Assessment of Potentially Toxic Elements in Vegetables Grown along Akaki River in Addis Ababa and Potential Health Implications

Abstract

The present study was carried out to assess contamination of vegetables from five farmlands in Addis Ababa with toxic and potentially toxic elements (Cd, Pb, As, Cu, Zn, Cr, Co, Ni, Ba, B, Sr, V, Fe and Mn) and health risk concerns to consumers of these vegetables as well as farm soils and water used to irrigate the vegetables. Pollution levels were varied with metals and vegetable types. The average total metal accumulation (mg kg-1) in the vegetables was potato (245.54) > carrot (202.20) > Swiss chard (52.42) > lettuce (47.43) > cabbage (38.04) > Ethiopian kale (30.17). Results also revealed that the average concentrations (mg kg-1) of all elements in the vegetables were found in order of Pb (744.10) > Fe (288.5) > Mn (51.66) > Sr (50.12) > Zn (38.81) > Ba (35.51) > B (21.65) > Cu (7.95) > Cr (1.97) > Ni (1.14) > V (0.54) > Co (0.20) > As (0.08) > Cd (0.08). Many of the concentrations were higher than previously reported. The average metal concentration (mg kg-1) of vegetables by farm was Burayu (136.58) > Akaki (125.00) > Kolfea (54.19) > Goffa (37.11) > Kera (29.40). The concentration of Cr, Cd, Pb and Fe in most vegetables surpassed the maximum recommended levels. From health standpoint consuming lettuce, Swiss chard, carrot and potato may cause serious health risk to consumers than cabbage and Ethiopia kale due to the high level of toxic metal accumulation. Elevated levels of some heavy metals were detected in the soil and irrigation water (Cd, Pb, As, Cu, Zn, Cr, Co, Ni, Ba, B, Sr, V, Fe and Mn) suggesting contamination from various the industrial and municipal discharges to the local river network. The present study highlights the immediate need for proper treatment and disposal of wide range of effluents and waste materials that currently enter the Akaki River and its tributary and farmlands as well as regular monitoring of potential contaminants in soil, water and vegetables and enforcement of standards.

Keywords: Potentially toxic elements, contamination, plant uptake, health risk