A systematic review on the sources and health risk of heavy metal contamination in environmental and food systems in Uganda

Abstract

This study systematically reviewed research on heavy metal contamination in environmental and food systems in Uganda using the PRISMA 2020 data reporting method and the PICOS framework. An extensive literature search of published papers on heavy metal contamination in Uganda's environment and food systems was conducted in PubMed, Web of Science, and Scopus databases up to May 21, 2024. Boolean operators (AND/OR/NOT) were applied to develop search strategies tailored to each database. Following duplicate removal, title and abstract screening, and full-text assessment using the Rayyan platform, 39 articles were included in the final review. Data were extracted from each study using a standardized template that captured metal type, contamination source, concentration levels, affected food or environmental matrix, geographic location, and toxicological impact. Data were synthesized using a descriptive and narrative approach. Key sources of contamination include industrial and municipal waste, agricultural practices, and emissions from transport and manufacturing. Among the metals, lead was the most mentioned across studies. Regional analysis revealed that Central Uganda had the highest reports on heavy metals, while Northern Uganda remains critically understudied. Ecologically, heavy metals threaten soil fertility, aquatic biodiversity, and agricultural sustainability. Contamination of staple foods with lead, cadmium, and mercury poses significant public health risks, particularly for children and pregnant women. Strengthened environmental monitoring, targeted regional investigations, and improved food safety surveillance within a One Health framework are urgently recommended.