Table 6.

The National Research Council’s Modified Version of the Stressor-Based Approach to Cumulative Risk Assessment, where the Primary Goal is to Discriminate among Risk Management Options [2].

Phase	Modified Stressor-Based Approach (Focus on Evaluation and Comparison of Risk Management Options)
Step 1	- develop conceptual model describing stressors and ways they cause effects, emphasizing those that would be significantly influenced by risk management option under study - identify receptors and end points affected by these stressors - review the conceptual model, including stressors, receptors, and end points with stakeholders as part of initial planning and scoping
Step 2	- use available scientific evidence and screening-level benefit calculations to make initial determination of which stressors should be included - review and re-evaluate planning and scoping activities based on stakeholder feedback - focus only on stressors that contribute to end points of interest for risk management options and are either differentially affected by various risk management options or influence the benefits of stressors that are differentially affected
Step 3	- evaluate the benefits of different risk management options with appropriate characterization of uncertainty, including quantification of the effects of individual stressors and bounding calculations of any possible interaction effects
Step 4	- conclude the analysis if results of Step 3 are sufficient to discriminate among risk management options given other economic, social, and political factors; otherwise, sequentially refine the analysis as needed, taking into account potential interactions among stressors