Table 6.

Functional characteristics of four heavy elements.

Elements	Main Concentrated Parts	Major Harms	Primary Contact Pathway	Excretion	References
Lead	Bones	Reproductive system inj- ury, preterm delivery, miscarriage, infertility in women, abnormal prostate function in men	Air, water, food	Urine, feces	[84,85,86]
Cadmium	Kidneys, liver, testes, etc.	The male reproductive function suffers damage, with some toxicity to the testes	Soil, food	Urine, feces	[19,87,88]
Mercury	CNS (central nervous system), digestive system, and kidneys, among others	Blood mercury levels higher than 8 mg/L reduce sperm quality and fertility, and cause damage to the respiratory system, skin, blood, and eyes	Food, air	Urine, feces	[89,90,91]
Arsenic	Liver, lung, kidneys, skin, etc.	Pulmonary disease, repro- ductive problems, vascular disease, gangrene. Preterm birth, miscarriage, stillbirth	Water, air, food, soil	Urine, feces	[90,92,93,94]