Cyanide in Water: Lethal Risks, Mechanism & Emergency Treatment

Cyanide Toxicity in Water

Yes, cyanide in water is lethal. Dissolved cyanide forms hydrocyanic acid (HCN), a rapidly acting metabolic poison.

Mechanism of Toxicity

Cyanide binds cytochrome c oxidase (Complex IV) in the mitochondrial electron transport chain → halts oxidative phosphorylation → cells cannot use O₂ → cytotoxic hypoxia → lactic acidosis → multi-organ failure → death.

Lethal Dose

• Oral LD₅₀ (human): ~1–2 mg/kg (70–140 mg for 70 kg adult).
• Inhalation: 100–300 ppm fatal in minutes.
• Skin absorption possible (less efficient).

Sources of Exposure

• Industrial: metal plating, mining (gold cyanidation), jewelry, photography, synthetic fibers.
• Fire smoke (wool, silk, nylon, polyurethane combustion).
• Fumigation, rodenticides (historical).
• Natural: amygdalin in apricot kernels, cassava (improper processing).

Clinical Presentation

• Sudden collapse, seizure, coma, cardiac arrest.
• Cherry-red skin (rare, postmortem).
• Bitter almond odor (genetic inability to smell in ~40%).
• Lactic acidosis, high venous O₂ (arterial-venous O₂ difference ↓).

Emergency Treatment

1. Remove from exposure; ABCs.
2. Hydroxocobalamin (Cyanokit) 5g IV – preferred: binds CN⁻ → cyanocobalamin (B12) renally excreted. Safe, no methemoglobinemia.
3. Alternative: Nitrite (amyl/sodium) → methemoglobin → binds CN⁻ + sodium thiosulfate → thiocyanate (renal excretion). Risk: methemoglobinemia, hypotension.
4. Supportive: O₂, bicarbonate, vasopressors, dialysis if renal failure.

Prevention

Engineering controls, PPE, cyanide antidote kits in high-risk workplaces, water monitoring.