Global and Local Perspectives on Heavy Metal Contamination and Associated Human

Abstract

Heavy metal contamination of ecosystems represents a significant global threat to both environmental integrity and human health. This comprehensive review synthesizes evidence from 205 scientific studies to analyse the global panorama and a detailed Nigerian case study on heavy metal bioaccumulation in fish and the associated human health risks. The analysis reveals severe and widespread contamination, with South Asia and specific African regions, particularly Nigeria’s Niger Delta, identified as critical hotspots. Heavy metals such as lead, cadmium, mercury, and arsenic remain highly prevalent across aquatic and terrestrial food chains, frequently exceeding international limits and demonstrating strong tissue-specific bioaccumulation particularly in liver, kidney, and fatty tissues. Furthermore, carcinogenic risks from arsenic and other metals often surpass acceptable limits, indicating a long-term cancer threat to regular consumers. The Nigerian context underscores unique exacerbating factors, including extreme pollution from petroleum activities and the alarming role of traditional smoke drying, which can concentrate toxic metals in fish by over 100%, dramatically amplifying consumer exposure. This review identifies major gaps in current research and surveillance, including inconsistent risk assessment methods, limited contaminant speciation, underrepresentation of modern pesticides, a lack of data on metal mixtures and human biomarkers, and insufficient cumulative risk assessment for multi-chemical exposures. To address this silent public health crisis, the conclusion proposes an integrated framework of actions, including the urgent standardization of monitoring, stringent enforcement of industrial pollution controls, targeted consumer safety advisories, and the promotion of safer food processing technologies and sustainable aquaculture.