An Assessment of trace metals in selected Leafy vegetables in Lagos state

Abstract

Man’s existence, survival and wellbeing are tied to the quality of the resources in the environment. Globally as population increases with industrial development, the resources in the environment becomes threatened due to heightened level of pollution especially in the cities. Leafy vegetables can be exposed to trace metals contamination because they are commonly grown within the urban and peri-urban areas due to their perishability. Thus, this study assessed the levels of cadmium (Cd), chromium (Cr), lead (Pb), copper (Cu), zinc (Zn) and iron (Fe) in 5 leafy vegetables’ samples of Telfairia occidentalis, Celosia argentea, Corchorus olitorius, Talinum triangulare and Vernonia amygdalina sourced from two markets in Lagos state. The metals determination was analyzed using Atomic Absorption Spectrophotometer (AAS). The daily intake of metals and the non- carcinogenic health risks through these vegetables’ consumption were calculated. Cd was not detected in all the vegetables, while Pd and Cr were only observed in T. Occidentalis (20.82 mg kg-1) and in C. olitorius (7.89 mg kg-1) from Oyingbo and Mile 12 markets respectively. Among the trace metals, Fe had the highest concentration in all the vegetables with a range between 392.66 – 2,072.97 mg kg-1 and 573.13 – 1,255.38 mg kg-1 in Mile 12 and Oyingbo markets, respectively. Zn concentration was significantly different among the vegetables in both markets with the highest concentration in C. argentea (308.33 mg kg-1), T. triangulare (303.96 mg kg-1), and lowest in C. olitorius (97.1 mg kg-1) and V. amygdalina (102.33 mg kg-1) in Mile 12 and Oyingbo market respectively. Besides, Cu had the lowest concentration ranging between 4.55 – 33.34 mg kg-1 and 0.17 – 7.34 mg kg-1. The levels of Pb, Cr, Zn and Fe were above allowable limits by FAO/WHO (1996). The daily intake of metals due to the exposure of the analyzed metal were above the permitted limit per day, except for Cu. The target hazard quotient and hazard risk index for each metal were above one (1) in all the vegetables. This indicates non- carcinogenic risks from the vegetables if consumed by humans regularly. This study suggests the need for improvement on pollution control measures and continuous monitoring of these vegetables for human’s safety. Keywords: Pollution. Trace metals. Leafy vegetables. Health risks. Markets. Lagos.