ALBERT

Notes: For continuous data, risk is defined here as the proportion of animals with values above a large percentile, e.g., the 99th percentile or below the 1st percentile, for the distribution of values among control animals. It is known that reducing the standard deviation of measurements through improved experimental techniques will result in less stringent (higher) doses for the lower confidence limit on the benchmark dose that is estimated to produce a specified risk of animals with abnormal levels for a biological effect. Thus, a somewhat larger (less stringent) lower confidence limit is obtained that may be used as a point of departure for low-dose risk assessment. It is shown in this article that it is important for the benchmark dose to be based primarily on the standard deviation among animals, sa, apart from the standard deviation of measurement errors, sm, within animals. If the benchmark dose is incorrectly based on the overall standard deviation among average values for animals, which includes measurement error variation, the benchmark dose will be overestimated and the risk will be underestimated. The bias increases as sm increases relative to sa. The bias is relatively small if sm is less than one-third of sa, a condition achieved in most experimental designs.

Notes: For diseases with more than one risk factor, the sum of probabilistic estimates of the number of cases caused by each individual factor may exceed the total number of cases observed, especially when uncertainties about exposure and dose response for some risk factors are high. In this study, we outline a method of bounding the fraction of lung cancer fatalities not due to specific well-studied causes. Such information serves as a “reality check” for estimates of the impacts of the minor risk factors, and, as such, complements the traditional risk analysis. With lung cancer as our example, we allocate portions of the observed lung cancer mortality to known causes (such as smoking, residential radon, and asbestos fibers) and describe the uncertainty surrounding those estimates. The interactions among the risk factors are also quantified, to the extent possible. We then infer an upper bound on the residual mortality due to “other” causes, using a consistency constraint on the total number of deaths, the maximum uncertainty principle, and the mathematics originally developed of imprecise probabilities.

Notes: A strong inverse correlation was observed between the polycyclic aromatic hydrocarbon (PAH) mass fraction desorbed, a surrogate measure of bioavailability, and relative carcinogenicity, as quantified by potency equivalency factors (PEFs), for two study sediments from the New York/New Jersey Harbor estuary. Because compounds with the highest toxicity, such as dibenz(a,h)anthracene and benzo(a)pyrene (BAP), also tended to be the least rapidly and least extensively desorbed, the U.S. Environmental Protection Agency (EPA) default guidance may dramatically overestimate risk from exposure to PAH-contaminated soils or sediments. A “relative risk index” (RRI) was developed to account for the combined effects of compound-specific bioavailability and toxic potency in estimating excess cancer risk. Using this approach, estimated excess cancer risk may be diminished by as much as a factor of 159 times versus default EPA guidance. Also, the hierarchy of estimated risk between study sediments and among treatment fractions of study sediments differed using the two approaches, implying that the default approach may inaccurately determine site clean-up priorities. The percentage contribution of each potentially carcinogenic priority PAH to total excess cancer risk was computed under various scenarios. In each case, the contribution of BAP to total excess cancer risk was remarkably invariable, for example, ranging from 48% to 52% in one sediment, and 44% to 54% in the other, over four different exposure durations. These results suggest that BAP may be an excellent indexing compound for gauging relative exposure risk across sediments. Other important contributors to total excess cancer risk were benz(a)anthracene and dibenz(a,h)anthracene. Together, these three compounds comprised nearly 90% of total excess cancer risk from all PAHs in every scenario. This integrated RRI approach may enable regulators to more accurately gauge relative risks and make more informed sediment management decisions.

Notes: The effectiveness of a probabilistic risk assessment (PRA) depends on the quality and relevance of the output from exposure and risk models, which, in turn, depends on the critical inputs to the assessment. These critical inputs are often in the form of probabilistic exposure factor distributions that are derived for the given risk scenario. Deriving probabilistic distributions for model inputs can be time consuming and subjective. The absence of a standard approach for developing these distributions can result in PRAs that are inconsistent and difficult to review by regulatory agencies. We present an approach that reduces subjectivity in the distribution development process without limiting the flexibility needed to prepare relevant PRAs. The approach requires two steps. First, we analyze data pooled at a population scale to (i) identify the most robust demographic descriptors within the population for a given exposure factor, (ii) partition the data into subsets based on these variables, and (iii) construct archetypal distributions for each subpopulation. Second, we sample from these archetypal distributions according to site- or scenario-specific conditions to simulate exposure factor values and use these values to construct the scenario-specific input distribution. The archetypal distributions developed through Step 1 provide a consistent basis for developing scenario-specific distributions so risk assessors will not have to repeatedly collect and analyze raw data for each new assessment. We demonstrate the approach for two commonly used exposure factors—body weight (BW) and exposure duration (ED)—using data that are representative of the U.S. population. For these factors we provide a first set of subpopulation-based archetypal distributions and demonstrate methods for using these distributions to construct relevant scenario-specific probabilistic exposure factor distributions.

Notes: When stricken by a terrorist attack, a war, or a natural disaster, an economic unit or a critical infrastructure may suffer significant loss of productivity. More importantly, due to interdependency or interconnectedness, this initial loss may propagate into other systems and eventually lead to much greater derivative loss. This belongs to what is known as a cascading effect. It is demonstrated in this article that the cascading effect and the derivative loss can be significantly reduced by effective risk management. This is accomplished by deliberately distributing the initial inoperability to other systems so that the total loss (or inoperability) is minimized. The optimal distribution strategy is found by a linear programming technique. The same risk management can also be applied to situations where objectives need to be prioritized. A case study featuring 12 economic sectors illustrates the theory. The result suggests that using the same amount of resources, minimizing risk (inoperability) of infrastructures will generally give rise to highest payoff, whereas overlooking it may result in greatest total loss. The framework developed in this work uses a steady-state approach that applies primarily to managing situations where the attack is catastrophic resulting in very long recovery time.

Notes: Species invasions are extremely common and are vastly outpacing the ability of resource agencies to address each invasion, one species at a time. Management actions that target the whole landscape or ecosystem may provide more cost-effective protection against the establishment of invasive species than a species-by-species approach. To explore what ecosystem-level actions might effectively reduce invasions, we developed a multispecies, multihabitat metapopulation model. We assume that species that successfully establish themselves outside their native range tend to be habitat generalists and that a tradeoff exists between competitive ability and habitat breadth, such that habitat specialists are competitively superior to habitat generalists. In this model, habitat destruction, fragmentation, and short-term disturbances all favor invasion by habitat generalists, despite the inferior competitive abilities of generalist species. Our model results illustrate that providing relatively undisturbed habitat and preventing further habitat degradation and fragmentation can provide a highly cost-effective defense against invasive species.

Notes: In November 2001, the Monterey Institute of International Studies convened a workshop on bioterrorism threat assessment and risk management. Risk assessment practitioners from various disciplines, but without specialized knowledge of terrorism, were brought together with security and intelligence threat analysts to stimulate an exchange that could be useful to both communities. This article, prepared by a subset of the participants, comments on the workshop's findings and their implications and makes three recommendations, two short term (use of threat assessment methodologies and vulnerability analysis) and one long term (application of quantitative risk assessment and modeling), regarding the practical application of risk assessment methods to bioterrorism issues.

Notes: This article presents an approach to the problem of terrorism risk assessment and management by adapting the framework of the risk filtering, ranking, and management method. The assessment is conducted at two levels: (1) the system level, and (2) the asset-specific level. The system-level risk assessment attempts to identify and prioritize critical infrastructures from an inventory of system assets. The definition of critical infrastructures offered by Presidential Decision Directive 63 was used to determine the set of attributes to identify critical assets—categorized according to national, regional, and local impact. An example application is demonstrated using information from the Federal Highway Administration National Bridge Inventory for the State of Virginia. Conversely, the asset-specific risk assessment performs an in-depth analysis of the threats and vulnerabilities of a specific critical infrastructure. An illustration is presented to offer some insights in risk scenario identification and prioritization, multiobjective evaluation of management options, and extreme-event analysis for critical infrastructure protection.

Notes: The article considers point processes most commonly used in reliability and risk analysis. Short-term and long-term behavior for the point processes used as models for repairable systems1 are introduced. As opposed to the long term, the term short term implies that a process is observed during an interval limited by a time close to the mean (or the median) of the respective underlying distribution. A new simple upper bound is proposed on the cumulative intensity function of the renewal process and G-renewal process with an increasing failure rate underlying distribution. The new bound is compared with some known bounds for the renewal process. Finally, a formal definition of “a boundary point” between the short-term repairable system behavior and long-term behavior is introduced. This point can also be used as a lower time limit beyond which the “long-term” Barlow and Proschan bound for the renewal process with NBUE underlying distribution could be effectively applied.

