How does the toxicity of zinc compare with that of cadmium and mercury?

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Periodic table — zinc group element Modern version of the periodic table of the elements (printable).

The toxicity of the elements in the zinc group increases sharply in the order of zinc, cadmium, and mercury.1

Zinc: This element has low toxicity. While it can cause vomiting at high concentrations (exceeding 800 parts per million) or temporary respiratory issues if inhaled, it is generally well-tolerated by the human skin, and fatal poisoning is rare.1
Cadmium: The toxic hazards of cadmium are significantly higher than those of zinc. It is a potent respiratory poison when inhaled as dust or fumes, and ingestion of even small quantities can lead to severe gastrointestinal distress and, in some cases, death.1
Mercury: Mercury and its compounds are highly toxic. They pose serious risks through inhalation, ingestion, or skin absorption. Acute poisoning primarily damages the kidneys, while organic mercury compounds—particularly alkyl salts—can penetrate the central nervous system, leading to severe neurological damage and potential fatalities.1

Due to these significant health risks, the use of mercurial fungicides and the discharge of mercury-containing industrial wastes have been subject to strict prohibitions and regulations.1