bluuebunny/crossref_metadata_2025 huggingface dataset:
Attitudes Toward Managing Hazardous Waste: What Should Be Cleaned Up and Who Should Pay for It?
Authors: Baron Jonathan , Gowda Rajeev , Kunreuther Howard
Published: May 2006

Hazardous waste policy in the United States uses a liability‐based approach, including strict, retroactive, and joint and several liability. To assess attitudes toward these basic principles of liability, and toward priorities for clean‐up of wastes, a questionnaire was mailed to legislators, judges, executives of oil and chemical companies, environmentalists, and economists. The questionnaire consisted of abstract, simplified cases, which contrasted basic principles rather than dealing with real‐world scenarios. Subjects were asked how they would allocate clean‐up costs between companies and government as a function of such factors as adherence to standards, adoption of best available technology (BAT), and influence of penalties on future behavior. Most subjects felt that, if the company followed government standards or used the best available technology (BAT), it should pay for only a portion of the clean‐up cost, with the government paying the rest. In general, responses did not support the principles underlying current law–strict, retroactive, and joint‐and‐several liability. Most subjects were more interested in polluters paying for damages than in deterrence or future benefit–even to the extent that they would have “harmless” waste sites cleaned up. A bias was found toward complete clean‐up of some sites, or “zero risk.” Different groups of subjects gave similar answers, although more committed environmentalists were more willing to make companies pay and to clean up waste regardless of the cost.
Risk‐Based Ranking of Dominant Contributors to Maritime Pollution Events
Authors: Wheeler Timothy A.
Published: May 2006

This report describes a conceptual approach for identifying dominant contributors to risk from maritime shipping of hazardous materials. Maritime transportation accidents are relatively common occurrences compared to more frequently analyzed contributors to public risk. Yet research on maritime safety and pollution incidents has not been guided by a systematic, risk‐based approach. Maritime shipping accidents can be analyzed using event trees to group the accidents into “bins,” or groups, of similar characteristics such as type of cargo, location of accident (e.g., harbor, inland waterway), type of accident (e.g., fire, collision, grounding), and size of release. The importance of specific types of events to each accident bin can be quantified. Then the overall importance of accident events to risk can be estimated by weighting the events' individual bin importance measures by the risk associated with each accident bin.
Perceived Risk, Dread, and Benefits
Authors: Gregory Robin , Mendelsohn Robert
Published: May 2006

This paper uses regression techniques to take a second look at a classic risk‐perception data set originally collected by Paul Slovic, Sarah Lichtenstein, and Baruch Fischhoff. As discussed in earlier studies, the attributes expected mortality, effects on future generations, immediacy, and catastrophic potential all significantly affect risk ratings. However, we find that perceived risk and dread show different regression patterns; most importantly, only perceived risk ratings correlate with expected mortality. In addition, average risk ratings are found to be significantly affected by perceived individual benefits, which suggests that perceptions of risk are net rather than gross indicators of harm.
Siting Noxious Facilities: A Test of the Facility Siting Credo
Authors: Kunreuther Howard , Fitzgerald Kevin , Aarts Thomas D.
Published: May 2006

Over the past decade it has become increasingly difficult to site noxious facilities, despite the fact that there is a growing need to do so. To address this problem, a set of guidelines for a fairer, wiser, and more workable siting process—the Facility Siting Credo—was developed during a National Facility Siting Workshop in 1990. This paper presents an empirical test of these guidelines. A questionnaire based on the Credo was completed by stakeholders in 29 waste facility siting cases, both successful and unsuccessful, across the United States and Canada. Using an independent determination of outcome (success), a preliminary ranking of the importance of various Credo principles was obtained. The data reveal that establishing trust between the developer and host community is an important factor in facilitating the siting process. The siting process is most likely to be successful when the community perceives the facility design to be appropriate and to satisfy its needs. Public participation also is seen to be an important process variable, particularly if it encourages a view that the facility best meets community needs. Moreover, a siting process where communities volunteer to host facilities is an approach that holds promise for meeting many of these key success criteria.
The Risks of Licensing Persons with Diabetes to Drive Trucks
Authors: Songer Thomas J. , Lave Lester B. , LaPorte Ronald E.
Published: May 2006