Notes: The U.S. Environmental Protection Agency has begun discussions to consider its assessment of asbestos toxicity related to mineral form and fiber size. Brake workers are typically exposed to short chrysotile fibers. To explore the mesothelioma risk among brake workers, considering other occupational exposures to asbestos, data from a study that was published previously were obtained and the analysis was extended. The National Cancer Institute provided data from a case-control study of mesothelioma. Because many participants with a history of brake work also had employment in other asbestos-related occupations, mesothelioma cases and controls were compared for a history of brake work, controlling for employment in eight occupations with potential asbestos exposure. A stratified analysis was also performed excluding those with any of the eight occupations. Possible interactions between brake work and other occupational exposures related to risk of mesothelioma were also examined. The odds ratio (OR) for employment in brake installation or repair was 0.71 (95% CI: 0.30–1.60) when controlled for insulation or shipbuilding. When a history of employment in any of the eight occupations with potential asbestos exposure was controlled, the OR was 0.82 (95% CI: 0.36–1.80). ORs did not increase with increasing duration of brake work. Exclusion of those with any of the eight exposures resulted in an OR of 0.62 (95% CI: 0.01–4.71) for occupational brake work. There was no evidence of an interaction between brake work and other occupational exposures. These latter analyses were based on small numbers of exposed cases. The results are consistent with the existing literature indicating that brake work does not increase the risk of mesothelioma and adds to the evidence that fiber type and size are important determinants of mesothelioma risk.

Notes: Sensitivity analysis (SA) methods are a valuable tool for identifying critical control points (CCPs), which is one of the important steps in the hazard analysis and CCP approach that is used to ensure safe food. There are many SA methods used across various disciplines. Furthermore, food safety process risk models pose challenges because they often are highly nonlinear, contain thresholds, and have discrete inputs. Therefore, it is useful to compare and evaluate SA methods based upon applications to an example food safety risk model. Ten SA methods were applied to a draft Vibrio parahaemolyticus (Vp) risk assessment model developed by the Food and Drug Administration. The model was modified so that all inputs were independent. Rankings of key inputs from different methods were compared. Inputs such as water temperature, number of oysters per meal, and the distributional assumption for the unrefrigerated time were the most important inputs, whereas time on water, fraction of pathogenic Vp, and the distributional assumption for the weight of oysters were the least important inputs. Most of the methods gave a similar ranking of key inputs even though the methods differed in terms of being graphical, mathematical, or statistical, accounting for individual effects or joint effect of inputs, and being model dependent or model independent. A key recommendation is that methods be further compared by application on different and more complex food safety models. Model independent methods, such as ANOVA, mutual information index, and scatter plots, are expected to be more robust than others evaluated.

Notes: Previous studies have shown that the fatality rate among hazardous waste remediation workers is likely to exceed the fatality rate averted among the public by remediation. The implication is that much hazardous waste remediation is inappropriate on a strictly risk-based basis. Such analyses ignore the fact that the same hazardous waste workers would be engaged in other work with similar or perhaps greater safety risks, and that in any case the single greatest cause of occupational fatalities is traffic accidents, hence distance traveled may be a more important predictor than type of work performed.

Notes: Chemical risk protection in the workplace relies partly on informing workers about possible risks using material safety data sheets (MSDS). This article reports on phase 2 of a project (phase 1 reported in Cox et al.), which employed a mental models approach to improve on data sheets as communicative interventions for perchloroethylene in dry cleaning and rosin-based solder flux in the electronics industry within small businesses in the United Kingdom (small enterprises (SEs) 〈 25 employees in the workplace). It focuses on the efficacy of a multimethod evaluation strategy to assess (1) the capacity of a mental models approach to yield contextually relevant data for intervention design and (2) the effectiveness of the strategy itself in validating the mental models data. The evaluation was conducted using postal questionnaires and semi-structured verbal protocols to provide responses to the alternative intervention content and to prioritize risk messages. User discussion groups were then employed, particularly as a means of establishing whether contextual information could be obtained that would differ qualitatively from the kind elicited through individual (semi) structured methods. We conclude that the mental models approach as part of an iterative process including systematic multimethod evaluation is successful in supporting the design of relevant communications to the users of chemicals. The overall viability of communicative interventions in the context of health and safety in small businesses remains in question. Future research might aim to develop a more holistic approach to interventions in complex occupational contexts.

Notes: This article develops a decision-theoretic methodology for the risk-adjusted mission value (RAMV) for selecting between alternative missions in the presence of uncertainty in the outcomes of the missions. This methodology permits trading off mission risk for mission value, something that probabilistic risk analysis cannot do unless it explicitly incorporates both mission value and risk aversion of the project management. The methodology, in its complete implementation, is consistent with the decision theory known as expected utility theory, although it differs from conventional decision theory in that the probabilities and all but one of the utilities are not those of the decision maker. The article also introduces a new interpretation of risk aversion. The methodology is consistent with the elementary management concept concerning division of labor. An example is presented for selecting between discrete alternatives—four landing sites on Mars. A second example is presented for selecting among a set of continuous alternatives—a comet flyby distance. The methodology is developed within the context of scientific missions, but the methodology is equally applicable to any situation requiring outcome value judgments, probability judgments, and risk aversion judgments by different constituencies.

Notes: Multimodal distribution functions that result from Monte Carlo simulations can be interpreted by superimposing joint probability density functions onto the contour space of the simulated calculations. The method is demonstrated by analysis of the pathway of a radioactive groundwater contaminant using an analytical solution to the transport equation. Simulated concentrations at a fixed time and distance produce multimodal histograms, which are understood with reference to the parameter space for the two random variables—velocity and dispersivity. Numerical integration under the joint density function up to the contour of the analytical solution gives the probability of contaminant exceeding a target concentration. This technique is potentially more efficient than Monte Carlo simulation for low probability events. Visualization of parameter space is restricted to two random variables. Nevertheless, analyzing the two most pertinent random variables in a simulation might still offer insights into the multimodal nature of output histograms.

Notes: In Australia-Salmon, the WTO Appellate Body found Australia to be in violation of the WTO SPS Agreement based on the inconsistency of the “appropriate level of protection” underlying various SPS measures. Article 5.5 of the SPS Agreement prohibits arbitrary or unjustifiable distinctions in “appropriate levels of protection” if such distinctions result in discrimination or a disguised restriction on international trade. In Australia-Salmon, Canada challenged Australia's import ban on salmon. Australia permitted the entry of other fish products that were known to host some of the same diseases cited by Australia in justifying its salmon import ban. The distinction in the “appropriate levels of protection” between Australia's regulation of salmon and its treatment of these other fish products was found to be “arbitrary or unjustified” and to have “resulted in a restriction on international trade.”Australia-Salmon was the first WTO decision to find an Article 5.5 violation. Canada successfully made a “weakest link” argument to undercut Australia's regulatory justification. The decision rests on the relationship between the risk purportedly justifying the salmon import ban and the risk seemingly ignored in Australia's treatment of other fish products—the regulatory “situations” compared concerned the identical pathogens with the identical potential consequences. As such, Australia-Salmon may be an example of a category of regulatory “chains” that are peculiarly exposed to Article 5.5 challenge. In responding to the Appellate Body's ruling, Australia reduced its limits on salmon and imposed new restrictions on the other fish products. The outcome suggests that a challenge of one SPS measure under Article 5.5 may lead to the imposition of new restrictions on other imported products—an unexpected result for the free trade regime.

Notes: Various methods exist to calculate confidence intervals for the benchmark dose in risk analysis. This study compares the performance of three such methods in fitting nonlinear dose-response models: the delta method, the likelihood-ratio method, and the bootstrap method. A data set from a developmental toxicity test with continuous, ordinal, and quantal dose-response data is used for the comparison of these methods. Nonlinear dose-response models, with various shapes, were fitted to these data. The results indicate that a few thousand runs are generally needed to get stable confidence limits when using the bootstrap method. Further, the bootstrap and the likelihood-ratio method were found to give fairly similar results. The delta method, however, resulted in some cases in different (usually narrower) intervals, and appears unreliable for nonlinear dose-response models. Since the bootstrap method is more time consuming than the likelihood-ratio method, the latter is more attractive for routine dose-response analysis. In the context of a probabilistic risk assessment the bootstrap method has the advantage that it directly links to Monte Carlo analysis.

Notes: This study investigated the prevalence of both accurate and erroneous earthquake-related beliefs among a sample of Southern California college students and the relationship between their endorsement of earthquake beliefs and adoption of seismic hazard adjustments. In addition, the study examined the effects of an experimental earthquake education program and the impact of need for cognition on this program. The data revealed a significant degree of agreement with earthquake myths, a generally low level of correlation between earthquake beliefs and the level of hazard adjustments, and a significant effect of hazard information on the endorsement of accurate earthquake beliefs and increases in hazard adjustment. Compared with the “Earthquake Facts (Only)” format, an “Earthquake Myths versus Facts” format was slightly more useful for dispelling erroneous beliefs. Further, there was a tendency for those who were high in need for cognition to have higher levels of hazard adjustment. Finally, there was weak support for the hypothesis that those who were low in need for cognition would develop more accurate earthquake beliefs and higher levels of hazard adjustment in the “Earthquake Myths versus Facts” information condition.

