Which term describes a substance that interferes with oxygenation of tissue?

• A. Asphyxiant
• B. Poison
• C. Mutagen
• D. Carcinogen

Answer: (A)

Interfering with oxygen delivery to tissues is the defining feature of an asphyxiant. Asphyxiants can work in two main ways: simple asphyxiants dilute or displace the oxygen in the environment (for example, nitrogen or argon), reducing the amount of oxygen available to breathe; chemical asphyxiants disrupt the body's use of oxygen at the cellular level (for instance, cyanide inhibits cellular respiration, while carbon monoxide binds to hemoglobin and prevents oxygen from getting to tissues). In a hazmat context, recognizing asphyxiants helps explain why rapid ventilation and prompt removal from the affected area are critical. The other terms describe toxicity by different mechanisms: a general poison can harm in many ways, a mutagen causes genetic mutations, and a carcinogen increases cancer risk, none of which specifically denote interference with tissue oxygenation.