Assessment of heavy metals pollution in vegetables grown on irrigated soil and their potential threat to human health and global food security

Heavy metals accumulation in vegetables grown on irrigated soils are affected by human-and natural activities. They represent a serious global concern due to the presence of harmful elements in the water used for irrigation that later accumulate in the soil at high level, affecting soil quality, crops and human health. Within the rhizosphere, metals severely affect microbiome and vegetables physiological function, which can compromise vegetable qualities and through their accumulation present a serious threat to consumers. Factors that influence heavy metal availability include the pH, organic matter, crop- and microbial deposits. Plant and associated symbiotic bacteria have evolved strategies to mitigate metal bacterial secretion into rhizosphere, including the siderophores, phytohormones, antibiotics, mucilage, organic acids, phenols, polypeptides, exopolysaccharides (EPS), as well as inorganic ligands such as NH4+, PO43-, and more may chelate heavy metal ions, desirable to decrease the availability and the uptake of heavy metals in plant and bacteria, potentially beneficial to plants and humans. This review focuses on the source of heavy metals in irrigated soils where vegetables are grown, mobility/availability of metals in such soil, uptake/accumulation by the plant, toxicity of these heavy metals to vegetables and human, and the mitigation strategies used by plants and bacteria to reduce the impact of metals on humans via the food chain.