Notes: Recent research finds that perceived risk is closely associated with race and gender. In surveys of the American public a subset of white males stand out for their uniformly low perceptions of environmental health risks, while most nonwhite and nonmale respondents reveal higher perceived risk. Such findings have been attributed to the advantageous position of white males in American social life. This article explores the linked possibility that this demographic pattern is driven not simply by the social advantages or disadvantages embodied in race or gender, but by the subjective experience of vulnerability and by sociopolitical evaluations pertaining to environmental injustice. Indices of environmental (in)justice and social vulnerability were developed as part of a U.S. National Risk Survey (n= 1,192) in order to examine their effect on perceived risk. It was found that those who regarded themselves as vulnerable and supported belief statements consistent with the environmental justice thesis offered higher risk ratings across a range of hazards. Multivariate analysis indicates that our measures of vulnerability and environmental (in)justice predict perceived risk but do not account for all of the effects of race and gender. The article closes with a discussion of the implications of these findings for further work on vulnerability and risk, risk communication, and risk management practices generally.

Notes: A common problem in ethics is that people often desire an end but fail to take the means necessary to achieve it. Employers and employees may desire the safety end mandated by performance standards for pollution control, but they may fail to employ the means, specification standards, necessary to achieve this end. This article argues that current (de jure) performance standards, for lowering employee exposures to ionizing radiation, fail to promote de facto worker welfare, in part because employers and employees do not follow the necessary means (practices known as specification standards) to achieve the end (performance standards) of workplace safety. To support this conclusion, the article argues that (1) safety requires attention to specification, as well as performance, standards; (2) coal-mine specification standards may fail to promote performance standards; (3) nuclear workplace standards may do the same; (4) choosing appropriate means to the end of safety requires attention to the ways uncertainties and variations in exposure may mask violations of standards; and (5) correcting regulatory inattention to differences between de jure and de facto is necessary for achievement of ethical goals for safety.

Notes: 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. 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.

Notes: Recent articles by Busza et al. (BJSW) and Dar et al. (DDH) argue that astrophysical data can be used to establish small bounds on the risk of a “killer strangelet” catastrophe scenario in the RHIC and ALICE collider experiments. The case for the safety of the experiments set out by BJSW does not rely solely on these bounds, but on theoretical arguments, which BJSW find sufficiently compelling to firmly exclude any possibility of catastrophe.Nonetheless, DDH and other commentators (initially including BJSW) suggested that these empirical bounds alone do give sufficient reassurance. This seems unsupportable when the bounds are expressed in terms of expectation value—a good measure, according to standard risk analysis arguments. For example, DDH's main bound, pcatastrophe 〈 2 × 10−8, implies only that the expectation value of the number of deaths is bounded by 120; BJSW's most conservative bound implies the expectation value of the number of deaths is bounded by 60,000.This article reappraises the DDH and BJSW risk bounds by comparing risk policy in other areas. For example, it is noted that, even if highly risk-tolerant assumptions are made and no value is placed on the lives of future generations, a catastrophe risk no higher than ≈10−15 per year would be required for consistency with established policy for radiation hazard risk minimization. Allowing for risk aversion and for future lives, a respectable case can be made for requiring a bound many orders of magnitude smaller.In summary, the costs of small risks of catastrophe have been significantly underestimated by BJSW (initially), by DDH, and by other commentators. Future policy on catastrophe risks would be more rational, and more deserving of public trust, if acceptable risk bounds were generally agreed upon ahead of time and if serious research on whether those bounds could indeed be guaranteed was carried out well in advance of any hypothetically risky experiment, with the relevant debates involving experts with no stake in the experiments under consideration.

Notes: Despite many claims for and against the use of risk comparisons in risk communication, few empirical studies have explored their effect. Even fewer have examined the public's relative preferences among different kinds of risk comparisons. Two studies, published in this journal in 1990 and 2003, used seven measures of “acceptability” to examine public reaction to 14 examples of risk comparisons, as used by a hypothetical factory manager to explain risks of his ethylene oxide plant. This study examined the effect on preferences of scenarios involving low or high conflict between the factory manager and residents of the hypothetical town (as had the 2003 study), and inclusion of a claim that the comparison demonstrated the risks' acceptability. It also tested the Finucane et al. (2000) affect hypothesis that information emphasizing low risks—as in these risk comparisons—would raise benefits estimates without changing risk estimates. Using similar but revised scenarios, risk comparison examples (10 instead of 14), and evaluation measures, an opportunity sample of 303 New Jersey residents rated the comparisons, and the risks and benefits of the factory. On average, all comparisons received positive ratings on all evaluation measures in all conditions. Direct and indirect measures showed that the conflict manipulation worked; overall, No-Conflict and Conflict scenarios evoked scores that were not significantly different. The attachment to each risk comparison of a risk acceptability claim (“So our factory's risks should be acceptable to you.”) did not worsen ratings relative to conditions lacking this claim. Readers who did or did not see this claim were equally likely to infer an attempt to persuade them to accept the risk from the comparison. As in the 2003 article, there was great individual variability in inferred rankings of the risk comparisons. However, exposure to the risk comparisons did not reduce risk estimates significantly (while raising benefit estimates), and Conflict-Claim respondents found the risk of the hypothetical factory less acceptable than No-Conflict respondents. Results suggest that neither risk comparisons nor risk acceptability claims are automatically anathema to audiences, but they may have tiny or unintended effects on audience judgments about risky situations.

Notes: It is believed that food hygiene precautions in domestic kitchens are an important strategy in efforts to reduce the incidence of sporadic food poisoning, but recent research has shown that people who have suffered food poisoning handle the same types of foods and adopt similar food hygiene precautions in their kitchens to the rest of the population. This suggests the need to examine other factors. A case-control study of sporadic Salmonella food poisoning was conducted to investigate several domestic kitchen risk factors. Measures of perception of risk, knowledge, and control associated with food poisoning in case and control respondents are reported here. It was found that perceived personal risk from food poisoning in the home was less than perceived risk to other people. In contrast, ratings of personal knowledge about food poisoning and personal control over food poisoning in the home were seen to be greater than other people's knowledge and control. There were no differences between the cases and the controls in their ratings of knowledge about food poisoning or their control over food poisoning. However, cases perceived their personal risk from food poisoning to be higher than controls. Both case and control samples exhibited optimistic bias but this was reduced in the case sample, suggesting that experience with food poisoning may reduce optimistic bias.

Notes: Risk assessment is an established methodology for environmental and public health issues. However, economists' core approach to both risk assessment and risk management, benefit-cost analysis, often fails to transparently evaluate variability in a way that is a trademark of quantitative risk assessment. Concurrently, environmental advocates are proposing new management criteria based on a vaguely framed “Precautionary Principle.” This manuscript demonstrates how risk assessment techniques for characterizing variability, benefit-cost analysis, and decision-making criteria under uncertainty and irreversibility can be combined. The result is a quantifiable, case-specific, and risk-dependent “precautionary” threshold for action compared to standard benefit-cost approaches. The Clean Air Act and the regulation of genetically modified corn provide applications.

Notes: Numerous governments have introduced regulations governing the use of mobile (cellular) telephones while driving. Despite significant research into the “objective” risks, there is relatively little research into risk perceptions either in relation to other in-car distractions or with respect to the factors underlying such perceptions. The current article reports on two studies addressing these issues. Study 1 (N= 199) found that whereas the use of hand-held sets is seen as one of the riskiest activities to perform while driving, the risks of using a hands-free kit are perceived to be relatively small. Study 2 (N= 1,320) found that nearly half of all drivers in the sample with a mobile phone reported having used it while driving and that, overall, the probability of having an accident was perceived to be less for oneself than for one's peers, indicating an optimistic bias. Two factors underpinned risk perceptions, “impact” including perceived severity and equitability, and “controllability” including immediacy, detectability, and probability. While higher “impact” scores were associated with increased preferences for restrictions on the use of hand-held mobiles while driving, the “controllability” scores moderated this relationship such that when perceived “controllability” was low, restriction preferences were high irrespective of perceived “impact.” However, when “controllability” was high, restriction preferences remained high when “impact” was high but were low when “impact” was low. Given the growing number of in-car technological innovations, it is suggested that regulators act strategically, rather than finding themselves developing a series of “hazard-specific” regulations, which may ultimately lack coherence.

Notes: The evaluation studies of the proposed repository for long-term storage of spent nuclear fuel and high-level nuclear waste at Yucca Mountain, Nevada, are underway. Fulfillment of the requirements for limiting dose to the public, which includes containment of the radioactive waste emplaced in the proposed repository and subsequent slow release of radionuclides from the Engineered Barrier System (EBS) into the geosphere, will rely on a robust waste container design, among other EBS components. Part of the evaluation process involves sensitivity studies aimed at elucidating which model parameters contribute most to the waste package and overlying drip shield degradation characteristics. The model parameters identified for this study include (1) general corrosion rate parameters and (2) stress corrosion cracking (SCC) parameters. Temperature dependence and parameter uncertainty are evaluated for the general corrosion rate model parameters while for the SCC model parameters, uncertainty treatment of stress intensity factor, crack initiation threshold, and manufacturing flaw orientations are evaluated. Based on these evaluations new uncertainty distributions are generated and recommended for future analyses. Also, early waste package failures due to improper heat treatment were added to the waste package degradation model. The results of these investigations indicate that the waste package failure profiles are governed by the manufacturing flaw orientation model parameters.

