Figure 1.
Sources of Cd and its transmission pathways in the environment. This figure shows the process of Cd deposition, accumulation, cycling in the environment, and enrichment in plants, animals, and humans through the food chain. Cd exists in different chemical forms in each pathway, such as in water bodies, where it is mainly in the form of chloride [15], in coal combustion and dust formed in non-ferrous metal production, where it mainly contains CdS and CdSO4 [16], and in phosphorus fertilizers in the form of Cd(H2PO4)2 and CdHPO4 [17].