## 1 Introduction  
Due to growing urbanization and population, the demand for food crops is increasing rapidly, and it is in fact exerting pressure, particularly on peri-urban agriculture. Increasing anthropogenic activities contribute to metal pollution in marginal places of agricultural land, resulting in a severe environmental cue [1]. Sources of metal pollution include natural (volcanic eruptions), agricultural (fertilizers, pesticides, wastewater), and anthropogenic (industrial and household effluents, traffic emission, mining, and smelting) activities that release high amounts of metals in soil, water, and the biosphere [2]. Thus, the presence of metal pollutants in marginal places of agricultural land is the most alarming matter as vegetables being contaminated with harmful metals cause easy entry into the food chain. Although certain metals such as Cu, Zn, Mn, Co, Cr, etc., are essential micronutrients for microbes, plants, and animals, they are of considerable concern due to their toxicity at higher concentrations [3]. Wastewater irrigation to agricultural land is also a contributing factor in the increase in metal elements in the soil. In Pakistan, polluted water (industrial effluents or untreated sewage water) is directly discharged into croplands being used for growing vegetables and other crops [4]. Faisalabad is one of the industrial cities where there is no proper treatment facility for wastewater disposal [5]. Due to the shortage of canal water for irrigation, untreated wastewater taken out from the nearby wastewater stabilization ponds is used to irrigate the agricultural land of Chakera village. This is a direct example of untreated wastewater irrigation in Chakera lands [6]. Large quantities of industrial effluents and sewage sludge are potential sources of metal contamination in water and soil environments due to their direct discharge into surface water bodies [7]. As a result, vegetables grown with wastewater irrigation accumulate metals from the polluted soil and water, thus exceeding safe limits [8; 9]. The use of effluents/ wastewater over a long period of time to grow vegetables results in the uptake of toxic metals by crops with a possibility of their excess in the food chain. One of the effects of these toxic metals in soil is the eventual inhibition of many physiologic and metabolic pathways in plants [10]. These metals reduce the uptake of water and nutrients in plants by damaging the root system [11]. Chlorosis and enzymatic disturbances are also mainly caused by increasing concentrations of metals [12; 13]. The persistence of metals in soils and their assimilation depends on their form and uptake by plants [14]. For instance, some metal ions like Pb are absorbed by soil but are rarely translocated to plants, while Cd is less mobile in soil but can be easily absorbed by plants [11]. Moreover, metal uptake by plants largely depends on soil type, plant species, and growth stage, and they passively transport from roots to shoots via xylem vessels [15]. Some metals are poorly mobile in the phloem, and they do not accumulate in storage organs, i.e., fruits and seeds, due to low transpiration rates. According to [PERSON] and [PERSON] [16], the accumulated concentration of metals in vegetables per unit of dry matter is in the following order: leaves > fresh fruits > seeds. Metals are readily taken up from the soil and accumulate in edible parts of vegetables and fruits. Therefore, the metal-induced contamination of the human food chain occurs via the direct consumption of those edible parts by humans [17; 18]. The ingestion of vegetables contaminated with metals through foodstuffs over a long period results in higher metal concentrations in humans that may cause several disorders such as kidney, liver, and cardiovascular problems [19]. Certain heavy metals pose health risks in humans when they enter the human body. Most of these metals affect multi-organ systems, where they prove to be very toxic.