What is the source in an exposure pathway?

• A. The receptor population.
• B. The exposure point.
• C. The origin of environmental contamination.
• D. The movement of a contaminant through air, soil, or water.

Answer: (C)

Source in an exposure pathway refers to the origin of environmental contamination—the starting point from which a contaminant enters the environment. It could be a leaking storage tank, a contaminated site, or industrial discharge that introduces the contaminant. This is different from the receptor population (the people or organisms that may be exposed), the exposure point (where exposure occurs, such as a drinking water tap), or transport (the movement of the contaminant through air, soil, or water). Understanding the source helps explain how contamination begins and sets up the sequence leading to potential exposure, such as a solvent leak entering groundwater and eventually reaching a drinking water supply.