success against objectives. Here again, the decision is outside the realm of science, because it reflects societal valuation, which is the domain of policymakers and stakeholders.

Ecological risk assessment is “the characterization of the adverse ecological effects of environmental exposures to hazards imposed by human activities” (National Research Council, 1993). This chapter describes two approaches to ecological risk assessment and discusses their utility for the management of benthic habitats. The exposure assessment model has been borrowed from the fields of human health and toxicology. It focuses on one risk at a time (National Research Council, 1983, 1993), it is quantitative, and it has been used in the policy arena to set standards and propose controls. The human health risk assessment framework was modified in 1993 for use in ecological risk assessment by the National Research Council’s Committee on Risk Assessment Methodology. A modified model is described below.

FIGURE 5.1 Elements of risk assessment and risk management (modified from National Research Council, 1993).

The second method described here is comparative risk assessment. This method compares several types of risks and allows evaluation of the effects of a variety of stressors as opposed to a single stressor on seafloor habitat. Comparative assessments are used by policymakers to allocate resources and to set management priorities. In addition to data, they rely on expert judgment, scientific inference, and deliberation.

EXPOSURE ASSESSMENT MODEL

The exposure assessment model has three phases: research, risk assessment, and risk management (Figure 5.1). Policy mandates provide the regulatory framework of scientific research, monitoring, and validation, which provide important input at every stage. EFH provisions within the Sustainable Fisheries Act provide the context for risk management. The act requires the identification and minimization of threats to EFH. Evaluation of regulatory options to meet the



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