Which exposure route is the most common and carries the highest risk?

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

Answer: (B)

When thinking about exposure routes, the route that most often leads to systemic exposure is inhalation because airborne contaminants—dust, fumes, gases—are readily encountered and can be breathed in continuously in work and daily environments. The lungs provide a large surface area and thin absorption barriers, so many substances cross into the bloodstream quickly from the alveoli, leading to rapid and widespread health effects. Ingestion involves swallowing material and then passing it through the digestive system, where some dose is reduced by first-pass metabolism in the liver. Dermal exposure depends on skin permeability and is typically slower and more limited by the skin barrier. Injection is not common in environmental settings and requires a breach of the skin with direct entry into the bloodstream. For these reasons, inhalation is the most common exposure route and commonly carries the highest risk.