Notes: Because of the increase in workplace automation and the diversification of industrial processes, workplaces have become more and more complex. The classical approaches used to address workplace hazard concerns, such as checklists or sequence models, are, therefore, of limited use in such complex systems. Moreover, because of the multifaceted nature of workplaces, the use of single-oriented methods, such as AEA (man oriented), FMEA (system oriented), or HAZOP (process oriented), is not satisfactory. The use of a dynamic modeling approach in order to allow multiple-oriented analyses may constitute an alternative to overcome this limitation. The qualitative modeling aspects of the MORM (man-machine occupational risk modeling) model are discussed in this article. The model, realized on an object-oriented Petri net tool (CO-OPN), has been developed to simulate and analyze industrial processes in an OH&S perspective. The industrial process is modeled as a set of interconnected subnets (state spaces), which describe its constitutive machines. Process-related factors are introduced, in an explicit way, through machine interconnections and flow properties. While man-machine interactions are modeled as triggering events for the state spaces of the machines, the CREAM cognitive behavior model is used in order to establish the relevant triggering events. In the CO-OPN formalism, the model is expressed as a set of interconnected CO-OPN objects defined over data types expressing the measure attached to the flow of entities transiting through the machines. Constraints on the measures assigned to these entities are used to determine the state changes in each machine. Interconnecting machines implies the composition of such flow and consequently the interconnection of the measure constraints. This is reflected by the construction of constraint enrichment hierarchies, which can be used for simulation and analysis optimization in a clear mathematical framework. The use of Petri nets to perform multiple-oriented analysis opens perspectives in the field of industrial risk management. It may significantly reduce the duration of the assessment process. But, most of all, it opens perspectives in the field of risk comparisons and integrated risk management. Moreover, because of the generic nature of the model and tool used, the same concepts and patterns may be used to model a wide range of systems and application fields.

Notes: The bounding analysis methodology described by Ha-Duong et al. (this issue) is logically incomplete and invites serious misuse and misinterpretation, as their own example and interpretation illustrate. A key issue is the extent to which these problems are inherent in their methodology, and resolvable by a logically complete assessment (such as Monte Carlo or Bayesian risk assessment), as opposed to being general problems in any risk-assessment methodology. I here attempt to apportion the problems between those inherent in the proposed bounding analysis and those that are more general, such as reliance on questionable expert elicitations. I conclude that the specific methodology of Ha-Duong et al. suffers from logical gaps in the definition and construction of inputs, and hence should not be used in the form proposed. Furthermore, the labor required to do a sound bounding analysis is great enough so that one may as well skip that analysis and carry out a more logically complete probabilistic analysis, one that will better inform the consumer of the appropriate level uncertainty. If analysts insist on carrying out a bounding analysis in place of more thorough assessments, extensive analyses of sensitivity to inputs and assumptions will be essential to display uncertainties, arguably more essential than it would be in full probabilistic analyses.

Notes: This article describes a simple model for quantifying the health impacts of toxic metal emissions. In contrast to most traditional models it calculates the expectation value of the total damage (summed over the total population and over all time) for typical emission sites, rather than “worst-case” estimates for specific sites or episodes. Such a model is needed for the evaluation of many environmental policy measures, e.g., the optimal level of pollution taxes or emission limits. Based on the methodology that has been developed by USEPA for the assessment of multimedia pathways, the equations and parameters are assembled for the assessment of As, Cd, Cr, Hg, Ni, and Pb, and some typical results are presented (the dose from seafood is not included and for Hg the results are extremely uncertain); the model is freely available on the web. The structure of the model is very simple because, as we show, if the parameters can be approximated by time-independent constants (the case for the USEPA methodology), the total impacts can be calculated with steady-state models even though the environment is never in steady state. The collective ingestion dose is found to be roughly 2 orders of magnitude larger than the collective dose via inhalation. The uncertainties are large, easily an order of magnitude, the main uncertainties arising from the parameter values of the model, in particular the transfer factors. Using linearized dose-response functions, estimates are provided for cancers due to As, Cd, Cr, and Ni as well as IQ loss due to Pb emissions in Europe.

Notes: Recent qualitative analyses warn of potential future human health risks from emergence of antibiotic resistance in food-borne pathogens due to the use of similar antimicrobial drugs in both food animals and human medicine. While historical data suggest that human health risks from some animal antimicrobials, such as virginiamycin (VM), have remained low (McDonald et al., 2001), there is a widespread concern that “resistance epidemics” or endemics could arise in the future. How reassuring is the past about the future? This article applies quantitative risk assessment methods to help find out, using human health risks from VM and the nearly identical human antimicrobial quinupristin-dalfopristin (QD) as a case study. A dynamic simulation model is used to predict the risks of emerging resistance to human antimicrobials in human populations from given input assumptions. Bayesian Monte Carlo uncertainty analysis allows past data to constrain and inform selection of input parameter values, and thus to predict the possible future resistance patterns that are consistent with historical data. The results show that health risks from VM use in food animals are highly sensitive to the human prescription rate of QD. For realistic prescription rates, quantitative risks are less than 1 × 10−6 even for members of the most-threatened (ICU patient) population, while societal risks are 〈1 excess statistical death per year for the whole U.S. population. Such quantitative estimates complement more qualitative assessments that discuss the possibility of future “resistance epidemics” (or endemics) without quantifying their probabilities.

Notes: During the 21st century, environmental challenges are likely to intensify across the world and possibly lead to violent conflicts. Strategies for conflict avoidance will be incomplete unless they recognize, discuss, and mitigate regional environmental stress factors. Comparative risk assessment (CRA) is one of the most critical tools emerging to influence modern environmental policies and is increasingly used to create a common language to help reconcile competing interests in development and environmental disputes around the world. This article considers the environmental challenges facing the Middle East in light of their “transboundary” nature and proposes CRA as a framework for setting environmental priorities and reducing tensions in the region.

Notes: This article introduces a human error analysis or human reliability analysis methodology, AGAPE-ET (AGuidance And Procedure for Human Error Analysis for Emergency Tasks), for analyzing emergency tasks in nuclear power plants. The AGAPE-ET method is based on a simplified cognitive model and a set of performance-influencing factors (PIFs). At each cognitive function, error-causing factors (ECF) or error-likely situations have been identified considering the characteristics of the performance of each cognitive function and the influencing mechanism of the PIFs on the cognitive function. Then, a human error analysis procedure based on the error analysis factors is organized to cue or guide the analyst in conducting the human error analysis. The method can be characterized by the structured identification of weak points of the task required to be performed and by the efficient analysis process such that the analyst has only to carry out the analysis with the necessary cognitive functions. Through the application, AGAPE-ET showed its usefulness, which effectively identifies the vulnerabilities with respect to cognitive performance as well as task execution, and that helps the analyst directly draw specific error reduction measures through the analysis.

Notes: Decision problems depending on extrapolation promise to become increasingly important. The key problem is determining if the model being used for extrapolation is going to give reasonable results, or err in a dangerous manner. Ideally, as one proceeds from investigation to decision, some guidance should be present based on the goal as to which investigation will reduce the risk the most given the cost. In this report, a very simple version of the problem is formalized and examined. The result is, interestingly, that the best evidence in support of the favored model is a null result in the experiment most likely to raise doubt over that model. The theory is applied to a simple example drawn from accelerated testing.

Notes: Understanding of risk views in multiethnic societies and in a globalizing world may be enhanced by use of measures of ethnic identity and acculturation. Ethnic identity includes such attributes as positive attitudes about one's ethnic group and a sense of belonging to it, voluntary and frequent association with other ethnic group members, and ethnic practices (preferred music, food, language; attendance at ethnic festivities). Acculturation is absorption of the “host” society's cultural norms, beliefs, attitudes and behavior patterns by immigrants, or by other groups historically excluded from the larger society. Both generic and ethnicity-specific measures of these concepts are available in the literature. This Perspective reviews the literature on risk implications of these concepts, how the nature of these measures presents both opportunities and challenges to risk researchers, and the degree to which ethnic identity and acculturation may be correlated with sociodemographic factors. Conceptual and methodological suggestions are made for risk research using these concepts, and hypotheses are offered about what such research might find.

Notes: Previous research has reported strong consumer perception that genetically modified (GM) food crops may lead to adverse outcomes in a number of different areas. This is despite the widespread promulgation of the potential benefits and opportunities ascribed to the same technology by many scientists and other experts. A computer-based information gathering and evaluation task was completed by 198 adults to assess the extent to which their initial focus on the dangers or opportunities of genetic modification, or both, could be ascribed to the manner in which they gathered information on the topic (heuristically vs. systematically). Results did not confirm the hypothesis that initial focus (risks, benefits, or both) predicted ongoing information gathering and evaluation behavior. Moreover, also contrary to prediction, most participants primarily used systematic strategies when deriving their initial position, regardless of that opinion. Participants found it difficult to achieve a balanced perspective on GM food crop, even though balanced argument, as measured by order of story selection and time spent reading, was preferred as the source of information. Perceived importance is probably the most influential variable determining information gathering about issues or events to which a level of risk is attached.

