What is classified as a blood agent when used as a terrorist weapon?

Hydrogen cyanide is classified as a blood agent due to its mechanism of action in the body. Blood agents are toxic compounds that can be absorbed into the bloodstream through inhalation or dermal contact, and they interfere with the body’s ability to utilize oxygen at the cellular level. When hydrogen cyanide is inhaled or comes in contact with skin, it quickly enters the bloodstream and inhibits the enzyme cytochrome c oxidase. This enzyme is critical for the electron transport chain in cellular respiration, and its inhibition leads to cellular asphyxiation, making it extremely harmful.

Chlorine gas is primarily a choking agent, causing damage to the respiratory system, while carbon monoxide is classified as a simple asphyxiant that interferes with the blood's ability to transport oxygen but does not act directly by inhibiting enzymatic processes in the same manner as blood agents. Sarin gas, on the other hand, is a nerve agent that disrupts the nervous system by inhibiting acetylcholinesterase, leading to a different mechanism of toxicity compared to the systemic effects seen with blood agents like hydrogen cyanide.