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OCR for page 286
Issues in Risk Assessment That approach is already being adopted, as evidenced by the phaseout of CFCs, reduction of chlorine bleaching agents in the manufacture of paper products, and the Administration's recent proposal for ''debt for nature" swaps with developing nations. In conclusion, Dr. Yosie stated that we should develop a capability for ecological risk assessment that is forward-looking and prevention-oriented, as well as backward-looking and remediation-oriented. D. Warner North: Relationship Of Workshop To Nrc's 1983 Red Book Report D. Warner North, a member of the committee that produced the 1983 NRC report Risk Assessment in the Federal Government: Managing the Process, provided an overview of the purpose and potential of risk assessment as portrayed in that report. Dr. North argued that the descriptions of the principles of risk assessment and the process for carrying out risk assessment in the 1983 report, which has had a substantial impact on the conduct of human health risk assessment, provide lessons and insights that apply to ecological risk assessment. In Dr. North's view, the purpose of the 1983 committee effort was not to provide a summary of risk assessment, but to seek institutional mechanisms for carrying out risk assessment that would be effective in supporting contentious regulatory decisions. The committee found the basic problem in human health risk assessment to be incompleteness of data—a finding that clearly applies to ecological risk assessment as well. That problem is resolved, not by altering institutional arrangements for performing risk assessment, but by improving the process by which risk assessments are made. Perhaps the most widely reproduced part of the 1983 report is its description of the elements of risk assessment and risk management. These are reproduced in the current committee report as Figure 3-1 (Chapter 3). The elements collectively provide a bridge between science and risk management, which might be more generally denoted as policy. Risk assessment can provide a consistent process for summarizing science to support regulatory decision-making by federal agencies. The process of providing the scientific basis must be consistent and flexible
OCR for page 287
Issues in Risk Assessment before regulatory policies for managing risks can be evolved that are consistent and yet permit change based on the evolution of scientific knowledge. Scientific knowledge is incomplete, and the multiplicity of resulting uncertainties needs to be dealt with by making choices among sets of scientifically plausible options. Rather than having those critical choices left to the discretion of individual risk assessors or the influence of risk managers, who might desire to regulate or not regulate in a specific situation on the basis of nonscientific considerations, the 1983 report suggests these choices can be made systematically with a risk assessment policy that is consistent with science and permits exceptions based on science. The report presents as its lead recommendation that regulatory agencies should maintain a clear conceptual distinction between assessment of risks and the consideration of risk management alternatives; that is, the scientific findings and policy judgments embodied in risk assessments should be explicitly distinguished from the political, economic, and technical considerations that influence the design and choice of regulatory strategies. The implication is that the scientific issues resulting from gaps in data and in theoretical understanding should be dealt with in a consistent and predictable way. Furthermore, the scientific issues should be carefully distinguished from nonscientific issues on which policy discretion is expected and for which the decision-maker is held responsible. It can be argued that health risk assessment practice has gone too far in separating risk assessment and risk management. The 1983 report advocated conceptual distinction, not separation. The report states that the importance of distinguishing between risk assessment and risk management does not imply that they should be isolated from each other; in practice they interact, and communication in both directions is desirable and should not be disrupted. Furthermore, risk assessment must serve an assortment of functions in support of risk management, from initial screening and priority-setting exercises to major regulatory decisions with profound economic and public health consequences. Simple procedures appropriate for screen-
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Issues in Risk Assessment ing and priority-setting "may have to yield to more sophisticated and detailed scientific arguments when a substance's commercial life is at stake and the agency's decision may be challenged in court." Unfortunately, the same simple procedures used for health risk assessment in simple screening applications have often been used for risk assessment in support of major regulatory decisions as well. Rarely has the flexibility been used to bring in "more sophisticated and detailed scientific arguments" to replace the default assumptions, even though such departures are permitted under health risk assessment guidelines. Dr. North then returned to a discussion of the four elements or steps in the risk assessment paradigm. Not all these steps are always required: a risk assessment might stop with the first step, hazard identification. The definitions of the steps can be translated from the context of health risk to the context of ecological risk quite readily: Hazard identification. The determination of whether a particular chemical (stress agent) is or is not causally linked to particular ecological effects. Dose-response assessment. The determination of the relation between the magnitude of exposure and the probability of occurrence of the effects in question. Exposure assessment. The determination of the extent of exposure before or after application of regulatory controls. Risk characterization. The description of the nature and often the magnitude of ecological risk, including attendant uncertainty. However, the terms magnitude of exposure and extent of exposure might require replacement with a more general measure of ecological stress. The major thrust of the 1983 report was not to recommend that risk assessment be carried out with the four steps. Rather, most of the recommendations addressed the process of summarizing the science in support of risk management. In addition to the first recommendation on the conceptual distinction between risk assessment and risk management, the report recommended that risk assessments be made publicly available as written documents in advance of regulatory decisions and that such risk assessments be subjected to peer review by scientists from outside the agency. Uniform guidelines should be developed for the use of federal agencies in the risk assessment process, and these guidelines