Science and Decisions Advancing Risk Assessment (2009) / Chapter Skim
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3 The Design of Risk Assessments
3 The Design of Risk Assessments
Pages 65-92
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From page 65... ...
Given that there are inevitable constraints on efforts to assess risk and multiple objectives to be met, the selection of appropriate elements of process and the specification of required elements of the final product constitute a complex design challenge. Well-designed risk-assessment processes create products that serve the needs of a community of consumers, including risk managers, community and industrial stakeholders, risk assessors themselves, and ultimately the public.
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From page 66... ...
. Risk Assessment as a Decision-Support Product The process of risk assessment involves generation of a number of individual products that are combined to form a final product (which is often referred to as "the risk assessment")
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From page 67... ...
. It is also captured in guidance documents for ecologic risk assessment and cumulative risk assessment (EPA 1992, 1998, 2003)
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From page 68... ...
Inclusiveness of Scope For various reasons, human health risk assessment has traditionally focused on single cause-effect pathways that involve a single chemical and single identified adverse effect. The narrowness of scope is frequently questioned with respect to both its scientific merits and its relevance to decision contexts of considerably greater scope.
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From page 69... ...
Product and process TABLE 3-1 Transition in EPA Human Health Risk-Assessment Characteristics According to EPA (1997) Old New Single end point Multiple end points Single source Multiple sources Single pathway Multiple pathways Single route of exposure Multiple routes of exposure Central decision-making Community-based decision-making Command and control Flexibility in achieving goals One-size-fits-all response Case-specific responses Single-medium-focused Multiple-media-focused Single-stressor risk reduction Holistic reduction of risk Source: EPA 1997.
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From page 70... ...
The use of defaults is necessary to complete risk assessments in the presence of substantial uncertainties and the embedded policy choices can have profound impacts on the risk-assessment findings and the associated decision-making functions. In addition to the science-policy assumptions that are easily recognizable, the process should take account of the presence of key subjective elements in evidence-gathering and integration that can influence the results of risk assessment.
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From page 71... ...
Given the lack of specificity in the operational definition of transparency, some effort is required during the early design period to achieve agreement among risk assessors and those seeking or responsible for ensuring transparency on the attributes that are sought and how they will be implemented. Compliance with Statutes and Administrative Law Requirements Some risk-assessment activities must comply with a variety of requirements imposed on federal policy-making activities, with the level of requirements depending on the risk assessment and the statutes that govern them.
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From page 72... ...
They also need to consider the impacts of decisions that patients themselves make in response to information about risks. In the same way, health and environmental risk-assessment and risk-management processes need to consider the complete impact of risk-assessment products and decisions given their inevitable potential to inadvertently contribute to increased risk.
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From page 73... ...
and problem formulation (a technically oriented process that assists assessors in operationally structuring the assessment) have emerged as additional distinct but related stages in both the human health and ecologic risk-assessment paradigms (EPA 1992, 1998, 2003, 2004a)
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From page 74... ...
and stakeholders in which assessors have a supporting role, and problem formulation involves a discussion between decision-makers and assessors (and technically oriented stakeholders) to develop a detailed technical design for the assessment that reflects the broad conceptual design developed in the scoping stage.
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From page 75... ...
NRC (1993) advocated for the integration of ecologic risks into the 1983 Red Book paradigm, and expressed a need to extend this paradigm to include the need for interaction between risk assessment and management at the early stages of a risk assessment, based on experience in ecologic assessment.
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From page 76... ...
Although present EPA guidance (for example, on ecologic risk assessment, cumulative risk assessment, and air toxics) does not contain exact language calling for the explicit identification of decision-making options during the planning and scoping stage, it does allow preliminary consideration of regulatory or other management options.
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From page 77... ...
The problem-formulation stage, whose specific products are a conceptual model and an analysis plan, develops the specific technical details for the assessment laid out during planning and scoping. Problem Formulation The extension of the concept of "problem formulation" to human health risk assessment first emerged during a 1991 National Research Council–sponsored risk-assessment workshop where the absence of such an activity in health risk assessment and the criticality of its use for ecologic risk assessment were discussed (NRC 1993)
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From page 78... ...
78 FIGURE 3-2 Illustration of the scope of a risk assessment, indicating both pathways considered (bold lines) and pathways not considered.