Notes: A study (N= 198) was conducted to examine hypotheses derived from an emotion-based model of stigma responses to radiation sources. A model of stigma susceptibility is proposed in which affective reactions and cognitive worldviews activate predispositions to appraise and experience events in systematic ways that result in the generation of negative emotion, risk perceptions, and stigma responses. Results of structural equation modeling supported the hypotheses. Radiation sources that scored higher on a measure of stigma were included in the analyses (i.e., nuclear power plants, radioactive waste from nuclear power plants, radiation from nuclear weapons testing). Individual differences in negative reactivity and worldviews were associated with the strength of emotional appraisals that were associated, in turn, with negative emotion toward stigmatized radiation sources. As hypothesized, the model fit better with perceived risk as a function of negative emotion rather than vice versa. Finally, a measure of stigma was associated with negative emotion and, to a lesser extent, with risk perceptions. Risk communication about stigmatized objects may benefit from a more complete understanding of how affective and emotional reactions are constructed and the routes through which they affect responses and behaviors.

Notes: Decreasing acceptance of biotechnologies over time has been reported in Europe. Studies claim that attitudes are negative, even hostile, and that people are very worried about genetic engineering in food and medicine. However, such studies are mostly based on surveys and these have significant methodological problems, such as low response rates, which may indicate that only those with strong views respond, thus biasing the sample. Here an alternative method, involving “topic-blind” recruitment of participants and a behavioral measure (food tasting), was used. We show that in a topic-blind sample of 100 individuals, 93% willingly tasted and ate what they believed to be genetically modified (GM) food in an experimental setting, and 48% said they would buy GM food in the future, results that are surprising in the context of other reports about attitudes and intentions toward GM food. Purchasers and nonpurchasers differed in their attitudes toward GM food on key risk-related scales (particularly on a dread-not dread scale—a measure of integral affect—and an ethical-unethical scale). Despite these differences, however, and despite their negative attitude, most nonpurchasers (85.7%) still tasted the GM apple. Incidental affect (state stress and trait worry) was not found to influence risk-related judgments about GM food. Integral affect (dread of GM plants and animals used for food) and concerns about the future risks of GM animals in food were found to be key predictors of willingness to purchase GM food.

Notes: A joint workshop was convened by the Society for Risk Analysis Ecological Risk Assessment Specialty Group and the Ecological Society of America Theoretical Ecology Section to provide independent scientific input into the formulation of methods and processes for risk assessment of invasive species. In breakout sessions on (1) the effects of invasive species on human health, (2) effects on plants and animals, (3) risk analysis issues and research needs related to entry and establishment of invasive species, and (4) risk analysis issues and research needs related to the spread and impacts of invasive species, workshop participants discussed an overall approach to risk assessment for invasive species. Workshop participants agreed on the need for empirical research on areas in which data are lacking, including potential invasive species, native species and habitats that may be impacted by invasive species, important biological processes and phenomena such as dispersal, and pathways of entry and spread for invasive species. Participants agreed that theoretical ecology can inform the process of risk assessment for invasive species by providing guidelines and conceptual models, and can contribute to improved decision making by providing a firm biological basis for risk assessments.

Notes: A new computer system is being developed to classify U.S. air travelers by the degree of terrorist threat they might pose. Reports indicate that the system—called CAPPS II—would use large amounts of information about each passenger, perhaps including such personal details as his or her magazine-subscription behavior. We argue that what is publicly known about CAPPS II raises questions about how substantially the system would improve aviation security. We discuss conditions under which CAPPS II could yield safety benefits, but suggest that it might be more prudent to view the system as one component of future security arrangements rather than the centerpiece of these arrangements.

Notes: Decisions about management of invasive species are difficult for all the reasons typically addressed by multiattribute decision analysis: uncertain outcomes, multiple and conflicting objectives, and many interested parties with differing views on both facts and values. This article illustrates how the tools of multiattribute analysis can improve management of invasive species, with an emphasis on making explicit the social values and preferences that must inform invasive species management. Risk assessment protocols developed previously for invasive species management typically suffer from two interacting flaws: (1) separating risk assessment from risk management, thus disrupting essential connections between the social values at stake in invasive species decisions and the scientific knowledge necessary to predict the likely impacts of management actions, and (2) relying on expert judgment about risk framed in qualitative and value-laden terms, inadvertently mixing the expert's judgment about what is likely to happen with personal preferences. Using the values structuring and probability-modeling elements of formal decision analysis can remedy these difficulties and make invasive species management responsive to both good science and public values. The management of feral pigs in Hawaiian ecosystems illustrates the need for such an integrated approach.

Notes: Exotic pests are serious threats to North American ecosystems; thus, economic analysis of decisions about eradication, stopping, or slowing their spread may be critical to ecosystem management. The proposed bioeconomic model assumes that the rate of population expansion can be reduced (even to negative values in a case of eradication) if certain management actions are taken along the population front. The area of management can be viewed as a dynamic barrier zone that moves together with the population front. The lower is the target rate of spread, the higher would be both benefits and costs of the project. The problem is to find the optimal target rate of spread at which the present value of net benefits from managing population spread reaches its maximum value. If a population spreads along an infinite habitat strip, the target rate of spread is optimal if the slope of the cost function versus the rate of spread is equal to the ratio of the average pest-related damage per unit time and unit area to the discount rate. In a more complex model where the potential area of expansion is limited, two local maxima of net benefits may exist: one for eradication and another for slowing the spread. If both maxima are present, their heights are compared and the strategy that corresponds to a higher value of net benefits is selected. The optimal strategy changes from eradication to slowing the spread and finally to doing nothing as the area occupied by the species increases. The model shows that slowing the spread of pest species generates economic benefits even if a relatively small area remains uninfested. The cost of slowing the spread can be estimated from a model of population expansion via establishment of isolated colonies beyond the moving front. The model is applied to managing the spread of the gypsy moth (Lymantria dispar) populations in the United States.

Notes: Risk related to economic values is treated by many disciplines, including safety and production engineering, business, and project management. Within each of these and across these disciplines different nomenclature and principles are adopted for describing and communicating risk. The situation is rather confusing. In this article, we review various approaches and concepts that are used to express risk. We present and discuss a unifying approach for dealing with economic risk, with uncertainty being the key risk concept. The approach represents a rethinking on how to implement the Bayesian paradigm in practice to support decision making.

Notes: Many environmental data sets, such as for air toxic emission factors, contain several values reported only as below detection limit. Such data sets are referred to as “censored.” Typical approaches to dealing with the censored data sets include replacing censored values with arbitrary values of zero, one-half of the detection limit, or the detection limit. Here, an approach to quantification of the variability and uncertainty of censored data sets is demonstrated. Empirical bootstrap simulation is used to simulate censored bootstrap samples from the original data. Maximum likelihood estimation (MLE) is used to fit parametric probability distributions to each bootstrap sample, thereby specifying alternative estimates of the unknown population distribution of the censored data sets. Sampling distributions for uncertainty in statistics such as the mean, median, and percentile are calculated. The robustness of the method was tested by application to different degrees of censoring, sample sizes, coefficients of variation, and numbers of detection limits. Lognormal, gamma, and Weibull distributions were evaluated. The reliability of using this method to estimate the mean is evaluated by averaging the best estimated means of 20 cases for small sample size of 20. The confidence intervals for distribution percentiles estimated with bootstrap/MLE method compared favorably to results obtained with the nonparametric Kaplan–Meier method. The bootstrap/MLE method is illustrated via an application to an empirical air toxic emission factor data set.

Notes: The maritime industry is moving toward a “goal-setting” risk-based regime. This opens the way to safety engineers to explore and exploit flexible and advanced risk modeling and decision-making approaches in the design and operation processes. In this article, following a brief review of the current status of maritime risk assessment, a design/operation selection framework and a design/operation optimization framework are outlined. A general discussion of control engineering techniques and their application to risk modeling and decision making is given. Four novel risk modeling and decision-making approaches are then outlined with illustrative examples to demonstrate their use. Such approaches may be used as alternatives to facilitate risk modeling and decision making in situations where conventional techniques cannot be appropriately applied. Finally, recommendations on further exploitation of advances in general engineering and technology are suggested with respect to risk modeling and decision making.

Notes: General patterns of bias in risk beliefs are well established in the literature, but much less is known about how these biases vary across the population. Using a sample of almost 500 people, the regression analysis in this article yields results consistent with the well-established pattern that small risks are overassessed and large risks are underassessed. The accuracy of these risk beliefs varies across demographic factors, as does the switch point at which people go from underassessment to overassessment, which we found to be 1,500 deaths annually for the full sample. Better educated people have more accurate risk beliefs, and there are important differences in the risk perception by race and gender that also may be of policy interest.

Notes: Genetically modified (GM) crops have met with widespread approval among scientists and policy makers in the United States, but public approval of GM crops, both domestically and abroad, is progressing much more slowly. An underlying cause of public wariness may be that both nations and individual consumers do not perceive significant benefits to themselves from GM crops, while fearing the risks they may incur. In this study, an economic analysis is conducted to determine whether the benefits of one type of GM corn, Bt corn (genetically modified to resist damage from the ECB and Southwestern corn borer), outweigh the potential risks; and who the “winners” and “losers” are among stakeholder groups that may be affected by Bt corn. It is found that Bt corn growers, consumers, and industry all benefit from Bt corn adoption, though the purported health and environmental benefits of reducing chemical pesticide usage through Bt corn are negligible. Though the aggregated public benefit is large, the welfare gain to individual consumers is small and may not make up for perceived risks. While environmental and health risks of Bt corn are unlikely, the potential market risks—impacting both the organic corn market and total U.S. corn exports—are found to be significant. Currently, distributional analysis is not a part of regulatory decision making of Bt corn in the United States; yet it may help to explain why decision makers at both the government and individual-consumer levels have failed to embrace Bt corn and other GM crops.

