Which route of exposure is most associated with entering the body through the lungs?

• A. Injection
• B. Inhalation
• C. Dermal contact
• D. Ingestion

Answer: (B)

Inhalation is the route that best aligns with substances entering the body through the lungs because airborne chemicals are breathed into the respiratory tract and directly reach the gas-exchange surfaces. The alveolar region of the lungs has a huge surface area and an extremely thin barrier between air and blood, surrounded by a dense network of capillaries. This design allows vapors, gases, and fine aerosols to cross into the bloodstream rapidly, making inhalation a fast and significant route of exposure for many hazards.

Other routes involve different barriers and processes. Ingestion must pass through the digestive system and often undergo first-pass metabolism in the liver, slowing and altering absorption. Dermal contact has to penetrate the skin’s protective layers, which slows absorption and often limits systemic exposure. Injection bypasses many barriers entirely by delivering substances directly into the bloodstream, not through the lungs. So the lungs are most directly associated with entry via inhalation.