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From page 79... ...
Although the conceptual model serves as a guide for determining what types, amount, and quality of data are needed for the assessment to address the issues and concerns of interest to decision-makers, the analysis plan matches each element of the conceptual model with the analytic approach that the assessors initially intend to use to develop data or otherwise represent that element. Box 3-4 lists some of the major elements of an analysis plan (from EPA 2004a)
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From page 80... ...
and guidance for their conduct is available, the question remains as to whether EPA or other public agencies, the regulated community, or their contractors are taking full advantage of them to focus, refine, and improve human health and ecologic risk-assessment efforts. The question warrants attention in that continued inattention to the importance of planning and scoping and of problem formulation can be expected to yield human health risk assessments (by EPA and others)
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From page 81... ...
The idea that there are risks (for example, prolonged exposure to a hazard, or stress in the community awaiting an assessment of health risks) that may be associated with waiting for a particular study to be completed or for a scientific consensus to emerge is not readily incorporated into the standard scientific paradigm.
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From page 82... ...
In a VOI analysis, an information source is valued solely on the basis of the probability and magnitude of its potential impacts on a specific decision at a specific time with a specific state of prior knowledge. Therefore, it is a common and expected result of VOI analysis to estimate that an information source, which may otherwise be considered valuable as a general scientific matter, has little or no value in support of a particular decision.
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From page 83... ...
of Information of Information FIGURE 3-3 Schematic of the application of value-of-information analysis to assess the impacts of additional studies in a specific decision context. Information opportunities that address uncertainties in Figure 3-3.eps the baseline model are considered with respect to the changes they would have on the decision-maker's preferred decision option and the associated change in net benefits.
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From page 84... ...
Despite the potential benefits, it is important to note that a VOI analysis is not considered to be generally superior to the use of expert scientific judgment about the importance of a scientific investigation; rather, it answers a much narrower question about the importance of a study for the outcome of a specific decision and is not appropriate as a general measure of the scientific merit and broader utility of a study. For example, in the context of some specific decision, a VOI analysis might place great value on a small survey to estimate the fraction of businesses using a near-obsolete technology and very little value on a large, well-designed, and broadly important scientific study when considering only the narrow purposes of the specific decision at hand.
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From page 85... ...
As a result, there is likely to be only a small proportion of risk assessments and decision contexts that meet the criteria where a formal VOI is possible (for example, having clear decision rules and prior estimates of uncertainty) and for which the stakes are high enough to make a VOI analysis cost-effective.
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From page 86... ...
An important aspect of instilling the benefits that are analogous to VOI analysis will be in drawing explicit causal linkages, even if expressed qualitatively, between risk-assessment design options and the ultimate impact on the decision-making environment. In this way, the potential for the "value-of-methods" approach is limited in an analogous way by one of the barriers in the formal VOI approach.
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From page 87... ...
Whereas VOI analysis considers the impact of information on the decision outcome (the "ends") , this type of analysis would consider the impact of diverse risk-assessment methods on the overall quality of decision support (the "means")
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From page 88... ...
Unless clear reasons are brought forward at some stage, such as in the formative design stage of risk assessment, to support the need for such a definitive human causality assessment, the committee sees no reason for the agency to
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From page 89... ...
WOE classification provides an example of distinctions between the formal VOI analysis and the less formal value-of-methods analysis. The fact that these finer distinctions in WOE classification are not used further in risk assessment or in any apparent decision rule used by EPA suggests placing no value on the exercise to seek these distinctions, when the potential benefit is viewed purely from a formal VOI analysis perspective (as illustrated in Figure 3-3)
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From page 90... ...
• The committee recommends that EPA consider the adoption of formal VOI methods for highly quantified and well-structured decision-making problems, particularly those with very high stakes, clear decision rules, and the possibility of substantial risks associated with delays in decision-making. For the great majority of decisions that are not readily amenable to formal VOI analysis, the committee recommends that EPA develop a structured evaluation method that exploits, in a less quantitative fashion than formal VOI analysis, a causal understanding of the impact of new information in specific decision-making situations.
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From page 91... ...
2005b. Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities.
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From page 92... ...
2004. Value of information analysis in environmental health risk management decisions: Past, present, and future.
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