Introduction to Exposure Assessment

Definition of Exposure Assessment

Exposure assessment is defined as the science that describes how an individual or population comes in contact with an agent, including quantification of the amount of the agent across space and time, for individuals and populations (Lioy, 1990).

Human exposure requires the “simultaneous occurrence of two events: the presence of an agent at a particular point in space and time and the presence of a person at the same location and time” (WHO, 2000). Once exposure has occurred, a continuum of biologic changes can be detected. These changes may serve as markers of the initial exposure, internal dose, biologically effective dose, altered structure or function with no ensuing pathologic effect, or potential or actual disease (EPA, 1992; WHO, 2000).

In the field of exposure assessment, the human body is regarded as having a hypothetical outer boundary which separates the inside of the body from the outside of the body (EPA, 1992). As used in this class, exposure to an agent is the contact of that agent with the outer boundary. An exposure assessment is the quantitative or qualitative evaluation of the intensity, frequency, and duration of contact, and often evaluates the rates at which an agent crosses the boundary (agent intake or uptake rates), the routes by which it crosses the boundary (e.g., oral, inhalation, dermal), and the resulting amount of the agent that actually crosses the boundary (a dose) and the amount absorbed (internal dose) (EPA, 1992; WHO 2000).