Heavy metal contamination as a major environmental and public health concern - A Review

Abstract

Heavy metal contamination remains a major global environmental and public health issue because of the persistence, bioaccumulation, and toxicity of metals including lead, mercury, cadmium, arsenic, and chromium. This study combines bibliometric and qualitative reviews to evaluate research trends and health hazards associated with heavy metal pollution. Data retrieved from the Scopus database (2014–2025) produced 18,930 documents, refined to 7,768 English-language research articles after excluding conference papers, reviews, and errata. VOSviewer, MapPlot, and OriginPro were used to analyze publication trends, research productivity, citation impact, and keyword networks. Contributions came from 174 countries, with 22 meeting the threshold of at least 50 publications and 5,000 citations. China and the United States recorded the highest outputs and citation impacts, while Nigeria contributed about 205 publications with over 5,000 citations, reflecting growing but limited African participation. Among 552 publication outlets, 12 major journals met productivity thresholds and accumulated more than 50,000 citations. Keyword analysis identified 41,618 terms, with 918 significant keywords grouped into seven thematic clusters that guided the qualitative review. The synthesis showed that heavy metals cause toxicity through oxidative stress, enzyme inhibition, mitochondrial dysfunction, genotoxicity, endocrine disruption, and imbalance of essential metal homeostasis, resulting in neurological, renal, hepatic, cardiovascular, reproductive, immune, and carcinogenic disorders. A Nigerian case study highlighted persistent exposure risks and regulatory challenges. Overall, the study provides an integrated evidence base to support environmental monitoring, risk assessment, policy formulation, and sustainable mitigation of heavy metal pollution.