Notes: One measure of the potency of compounds that lead to the effects through ligand-dependent gene transcription is the relative affinity for the critical receptor. Endocrine active compounds that are presumed to act principally through binding to the estrogen receptor (e.g., estradiol, genistein, bisphenol A, and octylphenol) comprise one class of such compounds. For making simple comparisons, receptor-binding affinity has been equated to in vivo potency, which consequently defines the dose-response characteristics for the compound. Direct extrapolation of in vitro estimated affinities to the corresponding in vivo system and to specific species or life stages (e.g., neonatal, pregnancy) can be misleading. Accurate comparison of the potency of endocrine active compounds requires characterization of biochemical and pharmacokinetic factors that affect their free concentration. Quantitative in vitro and in vivo models were developed for integrating pharmacokinetics factors (e.g., serum protein and receptor-binding affinities, clearance) that affect potency. Data for parameterizing these models for several estrogenic compounds were evaluated and the models exercised. While simulations of adult human or rat sera were generally successful, difficulties in describing early life stages were identified. Exogenous compounds were predicted to be largely ineffective at competing estradiol off serum-binding proteins, suggesting this was unlikely to be physiologically significant. Discrepancies were identified between relative potencies based upon modeling in vitro receptor-binding activity versus in vivo activity in the presence of clearance and serum-binding proteins. The examples illustrate the utility of this approach for integrating available experimental data from in vitro and in vivo studies to estimate the relative potency of these compounds.

Notes: The development of engineered containment and control systems for contaminated sites must consider the environmental setting of each site. The behaviors of both contaminated materials and engineered systems are affected by environmental conditions that will continue to evolve over time as a result of such natural processes as climate change, ecological succession, pedogenesis, and landform changes. Understanding these processes is crucial to designing, implementing, and maintaining effective systems for sustained health and environmental protection. Traditional engineered systems such as landfill liners and caps are designed to resist natural processes rather than working with them. These systems cannot be expected to provide long-term isolation without continued maintenance. In some cases, full-scale replacement and remediation may be required within 50 years, at an effort and cost much higher than for the original cleanup. Approaches are being developed to define smarter containment and control systems for stewardship sites, considering lessons learned from implementing prescriptive waste disposal regulations enacted since the 1970s. These approaches more effectively involve integrating natural and engineered systems; enhancing sensors and predictive tools for evaluating performance; and incorporating information on failure events, including precursors and consequences, into system design and maintenance. An important feature is using natural analogs to predict environmental conditions and system responses over the long term, to accommodate environmental change in the design process, and, as possible, to engineer containment systems that mimic favorable natural systems. The key emphasis is harmony with the environment, so systems will work with and rely on natural processes rather than resisting them. Implementing these new integrated systems will reduce current requirements for active management, which are resource-intensive and expensive.

Notes: Modern theories in cognitive psychology and neuroscience indicate that there are two fundamental ways in which human beings comprehend risk. The “analytic system” uses algorithms and normative rules, such as probability calculus, formal logic, and risk assessment. It is relatively slow, effortful, and requires conscious control. The “experiential system” is intuitive, fast, mostly automatic, and not very accessible to conscious awareness. The experiential system enabled human beings to survive during their long period of evolution and remains today the most natural and most common way to respond to risk. It relies on images and associations, linked by experience to emotion and affect (a feeling that something is good or bad). This system represents risk as a feeling that tells us whether it is safe to walk down this dark street or drink this strange-smelling water. Proponents of formal risk analysis tend to view affective responses to risk as irrational. Current wisdom disputes this view. The rational and the experiential systems operate in parallel and each seems to depend on the other for guidance. Studies have demonstrated that analytic reasoning cannot be effective unless it is guided by emotion and affect. Rational decision making requires proper integration of both modes of thought. Both systems have their advantages, biases, and limitations. Now that we are beginning to understand the complex interplay between emotion and reason that is essential to rational behavior, the challenge before us is to think creatively about what this means for managing risk. On the one hand, how do we apply reason to temper the strong emotions engendered by some risk events? On the other hand, how do we infuse needed “doses of feeling” into circumstances where lack of experience may otherwise leave us too “coldly rational”? This article addresses these important questions.

Notes: This article estimates the risk of tuberculosis (TB) transmission on a typical commercial airliner using a simple one box model (OBM) and a sequential box model (SBM). We used input data derived from an actual TB exposure on an airliner, and we assumed a hypothetical scenario that a highly infectious TB source case (i.e., 108 infectious quanta per hour) travels as a passenger on an 8.7-hour flight. We estimate an average risk of TB transmission on the order of 1 chance in 1,000 for all passengers using the OBM. Applying the more realistic SBM, we show that the risk and incidence decrease sharply in a stepwise fashion in cabins downstream from the cabin containing the source case assuming some potential for airflow from more contaminated to less contaminated cabins. We further characterized spatial variability in the risk within the cabin by modeling a previously reported TB outbreak in an airplane to demonstrate that the TB cases occur most likely within close proximity of the source TB patient.

Notes: In 1996, an outbreak of E. coli O157:H7-associated illness occurred in an elementary school in Japan. This outbreak has been studied in unusual detail, making this an important case for quantitative risk assessment. The availability of stored samples of the contaminated food allowed reliable estimation of exposure to the pathogens. Collection of fecal samples allowed assessment of the numbers infected, including asymptomatic cases. Comparison to other published dose-response studies for E. coli O157:H7 show that the strain that caused the outbreak studied here must have been considerably more infectious. We use this well-documented incident as an example to demonstrate how such information on the response to a single dose can be used for dose-response assessment. In particular, we demonstrate how the high infectivity limits the uncertainty in the low-dose region.

Notes: In November 2001, the University of Michigan hosted one of the first dialogues among international trade law scholars and scientists in the field of risk assessment with the goal of identifying critical areas of misunderstanding between the two fields. This article discusses key issues that need to be addressed in order to better harmonize the scientific and legal systems of evidence within the context of trade disputes and trade law and presents the recommendations that emerged from the Michigan meeting.

Notes: This article considers the role of scientific rationality in understanding statements of risk produced by a scientific community. An argument is advanced that, while scientific rationality does impose constraints on valid scientific justifications for restrictions on products and practices, it also provides flexibility in the judgments needed to both develop and apply characterizations of risk. The implications of this flexibility for the understanding of risk estimates in WTO and NAFTA deliberations are explored, with the goal of finding an intermediate ground between the view that science unambiguously justifies or rejects a policy, and the view that science is yet another cultural tool that can be manipulated in support of any decision. The result is a proposal for a dialogical view of scientific rationality in which risk estimates are depicted as confidence distributions that follow from a structured dialogue of scientific panels focused on judgments of evidence, evidential reasoning, and epistemic analysis.

Notes: Risk analysis has been recognized and validated in World Trade Organization (WTO) decision processes. In recent years the precautionary principle has been proposed as an additional or alternative approach to standard risk assessment. The precautionary principle has also been advocated by some who see it as part of postmodern democracy in which more power is given to the public on health and safety matters relative to the judgments of technocrats. A more cynical view is that the precautionary principle is particularly championed by the European Community as a means to erect trade barriers. The WTO ruling against the European Community's trade barrier against beef from hormone-treated cattle seemed to support the use of risk assessment and appeared to reject the argument that the precautionary principle was a legitimate basis for trade barriers. However, a more recent WTO decision on asbestos contains language suggesting that the precautionary principle, in the form of taking into account public perception, may be acceptable as a basis for a trade barrier. This decision, if followed in future WTO trade disputes, such as for genetically modified foods, raises many issues central to the field of risk analysis. It is too early to tell whether the precautionary principle will become accepted in WTO decisions, either as a supplement or a substitute for standard risk assessment. But it would undermine the value of the precautionary principle if this principle were misused to justify unwarranted trade barriers.

Notes: Based on the data from the integrated Danish Salmonella surveillance in 1999, we developed a mathematical model for quantifying the contribution of each of the major animal-food sources to human salmonellosis. The model was set up to calculate the number of domestic and sporadic cases caused by different Salmonella sero and phage types as a function of the prevalence of these Salmonella types in the animal-food sources and the amount of food source consumed. A multiparameter prior accounting for the presumed but unknown differences between serotypes and food sources with respect to causing human salmonellosis was also included. The joint posterior distribution was estimated by fitting the model to the reported number of domestic and sporadic cases per Salmonella type in a Bayesian framework using Markov Chain Monte Carlo simulation. The number of domestic and sporadic cases was obtained by subtracting the estimated number of travel- and outbreak-associated cases from the total number of reported cases, i.e., the observed data. The most important food sources were found to be table eggs and domestically produced pork comprising 47.1% (95% credibility interval, CI: 43.3–50.8%) and 9% (95% CI: 7.8–10.4%) of the cases, respectively. Taken together, imported foods were estimated to account for 11.8% (95% CI: 5.0–19.0%) of the cases. Other food sources considered had only a minor impact, whereas 25% of the cases could not be associated with any source. This approach of quantifying the contribution of the various sources to human salmonellosis has proved to be a valuable tool in risk management in Denmark and provides an example of how to integrate quantitative risk assessment and zoonotic disease surveillance.

