Exposure Assessment

Epidemiologic Approaches to Exposure Assessment

Exposure assessment in epidemiology can be broken into various phases that include (1) identification and characterization of the exposed population; (2) evaluation of potential exposure pathways; (3) assessment of the frequency, intensity, and duration of exposure; and (4) exposure classification.

The first issue to consider in exposure assessment is choosing the group that represents the most appropriate and feasible population to study, given the specific research questions. Often, worker populations are selected because of the availability of exposure information and the fact that higher exposures typically occur in workplace settings; however, it may be more appropriate to study specific community members, consumers, or the general population depending on the research question. Most environmental or occupational epidemiologic studies estimate exposure for groups of individuals who are expected to share similar exposure characteristics (e.g., levels, variation).

The second issue to consider is the potential route of exposure, which can include dermal uptake, oral intake via ingestion or mouthing (for children), inhalation, or a combination of pathways. In the case of physical agents (e.g., electric or magnetic fields), simply being present in a field or experiencing a physical force constitutes the route of exposure. For exposure to occur, a ‘complete’ exposure pathway must exist. Examples of incomplete pathways, which prevent exposure to contaminants, include a concrete cap in a foundation that could prevent intrusion of a soil contaminant into a home, or vegetative cover that could reduce release of metal-laden dusts. The amount of agent taken into the body depends on various characteristics such as particle size (for inhalation), bioavailability, human behavior, whether natural barriers or personal protective equipment prevent actual exposure, and whether the substance is transformed within the body.

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