Accumulation of toxic metals in vegetable crops and associated dietary exposure risks to human health

Abstract Heavy metal contamination in food systems has emerged as a critical global concern due to its persistent nature and serious implications for food safety and public health. Rapid industrialization, urban expansion, and unsustainable agricultural practices especially the use of untreated wastewater for irrigation have contributed significantly to the accumulation of toxic metals in agricultural soils and edible crops. This review synthesizes current knowledge on the mechanisms of heavy metal uptake, translocation, and accumulation in vegetable crops, with a particular focus on how these processes affect the entry of harmful metals into the human food chain. Key physiological and molecular mechanisms, including the role of metal transporters and detoxification strategies within plant tissues, are discussed with relevance to food safety and phytoremediation. The paper also critically evaluates human health risks associated with dietary exposure to heavy metals, using metrics such as chronic daily intake (CDI), hazard quotient (HQ), and total cancer risk (TCR). Importantly, the review identifies key knowledge gaps such as inconsistent data on crop-specific uptake patterns, lack of long-term human health studies, and insufficient attention to emerging contaminants and outlines directions for future research. Evidence from recent studies shows that metal concentrations in commonly consumed vegetables often exceed FAO/WHO permissible limits, especially in regions using contaminated irrigation sources. To mitigate these risks, the review underscores the urgent need for stricter wastewater regulations, improved soil management practices, and the development of low-accumulating crop varieties. This integrative perspective aims to inform both scientific inquiry and policy decisions for safer and more sustainable food production.