bluuebunny/crossref_metadata_2025 huggingface dataset:
Generalized Quantification of Risk Associated with Extreme Events1
Authors: Mitsiopoulos James , Haimes Yacov Y.
Published: May 2006

In the partitioned multiobjective risk method (PMRM) the probability axis is typically partitioned into three regimes: high‐exceedance low‐consequence, intermediate‐exceedance intermediate‐consequence, and low‐exceedance high‐consequence (LE/HC). For each regime, the PMRM generates a conditional expected risk‐function given that the damage lies within the regime. The theme of this paper is the conditional expected‐risk function for the LE/HC regime. This function, denoted by f4(.), captures the behavior of the “extreme events” of an underlying decision‐making problem. The PMRM offers two advantages: (a) it isolates LE/HC events, allowing the decision‐maker(s) to focus on the impacts of catastrophies; and (b) it generates more valuable information than that obtained from the common unconditional expected‐risk function. Theoretical problems may arise from uncertainty about the behavior of the tail of the risk curve describing the underlying frequency of damages. When the number of physical observations in small (e.g., in flood frequency analysis), the analyst is forced to make assumptions about the density of damages. Each succeeding distributional assumption will generate a different value of f4(.). An added dimension of difficulty is also created by the sensitivity of f4(.) to the choice of the boundary of the LE/HC regime. This paper has two overall objectives: (a) to present distribution‐free results concerning the magnitude of f4(.); and (b) to use those results to obtain a distribution‐free estimate of the sensitivity of f4(.) to the choice of the boundary of the LE/HC regime. The above objectives are realized by extending, and further developing, existing inequalities for continuously distributed random variables.
Risk Communication and Social Choices: The Discussion Heats Up
Authors: Cumming Robert B.
Published: May 2006

Environmental Hazards: Communicating Risks as a Social Process Sheldon Krimsky and Alonzo Plough Dover, MA: Auburn House Publishing Co.
Optimizing Risk Analysis Relating to External Safety in The Netherlands
Authors: Van Eijndhoven Josée C.M. , Van Ravenzwaaij Ardaan
Published: May 2006

Risk analyses in The Netherlands have been optimized so that they now express risks in a numerical form suitable for comparison to national safety standards. This factor is more important to national government than to local authorities; other factors relevant for local authorities are given less emphasis or even completely omitted from the results of the analysis. From a comparison of 16 risk analyses carried out during the last decade, it became clear that in the last 5 years the methods of risk analyses related to external safety have become unified. Results are now presented in terms of individual risk contours and in terms of F‐N curves (accident frequency vs. exceeded number of fatalities). This unification seems to be a result of government policy. First, the implementation of the post‐Seveso‐directive (501/82/EC) in The Netherlands obliges a number of industries to provide the authorities with a quantitative risk assessment. Second, the government has set standards for the maximum permissible risk in residential areas. A unified type of risk analysis is a tool to achieve both these policies. From interviews with local government authorities, however, it has become clear that they need and use some quantitative risk information that is not provided by the unified analysis. They feel they need figures that provide insight into the effects of incidents and into the way effects may change as a result of safety measures. Ultimately, government policy may mean that local officials receive less information than before.
Risk Perceptions and Food Choice: An Exploratory Analysis of Organic‐ Versus Conventional‐Produce Buyers
Authors: Hammitt James K.
Published: May 2006

Consumer choice between organically (without pesticides) and conventionally grown produce is examined. Exploratory focus‐group discussions and questionnaires (N= 43) suggest that individuals who purchase organically grown produce believe it is substantially less hazardous than the conventional alternative and are willing to pay significant premiums to obtain it (a median 50% above the cost of conventional produce). The value of risk reduction implied by this incremental willingness to pay is not high relative to estimates for other risks, since the perceived risk reduction is relatively large. Organic‐produce consumers also appear more likely than conventional‐produce consumers to mitigate other ingestion‐related risks (e.g., contaminated drinking water) but less likely to use automobile seatbelts.
Software Listings
Authors: Moskowitz Paul D.
Published: May 2006

