American Chemical Society (ACS) Laboratory Safety Practice Test 2026 – All-in-One Guide to Mastering Lab Safety Procedures!

Inhalation is the route of exposure that specifically involves the direct entry of a toxic substance into the body through the respiratory system. When a person breathes in, airborne toxins can enter the lungs, where they can be rapidly absorbed into the bloodstream due to the large surface area and thin membrane of the alveoli. This method of exposure is particularly concerning because it can lead to quick systemic effects, as many substances can bypass the digestive and metabolic processes that would otherwise alter their impact.

Looking at the other options, ingestion refers to the intake of substances through the mouth, which processes the toxins differently as they must pass through the digestive system. Absorption typically involves the uptake of toxins through the skin or mucous membranes, which is a separate mechanism from inhalation. Injection involves a substance being delivered directly into the body, often through a needle, bypassing the respiratory system entirely. Thus, inhalation is the only route that relates directly to breathing in toxic substances.