The 1990 Americans with Disabilities Act forbids employers to bar disabled persons from jobs unless employers can show the disabled person cannot perform the tasks. The Federal Highway Administration will not license persons with diabetes mellitus to drive commercial motor vehicles in interstate commerce. These individuals may experience severe hypoglycemia, greatly increasing their risk of losing control of the truck. This prohibition is currently being reexamined. We describe the disease process leading to severe hypoglycemia and its physical manifestations. To quantify the risks of licensing persons with diabetes to use insulin, we first estimate the number of potential insulin‐using drivers. We estimate that 1420 insulin‐using persons would seek licenses in the United States if they were permitted to do so (920 noninuslin dependent and 500 insulin dependent). Next, we estimate the annual incidence of mild and severe hypoglycemia in these populations. The third step is to estimate the number of hypoglycemic episodes while driving. Estimating the likelihood of a crash due to a mild or severe hypoglycemic episode is the fourth step. We estimate that an additional 42 crashes each year would occur if insulin using persons were licensed to drive commercial motor vehicles in interstate commerce (20 from insulin dependent and 22 from non‐insulin dependent drivers).
Safety Investment and the Value of Life and Injury
Authors: Soby Barbara A. , Ball David J. , Ives Dawn P.
Published: May 2006

The requirement to reduce risk is moderated under British law by the notion of practicability or reasonable practicability. This implies that a balance should be struck, inter alia, between the costs of a risk‐reducing measure and its benefits in terms of life‐saving and injury avoidance. Clearly, were lives and injuries valued in monetary terms, balances and imbalances would be all the more easily identified. This paper reports on progress on the application of the Relative Utility Loss Approach to the valuation of injuries in the consumer and transportation spheres in the United Kingdom. Although the tools are as yet imperfect, striking accord is noticed between valuations of a range of serious and slight injuries obtained using three health state utility indices of disparate origin.
Risk Assessment for Aflatoxin: An Evaluation Based on the Multistage Model
Authors: Bowers J. , Brown B. , Springer J. , Tollefson L. , Lorentzen R. , Henry S.
Published: May 2006

Lifetime cancer potency of alfatoxin was assessed based on the Yeh et al. study from China in which both aflatoxin exposure and hepatitis B prevalence were measured. This study provides the best available information for estimating the carcinogenic risk posed by aflatoxin to the U.S. population. Cancer potency of aflatoxin was estimated using a biologically motivated risk assessment model. The best estimate of aflatoxin potency was 9 (mg/kg/day)−1 for individuals negative for hepatitis B and 230 (mg/kg/day)−1 for individuals positive for hepatitis B.
Perceived Risk, Trust, and Democracy
Authors: Slovic Paul
Published: May 2006

Risk management has become increasingly politicized and contentious. Polarized views, controversy, and overt conflict have become pervasive. Risk‐perception research has recently begun to provide a new perspective on this problem. Distrust in risk analysis and risk management plays a central role in this perspective. According to this view, the conflicts and controversies surrounding risk management are not due to public ignorance or irrationality but, instead, are seen as a side effect of our remarkable form of participatory democracy, amplified by powerful technological and social changes that systematically destroy trust. Recognizing the importance of trust and understanding the “dynamics of the system” that destroys trust has vast implications for how we approach risk management in the future.
The Possibility for “Natural” Generation of Chlorinated Organic Compounds
Authors: Haas Charles N.
Published: May 2006

There is continuing concern for the exposure of persons to various chlorinated organics via the environment, for example, chlorinated disinfection byproducts in drinking water.(1) Some of these may be carcinogenic,(2) although the evidence is far from strong.(3) There is an accumulating body of evidence that one of the normal human immunological responses to foreign agents is the generation of hypochlorous acid. This evidence will be summarized. The possibility that this HOCl generated in vivo could result in the formation of organo‐chlorine compounds does not appear to have been seriously considered. Based on best available information, the amount of such byproduct formation will be estimated.
Leukemia Risk Associated with Benzene Exposure in the Pliofilm Cohort. II. Risk Estimates
Authors: Paxton Mary B. , Chinchilli Vernon M. , Brett Susan M. , Rodricks Joseph V.
Published: May 2006

The detailed work histories of the individual workers composing the Pliofilm cohort represent a unique resource for estimating the dose‐respoonse for leukemia that may follow occupational exposure to benzene. In this paper, we report the results of analyzing the updated Pliofilm cohort using the proportional hazards model, a more sophisticated technique that uses more of the available exposure data than the conditional logistic model used by Rinskyet al.The more rigorously defined exposure estimates derived by Paustenbachet al.are consistent with those of Crump and Allen in giving estimates of the slope of the leukemogenic dose‐response that are not as steep as the slope resulting from the exposure estimates of Rinskyet al.We consider estimates of 0.3‐0.5 additional leukemia deaths per thousand workers with 45 ppm‐years of cumulative benzene exposure to be the best estimates currently available of leukemia risk from occupational exposure to benzene. These risks were estimated in the proportional hazards model when the exposure estimates of Crump and Allen or of Paustenbachet al.were used to derive a cumulative concentration‐by‐time metric.
Assessing the Relationship Between Environmental Lead Concentrations and Adult Blood Lead Levels
Authors: Bowers Teresa S. , Beck Barbara D. , Karam Hala S.
Published: May 2006

