**5. Entrance of heavy metals into our food chain**

Compared to other contaminants, heavy metals are considered to pose the main threats to food safety [7]. The natural ecosystem services are degraded by heavy metals being present in contaminated soils, which ultimately impact human health through the food chain. Due to their abundance of advantageous and necessary nutrients and minerals, vegetables are a significant component of the human diet. Unfortunately, plants can absorb and accumulate excessive amounts of heavy metals in both edible and inedible sections of their bodies. Heavy metal concentrations in vegetables (fruit, leafy vegetables, and root vegetables) have been found to be high in recent years. Finally, the accumulation of heavy metals in vegetables and edible crop components in sewage sludge-contaminated soils is a cause for considerable worry due to the negative and permanent consequences that metals have on both human and animal health overall through the food chain [9].

#### **5.1 Sewage wastewater used in agriculture**

Nitrogen and phosphorous are found in sewage sludge, particularly because of the nitrification and denitrification phases of the wastewater treatment process. As a result, sludge has special nutritional properties because it contains nutrients that are necessary for plant growth. Sludge may also contain other substances, therefore, that can be hazardous if they get into the human food chain [10].
