Abstract
Levels of some trace metals (Cu, Zn, Cd, Pb and Mn) were investigated in roadside soil and the leaves of a common perennial vegetable (Vernonia amygdalina). Soil and vegetable samples were collected from roadsides of three major roads in Abak (Ikot Ekpene road, Ikot Abasi road and Uyo road). The samples were digested using standard methods and analysed using Unicam 939/959 atomic absorption spectrophotometer. The results revealed that the levels of all the metals in soil samples were higher than the levels of metals in the corresponding vegetable. The metal levels in both the soil and vegetable samples were in the order: Cu > Zn > Pb > Mn > Cd. Cu, Cd and Pb with the levels of 106.71, 0.25 and 0.54 mg/kg, respectively, in plant samples respectively were higher than the WHO maximum permissible limits of 73.30 mg/kg for Cu; 0.20 mg/kg for Cd and 0.30 mg/kg for Pb. Zn (45.25 mg/kg) and Mn (0.47 mg/kg) were below the maximum permissible limits of 99.40 mg/kg for Zn and 500 mg/kg for Mn. Further analysis of the V. amygdalina pollution status using transfer factor (TF) revealed that Zn had the highest TF value of 0.5 while Cd recorded the lowest of 0.019. The toxic risk (hazard quotient) for adults and children consuming the V. amygdalina leaves showed that Cu was greater than one (1) and other metals were generally low and within safe limits. The Hazard indices were greater than 1 for both adults (1.69E+0) and children (1.94E+0). This implies that the trace metal contamination was capable of posing health hazard to consumers of this plant.
Highlights
The herb known as bitter leaf (Vernonia amygdalina) is a shrub or small tree that can reach 23 feet in height when fully grown
This study was conducted to quantify the levels of some trace metals in leaves of a common perennial vegetable (V. amygdalina) grown along the roadsides of three major roads in Abak and to assess the health risks associated with the consumption of the vegetable
This indicates that the consumers of V. amygdalina plant from the roadsides of these major roads are at potential health risks
Summary
The herb known as bitter leaf (Vernonia amygdalina) is a shrub or small tree that can reach 23 feet in height when fully grown. The herb is an indigenous African plant; which grows in most parts of sub-Saharan Africa It is a medicinal plant and fresh bitter leaf is of great importance in human diet because of the presence of vitamins and mineral salts [1]. Different vegetables are cultivated on the roadsides of major roads in Abak These vegetables are exposed to trace metal contaminations as a result of atmospheric deposition due to anthropogenic activities like vehicular emission, industrial emission and burning of all forms of wastes along the roadsides. These are in addition to the plants uptake from the soil, as a result of the agricultural practices adopted by the farmers to increase productivity. This study was conducted to quantify the levels of some trace metals in leaves of a common perennial vegetable (V. amygdalina) grown along the roadsides of three major roads in Abak and to assess the health risks associated with the consumption of the vegetable
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