152 The World Health Report 2002 Defining what is"highly uncertain"depends on context. Risks may be highly uncertain because they are hidden risks, that are unstudied or insufficiently thought about Risks may be hidden because they are unknown or rare phenomena; they are common phenomena that are statistically invisible(which might happen if data are gathered in categories that fail to reveal the risk); or they have been ignored because it was thought that nothing could be done about them; fresh controversies. There is inadequate and inconclusive information, but it can be reasonably expected that new information will be obtained which may well resolv outstanding key questions persistent controversies, which endure even after a great deal of research to try to resolve them. Persistence of controversy is likely to be reinforced by differences in political or academic perspectives which inhibit communication between the parties and impede the establishment of common terms and agreement on approaches to information gathering. Special interest groups play a role in fostering controversy For any given risk, some or all of these categories can be a part of its development. For example, an unknown risk such as bovine spongiform encephalopathy(BSe)may emerge as a surprise, lead to serious controversies, and later on become familiar. Assessment and management of highly uncertain risks can be adaptive, based on the following principles. Management should start with what is already known, acknowledge openly the major scientific uncertainties, and highlight uncertainties about human behaviour that affect the risk t new information might become available on what time scales, and what it might show A summary of this analysis should form a distinct section of Development of a plan for acquiring and managing nev of the plan as a portion of the management options to be considered Management goals should be defined broadly so that growing knowledge can be effectively utilize the acquisition of new knowledge should be one of these goals everything right the first time, especially when uncertainties are large There may be threats that are irreversible, affect a large number of people, or rapidly expand the problem. Rapid diagnosis and response are therefore appropriate, and can of ten prevent major damage from occurring especially in situations involving irreversible changes or rapid spread of the uncertain hazard. Characteristics of hazards such as persistence, irreversibility, and depth and breadth of impact are thus of particular concern Within the realm of highly uncertain risks, it is important to recognize that adaptive anagement should not be confined to particular, already specified, hazards. Rather, order to use limited resources effectively, there should be investment in risk management efforts which do not focus on particular hazards but which will improve capabilities for identifying emerging hazards and for coping with them he management of highly uncertain risks involves infrastructure development in various international and national public agencies. The aims of such agencies are to search fo hidden hazards, maintain a capability for responding to surprises and controversies, moni-152 The World Health Report 2002 Defining what is “highly uncertain” depends on context. Risks may be highly uncertain because they are: • hidden risks, that are unstudied or insufficiently thought about. Risks may be hidden because they are unknown or rare phenomena; they are common phenomena that are statistically invisible (which might happen if data are gathered in categories that fail to reveal the risk); or they have been ignored because it was thought that nothing could be done about them; • surprises; • fresh controversies. There is inadequate and inconclusive information, but it can be reasonably expected that new information will be obtained which may well resolve outstanding key questions; • persistent controversies, which endure even after a great deal of research to try to resolve them. Persistence of controversy is likely to be reinforced by differences in political or academic perspectives which inhibit communication between the parties and impede the establishment of common terms and agreement on approaches to information gathering. Special interest groups play a role in fostering controversy. For any given risk, some or all of these categories can be a part of its development. For example, an unknown risk such as bovine spongiform encephalopathy (BSE) may emerge as a surprise, lead to serious controversies, and later on become familiar. Assessment and management of highly uncertain risks can be adaptive, based on the following principles. • Management should start with what is already known, acknowledge openly the major scientific uncertainties, and highlight uncertainties about human behaviour that affect the risk. • Explicit analysis of what new information might become available on what time scales, and what it might show. A summary of this analysis should form a distinct section of the assessment. • Development of a plan for acquiring and managing new information and presentation of the plan as a portion of the management options to be considered. Management goals should be defined broadly so that growing knowledge can be effectively utilized; the acquisition of new knowledge should be one of these goals. • Improving assessment and performance is necessarily iterative; it is impossible to get everything right the first time, especially when uncertainties are large. There may be threats that are irreversible, affect a large number of people, or rapidly expand the problem. Rapid diagnosis and response are therefore appropriate, and can of￾ten prevent major damage from occurring, especially in situations involving irreversible changes or rapid spread of the uncertain hazard. Characteristics of hazards such as persistence, irreversibility, and depth and breadth of impact are thus of particular concern. Within the realm of highly uncertain risks, it is important to recognize that adaptive management should not be confined to particular, already specified, hazards. Rather, in order to use limited resources effectively, there should be investment in risk management efforts which do not focus on particular hazards but which will improve capabilities for identifying emerging hazards and for coping with them. The management of highly uncertain risks involves infrastructure development in various international and national public agencies. The aims of such agencies are to search for hidden hazards, maintain a capability for responding to surprises and controversies, moni-