RISKPRO support (301) 953–2700, General Sciences Corporation, 6100 Chevy Chase Drive, Laurel, Maryland 20707. RISKPRO is available for IBM and IBM‐compatible XTs, ATs, PS 2s and 80386 personal computers with EGA or VGA graphic adapters. In addition, General Sciences Corporation supports RISKPRO on VAX/VMS systems. For PC RISKPRO, $375 for Core System. Additional modules range from $150 to $1495. A special package price is $5300. The VAX RISKPRO price varies by size of computer. Contact GSC for details.
A Methodology for Grouping Source Terms for Consequence Calculations in Probabilistic Risk Assessments
Authors: Iman Ronald L. , Helton Jon C. , Johnson Jay D.
Published: May 2006

The individual plant analyses in the U.S. Nuclear Regulatory Commission's reassessment of the risk from commercial nuclear power plants (NUREG‐1150) consist of four parts: systems analysis, accident‐progression analysis, source‐term analysis, and consequence analysis. Careful definition of the interfaces between these parts is necessary for both information flow and computational efficiency. This paper describes the procedure used to define the interface between the source‐term analysis and the consequence analysis. This interface is accomplished by forming groups of source terms with similar properties and then performing one set of MACCS calculations for each group.
Connecticut's Dioxin Ambient Air Quality Standard
Authors: Rao Hari V. , Brown David R.
Published: May 2006

Connecticut is the first state in the country to have adopted an ambient air quality standard for dioxins at 1 pg/m3, 2,3,7,8‐TCDD equivalents, as annual average. This paper describes the scientific basis and the methodology used by the State Department of Health Services (the risk assessment agency) in assisting the Department of Enviromental Protection (the risk management agency) to establish a health‐based dioxin standard. This standard protects the public health from the aggregate effect of all sources of dioxin emissions in the vapor and particulate phases. The risk assessment methodology included: a limit on total daily dioxin exposure from all media and sources based on reproductive effects; a multimedia nonsource‐specific exposure assessment; an apportionment by media of the health‐based limit (including background dosing rate); an evaluation of inhalation bioavailability and cancer risk based on a calculation of a range of upperbound cancer risk estimates using different potency, bioavailability, and particle phase assumptions.
Multiobjective Decision‐Tree Analysis1
Authors: Haimes Yacov Y. , Li Duan , Tulsiani Vijay
Published: May 2006

Single‐objective‐based decision‐tree analysis has been extensively and successfully used in numerous decision‐making problems since its formal introduction by Howard Raiffa more than two decades ago. This paper extends the traditional methodology to incorporate multiple noncommensurate objective functions and use of the conditional expected value of the risk of extreme and catastrophic events. The proposed methodology considers the cases where (a) a finite number of actions are available at each decision node and (b) discrete or continuous states of nature can be presented at each chance node. The proposed extension of decision‐tree analysis is introduced through an example problem that leads the reader step‐by‐step into the methodological procedure. The example problem builds on flood warning systems. Two noncommensurate objectives—the loss of lives and the loss of property (including monetary costs of the flood warning system)–are incorporated into the decision tree. In addition, two risk measures—the common expected value and the conditional expected value of extreme and catastrophic events—are quantified and are also incorporated into the decision‐making process. Theoretical difficulties associated with the stage‐wise calculation of conditional expected values are identified and certain simplifying assumptions are made for computational tractibility. In particular, it is revealed that decisions concerning experimentation have a very interesting impact on the noninferior solution set of options—a phenomenon that has no equivalence in the single‐objective case.
Electric‐Utility Resource Planning and Decision‐Making: The Importance of Uncertainty
Authors: Hirst Eric , Schweitzer Martin
Published: May 2006

