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Acceptable risk
Journal of Occupational Accidents, 7 (1986) 291-293 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
291
Book Review
Risk, by Baruch Fischoff, Sarah Lichtenstein, Paul Slavic, Stephen L. Derby and Ralph L. Keeney, Cambridge University Press, Cambridge, 1984,185 pp., $5.95, ISBN O-521-27892-9.
Acceptable
Perhaps not surprisingly the first chapter of this book is entitled “How safe is safe enough?” This is a question that is increasingly being asked about the measures necessary to control the hazards which exist in, or are being introduced into, our technological society. Accidents such as the recent disaster at Bhopal in which more than 2000 people died as a result of an accidental release of methyl isocyanate gas result in further debate about the “acceptability” of the risks generated by industrial activity. This book, as its title implies, is aimed at anyone who may be involved in such debates and in particular at those who have to make acceptable-risk decisions, or set regulatory standards, or professionals who manage or assess risk. The emphasis is on technological hazards that pose a threat to life or health. The underlying influence of the human element in this area is neatly summarised: “People create both technological hazards and the schemes for managing them. They decide what their needs are, accept technologies that address those needs, assess the risks and benefits of these technologies, use them wisely or unwisely, see or miss the need for ameliorative action when things go wrong and so forth. As consumers, voters, legislators, regulators, operators and promoters, people shape the world within which technologies operate and thus determine the degree of hazard that these technologies pose”. The book focuses on the extent to which various approaches to decision making provide a complete answer to acceptable-risk questions. It is divided into ten chapters. Chapter 1 offers a basic frame work for ~on~eptu~is~g acceptable risk questions which are implicit in “How safe is safe enough?” as decision problems. In essence they reduce to a choice among alternative courses of action (at least one of which poses a threat to life or health). The authors emphasise that the decision on which option is most attractive is inherently situation specific, that there are no universally acceptable options (or risks, costs or benefits) and that no level of risk can be specified such that risks less than that level are acceptable and risks greater than that level are unacceptable. Chapter 2 attempts to characterise real acceptable-risk decisions in terms of five generic complexities: (a) uncertainty about how to define the decision problem (b) difficulties in assessing the facts (includ~g expert judgement) (c) difficulties in assessing the relevant values (d) uncertainties about the human element in the decision making process and (e) Difficulties in assessing the quality of the decisions that are produced.
292
This is a very interesting chapter which, inter alia, considers the layman’s perception of risk and whether the public could be better informed. Sensitivity analysis is also discussed and attention is drawn to the possibility of judgemental biases and over-confidence on the part of the analyst threatening the validity of such analyses, i.e., they represent “a sort of analytical common-mode failure”. This last statement, in my view, is more appropriate for an uncertainty analysis rather than a one-at-a-time or a simple multivalued sensitivity analysis. On area (e) above I must concur with the statements made by the authors such as “To guide social policy, an approach to acceptable-risk decisions must be able to assess its own limits and to inform us of that assessment. Because the methodology needed for this task is in a rather primitive state, we must rely heavily on our own experience and intuitions. As elsewhere these judgements can lead us astray, producing too much or too little confidence in the quality of decisions”. In Chapter 3 current acceptable-risk decision making is reviewed and three generic methods identified. These are: formal analysis, typified by costbenefit and decision analysis; “bootstrapping approaches” which use historical collateral evidence on risk levels as a guide to setting new safety standards; and professional judgement which relies on the wisdom of the best available technical experts. Each of these methods have different strengths and weaknesses, Seven criteria for choosing between them are presented and discussed. “Determining the relative importance of these criteria is a political matter that underlies the choice of a method”. The next three chapters characterise, in turn, the three main strategies described in Chapter 3 in terms of how they tackle the generic complexities described in Chapter 2. An assessment is made of the adequacy of each approach for resolving acceptable-risk questions in terms of the seven criteria presented in Chapter 3, i.e., comprehensiveness, logical soundness, practicality, openness to evaluation, political acceptability, compatibility with institutions, and conduciveness to learning. Chapter 7 compares the three approaches with each other and their relative ability to cope with particular kinds of acceptable-risk problems such as “setting standards for a component of a complex technology” or “deciding the fate of a new technology”. In Chapter 8 the authors summarise their findings and make some suggestions about acceptable risk problems and their man~ement. Chapter 9 makes recommendations for improving acceptablerisk decision making. These follow logically from the previous chapters and are directed at the technical community, the public, the market place and government. For example “Government should establish clearer guidelines and authority for dealing with public risks”. The final chapter presents proposals for reducing the uncertainties that arise in the five general areas of difficulty reviewed in Chapter 2 and offers an agenda for research needed to improve society’s decision making capacity. “Given the enormous stakes riding on acceptable-risk decisions, our investment in research seems very small”.
293
The book, which is well written and interspersed with many useful summaries, is in fact a paperback version of the original hardback volume published in 1981. The material therefore is mainly based on work published in or before 1980 but that should not detract from the utility of the very useful guidance this book offers on decision making problems, particularly in the health and safety field. That problem is tackled from many angles and difficulties associated with present approaches, and biases in their application are exposed. Given the complexities of the area addressed, Fischhoff and his collaborators are to be congratulated on a thorough and systematic appraisal of acceptable-risk decision making strategies, their strengths and weaknesses, and the inevitable philosophical and controversial matters that such decision making raises. C. NUSSEY
291
Book Review
Risk, by Baruch Fischoff, Sarah Lichtenstein, Paul Slavic, Stephen L. Derby and Ralph L. Keeney, Cambridge University Press, Cambridge, 1984,185 pp., $5.95, ISBN O-521-27892-9.
