What Do We Know About Making Risk Comparisons?

The risks of unfamiliar technologies are often evaluated by comparing them with the risks of more familiar ones. Such risk comparisons have been criticized for neglecting critical dimensions of risky decisions. In a guide written for the Chemical Manufacturers Association, Covello et al. (¹) have summarized these critiques and developed a taxonomy that characterizes possible risk comparisons in terms of their acceptability (or objectionableness). We asked four diverse groups of subjects to judge the acceptability of 14 statements produced by Covello et al. as examples of their categories. We found no correlation between the judgments of acceptability produced by our subjects and those predicted by Covello et al. .     

Stability and Inoculation of Risk Comparisons'' Effects Under Conflict: Replicating and Extending the "Asbestos Jury" Study by Slovic et al.

Promotion or criticism of risk comparisons in risk communication has far exceeded empirical tests of their effects. Slovic et al. (1990) experimented with a hypothetical jury trial in which an asbestos-installing firm was accused of subjecting school occupants to unreasonable risk. A risk comparison sharply reduced subjects' estimates of risk and judgments that the firm was guilty, but a critique of the risk comparison had risk estimates and guilt judgments rebounding to the original (without risk comparison) level. Slovic et al. concluded that risk comparisons' effects were highly unstable, at least in conflict-ridden situations such as a jury trial. The present study replicates and extends this important study, using the same stimuli and questions. The respective effects of the risk comparison and the critique recurred, although much less sharply than in Slovic et al. Moreover, judgments of guilt, risk, and other aspects of the case seemed shaped more by demographics and beliefs about risk generically (e.g., about the likelihood of cancer after exposure to a carcinogen) than by either risk comparison or critique. A variant design, in which the defense's expert witness dismissed potential criticisms of the risk comparison, appeared to "inoculate" people against shifting their views after seeing the critique. Overall, these results show that risk comparisons might change some beliefs about risks in conflict and that "inoculation" can reduce vulnerability to criticism. However, the results also show strong limits on effects of both comparisons and their critiques: they shifted only a minority of judgments and had small effects relative to people's social locations and prior risk beliefs.     

基于ARCH-Expectile方法的VaR和ES尾部风险测量

甄别和确定风险因素的贡献是资产或资产组合风险管理的重要研究内容。近十年,下端风险越来越受到关注,在险价值（Value at Risk,VaR）和预期不足（Expected Shortfall,ES）是资产组合风险管理中两个常用的风险度量工具。Kuan等^[1]在一类条件自回归模型（CARE）下提出了基于expectile的VaR度量-EVaR。本文扩展了Kuan等^[2]的CARE模型到带有异方差的数据,引入ARCH效应提出了一个线性ARCH-Expectile模型,旨在确定资产或资产组合的风险来源以及评估各风险因素的贡献大小,并应用expectile间接评估VaR和ES风险大小。同时给出了参数的两步估计算法,并建立了参数估计的大样本理论。最后,将本文所提出的方法应用于民生银行股票损益的风险分析,从公司基本面、市场流动性和宏观层面三个方面选取影响股票损益的风险因素,分析结果表明,各风险因素随股票极端损失大小的水平不同,其风险因素的来源及其大小和方向也是随之变化的。     

Risk Assessment for Aflatoxin: III. Modeling the Relative Risk of Hepatocellular Carcinoma

Estimates have been made of the cancer potency of aflatoxin exposure among the U.S. population. Risk modeling is used to assess the dose-response relationship between aflatoxin exposure and primary liver cancer, controlling for hepatitis B virus (HBV), based on data provided by the Yeh et al. study in China. A relative risk model is proposed as a more appropriate alternative to the additive ("absolute" risk) model for transportation of risk coefficients between populations with different baseline rates. Several general relative risk models were examined; the exponential model provided the best fit. The Poisson regression method was used to fit the relative risk model to the grouped data. The effects of exposure to aflatoxin (AFB1) and hepatitis B infection were both found to be statistically significant. The risk of death from liver cancer for those exposed to AFB1 relative to the unexposed population, increases by 0.05% per ng/kg/day exposure of AFB1 (p less than 0.001). The results also indicated a 25-fold increase in the risk of death from liver cancer among those infected with hepatitis B virus, relative to noncarriers (p less than 0.0001). With a hepatitis prevalence rate of 1%, the aflatoxin intake level associated with liver cancer lifetime excess risk of 1 x 10(-5) for the U.S. population was estimated as 253 ng/day, based on a liver cancer baseline rate of 3.4/100,000/yr.     

