Which route of exposure involves substances entering the bloodstream typically through the skin?

The correct answer is absorption. This route of exposure occurs when harmful substances come into contact with the skin or mucous membranes and are then taken into the bloodstream. This can happen through various means such as through intact skin or through an open wound where the substance may bypass the skin barrier.

In contrast, inhalation refers to substances entering the body through the respiratory system, while ingestion involves substances being consumed through the mouth and entering the digestive system. Injection, on the other hand, typically refers to the introduction of a substance directly into the bloodstream via a syringe or similar device, rather than through the skin in a manner categorized as absorption. Understanding these routes of exposure is vital for assessing risk in hazardous materials incidents and implementing proper safety measures.