This paper presents a model for predicting blood lead levels in adults who are exposed to elevated environmental levels of lead. The model assumes a baseline blood lead level based on average blood lead levels for adults described in two recent U.S. studies. The baseline blood lead level in adults arises primarily from exposure to lead in diet. Media‐specific ingestion and absorption parameters are assessed for the adult population, and a biokinetic slope factor that relates uptake of lead into the body to blood lead levels is estimated. These parameters are applied to predict blood lead levels for adults exposed to a hypothetical site with elevated lead levels in soil, dust and air. Blood lead levels ranging from approximately 3‐57 μg/dl are predicted, depending on the exposure scenarios and assumptions.
What Do People Know About Global Climate Change? 2. Survey Studies of Educated Laypeople
Authors: Read Daniel , Bostrom Ann , Morgan M. Granger , Fischhoff Baruch , Smuts Tom
Published: May 2006

Drawing on results from earlier studies that used open‐ended interviews, a questionnaire was developed to examine laypeople's knowledge about the possible causes and effects of global warming, as well as the likely efficacy of possible interventions. It was administered to two well‐educated opportunity samples of laypeople. Subjects had a poor appreciation of the facts that (1) if significant global warming occurs, it will be primarily the result of an increase in the concentration of carbon dioxide in the earth's atmosphere, and (2) the single most important source of additional carbon dioxide is the combustion of fossil fuels, most notably coal and oil. In addition, their understanding of the climate issue was encumbered with secondary, irrelevant, and incorrect beliefs. Of these, the two most critical are confusion with the problems of stratospheric ozone and difficulty in differentiating between causes and actions specific to climate and more general good environmental practice.
Estimated Risk of Occupational Fatalities Associated with Hazardous Waste Site Remediation
Authors: Hoskin Alan F. , Leigh J. Paul , Planek Thomas W.
Published: May 2006

This study presents a method to assess short term traumatic fatality risks for workers involved in hazardous waste site remediation to provide a quantitative, rather than qualitative, basis for evaluating occupational exposures in remediation feasibility studies. Occupational employment and fatality data for the years 1979–1981 and 1983 were compiled from Bureau of Labor Statistics data for 11 states. These data were analyzed for 17 occupations associated with three common remediation alternatives: excavation and landfill, capping, and capping plus slurry wall. The two occupations with the highest death rates, truck driver and laborer, contributed most to total exposure hours in each alternative. Weighted average death rates were produced for each alternative and multiplied by respective total person‐years of exposure. The resultant expected number of fatalities was converted, using the Poisson distribution, to the risk of experiencingat leastone fatality, as follows: 0.149 for excavation and landfill, 0.012 for capping, and 0.014 for capping plus slurry wall. These risks were discussed in light of the need to obtain more reliable and comprehensive data than are currently available on the occupational safety and health risks associated with hazardous waste site remediation and the need for a more scientific, quantitative approach to remediation decisions involving risks to workers.
Reproducibility of the Dose‐Response Curve of Steroid‐Induced Cleft Palate in Mice
Authors: Freni Stan C. , Razzaghi Mehdi , Moore Gary E.
Published: May 2006

Pregnant CD‐1 mice were exposed to cortisone acetate at doses ranging from 20 to 100 mg/kg/ day on days 10‐13 by oral and intramuscular routes. Multiple replicate assays were conducted under identical conditions to assess the reproducibility of the dose–response curve for cleft palate. The data were fitted to the probit, logistic, multistage or Armitage‐Doll, and Weibull dose‐response model separately for each route of exposure. The curves were then tested for parallel slopes (probit and logistic models) or coincidence of model parameters (multistage and Weibull models). The 19 replicate experiments had a wide range of slope estimates, wider for the oral than for the intramuscular experiments. For all models and both routes of exposure the null hypothesis of equality of slopes was rejected at a significant level of p < 0.001. For the intramuscular group of replicates, rejection of slope equality could in part be explained by not maintaining a standard dosing regime. The rejection of equivalence of dose‐response curves from replicate studies showed that it is difficult to reproduce dose‐response data of a single study within the limits defined by the dose‐response model. This has important consequences for quantitative risk assessment, public health measures, or development of mechanistic theories which are typically based on a single animal bioassay.
On the Exact Hazard and Survival Functions of the MVK Stochastic Carcinogenesis Model
Authors: Zheng Qi
Published: May 2006

The MVK two‐stage carcinogenesis model is one of the most widely accepted mechanistic models in carcinogenesis modeling. However, due to a perceived difficulty in obtaining analytic solutions for the hazard and survival functions, approximations and numerical methods have been used to calculate these two fundamental quantities. This paper focuses on a special case of the homogeneous MVK model where the number of normal cells is constant. The probability generating function (pgf) for the number of tumor cells is derived, and the exact analytic solutions to the hazard and survival functions are obtained from the pgf.
Incorporation of Pharmacokinetics in Noncancer Risk Assessment: Example with Chloropentafluorobenzene
Authors: Clewell Harvey J. , Jarnot Bruce M.
Published: May 2006

