Public health implications of heavy metals in foods and drinking water in Ethiopia (2016 to 2020): systematic review.

Background: Besides their benefits, heavy metals are toxic, persistent, and hazardous to human health, even at their lower concentrations. Consumption of unsafe concentrations of food contaminated with heavy metals may lead to the disruption of numerous biological and biochemical processes in the human body. In developing country including Ethiopia, where untreated or partially treated wastewater is used for agricultural purposes, the problems related to the consumption foods contaminated with heavy metals may poses highest risk to human health. Therefore, this review was aimed to determine the public health implications of heavy metals in foods and drinking water in Ethiopia.

Methods: The articles published from 2016 to 2020 were identified through systematic searches of electronic databases that include MEDLINE/PubMed, EMBASE, CINAH, Google Scholar, WHO, and FAO Libraries. The data was extracted using a predetermined data extraction form using Microsoft Excel, 2016. The methodological quality of the included studies was assessed using mixed methods appraisal tool (MMAT) version 2018 and Joanna Briggs Institute Critical Appraisal tools to determine the relevance of the studies. Finally, the results were evaluated based on the FAO/WHO guidelines for foods and drinking water.

Results: A total of 1019 articles published from 2016 to 2020 were searched from various electronic databases and by manual searching on Google. Following the initial screening, 317 articles were retrieved for evaluation and 49 articles were assessed for eligibility, of which 21 studies were included in the systematic review. The mean concentration of Cr, Cd, Pb, As, Hg, Zn, Cu, Ni, Co, Fe and Mn in fruits and vegetables ranged from 2.068-4.29, 0.86-1.37, 1.90-4.70, 1.01-3.56, 3.43-4.23, 19.18-98.15, 4.39-9.42, 1.037-5.27, 0.19-1.0, 199.5-370.4, 0.26-869 mg/kg, respectively. The mean concentration Cr, Cd, Pb, As, Zn, and Fe in meat and milk ranged from 1.032-2.72, 0.233-0.72, 1.32-3.15, 0.79-2.96, 78.37-467.7, and 505.61-3549.9 mg/kg, respectively. The mean concentration of Cr, Cd, Pb, Zn, and Cu in drinking water ranged 0.0089-0.054, 0.02-0.0237, 0.005-0.369, 0.625-2.137, and 0.176-1.176 ml/L, respectively. The mean concentration of Cr, Cd, Pb, Zn, Cu, Ni, Co, Fe, and Mn in other edible cereals ranged from 0.973-2.165, 0.424-0.55, 0.65-1.70, 70.51-81.58, 14.123-15.98, 1.89-13.8, 1.06-1.59, 67.866-110.3, and 13.686-15.4 mg/kg, respectively.

Conclusion: This systematic review identified heavy metals in foods and drinking water and determined their public health implications. The results of this finding imply that the majority of the studies reported high concentrations of toxic heavy metals in foods and drinking water that are hazardous to human health. Therefore, effective food safety and risk-based food quality assessment are essential to protect the public health.