Managing Societal and Institutional Risk in Child Protection

Public sector services have been reshaped by two interacting factors: the growing dominance of risk management and the growing demands for transparency and accountability. For the caring professions, these have provoked radical reform. Using the child protection service as a case study, this article explores the impact of the changes on a service that deals with conflicting risks and has a poorly articulated knowledge base. Drawing on Rothstein et al. 's distinction between societal and institutional risks, it is argued that difficulties in managing societal risks are creating serious institutional risks. The latter are then being prioritized in the way the system operates. The preoccupation with such risks has been translated into concerted efforts to formalize the work of front line practitioners to make it transparent and auditable. Although done, in part, with the good intention of spreading good practice standards, this formalization has gone beyond the evidenced knowledge base to the extent that it is creating a new picture of "good practice" that omits significant dimensions of work and is distinct from measures of children's safety or welfare. Moreover, the process of formalization acts as an impediment to knowledge development in disciplines where such learning is urgently needed.     

On Funtowicz and Ravetz's “Decision Stake—System Uncertainties” Structure and Recently Developed Risk Perspectives

The Funtowicz and Ravetz model for classifying problem‐solving strategies into applied sciences, professional consultancy, and postnormal sciences is well known in the social science risk literature. The model is illustrated in a diagram based on the two axes: (i) decision stakes—the value dimension (costs, benefits) and (ii) the system uncertainties—the knowledge dimension. These axes resemble the same two dimensions that characterize some recently developed risk perspectives: (a) consequences and the severity of these consequences and (b) associated uncertainties. In this article, we make a detailed comparison of these two types of risk frameworks. We point to similarities and differences in motivation and use. A main conclusion of the article is that these risk perspectives all provide adequate scientific bases for the Funtowicz and Ravetz model. New insights are provided on the understanding of what the outcome stakes/consequences and uncertainty dimensions really capture in these perspectives and frameworks.     

Reassessing Benzene Cancer Risks Using Internal Doses

Human cancer risks from benzene exposure have previously been estimated by regulatory agencies based primarily on epidemiological data, with supporting evidence provided by animal bioassay data. This paper reexamines the animal-based risk assessments for benzene using physiologically-based pharmacokinetic (PBPK) models of benzene metabolism in animals and humans. It demonstrates that internal doses (interpreted as total benzene metabolites formed) from oral gavage experiments in mice are well predicted by a PBPK model developed by Travis et al. Both the data and the model outputs can also be accurately described by the simple nonlinear regression model total metabolites = 76.4x/(80.75 + x), where x = administered dose in mg/kg/day. Thus, PBPK modeling validates the use of such nonlinear regression models, previously used by Bailer and Hoel. An important finding is that refitting the linearized multistage (LMS) model family to internal doses and observed responses changes the maximum-likelihood estimate (MLE) dose-response curve for mice from linear-quadratic to cubic, leading to low-dose risk estimates smaller than in previous risk assessments. This is consistent with the conclusion for mice from the Bailer and Hoel analysis. An innovation in this paper is estimation of internal doses for humans based on a PBPK model (and the regression model approximating it) rather than on interspecies dose conversions. Estimates of human risks at low doses are reduced by the use of internal dose estimates when the estimates are obtained from a PBPK model, in contrast to Bailer and Hoel's findings based on interspecies dose conversion. Sensitivity analyses and comparisons with epidemiological data and risk models suggest that our finding of a nonlinear MLE dose-response curve at low doses is robust to changes in assumptions and more consistent with epidemiological data than earlier risk models.     