Noncancer risk assessment traditionally relies on applied dose measures, such as concentration in inhaled air or in drinking water, to characterize no‐effect levels or low‐effect levels in animal experiments. Safety factors are then incorporated to address the uncertainties associated with extrapolating across species, dose levels, and routes of exposure, as well as to account for the potential impact of variability of human response. A risk assessment for chloropentafluorobenzene (CPFB) was performed in which a physiologically based pharmacokinetic model was employed to calculate an internal measure of effective tissue dose appropriate to each toxic endpoint. The model accurately describes the kinetics of CPFB in both rodents and primates. The model calculations of internal dose at the no‐effect and low‐effect levels in animals were compared with those calculated for potential human exposure scenarios. These calculations were then used in place of default interspecies and route‐to‐route safety factors to determine safe human exposure conditions. Estimates of the impact of model parameter uncertainty, as estimated by a Monte Carlo technique, also were incorporated into the assessment. The approach used for CPFB is recommended as a general methodology for noncancer risk assessment whenever the necessary pharmacokinetic data can be obtained.
Combination of Cancer Data in Quantitative Risk Assessments: Case Study Using Bromodichloromethane
Authors: Velazquez Susan F. , McGinnis Patricia M. , Vater Sarah T. , Stiteler William S. , Knauf Linda A. , Schoeny Rita S.
Published: May 2006

There are often several data sets that may be used in developing a quantitative risk estimate for a carcinogen. These estimates are usually based, however, on the dose‐response data for tumor incidences from a single sex/strain/species of animal. When appropriate, the use of more data should result in a higher level of confidence in the risk estimate. The decision to use more than one data set (e.g., representing different animal sexes, strains, species, or tumor sites) can be made following biological and statistical analyses of the compatibility of these data sets. Biological analysis involves consideration of factors such as the relevance of the animal models, study design and execution, dose selection and route of administration, the mechanism of action of the agent, its pharmacokinetics, any species‐ and/or sex‐specific effects, and tumor site specificity. If the biological analysis does not prohibit combining data sets, statistical compatibility of the data sets is then investigated. A generalized likelihood ratio test is proposed for determining the compatibility of different data sets with respect to a common dose‐response model, such as the linearized multistage model. The biological and statistical factors influencing the decision to combine data sets are described, followed by a case study of bromodichloromethane.
Lactational Transfer of Tetrachloroethylene in Rats
Authors: Byczkowski Janusz Z. , Fisher Jeffrey W.
Published: May 2006

Tetrachloroethylene (PCE) is a commonly used organic solvent and a suspected human carcinogen, reportedly transferred to human breast milk following inhalation exposure. Transfer of PCE to milk may represent a threat to the nursing infant. A physiologically based pharmacokinetic (PBPK) model was developed to quantitatively assess the transfer of inhaled PCE into breast milk and the consequent exposure of the nursing infant. The model was validated in lactating rats. Lactating Sprague‐Dawley female rats were exposed via inhalation to PCE at concentrations ranging from 20‐1000 ppm, and then returned to their nursing, 10‐ to 11‐day‐old pups. Tetrachloroethylene concentrations in the air, blood, milk, and tissue were determined by gas chromatography and compared to model predictions. The model described the distribution of inhaled PCE in maternal blood and milk, as well as the nursed pup's gastrointestinal tract, blood, and tissue. Several computer simulations of PCE distribution kinetics in exhaled air, blood, and milk of exposed human subjects were run and compared with limited human data available from the literature. It is concluded that the PBPK model successfully described the concentration of PCE in both lactating rats and humans. Although predictions vs. observations were good, the model slightly underpredicted the peak whole pup PCE concentration and underpredicted systemic clearance of PCE from the pup.
Measures of Compounding Conservatism in Probabilistic Risk Assessment
Authors: Cullen Alison C.
Published: May 2006

Concern about the degree of uncertainty and potential conservatism in deterministic point estimates of risk has prompted researchers to turn increasingly to probabilistic methods for risk assessment. With Monte Carlo simulation techniques, distributions of risk reflecting uncertainty and/or variability are generated as an alternative. In this paper the compounding of conservatism(1) between the level associated with point estimate inputs selected from probability distributions and the level associated with the deterministic value of risk calculated using these inputs is explored. Two measures of compounded conservatism are compared and contrasted. The first measure considered, F, is defined as the ratio of the risk value, Rd, calculated deterministically as a function of n inputs each at the jth percentile of its probability distribution, and the risk value, Rj that falls at the jth percentile of the simulated risk distribution (i.e., F=Rd/Rj). The percentile of the simulated risk distribution which corresponds to the deterministic value, Rd, serves as a second measure of compounded conservatism. Analytical results for simple products of lognormal distributions are presented. In addition, a numerical treatment of several complex cases is presented using five simulation analyses from the literature to illustrate. Overall, there are cases in which conservatism compounds dramatically for deterministic point estimates of risk constructed from upper percentiles of input parameters, as well as those for which the effect is less notable. The analytical and numerical techniques discussed are intended to help analysts explore the factors that influence the magnitude of compounding conservatism in specific cases.
Use of Monte Carlo Simulation for Human Exposure Assessment at a Superfund Site
Authors: Smith Roy L.
Published: May 2006

