concentration of Zn, followed by spinach, and the least concentration in lettuce. Lettuce had the highest concentration of Cd, followed by pumpkin and spinach with the least concentration of Cd. The highest concentration of Cr was observed in spinach, followed by lettuce, while pumpkin had the least Cr concentration. This study revealed that the concentrations of Pb, Zn, and Cd were within acceptable limits according to WHO, while Cr was found above that limit. If ingested, the heavy metals result in bioaccumulation and biomagnification, which as well lead to human disorders with children at higher risks than adults.