Notes: Interdependency analysis in the context of this article is a process of assessing and managing risks inherent in a system of interconnected entities (e.g., infrastructures or industry sectors). Invoking the principles of input-output (I-O) and decomposition analysis, the article offers a framework for describing how terrorism-induced perturbations can propagate due to interconnectedness. Data published by the Bureau of Economic Analysis Division of the U.S. Department of Commerce is utilized to present applications to serve as test beds for the proposed framework. Specifically, a case study estimating the economic impact of airline demand perturbations to national-level U.S. sectors is made possible using I-O matrices. A ranking of the affected sectors according to their vulnerability to perturbations originating from a primary sector (e.g., air transportation) can serve as important input to risk management. For example, limited resources can be prioritized for the “top-n” sectors that are perceived to suffer the greatest economic losses due to terrorism. In addition, regional decomposition via location quotients enables the analysis of local-level terrorism events. The Regional I-O Multiplier System II (RIMS II) Division of the U.S. Department of Commerce is the agency responsible for releasing the regional multipliers for various geographical resolutions (economic areas, states, and counties). A regional-level case study demonstrates a process of estimating the economic impact of transportation-related scenarios on industry sectors within Economic Area 010 (the New York metropolitan region and vicinities).

Notes: We develop acceptance sampling plans assuming that the life test is truncated at a preassigned time. The lifetimes of the test units are assumed to follow the Birnbaum Saunders distribution. The minimum sample size necessary to ensure the specified average life is obtained and the operating characteristic values of the sampling plans and producer's risk are presented. An illustrative example is given.

Notes: Some program managers share a common belief that adding a redundant component to a system reduces the probability of failure by half. This is true only if the failures of the redundant components are independent events, which is rarely the case. For example, the redundant components may be subjected to the same external loads. There is, however, in general a decrease in the failure probability of the system. Nonetheless, the redundant element comes at a cost, even if it is less than that of developing the first one when both are based on the same design. Identical parts save the most in terms of design costs, but are subjected to common failure modes from possible design errors that limit the effectiveness of the redundancy. In the development of critical systems, managers thus need to decide if the costs of a parallel system are justified by the increase in the system's reliability. NASA, for example, has used redundant spacecraft to increase the chances of mission success, which worked well in the cases of the Viking and Voyager missions. These two successes, however, do not guarantee future ones. We present here a risk analysis framework accounting for dependencies to support the decision to launch at the same time a twin mission of identical spacecraft, given incremental costs and risk-reduction benefits of the second one. We illustrate this analytical approach with the case of the Mars Exploration Rovers launched by NASA in 2003, for which we had performed this assessment in 2001.

Notes: Environmental policymakers and regulators are often in the position of having to prioritize their actions across a diverse range of environmental pressures to secure environmental protection and improvements. Information on environmental issues to inform this type of strategic analysis can be disparate; it may be too voluminous or even absent. Data on a range of issues are rarely presented in a common format that allows easy analysis and comparison. Nevertheless, judgments are required on the significance of various environmental pressures and on the inherent uncertainties to inform strategic assessments such as “state of the environment” reports. How can decisionmakers go about this type of strategic and comparative risk analysis? In an attempt to provide practical tools for the analysis of environmental risks at a strategic level, the Environment Agency of England and Wales has conducted a program of developmental research on strategic risk assessment since 1996. The tools developed under this program use the concept of “environmental harm” as a common metric, viewed from technical, social, and economic perspectives, to analyze impacts from a range of environmental pressures. Critical to an informed debate on the relative importance of these perspectives is an understanding and analysis of the various characteristics of harm (spatial and temporal extent, reversibility, latency, etc.) and of the social response to actual or potential environmental harm from a range of hazards. Recent developments in our approach, described herein, allow a presentation of the analysis in a structured fashion so as to better inform risk-management decisions.

Notes: The purpose of this study was to verify the validity of a causal model that was made to predict the acceptance of gene-recombination technology. A structural equation model was used as a causal model. First of all, based on preceding studies, the factors of perceived risk, perceived benefit, and trust were set up as important psychological factors determining acceptance of gene-recombination technology in the structural equation model. An additional factor, “sense of bioethics,” which I consider to be important for acceptance of biotechnology, was added to the model. Based on previous studies, trust was set up to have an indirect influence on the acceptance of gene-recombination technology through perceived risk and perceived benefit in the model. Participants were 231 undergraduate students in Japan who answered a questionnaire with a 5-point bipolar scale. The results indicated that the proposed model fits the data well, and showed that acceptance of gene-recombination technology is explained largely by four factors, that is, perceived risk, perceived benefit, trust, and sense of bioethics, whether the technology is applied to plants, animals, or human beings. However, the relative importance of the four factors was found to vary depending on whether the gene-recombination technology was applied to plants, animals, or human beings. Specifically, the factor of sense of bioethics is the most important factor in acceptance of plant gene-recombination technology and animal gene-recombination technology, and the factors of trust and perceived risk are the most important factors in acceptance of human being gene-recombination technology.

Notes: This article describes an exploratory investigation of the risk perceptions of experts and novices in relation to helicopter operations, under conditions where the participants are matched on various characteristics previously found to affect perceptions, such as demographic, gender, and background factors. The study reports considerable evidence of perceptual differences between the two participant groups (i.e., expert pilots and candidate pilots). We find that the experts' perceptions of relative risks are more veridical, in terms of their higher correlation with the true relative frequencies. A significant positive correlation between the flight hours and the contextual risk-taking tendency is also shown, leading the experienced pilots' choices toward risky alternatives in scenarios—a potential result of their overconfidence based on superior task performance. Possible explanations are offered for the findings and potential avenues for future research are identified.

Notes: Environmental and human health issues associated with outdoor air pollution, such as ozone, sulfur dioxide, and other pollutants in metropolitan regions, are an area of growing concern for both policy officials and the general public. Increasing attention from the news media, new health data, and public debate over the effectiveness of clean air regulations have raised the importance of air quality in the public consciousness. While public perceptions of air quality have been studied thoroughly dating back to the 1960s, little empirical research has been conducted to explain the spatial aspects of these perceptions, particularly at the local level. Although recent studies suggest characteristics of local setting are important in shaping perceptions of air quality, the roles of proximity, neighborhood characteristics, and location have not been clarified. This study seeks to improve understanding of the major factors shaping public perceptions of air quality by examining the spatial pattern of local risk perception, the role of socioeconomic characteristics in forming these perceptions, and the relationship between perceived and scientifically measured air pollution. First, we map the spatial pattern of local air quality perceptions using Geographic Information Systems (GIS) across the Dallas and Houston metropolitan areas. Next, we explain these perceptions through local contextual factors using both bivariate correlations and multivariate regression analysis. Results indicate that perceptions of air quality in the study areas are not significantly correlated with air quality based on readings of air monitoring stations. Instead, perceptions appear to be influenced by setting (urban vs. rural), state identification, access to information, and socioeconomic characteristics such as age, race, and political identification. We discuss the implications of the findings and provide direction on how further research can provide a deeper understanding of the local contextual factors influencing public perceptions.

Notes: A wide variety of environmental contaminants adversely affect thyroid hormone (TH) homeostasis. Hypothyroidism and/or hypothyroxinemia during the early postnatal period in the rat leads to permanent structural damage and loss of function in the cochlea. A major uncertainty in assessing the risks of developmental exposure to thyroid-disrupting chemicals (TDCs) is the lack of a clear characterization of the dose-response relationship, especially in the lower region, between disruption of hormones and adverse consequences. The current work correlated early postnatal hypothyroxinemia with hearing loss in the adult rat. Linear regression was performed on the log transform for total serum thyroxine (T4) concentrations on postnatal day 14 or 21 versus dB(SPL) of hearing loss in adult animals developmentally exposed to TDCs. Regression analyses revealed a highly significant correlation between T4 concentration and hearing loss. In the rat, a 50–60% decrease in circulating T4 was needed to significantly impact hearing function. This correlation suggests that T4 serum concentrations at 14 or 21 days of postnatal age may be a good predictive biomarker in rodents of the adverse consequence of developmental exposure to TDCs.

Notes: Spatial decision-support tools are necessary for assessment and management of threats to biodiversity, which in turn is necessary for biodiversity conservation. In conjunction with the U.S. Geological Survey—Biological Resources Division's Species at Risk program, we developed a GIS-based spatial decision-support tool for relative risk assessments of threats to biodiversity on the U.S. Army's White Sands Missile Range and Fort Bliss (New Mexico and Texas) due to land uses associated with military missions of the two bases. The project tested use of spatial habitat models, land-use scenarios, and species-specific impacts to produce an assessment of relative risks for use in conservation planning on the 1.2 million-hectare study region. Our procedure allows spatially explicit analyses of risks to multiple species from multiple sources by identifying a set of hazards faced by all species of interest, identifying a set of feasible management alternatives, assigning scores to each species for each hazard, and mapping the distribution of these hazard scores across the region of interest for each combination of species/management alternatives. We illustrate the procedure with examples. We demonstrate that our risk-based approach to conservation planning can provide resource managers with a useful tool for spatial assessment of threats to species of concern.