This work presents a comparison of probabilistic and deterministic health risk estimates based on data from an industrial site in the northeastern United States. The risk assessment considered exposures to volatile solvents by drinking water ingestion and showering. Probability densities used as inputs included concentrations, contact rates, and exposure frequencies; dose‐response inputs were single values. Deterministic risk estimates were calculated by the “reasonable maximum exposure” (RME) approach recommended by the EPA Superfund program. The RME non‐carcinogenic risk fell between the 90th and the 95th percentile of the probability density; the RME cancer risk fell between the 95th percentile and the maximum. These results suggest that in this case (1) EPA's deterministic RME risk was reasonably protective, (2) results of probabilistic and deterministic calculations were consistent, and (3) commercially available software Monte Carlo software effectively provided multiple risk estimates recommended by recent EPA guidance.
An Improved Framework for Uncertainty Analysis: Accounting for Unsuspected Errors
Authors: Shlyakhter Alexander I.
Published: May 2006

I use an analogy with the history of physical measurements, population and energy projections, and analyze the trends in several data sets to quantify the overconfidence of the experts in the reliability of their uncertainty estimates. Data sets include (i) time trends in the sequential measurements of the same physical quantity; (ii) national population projections; and (iii) projections for the U.S., energy sector. Probabilities of large deviations for the true values are parametrized by an exponential distribution with the slope determined by the data. Statistics of past errors can be used in probabilistic risk assessment to hedge against unsuspected uncertainties and to include the possibility of human error into the framework of uncertainty analysis. By means of a sample Monte Carlo simulation of cancer risk caused by ingestion of benzene in soil, I demonstrate how the upper 95th percentiles of risk are changed when unsuspected uncertainties are included. I recommend to inflate the estimated uncertainties by default safety factors determined from the relevant historical data sets.
Uncertainty and Variability in Human Exposures to Soil Contaminants Through Home‐Grown Food: A Monte Carlo Assessment
Authors: McKone Thomas E.
Published: May 2006

This paper presents a general model for exposure to homegrown foods that is used with a Monte Carlo analysis to determine the relative contributions of variability (Type A uncertainty) and true uncertainty (Type B uncertainty) to the overall variance in prediction of the dose‐to‐concentration ratio. Although classification of exposure inputs as uncertain or variable is somewhat subjective, food consumption rates and exposure duration are judged to have a predicted variance that is dominated by variability among individuals by age, income, culture, and geographical region. Whereas, biotransfer factors and partition factors are inputs that, to a large extent, involve uncertainty. Using ingestion of fruits, vegetables, grains, dairy products, and meat and soils assumed to be contaminated by hexachlorbenzene (HCB) and benzo(a)pyrene (BaP) as cases studies, a Monte Carlo analysis is used to explore the relative contribution of uncertainty and variability to overall variance in the estimated distribution of potential dose within the population that consumes homegrown foods. It is found that, when soil concentrations are specified, variances in ratios of dose‐to‐concentration for HCB are equally attributable to uncertainty and variability, whereas for BaP, variance in these ratios is dominated by true uncertainty.
Sensitivity of Physiologically Based Pharmacokinetic Models to Variation in Model Parameters: Methylene Chloride
Authors: Clewell H. J. , Lee Tze‐san , Carpenter R. L.
Published: May 2006

The parameters in a physiologically based pharmacokinetic (PBPK) model of methylene chloride were varied systematically, and the resulting variation in a number of model outputs was determined as a function of time for mice and humans at several exposure concentrations. The importance of the various parameters in the model was highly dependent on the conditions (concentration, species) for which the simulation was performed and the model output (dose surrogate) being considered. Model structure also had a significant impact on the results. For sensitivity analysis, particular attention must be paid to conservation equations to ensure that the variational calculations do not alter mass balance, introducing extraneous effects into the model. All of the normalized sensitivity coefficients calculated in this study ranged between −1.12 and 1, and most were much less than 1 in absolute value, indicating that individual input errors are not greatly amplified in the outputs. In addition to ranking parameters in terms of their impact on model predictions, time‐dependent sensitivity analysis can also be used as an aid in the design of experiments to estimate parameters by predicting the experimental conditions and sampling points which will maximize parameter identifiability.
Propagation of Uncertainty in Risk Assessments: The Need to Distinguish Between Uncertainty Due to Lack of Knowledge and Uncertainty Due to Variability
Authors: Hoffman F. Owen , Hammonds Jana S.
Published: May 2006