Acceptable
Perhaps not surprisingly the first chapter of this book is entitled “How safe is safe enough?” This is a question that is increasingly being asked about the measures necessary to control the hazards which exist in, or are being introduced into, our technological society. Accidents such as the recent disaster at Bhopal in which more than 2000 people died as a result of an accidental release of methyl isocyanate gas result in further debate about the “acceptability” of the risks generated by industrial activity. This book, as its title implies, is aimed at anyone who may be involved in such debates and in particular at those who have to make acceptable-risk decisions, or set regulatory standards, or professionals who manage or assess risk. The emphasis is on technological hazards that pose a threat to life or health. The underlying influence of the human element in this area is neatly summarised: “People create both technological hazards and the schemes for managing them. They decide what their needs are, accept technologies that address those needs, assess the risks and benefits of these technologies, use them wisely or unwisely, see or miss the need for ameliorative action when things go wrong and so forth. As consumers, voters, legislators, regulators, operators and promoters, people shape the world within which technologies operate and thus determine the degree of hazard that these technologies pose”. The book focuses on the extent to which various approaches to decision making provide a complete answer to acceptable-risk questions. It is divided into ten chapters. Chapter 1 offers a basic frame work for ~on~eptu~is~g acceptable risk questions which are implicit in “How safe is safe enough?” as decision problems. In essence they reduce to a choice among alternative courses of action (at least one of which poses a threat to life or health). The authors emphasise that the decision on which option is most attractive is inherently situation specific, that there are no universally acceptable options (or risks, costs or benefits) and that no level of risk can be specified such that risks less than that level are acceptable and risks greater than that level are unacceptable. Chapter 2 attempts to characterise real acceptable-risk decisions in terms of five generic complexities: (a) uncertainty about how to define the decision problem (b) difficulties in assessing the facts (includ~g expert judgement) (c) difficulties in assessing the relevant values (d) uncertainties about the human element in the decision making process and (e) Difficulties in assessing the quality of the decisions that are produced.
292
This is a very interesting chapter which, inter alia, considers the layman’s perception of risk and whether the public could be better informed. Sensitivity analysis is also discussed and attention is drawn to the possibility of judgemental biases and over-confidence on the part of the analyst threatening the validity of such analyses, i.e., they represent “a sort of analytical common-mode failure”. This last statement, in my view, is more appropriate for an uncertainty analysis rather than a one-at-a-time or a simple multivalued sensitivity analysis. On area (e) above I must concur with the statements made by the authors such as “To guide social policy, an approach to acceptable-risk decisions must be able to assess its own limits and to inform us of that assessment. Because the methodology needed for this task is in a rather primitive state, we must rely heavily on our own experience and intuitions. As elsewhere these judgements can lead us astray, producing too much or too little confidence in the quality of decisions”. In Chapter 3 current acceptable-risk decision making is reviewed and three generic methods identified. These are: formal analysis, typified by costbenefit and decision analysis; “bootstrapping approaches” which use historical collateral evidence on risk levels as a guide to setting new safety standards; and professional judgement which relies on the wisdom of the best available technical experts. Each of these methods have different strengths and weaknesses, Seven criteria for choosing between them are presented and discussed. “Determining the relative importance of these criteria is a political matter that underlies the choice of a method”. The next three chapters characterise, in turn, the three main strategies described in Chapter 3 in terms of how they tackle the generic complexities described in Chapter 2. An assessment is made of the adequacy of each approach for resolving acceptable-risk questions in terms of the seven criteria presented in Chapter 3, i.e., comprehensiveness, logical soundness, practicality, openness to evaluation, political acceptability, compatibility with institutions, and conduciveness to learning. Chapter 7 compares the three approaches with each other and their relative ability to cope with particular kinds of acceptable-risk problems such as “setting standards for a component of a complex technology” or “deciding the fate of a new technology”. In Chapter 8 the authors summarise their findings and make some suggestions about acceptable risk problems and their man~ement. Chapter 9 makes recommendations for improving acceptablerisk decision making. These follow logically from the previous chapters and are directed at the technical community, the public, the market place and government. For example “Government should establish clearer guidelines and authority for dealing with public risks”. The final chapter presents proposals for reducing the uncertainties that arise in the five general areas of difficulty reviewed in Chapter 2 and offers an agenda for research needed to improve society’s decision making capacity. “Given the enormous stakes riding on acceptable-risk decisions, our investment in research seems very small”.
293
The book, which is well written and interspersed with many useful summaries, is in fact a paperback version of the original hardback volume published in 1981. The material therefore is mainly based on work published in or before 1980 but that should not detract from the utility of the very useful guidance this book offers on decision making problems, particularly in the health and safety field. That problem is tackled from many angles and difficulties associated with present approaches, and biases in their application are exposed. Given the complexities of the area addressed, Fischhoff and his collaborators are to be congratulated on a thorough and systematic appraisal of acceptable-risk decision making strategies, their strengths and weaknesses, and the inevitable philosophical and controversial matters that such decision making raises. C. NUSSEY