How do zinc cadmium and mercury differ in toxicity?

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

• Zinc: Toxicity is low. While excessive inhalation of zinc compounds can cause temporary symptoms like fever or coughing, these effects are not permanent. Fatal poisoning from ingestion is rare, and zinc is generally well-tolerated by human skin.1
• Cadmium: Toxic hazards are significantly higher than those of zinc. Ingestion can cause severe gastrointestinal distress, and inhalation of cadmium fumes is a serious respiratory hazard that can lead to fatal inflammation of the lungs. Chronic exposure is associated with kidney and liver injury.12
• Mercury: This element and its compounds are highly toxic. Acute poisoning primarily damages the kidneys. Organic mercury compounds, particularly alkyl salts, are especially dangerous because they can penetrate the central nervous system and are excreted only slowly, leading to severe neurological damage and potential death.13

It is a fundamental ethical principle to prioritize human safety and environmental health by strictly regulating the industrial use and disposal of these hazardous substances to prevent poisoning and ecological contamination.13