In quantitative uncertainty analysis, it is essential to define rigorously the endpoint or target of the assessment. Two distinctly different approaches using Monte Carlo methods are discussed: (1) the end point is a fixed but unknown value (e.g., the maximally exposed individual, the average individual, or a specific individual) or (2) the end point is an unknown distribution of values (e.g., the variability of exposures among unspecified individuals in the population). In the first case, values are sampled at random from distributions representing various “degrees of belief” about the unknown “fixed” values of the parameters to produce a distribution of model results. The distribution of model results represents a subjective confidence statement about the true but unknown assessment end point. The important input parameters are those that contribute most to the spread in the distribution of the model results. In the second case, Monte Carlo calculations are performed in two dimensions producing numerous alternative representations of the true but unknown distribution. These alternative distributions permit subject confidence statements to be made from two perspectives: (1) for the individual exposure occurring at a specified fractile of the distribution or (2) for the fractile of the distribution associated with a specified level of individual exposure. The relative importance of input parameters will depend on the fractile or exposure level of interest. The quantification of uncertainty for the simulation of a true but unknown distribution of values represents the state‐of‐the‐art in assessment modeling.
Understanding Uncertainty
Authors: Rowe William D.
Published: May 2006

There is more information we don't know than we do know for making most critical decisions involving risks. Our focus must be on understanding and effectively dealing with what we don't know. As a first step in achieving this focus, a classification of the types of uncertainties that must be addressed and the sources of these types of uncertainties is presented. The purpose is to provide a framework for discussion about addressing uncertainty, particularly in risk analyses.

Both uncertainty and variability of information are addressed using four main classes:

Metrical uncertainty and variability in measurement,

Structural uncertainty due to complexity, including models and their validation,

Temporal uncertainty in future and past states

Translational uncertainty in explaining uncertain results.

The factors that contribute uncertainty and error to these classes are identified, and their interrelationships indicated. Both subjective and objective aspects are addressed.
Stepping Out of Your Own Shadow: A Didactic Example of How Facing Uncertainty Can Improve Decision‐Making
Authors: Finkel Adam M.
Published: May 2006

Advocates of quantitative uncertainty analysis (QUA) have invested substantial effort in explaining why uncertainty is a crucial aspect of risk and yet have devoted much less effort to explaining how QUA can improve the risk manager's performance. This paper develops a teaching example, using a personal decision problem with subtle parallels to societal risk management, to show how choices made with increasing appreciation of uncertainty are superior ones. In the hypothetical, five analysts explain the same uncertain prospect (whether to invest in a volatile stock issue), with increasing attention to the nuances of uncertainty. The path through these different perspectives on the decision demonstrates four general points applicable to environmental risk management: (1) Various point estimates with equal claim to being “best estimates” can differ markedly from each other and lead to diametrically different choices; (2) “conservatism” has both relative and absolute meanings, with different implications for decision‐making; (3) both inattention to and fixation on “outliers” in the uncertainty distribution can lead the manager astray; and (4) the best QUA is one that helps discriminate among real options, that points to optimum pathways toward new information, and that spurs on the iterative search for new decision options that may outperform any of the initial ones offered.
Stigma Happens: Social Problems in the Siting of Nuclear Waste Facilities
Authors: Slovic Paul , Flynn James , Gregory Robin
Published: May 2006

The paper by Metz challenges the view that stigma associated with a nuclear waste repository might lead to significant economic losses to the host region. We have been invited to comment on the general issues raised by this paper. We find that much of the evidence presented in the paper consists of factual and conceptual errors and misrepresentations of the research literature. Based on our review of evidence documenting the social and economic impacts of perceived risk, we conclude that stigma is an important phenomenon that is symptomatic of fundamental problems with the way in which nuclear waste facilities are sited.
Public Perceptions of the Potential Hazards Associated with Food Production and Food Consumption: An Empirical Study
Authors: Sparks Paul , Shepherd Richard
Published: May 2006

Although public perceptions of food‐related hazards receive much media comment and debate, the research literature on such perceptions is sparse and piecemeal. In the reported study, 216 people completed a questionnaire relating to their perceptions of the “risk characteristics” of potential hazards associated with various aspects of food production and food consumption. Responses were examined via principal‐components analysis to obtain a structural representation of risk perception of the kind provided by Fischhoff, Slovic, and their colleagues in their seminal psychometric work.(1,2) A three‐component solution accounting for 87% of the variance was obtained, with the dimensions labeled as “severity,”“unknown,” and “number of people exposed.” The findings also yielded information pointing to evidence of the phenomenon of unrealistic optimism. We conclude that our findings offer a useful base upon which further in‐depth research integrating different perspectives on risk perception with respect to food‐related hazards may be developed.
Use of Biological Markers in Risk Assessment1
Authors: McMillan Alex , Whittemore Alice S. , Silvers Abraham , DiCiccio Yasamin
Published: May 2006