Exploring the Dimensionality of Trust in Risk Regulation

This article investigates possible differential levels of trust in government regulation across five different risk contexts and the relationship between a number of concepts that might be thought of as comprising distinctive "dimensions" of trust. It appeared that how people perceive government and its policies toward risk regulation was surprisingly similar for each of the five risk cases. A principal-component analysis showed that the various trust items could best be described by two dimensions: a general trust dimension, which was concerned with a wide range of trust-relevant aspects, such as competence, care, fairness, and openness, and a scepticism component that reflects a sceptical view regarding how risk policies are brought about and enacted. Again, the results were surprisingly similar across the five risk cases, as the same solution was found in each of the different samples. It was also examined whether value similarity has an additional value in predicting trust in risk regulation, compared to the more conventional aspects of trust. Based on the two independent trust factors that were found in this study, a typology of trust is proposed that ranges from full trust to a deep type of distrust. It is argued that for a functioning society it could well be more suitable to have critical but involved citizens in many situations.     

Are Some Risk Comparisons More Effective Under Conflict?: A Replication and Extension of Roth et al.

Despite many claims for and against the use of risk comparisons in risk communication, few empirical studies have explored their effect. Only one study, published by Roth et al. in this journal in 1990, has tested the 1988 predictions by Covello et al. as to the public's relative preferences for 14 kinds of risk comparisons as they might be used by a factory manager to explain risks of his ethylene oxide plant. That study found no correlations between the Covello predictions and seven different measures of "acceptability" of Covello's examples of each type of comparison. However, two critics of the Roth study, as well as its own authors, suggested that a scenario involving local risks, a conflict-ridden situation, and a plant manager unknown to the townspeople might better evoke Covello-like preferences than the distant, calm, friends-involving scenario used by Roth. The research reported here replicated the Roth study using the same scenario, risk comparison examples, and evaluation measures, and added a second scenario intended to replicate the conditions suggested by critics. Over 200 New Jersey residents answered the study questionnaire. The replication scenario reproduced Roth's results, and the conflict scenario also evoked no rankings correlated with Covello's predictions. Furthermore, neither agreement nor disagreement with five statements representing "conflict"--respondents' reports that the industrial-plant scenario made them angry, they lived near industry, they were concerned about industrial risks, people in their home town were angry about industrial pollution, and they worried "frequently" about long-term effects of pollution--correlated with Covello's predictions. Over half of all ratings ascribed to the comparisons in aggregate were positive, and most detailed comments offered by respondents also were positive, despite many criticisms and suggestions for their improvement. The wide variability in individuals' rankings also undermines the notion of any single ranking of preferred comparisons. These findings have implications for use of risk comparisons, but also reveal the inaccuracy of the field's assumptions about public reaction to industrial risk information, including risk comparison.     

Estimated Soil Ingestion Rates for Use in Risk Assessment

Assessing the risks to human health posed by contaminants present in soil requires an estimate of likely soil ingestion rates. In the past, direct measurements of soil ingestion were not available and risk assessors were forced to estimate soil ingestion rates based on observations of mouthing behavior and measurements of soil on hands. Recently, empirical data on soil ingestion rates have become available from two sources (Binder et al., 1986 and van Wijnen et al., 1986). Although preliminary, these data can be used to derive better estimates of soil ingestion rates for use in risk assessments. Estimates of average soil ingestion rates derived in this paper range from 25 to 100 mg/day, depending on the age of the individual at risk. Maximum soil ingestion rates that are unlikely to underestimate exposure range from 100 to 500 mg. A value of 5,000 mg/day is considered a reasonable estimate of a maximum single-day exposure for a child with habitual pica.     

