Effect of cadmium and lead on living organisms - transport, accumulation, metabolism

Heavy metals are metals and non-metals with molecular weights exceeding 20 and specific gravity above 5. The heavy metal cycle in the environment is linked to the food chain: soil - plant - animal - human. The transfer of metals to the higher link results in a cumulative increase in their content. Pollution with heavy metals has become a severe threat to the environment and food safety due to the rapid development of agriculture and industry and disturbances in the natural ecosystem induced by the enormous growth of the global population. Major sources of heavy metals in soil are bedrock, industrial and transport emissions, municipal management, and agriculture. Three main reasons for the toxicity of metals were found to be: participation of metals in enhancing the production of ROS (Reactive Oxygen Species) and modification of the activity of the antioxidant system, ability to react directly with proteins, resulting from the affinity between metals and thiol, histidine and carboxyl groups and leading to the attachment of metal ions to active sites of enzymes, structural elements of cells and proteins involved in cell transport, and replacement of elements necessary for metabolism, e.g. calcium in bones or iron in erythrocytes with metals, which leads to damage and changes in their structure and metabolism. The key solution towards decreasing the content of Cd and Pb in food is to limit or prevent their initial absorption by plants used for food or animal feed. However, due to the complexity of interactions between soil chemistry, varieties and species of plants and agronomic practices, additional research is needed.