Hydrogen cyanide blood agent has which lethality range?

• A. Very high lethality
• B. No lethality
• C. High lethality
• D. Low to moderate lethality

Answer: (D)

Hydrogen cyanide acts as a blood agent by blocking cellular respiration at the mitochondrial level, specifically inhibiting cytochrome c oxidase. This stops tissues from using oxygen, leading to rapid systemic hypoxia and potential death within minutes after exposure, especially in enclosed or poorly ventilated spaces. Because of how quickly and potently it acts, the lethality range is best described as very high—potentially fatal at low to moderate exposures with rapid onset. It’s not no lethality, and it’s not just low or moderate; the combination of rapid onset and strong toxic effect places hydrogen cyanide at the very high end of lethality in typical exposure scenarios.