Testing and Expanding a Model of Cognitive Processing of Risk Information

Scholars have begun to explore the role of modes of information processing and related audience characteristics in reactions to risky situations and risk information.((11, 12, 14, 17, 18, 20))"Information processing" concerns how people attend to and consider available information: systematic processors analyze messages and situations carefully, while heuristic processors skim and use cues (e.g., opinions of trusted reference groups) for quick judgments. This article uses scenarios about a semi-hypothetical industrial facility, in particular risk comparisons being considered by its manager for inclusion in a talk to the community, to explore the impact of information processing. Information insufficiency, self-assessed capacity to understand information, and information-seeking propensities are tested for potential effects on information processing about industrial risks by people living near industry. As well as testing established models, this article explores the additional explanatory value of involvement, relevance, and ability (Earle et al., 1990) and objective knowledge. Both existing model variables and new ones have significant effects on information seeking and information processing in this case, and partly confirm earlier results. Trumbo((17,18)) found that heuristic processors saw lower risk and systematic processors higher risk from suspected cancer clusters. In this study, reporting knowledge about local industrial risks as insufficient for one's purposes and self-reported avoidance of such information both raised ratings of the facility's risk and lowered ratings of its acceptability. Neither type of information processing significantly affected risk or acceptability judgments, but both increased risk ratings and heuristic processing had more effect than systematic processing. Positive ratings of risk comparisons' clarity and meaningfulness decreased risk and increased acceptability ratings, dominated other information variables in predictive power, and exceeded risk, benefit, and trust in contribution to acceptability judgments. Despite differences across studies in designs and variables, and the embryonic development of appropriate (self-reported) measures for use in field surveys, these results confirm the potential value of further research in how information seeking and processing affect risk beliefs and reactions to risk communications.     

Varying Risk Comparison Elements: Effects on Public Reactions

Expanding a limited empirical base on effects of risk comparisons, a pilot experiment explored how varying elements of such comparisons might influence public response. The scenario used was a hypothetical trial of an asbestos-installing firm for putting students and staff at a junior high school at "unreasonable risk," first used by Slovic et al. (1990). Study participants played the role of jurors in the trial, asked to rate the risk, the firm's guilt, whether it should be made liable for future health effects, whether the school should be occupied in its current condition, and whether the asbestos should be removed at a cost of 3 million dollars. Opportunity samples of New Jersey residents (n= 309) received information intended to vary four comparison attributes: number of dimensions of comparison; single versus multiple ways of expressing mortality; a narrative to explain and justify the risk comparison; and the hypothetical role of the participant (juror vs. parent). The dependent variable was a hazard scale constructed from four of the five postcomparison judgments. ANOVA found format variations swamped in their effect by concern about asbestos, with the absence of a narrative and the parental role being the only attributes that increased negative risk reactions. Multiple regression analyses found that multidimensionality, narrative, role, and the presence of any risk comparison at all had significant effects when these (plus death formats) were the only independent variables. However, only multidimensionality (which increased negative reactions) retained significance when asbestos concern, risk beliefs (no safe level of exposure to a carcinogen; any exposure leads to cancer), and demographic variables were added to the analysis. Concern and risk beliefs alone explained 33% of variance in hazard scores; adding demographics and risk comparison variables only raised explained variance to 36% (having children at home and being exposed to multidimensional risk comparisons raised scores; age and income lowered them). The results underline the potentially small effect of risk comparison information on risk views (at least between subjects), but offer some insight into aspects of message design left unexplored in empirical literature to date.     

Source Attribution of Food-Borne Zoonoses in New Zealand: A Modified Hald Model

A Bayesian approach was developed by Hald et al .^{( 1 )} to estimate the contribution of different food sources to the burden of human salmonellosis in Denmark. This article describes the development of several modifications that can be used to adapt the model to different countries and pathogens. Our modified Hald model has several advantages over the original approach, which include the introduction of uncertainty in the estimates of source prevalence and an improved strategy for identifiability. We have applied our modified model to the two major food-borne zoonoses in New Zealand, namely, campylobacteriosis and salmonellosis. Major challenges were the data quality for salmonellosis and the inclusion of environmental sources of campylobacteriosis. We conclude that by modifying the Hald model we have improved its identifiability, made it more applicable to countries with less intensive surveillance, and feasible for other pathogens, in particular with respect to the inclusion of nonfood sources. The wider application and better understanding of this approach is of particular importance due to the value of the model for decision making and risk management.     

