Assessment of Potential Human Health Risk Associated With Heavy Metals in Soil - Vegetables System Irrigated by Rift Valley Lake Ziway, Ethiopia

Metal contamination of vegetables is a major concern, especially in areas where irrigation has been used for a long time. The Central Ethiopian Rift Valley Region is highly affected due to the heavy use of agrochemicals throughout the year. Although some studies have been conducted on the concentration and level of heavy metal pollution, little attention has been paid to their impact on human health. This study determined the concentrations of nine metals (As, Cd, Cr, Co, Cu, Hg, Ni, Pb, and Zn) in a soils and vegetables (tomatoes and onions) irrigated by Lake Ziway, Ethiopia. An inductively coupled plasma optical emission spectrometer (ICP-OES) was used to determine the heavy metal levels. Moreover, the study evaluated the health risks associated with consuming contaminated vegetables by employing major indices, including non-carcinogenic and carcinogenic risks. The results showed that the mean concentrations of Pb, As, Hg, and Cr in all tomato and onion samples and the average Zn, Pb, Cd, and Hg levels in all soil samples exceeded the FAO/WHO threshold. Non-carcinogenic health risk estimates showed that As, Pb, Hg, and Co for children and Pb and Co for adults had THQ values greater than 1, indicating the possibility of systemic health risks. Carcinogenic health risk showed that Ni posed a risk of developing cancer for both adults and children, with values ranging from 10-3 to 10-1. In addition, children are likely to have a higher cancer risk due to exposure to As and Cr. Therefore, it is crucial to raise awareness among stakeholders and implement effective monitoring policies to safeguard public health both within and beyond the study area.