Which chemical is classified as a pulmonary agent?

• A. Phosgene
• B. Hydrogen cyanide
• C. Chlorine
• D. Ammonia

Answer: (A)

Pulmonary agents injure the lungs and interfere with gas exchange in the alveoli. Phosgene is a classic example because it damages the alveolar-capillary membranes and disrupts lung surfactant, leading to noncardiogenic pulmonary edema. The effects are notable for their potential delay—exposure can produce breathing difficulties hours after the incident, which is a hallmark of phosgene’s impact.

Hydrogen cyanide, by contrast, acts mainly as a systemic asphyxiant by inhibiting cellular respiration, causing rapid hypoxia throughout the body rather than initiating primary lung injury. Chlorine is a strong pulmonary irritant and choking agent that irritates and inflames the airways, but it doesn’t produce the same delayed, edema-prompting lung damage that phosgene does. Ammonia is another irritant that primarily harms mucous membranes and airways without the same primary lung edema mechanism.

So, the agent whose primary effect is injury to the lungs with possible delayed edema is phosgene.