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Science and Decisions: Advancing Risk Assessment Appendix F Case Studies of the Framework for Risk-Based Decision-Making In Chapter 8, we proposed a framework for risk-based decision-making in which an initial problem formulation and scoping phase is used to develop the analytic scope necessary to compare intervention options, risks and costs under existing conditions and with proposed interventions are assessed, and risk-management options are analyzed to inform decisions. We provide here three brief examples to demonstrate how the approach in Figure 8-1 might lead to a process and an outcome different from those of a conventional application of risk assessment. The examples are not meant to capture specific and current regulatory decisions in all their technical detail (and are perhaps caricatures of current decision-making paradigms) but are meant simply to illustrate some types of problems and how the framework would, in principle, address them. Similarly, while these examples would in principle involve multiple state and federal agencies under a variety of regulatory structures, they are meant to be more abstract examples of how the approach in Figure 8-1 would address risk management decisions. A CASE STUDY OF ELECTRICITY GENERATION Suppose that a new peaking power plant has been proposed to be sited in a low-income neighborhood that already contains other power-generating capacity or sources of similar pollutants. A conventional application of risk-assessment methods in this context might lead the proponent of the power plant to conduct analyses to determine whether the facility would contribute to exceedances of predefined risk thresholds—for example, greater than a 10−6 risk from air toxics for the maximally exposed person, a violation of ambient air quality standards for criteria pollutants. Issues related to alternative sites would typically be addressed in a separate part of the analysis, with argument of why the selected site is preferable, and no formal evaluations of alternative technologies and their implications for costs or benefits would be considered. Environmental-justice issues would typically be discussed but with no functional connection to the risk assessment or decision. The questions addressed by risk assessment applied in that fashion attempt to determine
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Science and Decisions: Advancing Risk Assessment whether there will be a “significant” problem if the plant is built with the proposed orientation. That sets up an adversarial relationship between the plant proponent and the local community in which the community is attempting to understand the intricacies of the risk assessment (which may have shown no “significant” increases in health risks) and is often operating under the assumption that the analysis has been manipulated in ways that the community does not understand or has not appropriately taken account of exposure and susceptibility conditions in the community. Whether the power plant is ultimately sited or not and whether the risk assessment represents best practice or not, this approach does not make optimal use of the insights that risk assessment can provide in that it focuses on only one alternative other than the status quo and provides limited information to stakeholders. An alternative orientation following Figure 8-1 would still use risk-assessment methods but as part of Phase I would instead ask about the best approach to fulfill a given societal need that would minimize net impacts (including health impacts, costs, and other dimensions). With this orientation, the regulatory body that would be permitting the proposed facility would first determine the societal objective of the facility, which could be to decrease the projected gap between electricity supply and demand in the region during periods of high electricity use. That objective could be met in numerous ways, including energy-efficiency efforts by the utility’s suppliers or customers, increased use of existing power plants, different storage technologies to meet peak power needs, or new power plants using different technologies (that is, alternative fuels and control technologies) in different locations. A donothing strategy and its implications would also be evaluated. Risk assessment can play a key role in distinguishing among the various options considered in combination with other methods and information. In phase I, the set of possible interventions would be determined collectively by all stakeholders with the end points that could inform decision-making (for example, effects on electricity cost per kilowatt-hour, population risk, distribution of risk among defined subpopulations, life-cycle impacts, and probability of blackouts and brownouts). Stakeholders may mutually decide that some end points are unimportant or that some should get greater weight than others, and this will inform the choice of methods. A comprehensive consideration of options at the outset would ensure that all relevant stakeholders were present, avoiding NIMBY outcomes in which an alternative site is chosen in a community that has not been involved in the process. The risk assessments and economic, technical, and other analyses would be oriented around the proposed interventions and would allow for explicit consideration of the tradeoffs among different desirable attributes of the decision and upfront transparency about the solution set, methods, and criteria for decision-making. For example, a clear presentation of the probability of blackouts under the do-nothing strategy and with alternative new facilities would help to demonstrate the importance of new capacity. One possible criticism of this approach is that stakeholder participation and