A 32-year-old male worker in a chemical manufacturing unit in Delhi is brought to the emergency department with sudden loss of consciousness, convulsions, and a peculiar smell on his breath. His skin appears flushed and he is in respiratory distress. Autopsy findings later reveal cherry-red discoloration of tissues. Which is the most common occupational source of cyanide poisoning in industrial settings?

Explanation

## Most Common Occupational Source of Cyanide Poisoning ### Electroplating and Metal Finishing — The Leading Industrial Exposure **Key Point:** Electroplating and metal finishing industries are the most common occupational sources of cyanide poisoning worldwide, including India. Cyanide salts (potassium cyanide, sodium cyanide) are used extensively in case-hardening of steel, electroplating of metals, and extraction of precious metals from ores. ### Why Electroplating is the Highest Risk 1. **High concentration of cyanide salts** — Used directly in plating baths and hardening processes 2. **Frequent worker exposure** — Through inhalation of dust, skin contact, and accidental ingestion 3. **Inadequate safety measures** — Particularly in small-scale and unorganized sectors in India 4. **Heat-accelerated volatilization** — Cyanide becomes gaseous when electroplating baths are heated ### Clinical Presentation in Acute Cyanide Poisoning | Feature | Mechanism | |---------|----------| | **Flushed skin** | Venous blood remains oxygenated (cannot be utilized by cells) | | **Cherry-red discoloration** | High oxygen saturation in venous blood due to blocked cytochrome c oxidase | | **Convulsions** | Severe hypoxia at cellular level despite normal arterial oxygen | | **Rapid loss of consciousness** | Immediate inhibition of aerobic respiration | | **Characteristic odor** | Almond-like smell (though not always detectable) | ### Mechanism of Cyanide Toxicity **High-Yield:** Cyanide binds irreversibly to the ferric iron (Fe³⁺) of cytochrome c oxidase in mitochondrial Complex IV, blocking the electron transport chain and halting aerobic respiration. This causes **histotoxic hypoxia** — cells cannot use oxygen despite adequate supply. ### Other Occupational Sources (Less Common) - **Pesticide manufacturing** — Cyanide used in some insecticide synthesis (less common in modern practice) - **Pharmaceutical production** — Cyanide as a reagent in organic synthesis (controlled, lower exposure risk) - **Textile dyeing** — Cyanide compounds in some dyes (minimal exposure compared to electroplating) **Clinical Pearl:** In India, small-scale electroplating units in industrial clusters (Delhi, Mumbai, Bangalore) have the highest incidence of occupational cyanide poisoning due to poor ventilation, lack of personal protective equipment, and inadequate worker training. ### Management Principles 1. **Immediate removal** from exposure source 2. **Oxygen therapy** — High-flow oxygen to increase dissolved oxygen 3. **Hydroxocobalamin** — Preferred antidote (binds cyanide to form cyanocobalamin) 4. **Sodium thiosulfate** — Enhances renal excretion of thiocyanate 5. **Supportive care** — Seizure control, ventilatory support **Warning:** Sodium nitrite (older antidote) is now less preferred in many countries due to risk of methemoglobinemia; hydroxocobalamin is the modern standard.