Notes: Risk perceptions of a series of biotechnology applications were examined in a public (nonexpert) sample and an expert sample. Compared with the experts, the public perceived all biotechnology applications as more risky. Both groups perceived food-related applications to be riskier than medical applications. Compared with the public, experts perceived both food and medical applications as less harmful and more useful. Experts also judged the risks posed from medical biotechnology applications as more familiar and acknowledged by people and science. Lay estimates of the risk of food applications were predicted by potential harm, potential benefits, science knowledge, and familiarity; experts' estimates were predicted only by harm and benefits. Lay estimates of the risk of medical applications were predicted by potential harm; experts' estimates were predicted by potential benefits, number and type of people exposed, and science knowledge. We discuss the implications of the results for risk communication about and management of different types of biotechnologies.

Notes: Shortly after the 2002 terrorist attacks in Bali, readers of Condé Nast Traveler magazine were surveyed regarding their views on the risks of travel to various destinations. Their risk estimates were highest for Israel, and lowest for Canada. Estimates for the different destinations correlated positively with (1) one another, (2) concern over aspects of travel that can make one feel at risk (e.g., sticking out as an American), (3) worries about other travel problems (e.g., contracting an infectious disease), and (4) attitudes toward risk. Respondents' willingness to travel to a destination was predicted well by whether their estimate of its risk was above or below their general threshold for the acceptability of travel risks. Overall, the responses suggest orderly choices, based on highly uncertain judgments of risks. Worry played a significant role in these choices, even after controlling for cognitive considerations, thereby supporting the recently proposed “risk as feelings” hypothesis.(1) Thus, even among people who have generally consistent and defensible beliefs, emotions may affect choices. These results emerged with people selected for their interest in and experience with the decision domain (travel), but challenged to incorporate a new concern (terror).

Notes: We examined the risk perception that is derived from hypothetical physician risk communications. Subjects (n= 217) completed a questionnaire on the Web for $3. Subjects were presented with four hypothetical cancer risk scenarios that included a physician risk communication in one of three risk communication formats: verbal only, verbal plus numeric probability as a percent, and verbal plus numeric probability as a fraction. In each scenario, subjects were asked to imagine themselves as the patient described and to state their perceived personal susceptibility to the cancer (i.e., risk perception) on a 0 to 100 scale, as well as responses to other measures. Subjects' risk perceptions were highly variable, spanning nearly the entire probability scale for each scenario, and the degree of variation was only slightly less in the risk communication formats in which a numeric statement of risk was provided. Subjects were more likely to overestimate than underestimate their risk relative to the stated risk in the numeric versions, and overestimation was associated with the belief that the physician minimized the risk so they wouldn't worry, innumeracy, and worry, as well as decisions about testing for the cancer. These results demonstrate significant gaps between the intended message and the message received in physician risk communications. Implications for medical decisions, patient distress, and future research are discussed.

Notes: The Allee effect is a nonlinear phenomenon exhibited in the population dynamics of sparse populations in which the per capita population growth rate increases with increasing population density. In sufficiently sparse populations, the Allee effect may lead to extinction and is known to generate a threshold in the probability of establishment when presented as a function of introduced population size or density. As introduced populations are generally small, Allee effects are probably common in biological invasions and their consideration is necessary for accurately assessing the risk of invasion by many species, including all sexually reproducing species. Bythotrephes longimanus, an invasive, freshwater, cladoceran zooplankter from Europe, is one such species. Here, I review a previously published model of the Allee effect for continuously sexually reproducing species. Then, I develop a new model for seasonally parthenogenetic species such as Bythotrephes, and thereby demonstrate the potential consequences of Allee effects. This result underscores the importance of considering nonlinear phenomena, including thresholds, when conducting risk analysis for biological introductions.

Notes: Little theoretical work has investigated how landscape structure affects invasive spread, even though broad-scale disturbances caused by habitat loss and fragmentation are believed to facilitate the spread of exotic species. Neutral landscape models (NLMs), derived from percolation theory in the field of landscape ecology, provide a tool for assessing the risk of invasive spread in fragmented landscapes. A percolation-based analysis of the potential for invasive spread in fragmented landscapes predicts that invasive spread may be enormously enhanced beyond some threshold level of habitat loss, which depends upon the species' dispersal abilities and the degree of habitat fragmentation. Assuming that invasive species spread primarily through disturbed areas of the landscape, poor dispersers may spread better in landscapes in which disturbances are concentrated in space, whereas good dispersers are predicted to spread better in landscapes where disturbances are small and dispersed (i.e., fragmented landscape). Assessing the risk of invasive spread in fragmented landscapes ultimately requires understanding the relative effects of landscape structure on processes that contribute to invasive spread—dispersal (successful colonization) and demography (successful establishment). Colonization success is predicted to be highest when 〉20% of the landscape has been disturbed, particularly if disturbances are large or aggregated in space, because propagules are more likely to encounter sites suitable for colonization and establishment. However, landscape pattern becomes less important for predicting colonization success if species are capable of occasional long-distance dispersal events. Invasive species are also more likely to persist and achieve positive population growth rates (successful establishment) in landscapes with clumped disturbance patterns, which can then function as population sources that produce immigrants that invade other landscapes. Finally, the invasibility of communities may be greatest in landscapes with a concentrated pattern of disturbance, especially below some critical threshold of biodiversity. Below the critical biodiversity threshold, the introduction of a single species can trigger a cascade of extinctions among indigenous species. The application of NLMs may thus offer new insights and opportunities for the management and restoration of landscapes so as to slow the spread of invasive species.

Notes: Emerging, rapid, multivalent, microbial diagnostic technologies can produce results in hours, as contrasted to the standard methods that require at least the better part of a week. Used in bioterrorism surveillance in medical settings, the new biodetectors could significantly reduce the time between a covert attack and its detection. By how much is determined by the intensity of sampling. If used to screen all patients reporting flu-like symptoms to their doctors, this basic level of “front-line” sampling would reduce life-threatening medical floundering and missteps and give responders 3–5 days of warning that they otherwise would not have had. Being miniaturized and amenable to mass production, these devices could reduce the cost of screening to a fraction of current costs and so it is tempting to imagine their use in more intensive bioterrorism screening programs aimed at the apparently healthy population, programs that could detect a covert attack even before the victims felt ill. This article examines the tradeoffs between surveillance effort and probability of detection for such programs. Dual-use deployment, where the biodetector provides some medically useful information in addition to bioterrorism surveillance, is discussed.

Notes: The extensive data from the Blair et al.(1) epidemiology study of occupational acrylonitrile exposure among 25,460 workers in eight plants in the United States provide an excellent opportunity to update quantitative risk assessments for this widely used commodity chemical. We employ the semiparametric Cox relative risk (RR) regression model with a cumulative exposure metric to model cause-specific mortality from lung cancer and all other causes. The separately estimated cause-specific cumulative hazards are then combined to provide an overall estimate of age-specific mortality risk. Age-specific estimates of the additional risk of lung cancer mortality associated with several plausible occupational exposure scenarios are obtained. For age 70, these estimates are all markedly lower than those generated with the cancer potency estimate provided in the USEPA acrylonitrile risk assessment.(2) This result is consistent with the failure of recent occupational studies to confirm elevated lung cancer mortality among acrylonitrile-exposed workers as was originally reported by O'Berg,(3) and it calls attention to the importance of using high-quality epidemiology data in the risk assessment process.

Notes: Experts agree that value of information (VOI) analyses provide useful insights in risk management decisions. However, applications in environmental health risk management (EHRM) remain largely demonstrative thus far because of the complexity in modeling and solving VOI problems. Based on this comprehensive review of all VOI applications published in the peer-reviewed literature of such applications, the complexity of solving VOI problems with continuous probability distributions as inputs in models emerges as the main barrier to greater use of VOI although simulation allows analysts to solve more complex and realistic problems. Several analytical challenges that inhibit greater use of VOI techniques include issues related to modeling decisions, valuing outcomes, and characterizing uncertain and variable model inputs appropriately. This comprehensive review of methods for modeling and solving VOI problems for applications related to EHRM provides the first synthesis of important methodological advances in the field. The insights provide risk analysts and decision scientists with some guidance on how to structure and solve VOI problems focused on evaluating opportunities to collect better information to improve EHRM decisions. They further suggest the need for some efforts to standardize approaches and develop some prescriptive guidance for VOI analysts similar to existing guidelines for conducting cost-effectiveness analyses.

Notes: This article discusses the use of quantitative risk assessment (QRA) in decision making regarding the safety of complex technological systems. The insights gained by QRA are compared with those from traditional safety methods and it is argued that the two approaches complement each other. It is argued that peer review is an essential part of the QRA process. The importance of risk-informed rather than risk-based decision making is emphasized. Engineering insights derived from QRAs are always used in combination with traditional safety requirements and it is in this context that they should be reviewed and critiqued. Examples from applications in nuclear power, space systems, and an incinerator of chemical agents are given to demonstrate the practical benefits of QRA. Finally, several common criticisms raised against QRA are addressed.