Measurements of intermediate end points in the carcinogenic process may reduce uncertainty in human risk assessment from bioassay data, by identifying sources of interspecies variation and dose nonlinearity. This paper describes desirable properties of such markers: persistence, predictive power, temporal relevance, and consistency across dose rate and species. We illustrate these properties by evaluating markers for squamous cell nasal carcinoma in rodents exposed to formaldehyde. We also discuss design issues for bioassays that evaluate markers and tumors simultaneously at necropsy.
A Unified Approach for Calculating Core Melt Frequency Caused by Internal and External Initiating Events
Authors: Heising Carolyn D. , de Oliveira Virgilio Lopes
Published: May 2006

A unified approach for calculating the core melt frequency of a specific reactor caused by both internal and external accident initiators is demonstrated. Two classes of internal initiators are examined: transients, of which turbine trip is the chosen example, and loss‐of‐coolant events of various sizes. The concepts of hazard and fragility analysis first proposed for seismic risk analysis are linked to the frequencies of internal initiating events, and to the plant response as a function of the event intensity. Uncertainties are propagated using discrete probability distribution (DPD) arithmetic. Advantages of this approach include mathematical and conceptual consistency, and an improved uncertainty analysis, which are important considerations if risk studies are to be utilized in decision‐making based on quantitative safety goals.
The Tradeoffs Associated with Rerouting Highway Shipments of Hazardous Materials to Minimize Risk
Authors: Glickman Theodore S. , Sontag Mary Anne
Published: May 2006

Recent legislative and regulatory activities at the federal level have focused attention on the highway routing of hazardous materials. The question is whether routes that minimize the risk of release accidents (i.e., the expected number of persons impacted by releases of hazardous materials) should be used in lieu of the routes that have the lowest operating costs. This policy issue is addressed for interstate shipments by using a national network model to determine the practical route and minimum risk route between each of 100 different origin‐destination pairs (state capitals). The resulting cost‐risk tradeoffs are then used to estimate the average cost of rerouting per fatality averted, the value of which turns out to be within the range of values for a number of familiar existing regulations.
Fitting the Two‐Stage Clonal Expansion Model Based on Exact Hazard to the ED01 Data Using SAS NLIN
Authors: Lensing Shelly Y. , Kodell Ralph L.
Published: May 2006

The two‐stage clonal expansion model is a popular model for carcinogenesis data. One common form of this model is based on the approximate hazard function. In certain situations, this formulation is not appropriate, and the exact hazard should be applied. However, the difficulty of implementing the model based on the exact hazard has deterred many from using it. This paper presents a program implementing the exact hazard model for piecewise constant dosing using SAS, a package that is readily available to most that are interested in this type of analysis. Also, an analysis of the ED01 data is presented using this program, and comparisons are made to an earlier analysis based on the approximate hazard. By allowing for an independent background tumor mechanism, an excellent fit to the bladder tumor incidence data was obtained.
Estimation of Acute Toxicity by Fitting a Dose‐Time‐Response Surface
Authors: Sun Kai , Krause Gary F. , Mayer Foster L. , Ellersieck Mark R. , Basu Asit P.
Published: May 2006

In acute toxicity testing, organisms are continuously exposed to progressively increasing concentrations of a chemical and deaths of test organisms are recorded at several selected times. The results of the test are traditionally summarized by a dose‐response curve, and the time course of effect is usually ignored for lack of a suitable model. A model which integrates the combined effects of dose and exposure duration on response is derived from the biological mechanisms of aquatic toxicity, and a statistically efficient approach for estimating acute toxicity by fitting the proposed model is developed in this paper. The proposed procedure has been computerized as software and a typical data set is used to illustrate the theory and procedure. The new statistical technique is also tested by a data base of a variety of chemical and fish species.
Uptake of Chloroform by Skin During Short Exposures to Contaminated Water
Authors: Islam Mohammad S. , Zhao Luhua , McDougal James N. , Flynn Gordon L.
Published: May 2006

Uptake of chloroform into hairless rat stratum corneum from dilute aqueous solutions was studied using tape‐stripping to determine amounts deposited in the skin under various environmental exposure scenarios. The length of exposure of sedated animals to the chloroform‐containing medium, the frequency and duration of tape‐stripping, and the number of tape‐strips per location were varied to map the stratum corneum substantivity of chloroform. Eight minutes immersion of the rat within a well‐stirred solution at 36°C was found to be adequate time for the gradient to be established fully across the stratum corneum. Penetration was progressively deeper as the exposure time increased. Substantial evaporative loss of chloroform from the aqueous medium of application seem to be responsible for lower cumulative amounts taken up when the same solution was held on the rat's skin within a stainless steel template of fixed area. Of the total uptake (29 mg) from a dilute stirred solution of chloroform (0.44 mg/ml) at 36°C, about 95% was systematically absorbed after a 30 min exposure as determined by residuals (measurement of bath concentrations).
The Social Benefits of Expedited Risk Assessments
Authors: Cranor Carl F.
Published: May 2006

