Perceiving Risks Risks that are both highly uncertain and highly dreaded are also clearly the most diffi- cult to predict and control. Two very important factors for dread were found to be global catastrophe and risks that involve members of future generations. The advent of glol terrorism and the development of genetically modified foods are two recent examples.Less dreaded risks tend to be those that are individual, controllable and easily reduced. The more acceptable risks are those that are known, observable and have immediate effects. In addition, the more equitable the risks, the more likely they are to be generally accepted. useful to consider perceptions of dread and unknown risk in relation to public health interventions for reducing risks. If risk factors are to be controlled, the interventions should be perceived to have low dread and a low risk of adverse events. Higher risks from such interventions will normally only be accepted by individuals in the higher risk groups However, population-wide interventions to reduce risk typically have to cover all people, even those at low risk. Thus interventions used in public health programmes need to have low dread and known low and acceptable levels of risk, combined with high safety levels. Typically, vaccination and screening programmes fall into this category, particularly as they are usually targeted at whole populations and involve many healthy people who are at low risk of getting ill and dying. The favourable perception of the public to prescribed medicines, for example, has been attributed to the direct benefits of such medicines and to the trust people place in their safety, achieved through research and testing carried out by medical and pharmaceutical professionals Figure 3. 1 Hazards for dread and riska not observable unknown to those exposed effect delayed risks unknown to science Food irradiation◆ Oral contraceptives Low dread risk Vaccinations. High dread risk controllable uncontrollable Pregnancy, childbirth. Surgery Alcoholic beverages◆ own risk risks known to science from interrelationships of 18 risk characteristics. Fador 3 (not shown)reflects the number of people exposed to the hazard and the degree of their personal exposure
Perceiving Risks 33 Risks that are both highly uncertain and highly dreaded are also clearly the most difficult to predict and control. Two very important factors for dread were found to be global catastrophe and risks that involve members of future generations. The advent of global terrorism and the development of genetically modified foods are two recent examples. Less dreaded risks tend to be those that are individual, controllable and easily reduced. The more acceptable risks are those that are known, observable and have immediate effects. In addition, the more equitable the risks, the more likely they are to be generally accepted. It is useful to consider perceptions of dread and unknown risk in relation to public health interventions for reducing risks. If risk factors are to be controlled, the interventions should be perceived to have low dread and a low risk of adverse events. Higher risks from such interventions will normally only be accepted by individuals in the higher risk groups. However, population-wide interventions to reduce risk typically have to cover all people, even those at low risk. Thus interventions used in public health programmes need to have low dread and known low and acceptable levels of risk, combined with high safety levels. Typically, vaccination and screening programmes fall into this category, particularly as they are usually targeted at whole populations and involve many healthy people who are at low risk of getting ill and dying. The favourable perception of the public to prescribed medicines, for example, has been attributed to the direct benefits of such medicines and to the trust people place in their safety, achieved through research and testing carried out by medical and pharmaceutical professionals. Food irradiation Lasers Nuclear power Water fluoridation Oral contraceptives Asbestos Radiation therapy Pesticides Diagnostic X-rays Vaccinations Antibiotics Anaesthetics Smoking Pregnancy, childbirth Surgery Alcoholic beverages Open-heart surgery Morphine Nerve gas Terrorism Low dread risk - controllable - not dreaded - not global catastrophic - consequences not fatal - equitable - individual - low risk to future generations - easily reduced - risk decreasing - voluntary - doesn't affect me Known risk - observable - known to those exposed - effect immediate - old risk - risks known to science Unknown risk - not observable - unknown to those exposed - effect delayed - new risk - risks unknown to science High dread risk - uncontrollable - dreaded - global catastrophic - consequences not fatal - not equitable - catastrophic - high risk to future generations - not easily reduced - risk increasing - involuntary - affects me Figure 3.1 Hazards for dread and riska a Adapted from: Slovic P, Fischhoff B, Lichtenstein S. Facts and fears: understanding perceived risk. In: Schwing RC, Albers WA Jr, editors. Societal risk assessment: how safe is safe enough? New York: Plenum; 1980. Locations of 20 hazards – instead of 90 in the original – on factor 1 (dread) and factor 2 (unknown risk) of the three-dimensional figure derived from interrelationships of 18 risk characteristics. Factor 3 (not shown) reflects the number of people exposed to the hazard and the degree of their personal exposure
The World Health Report 2002 DEFINING AND DESCRIBING RISKS TO HEALTH Risk assessment and management is a political as well as a scientific process, and public perceptions of risk and risk factors involve values and beliefs, as well as power and trust For policy-makers who are promoting intervention strategies to lower risks to health, it is obviously important, therefore, to understand the different ways in which the general public and health professionals perceive risks(19). As described in Chapter 2, use of the term"risk has many different meanings and this often causes difficulties in communication. This report uses the notions of the probability of a subsequent adverse health event, followed by its consequence which is mainly either morbidity or mortality While many scientists often assume that risks can be objectively verified, many social scientists argue that risk measures are inherently much more subjective. In addition, other members of the public have yet other notions of risk. How do people define and describe risk factors? How do they estimate risks? Answers to such questions obviously alter people's perceptions. Such information is needed, therefore, to improve communications and to predict public responses to public health interventions, including the introduction of new health technologies and risk factor and disease prevention programmes. Box 3. 