The route of exposure affecting the respiratory tracts that can cause ill effects is:

• A. Inhalation.
• B. Absorption.
• C. Ingestion.
• D. Injection.

Answer: (A)

Inhalation directly exposes the respiratory tract to airborne hazards, making it the route most linked to ill effects in the airways and lungs. Gases, vapors, dusts, and aerosols breathed in contact the nasal passages, throat, bronchi, and alveoli, causing irritation, coughing, wheezing, or more serious injuries like chemical pneumonitis or pulmonary edema. The size and nature of the contaminant influence where it deposits: larger particles irritate upper airways, while fine particles and vapors can reach deep into the lungs and may even enter the bloodstream, producing systemic effects.

Other routes—through the skin (absorption), by mouth (ingestion), or by injection—bypass much of the respiratory tract and are less likely to cause direct respiratory irritation, though they can cause other health issues. Inhalation remains the route most directly associated with respiratory tract effects.