The present regulation of carcinogens is quite slow; hundreds of substances that have tested positive for carcinogenicity in animal bioassays have not been addressed by the U.S. regulatory system. This carries with it unappreciated social, economic, and public health costs. However, there are readily available expedited approximation procedures for assessing the potency of carcinogens whose use has substantial benefits that outweigh any costs from less science‐intensive and less extensively documented assessments. These benefits can be seen by using a model to suggest the magnitude of social costs in regulating carcinogens by current conventional methods compared with expedited procedures for assessing the potency of known carcinogens. Two scenarios, one in accordance with current agency presumptions and one which assumes extreme unreliability in animal data and in the accuracy of potency assessments, compare conventional science‐intensive and expedited procedures. On both, the total social costs of expedited procedures are lower than conventional procedures across a wide range of values assigned for individual mistakes of under regulation and over regulation. It appears better to evaluate a larger universe of known carcinogens somewhat less intensively for each substance than to evaluate a small proportion of that same universe very carefully and delay considering the rest.
Significance of Exposure Assessment to Analysis of Cancer Risk from Inorganic Arsenic in Drinking Water in Taiwan
Authors: Brown Kenneth G. , Chen Chien‐Jen
Published: May 2006

The primary source of evidence that inorganic arsenic in drinking water is associated with increased mortality from cancer at internal sites (bladder, liver, lung, and other organs) is a large ecologic study conducted in regions of Southwest Taiwan endemic to Blackfoot disease. The dose‐response patterns for lung, liver, and bladder cancers display a nonlinear dose‐response relationship with arsenic exposure. The data do not appear suitable, however, for the more refined task of dose‐response assessment, particularly for inference of risk at the low arsenic concentrations found in some U.S. water supplies. The problem lies in variable arsenic concentrations between the wells within a village, largely due to a mix of shallow wells and deep artesian wells, and in having only one well test for 24 (40%) of the 60 villages. The current analysis identifies 14 villages where the exposure appears most questionable, based on criteria described in the text. The exposure values were then changed for seven of the villages, from the median well test being used as a default to some other point in the village's range of well tests that would contribute to smoothing the appearance of a dose‐response curve. The remaining seven villages, six of which had only one well test, were deleted as outliers. The resultant dose‐response patterns showed no evidence of excess risk below arsenic concentrations of 0.1 mg/l. Of course, that outcome is dependent on manipulation of the data, as described. Inclusion of the seven deleted villages would make estimates of risk much higher at low doses. In those seven villages, the cancer mortality rates are significantly high for their exposure levels, suggesting that their exposure values may be too low or that other etiological factors need to be taken into account.
Understanding Life‐Threatening Risks
Authors: Keeney Ralph L.
Published: May 2006

Modern science and medicine, and increasing prosperity, have brought many benefits to our society, but not without costs. One cost is that some of the technological innovations and new activities bring with them different and perhaps greater risks that threaten our lives. Any problem involving life‐threatening risks is complex, so it is difficult to think through all the implications of the alternatives proposed to address it. This paper presents a number of “facts” to guide constructive thinking about decisions concerning life‐threatening risks. The intent is to help us appraise alternatives, design public policy and laws, and communicate about specific risk problems.
Plurality of Worlds, Plurality of Risks
Authors: Limoges Camille , Cambrosio Alberto , Davignon Louis
Published: May 2006

Risk management decisions are not made only on the basis of expert risk assessment. In numerous instances, public controversy erupts, questioning the results of previous risk assessment procedures and shaping the development of risk management episodes. This article presents a case study of risk management in the context of a 1980s controversy over aerial spraying against a spruce budworm epidemic in Quebec and draws some general conclusions concerning the relationship between risk analysis and public controversies. Actors in public controversies define risks more broadly than risk assessment experts. Moreover, public controversies only partly concern issues of risk. They are first and foremost debates about social choices in which actors carry with them a multidimensional social experience of technology, trust, credibility and decision‐making institutions. This experience contributes to the construction of a plurality of emergent representations of what is at stake in a controversy, referred to in this paper as “worlds of relevance.” Analysis shows that in any given public controversy, there are not just two parties arguing against each other. Rather, several “worlds of relevance” can be found that link, in a variety of ways, a variety of entities not necessarily shared by all these worlds. Each “world of relevance” presents a different definition of what the issues and the stakes of the controversy are. Risks are only part of the picture, and they are embedded in “worlds of relevance” from which they take their significance. The successful management of a controversy entails the association of entities from different worlds.