evaluation of multiple competing options require substantial effort and could lead to delays in decision-making. However, the current paradigm often leads to intractable debates about minute details of the risk assessment (Did the proponent use the right dispersion model? Were emissions estimated appropriately? Where would the maximally exposed person live?) without consideration of whether a choice among options would be influenced by these details. An upfront investment of time and effort in developing options and scoping the problem should reduce debate and antagonism considerably in the long term, should reduce analytic effort by focusing it on the end points that would help to discriminate among options, and should allow more coordinated planning of multiple projects with the same general aims. It could also be argued that explicit presentation of the tradeoffs among cost, risk, blackout
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Science and Decisions: Advancing Risk Assessment probability, and equity would make decisions impossible because stakeholders would weigh these components differently, and there are no obvious bright-line distinctions. However, the current decision paradigm considers some of the factors implicitly while ignoring others without any explicit attempt to set priorities, so it is hard to argue that better understanding of the implications of decisions would not be beneficial. A final critique could be that stakeholders are ultimately concerned with the decision rather than the method. If this approach resulted in a conclusion that building the power plant in the low-income community were the optimal solution, residents of the community would be unhappy; if this approach resulted in a decision not to build a new facility, the proponents of the power plant would be unhappy (even if the process and analysis were transparent and agreed on). That may be impossible to avoid, but upfront consideration of scoping and decision criteria will at least reassure stakeholders that the criteria were not determined post hoc, and the rationale for the decision will be clearly presented. A CASE STUDY OF DECISION SUPPORT FOR DRINKING-WATER SYSTEMS Decision-makers and stakeholders seeking safe drinking water carry out their work in the face of a daunting array of microbial, chemical, climatic, operational, security and financial hazards. The capacity of risk assessment to support the societal goal of the provision of safe drinking water is an example of the critical need to reorient current risk-assessment practices away from the support of a series of disconnected single-hazard standard-setting processes and toward the provision of analytic support to facilitate the integration of complex health, ecologic, engineering, and economic elements of decision-making involved in providing safe drinking water. Risk-assessment activities that are directed toward the safety of drinking water primarily support standard-setting exercises. The setting of such standards does not represent the types of more concrete system-design risk-management decisions that have direct physical, biologic, and chemical impacts on the safety of drinking water, representing distal decisions with ambiguous connections to risk reduction rather than proximal decisions with clear causal connections to risk reduction. It is now generally understood that drinking water is best protected by an integrated risk-management approach in which multiple barriers are applied to protect against exposure to the hazards. The intervention options for drinking-water risk management include a complex set of decisions that affect system components that include sewage treatment, source-water selection and protection, multiple stages of water treatment, investments in operator training and information-management systems, changes in laboratory and monitoring practices, protection of the water in the distribution system, household water-use practices, and the capacity for effective emergency response that needs to be engaged when other barriers fail. It is inevitably a complex design problem to reduce risk from multiple sources that are subject to numerous competing constraints. The constraints include the fact that reducing some risks can increase others (the now classic problem of toxicity from disinfection byproducts that are produced in some processes aimed at reducing microbial risks or in choosing among sources of raw water that have varied microbial and chemical risk profiles). Other constraints include financial resources available in the short term and long term, the political and economic implications of issuing boil-water advisories, and the need to provide adequate protection to highly susceptible sub-populations (for example, in the case of persons with HIV/AIDS and the risk of cryptosporidiosis). The societal goal is ultimately not to set standards themselves but rather to minimize the net risk associated with the provision of drinking water given the aforementioned risks