Multimedia Benchmarking Analysis for Three Risk Assessment Models: RESRAD, MMSOILS, and MEPAS

This paper is one in a series that describes results of a benchmarking analysis initiated by the Department of Energy (DOE) and the United States Environmental Protection Agency (EPA). An overview of the study is provided in a companion paper by Laniak et al. presented in this journal issue. The three models used in the study—RESRAD (DOE), MMSOILS (EPA), and MEPAS (DOE)—represent analytically-based tools that are used by the respective agencies for performing human exposure and health risk assessments. Both single media and multimedia benchmarking scenarios were developed and executed. In this paper, the multimedia scenario is examined. That scenario consists of a hypothetical landfill that initially contained uranium-238 and methylene chloride. The multimedia models predict the fate of these contaminants, plus the progeny of uranium-238, through the unsaturated zone, saturated zone, surface water, and atmosphere. Carcinogenic risks are calculated from exposure to the contaminants via multiple pathways. Results of the tests show that differences in model endpoint estimates arise from both differences in the models' mathematical formulations and assumptions related to the implementation of the scenarios.     

How Do Cancer Risks Predicted From Animal Bioassays Compare with the Epidemiologic Evidence? The Case of Ethylene Dibromide

Cancer risks for ethylene dibromide (EDB) were estimated by fitting several linear non-threshold additive models to data from a gavage bioassay. Risks predicted by these models were compared to the observed cancer mortality among a cohort of workers occupationally exposed to the same chemical. Models that accounted for the shortened latency period in the gavaged rats predicted upper bound risks that were within a factor of 3 of the observed cancer deaths. Data from an animal inhalation study of EDB also were compatible with the epidemiologic data. These findings contradict those of Ramsey et al. (1978), who reported that extrapolation from animal data produced highly exaggerated risk estimates for EDB-exposed workers. This paper explores the reasons for these discrepant findings.     

Interspecific Scaling of Toxicity Data

This paper reexamines the scaling approaches used in cancer risk assessment and proposes a more precise body weight scaling factor. Two approaches are conventionally used in scaling exposure and dose from experimental animals to man: body weight scaling (used by FDA) and surface area scaling (BW0.67--used by EPA). This paper reanalyzes the Freireich et al. (1966) study of the maximum tolerated dose (MTD) of 14 anticancer agents in mice, rats, dogs, monkeys, and humans, the dataset most commonly cited as justification for surface area extrapolation. This examination was augmented with an analysis of a similar dataset by Schein et al. (1970) of the MTD of 13 additional chemotherapy agents. The reanalysis shows that BW0.75 is a more appropriate scaling factor for the 27 direct-acting compounds in this dataset.     

Characterising the Perceived Risks and Benefits of Some Health Issues

Previous work on perceived risk, particularly a study by Fischhoff et al. (1978), is critically examined with reference to its applicability to specific health related issues. Judgments were obtained from 159 subjects of 15 health-related items in terms of perceived risk, benefit, and a number of risk characteristics based on the Fischhoff et al. research. In addition, demographic details concerning sex of respondent, seat belt usage, smoking status, and birth order were collected. Using regression analyses it was found that the direction of the risk-benefit relationship was dependent on the issue being judged. Risk was found to be better explained by ratings of likelihood of mishap and likelihood of death as a consequence of mishap. Benefit was poorly explained by the risk characteristics and demographic data. However, subject group characteristics were shown to be important influences on risk and benefit perception in certain situations. The implications of these results for understanding behavioral decisions involving risk in relation to specific activities are discussed.     

期望效用视角下的风险对冲效率

与传统文献将风险下降比率作为风险对冲效率指标不同,本文引入期望效用理论来比较最小方差对冲策略、最小在险价值(VaR)对冲策略和最小条件在险价值(CVaR)对冲策略的对冲效率,从而将人们的风险态度同对冲策略选择联系起来,以实现不同风险态度的投资者选择不同风险对冲策略的目的。借用风险中性效用函数、二次效用函数和CARA效用函数,本文严格证明:在这三种对冲策略中,最小方差对冲策略过于保守,最小VaR对冲策略最为激进,风险厌恶程度大的投资者偏好最小方差对冲策略,风险中性投资者和风险厌恶程度小的投资者更偏好最小VaR对冲策略,最小CVaR对冲策略介于二者之间。