Determination of the Concentration of Selected Heavy Metals in Indigenous Plant: Telfairia occidentalis

Abstract

Telfairia occidentalis Hook. F. is an edible vegetable, rich in essential diet components and contains protein, vitamins, iron, calcium and other nutrients, which are not adequately supplied in our diet. However, Telfairia occidentalis is believed to contain heavy metals over a range of concentrations which could pose potential health risk to the consumers. The objective of this study was to determine whether the concentration of selected heavy metals present in Telfairia occidentalis cultivated in twenty Local Government areas of Lagos State, Nigeria, are within the acceptable range for human consumption. Telfairia occidentalis leaf samples were collected from twenty local government areas in Lagos State, washed thrice with water and air-dried prior to grounding into fine powder and sieved. The samples were digested with concentrated HNO3 and the concentrations of the metals were determined using the Buck 205 Atomic Absorption Spectrophotometer. The British Pharmacopoeia calibration plot method was adopted. All the Telfairia occidentalis samples (100%) from the 20 Local Governments in Lagos State contained arsenic and mercury below the USP oral component limit while 100% contained cadmium above the oral component limit. Twenty percent (20%) contained iron above the USP oral component limit. These metals could bio-accumulate in the biological system of people consuming this vegetable, thus posing potential health risk to consumers especially if consumed over a long period. We therefore suggest regular assessing of these metals in vegetables grown in these localities and that government should monitor and ensure proper disposal of waste within the environment in order to reduce the level of contamination of vegetables by heavy metals which are mainly resulting from industrial wastes and other sourcesof environmental pollution.