Presence of Heavy Metals in Vegetables Irrigated with Wastewater-Impacted Rivers and Its Health Risks in Ethiopia: Systematic Review.

Background: Vegetables play critical role in human nutrition and overall health. However, consumption of vegetables cultivated through wastewater-impacted river can be source of potentially toxic heavy metals, which can cause detrimental health effects when their concentration exceeds the recommended maximum levels. Despite growing body of evidence highlighting the dangers associated with heavy metal accumulation in vegetables, there remains critical gap in systematic assessments within Ethiopian context. Therefore, objective of this review is to reveal heavy metals concentrations in vegetables grown with wastewater-impacted river and assess associated public health risks.

Methodology: Research articles published in English were identified through systematic searching using electronic databases including PubMed, Google Scholar, WHO/FAO library, and searching from Google manually. The outcomes of interest were mean concentration of heavy metals in vegetables and associated health risks. Cross-sectional studies that met inclusion criteria were considered. Data were extracted by independent reviewers. Methodological quality of included studies was assessed using critical appraisal tools. Moreover, health risks of consumers were assessed through evaluating estimated daily intakes (EDI), Health Risk Index (HRI), and Hazard Index (HI).

Results: Nineteen articles were included in this systematic review. The findings revealed that the mean concentration of Pb, Cr, Cd, As, Hg, Cu, Ni, Zn, Mn, and Fe in tested vegetables ranged from: 0.28-7.68, 0.75-33.01, 0.14-3.93, 0.05-3.13, ND-4.25, 0.92-15.33, 2.13-13.1, 18.27-62.83, 8.83-331.8, and 177.8-1034.3 mg/kg (dry weight), respectively. The EDI of Pb, Cr, Cd, As, Hg, Cu, Ni, Zn, Mn, and Fe in vegetables was range from: 0.00104-0.0286, 0.00279-0.123, 0.00052-0.0146, 0.0000372-0.0116, 0.0124-0.0158, 0.00342-0.0439, 0.0079-0.0487, 0.068-0.23, 0.03-1.23, and 0.53-3.84 mg/kg/day, respectively. The HRI of toxic heavy metals for all vegetable types ranged as; Pb (0.26-7.15), Cr (0.00186-0.0820), Cd (0.52-14.6), As (0.12-38.7), and Hg (1.24-1.58). The HRI due to consumption of all vegetables was 35, 0.168, 46.6, 70, and 2.82 for Pb, Cr, Cd, As, and Hg, respectively indicating severe health impact except for Cr.

Conclusion: This review underscores health implications linked to consumption of vegetables cultivated using wastewater in Ethiopia. It revealed that the concentration of toxic heavy metals in vegetables grown with wastewater-affected water was higher than the maximum allowable safe limit set for edible vegetables by WHO that would be a public health risk.