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Science and Decisions: Advancing Risk Assessment and constraints. To that end, a series of decisions are made by the owners and operators of drinking-water systems. Some are discrete events, such as major investments in watershed protection, water-treatment technology, or construction of pipelines from distant water sources; some are continuous processes, such as treatment adjustments based on monitoring or customer complaints related to aesthetic properties of water. It is obvious that those decisions would ideally be made in the presence of the most complete understanding of their implications that can reasonably be provided. The decisions are complex, and the selected actions will inevitably balance competing public goals. In this context, the present committee’s goal for the conduct of risk assessment is the assembly and provision of information that describes (quantitatively and qualitatively) the implications of a set of intervention options, the characterization of the implications in the form of risk measures, and the characterization of the net risk that would be predicted in connection with the decision-maker’s choice of a particular change in the water-management system. In the recommended framework in Figure 8-1, the Environmental Protection Agency (EPA), subject to the continuing reality of standard-setting processes required by statute, would orient risk-assessment activities toward providing risk-informed decision-support tools to the more proximal risk managers and stakeholders. With the help of this reoriented form of risk assessment, locally accountable decision-makers and stakeholders would be empowered by EPA’s decision-support tools to make risk-informed decisions in designing and operating drinking-water systems. A CASE STUDY OF METHYLENE CHLORIDE IN TWO SECTORS The third example is based loosely on the regulatory response during the 1990s to the problems posed by methylene chloride (MeCl2), a ubiquitous solvent that is a neurotoxin and a rodent carcinogen and that exacerbates carboxyhemoglobin formation. The example considers some of the likely costs and benefits of various interventions to reduce MeCl2 risks in the workplace and in the general environment; its main point is to show that the outcome would depend heavily on how the regulatory agency chose to formulate the problem and potential intervention options. It also emphasizes that a too-narrow formulation of the problem, without consideration of intervention options at the outset, could exacerbate or fail to identify risk-risk tradeoffs. A conventional application of risk-assessment methods might attempt to determine the allowable MeCl2 concentration in ambient air to meet a defined risk threshold. In this case, the risk assessment supports a distal decision to set a risk-specific concentration. However, nothing would prevent facilities from complying with the standard by transferring the MeCl2risk to other chemicals or populations. They could substitute an unregulated (but potentially more toxic) solvent or simply change the production conditions so that less MeCl2 is emitted from stack and fugitive emission points but more is released into the workplace. Other tradeoffs are also possible; for example, the allegation has been made in the aircraft sector that one compliance strategy (reduction in the frequency of stripping and repainting) can lead to an increased safety risk if it compromises the airworthiness of the craft. An alternative strategy could involve finding the best available technology to control MeCl2 emissions. In this case, the exercise is reduced to arranging the existing control techniques in order of efficiency and choosing either the “best available technology” (the single most efficient) or some “good enough available technology,” as is done in the Maximum Achievable Control Technology (MACT) program under the Clean Air Act, which seeks to mandate the technology that corresponds to the average of the best-performing 12% of all current sources. As with any purely technology-based decision, the absolute risk reduction
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Science and Decisions: Advancing Risk Assessment achieved may be insufficient to be acceptable, or it might be too stringent in that its costs outweigh its benefits. In spite of the simplicity of the approach, it is unlikely to yield the optimal solution, and firms could still respond to the technology mandate by adverse substitution, risk-shifting, plant closure, or some other action. If the committee’s framework for risk-based decision-making (Figure 8-1) were used instead, the initial problem-formulation step could determine that the goal is to minimize the total impacts of the production and use of the products that currently consume MeCl2(such as assembled foam and repainted aircraft). Risk assessments (and economic and other analyses) would be used to compare the residual risks and economic costs of control of each of a set of possible interventions. If the analytic question is asked about the process or function rather than about the substance, the set of interventions can be more expansive, and risk-risk tradeoffs can be minimized (or at least confronted explicitly). Hypothetically, both EPA and the Occupational Safety and Health Administration might agree that for foam assembly, local ventilation plus carbon adsorption is the optimal solution for controlling MeCl2 or any similar solvent that might be substituted for it. Similarly, for aircraft repainting, the optimal solution might involve requiring (or encouraging) the use of nontoxic abrasive material rather than a volatile solvent to remove the old paint layer. The framework in Figure 8-1 could also allow the agencies to think more expansively and to seek global rather than local optima. Setting aside questions of agency scope, if the societal function were redefined as providing air travel rather than providing frequently repainted aircraft, intervention options might emerge for discussion that included changing the incentives to repaint so often, and this might broaden the analysis to include the impacts of jet-fuel use (fuel savings resulting from the coating, rather than painting, of planes). Even broader discussions of incentives for reducing the need for air travel might ensue; it is only the makeup of the involved participants and their preferences, subject to time and other logistical constraints, that dictates the scope of the interventions contemplated in this paradigm.
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