ABSTRACT
80The four major components of the ERA paradigm are problem formulation, exposure assessment, effects assessment, and risk characterization (U.S. EPA 1997; 1998; 1992; Suter et al. 2000). An ERA begins with problem formulation. Activities occurring during this phase include: defining the goals and spatial and temporal scale of the ERA; development of a site conceptual model; endpoint and nonhuman receptor species selection; and preliminary identification of contaminants of potential concern. Exposure assessment and effects assessment follow and can be performed simultaneously. Exposure assessment evaluates the fate, transport, and transformation of chemicals in the environment, and quantitative uptake and intake of these substances in receptor organisms. Effects assessment establishes the relationship between exposure levels and toxic effects in receptors. Risk characterization is the last step in the ERA and is where exposure and toxic effect information are combined to describe the likelihood of adverse effects in receptors.