2 illustrates male perceptions of sexual health risks and the need to use preventive measures against HIV infection and pregnancy A complicated question is how the mortality outcome associated with a particular risk factor should be expressed Even choosing or framing the end-point as death is surprising omplex and can make large differences in the way risk is both perceived and evaluated The following is a well-known example from occupational health, which shows how the choice of risk measure can make a technology appear less or more risky to health(21) Between 1950 and 1970, coal mining in the USa became much less risky if the measure of risk was taken to be accident deaths per million tons of coal produced, but it became more risky if risk was described in terms of accident deaths per 1000 miners employed. Which easure is more appropriate for decision-making? From a national perspective, and given the need to produce coal, deaths of miners per million tons of coal produced appears to be e more appropriate measure of risk. However, from the point of view of individual miners and their trade unions the death rate per thousand miners employed is obviously far more relevant. Since both measures for framing the risks in this industry are relevant, both should e considered in any risk management decision-making process Each way of summarizing deaths embodies its own set of inherent and subjective values (7). For example, an estimate based on reduction in life expectancy treats deaths of young people as more important than deaths of older people, who have less life expectancy to lose. However, counting all fatalities together treats all deaths of the young and old as equivalent. This approach also treats equally deaths immediately after mishaps and deaths that follow painful and lengthy debilitating diseases Such choices all involve subjective value judgements. For instance, using"number of deaths "may not distinguish deaths of people who engage in an activity by choice and benefit from it directly, from those of people who are exposed to a hazard involuntarily and who get no direct benefits. Each approach may be justifiable but uses value judgements about which deaths are considered to be the most undesirable. To overcome such problems, information should be framed in a variety of different ways so that such complexities are revealed to decision-makers
34 The World Health Report 2002 DEFINING AND DESCRIBING RISKS TO HEALTH Risk assessment and management is a political as well as a scientific process, and public perceptions of risk and risk factors involve values and beliefs, as well as power and trust. For policy-makers who are promoting intervention strategies to lower risks to health, it is obviously important, therefore, to understand the different ways in which the general public and health professionals perceive risks (19). As described in Chapter 2, use of the term “risk” has many different meanings and this often causes difficulties in communication. This report uses the notions of the probability of a subsequent adverse health event, followed by its consequence which is mainly either morbidity or mortality. While many scientists often assume that risks can be objectively verified, many social scientists argue that risk measures are inherently much more subjective. In addition, other members of the public have yet other notions of risk. How do people define and describe risk factors? How do they estimate risks? Answers to such questions obviously alter people’s perceptions. Such information is needed, therefore, to improve communications and to predict public responses to public health interventions, including the introduction of new health technologies and risk factor and disease prevention programmes. Box 3.2 illustrates male perceptions of sexual health risks and the need to use preventive measures against HIV infection and pregnancy. A complicated question is how the mortality outcome associated with a particular risk factor should be expressed. Even choosing or framing the end-point as death is surprisingly complex and can make large differences in the way risk is both perceived and evaluated. The following is a well-known example from occupational health, which shows how the choice of risk measure can make a technology appear less or more risky to health (21). Between 1950 and 1970, coal mining in the USA became much less risky if the measure of risk was taken to be accident deaths per million tons of coal produced, but it became more risky if risk was described in terms of accident deaths per 1000 miners employed. Which measure is more appropriate for decision-making? From a national perspective, and given the need to produce coal, deaths of miners per million tons of coal produced appears to be the more appropriate measure of risk. However, from the point of view of individual miners and their trade unions the death rate per thousand miners employed is obviously far more relevant. Since both measures for framing the risks in this industry are relevant, both should be considered in any risk management decision-making process. Each way of summarizing deaths embodies its own set of inherent and subjective values (7). For example, an estimate based on reduction in life expectancy treats deaths of young people as more important than deaths of older people, who have less life expectancy to lose. However, counting all fatalities together treats all deaths of the young and old as equivalent. This approach also treats equally deaths immediately after mishaps and deaths that follow painful and lengthy debilitating diseases. Such choices all involve subjective value judgements. For instance, using “number of deaths” may not distinguish deaths of people who engage in an activity by choice and benefit from it directly, from those of people who are exposed to a hazard involuntarily and who get no direct benefits. Each approach may be justifiable but uses value judgements about which deaths are considered to be the most undesirable. To overcome such problems, information should be framed in a variety of different ways so that such complexities are revealed to decision-makers