A PARADIGM FOR ECOLOGICAL RISK ASSESSMENT

The 1983 National Academy of Sciences paradigm for conducting human health risk assessment is considered with respect to ecological risk assessment. This four-step paradigm fails to capture key intrinsic differences between the two types of analysis, specifically: identity of risk targets and receptors; identity of the appropriate level of ecological organization at which the risk is expressed; variability of endpoint with respect to risk receptor; and the existence of risk cascades through ecological feedback loops. We propose an alternative paradigm that includes a preliminary step, receptor identification, in which chemical partitioning is combined with a conceptual model of the ecosystem to identify appropriate risk targets. In addition, we propose formal inclusion of endpoint identification and explicit consideration of risk cascades in a relationship assessment in which interactive feedback loops are considered in an iterative process. The proposed paradigm preserves the steps of hazard identification, exposure assessment, dose-response assessment (renamed response assessment) and risk characterization, although specific modifications are recommended.