Uncertainty is a critical factor that pervades all aspects of electric‐utility planning. Uncertainties about future load growth, about the continued performance of existing supply and demand resources, and about the costs, construction times, and operations of new resources greatly complicate utility resource acquisition. This paper discusses the factors that lead to uncertainty, reviews the methods that utilities use in planning and in acquiring resources, and suggests future research to help deal with these uncertainties. This review is based on assessments of the long‐term resource plans prepared by 10 utilities and one Public Service Commission, telephone interviews with staff at these 11 organizations and with staff at three consulting firms, and reviews of many other related publications.
Knowledge‐Based Representations of Risk Beliefs
Authors: Tonn Bruce E. , Travis Cheryl B. , Goeltz Richard T. , Phillippi Raymond H.
Published: May 2006

Beliefs about risks associated with two risk agents, AIDS and toxic waste, are modeled using knowledge‐based methods and elicited from subjects via interactive computer technology. A concept net is developed to organize subject responses concerning the consequences of the risk agents. It is found that death and adverse personal emotional and sociological consequences are most associated with AIDS. Toxic waste is most associated with environmental problems. These consequence profiles are quite dissimilar, although past work in risk perception would have judged the risk agents as being quite similar. Subjects frequently used causal semantics to represent their beliefs and “% of time” instead of “probability” to represent likelihoods. The news media is the most prevalent source of risk information although experiences of acquaintances appear more credible. The results suggest that “broadly based risk” communication may be ineffective because people differ in their conceptual representation of risk beliefs. In general, the knowledge‐based approach to risk perception representation has great potential to increase our understanding of important risk topics.
Small Group Studies of Regulatory Decision‐Making for Power‐Frequency Electric and Magnetic Fields
Authors: Hester Gordon , Morgan M. Granger , Nair Indira , Florig Keith
Published: May 2006

Three groups of lay opinion leaders were used in a group role‐playing decision exercise designed to explore problems in public risk management decision‐making. The application domain was possible risks from the 60 Hz electric and magnetic fields associated with high‐voltage power transmission lines. While there were differences in the make‐up and dynamics of the three groups, the structure and substantive content of the tasks undertaken dominated intergroup variation in terms of the factors that were most important to group members' decisions. The groups displayed sophistication in their identification of decision attributes and in many of the arguments they advanced, but experienced difficulties in structuring and making trade‐offs and decisions. The groups were not good at normalizing or otherwise manipulating quantitative information, and used it largely in the form it was received. Upper‐bound risk estimates were treated operationally in most group discussions as expected values. Several kinds of strong framing effects were observed in the use of cost and risk information. Specific quantitative results obtained must be treated with care but may provide a starting place for further work on the acceptable level of transmission line risk.
Risk Assessment for Carcinogens Under California's Proposition 65
Authors: Pease William S. , Zeise Lauren , Kelter Alex
Published: May 2006

Risk assessments for carcinogens are being developed through an accelerated process in California as a part of the state's implementation of Proposition 65, the Safe Drinking Water and Toxic Enforcement Act. Estimates of carcinogenic potency made by the California Department of Health Services (CDHS) are generally similar to estimates made by the U.S. Environmental Protection Agency (EPA). The largest differences are due to EPA's use of the maximum likelihood estimate instead of CDHS use of the upper 95% confidence bounds on potencies derived from human data and to procedures used to correct for studies of short duration or with early mortality. Numerical limits derived from these potency estimates constitute “no significant risk” levels, which govern exemption from Proposition 65's discharge prohibition and warning requirements. Under Proposition 65 regulations, lifetime cancer risks less than 10−5 are not significant and cumulative intake is not considered. Following these regulations, numerical limits for a number of Proposition 65 carcinogens that are applicable to the control of toxic discharges are less stringent than limits under existing federal water pollution control laws. Thus, existing federal limits will become the Proposition 65 levels for discharge. Chemicals currently not covered by federal and state controls will eventually be subject to discharge limitations under Proposition 65. “No significant risk” levels (expressed in terms of daily intake of carcinogens) also trigger warning requirements under Proposition 65 that are more extensive than existing state or federal requirements. A variety of chemical exposures from multiple sources are identified that exceed Proposition 65's “no significant risk” levels.
The Repeatability of Uncertainty and Sensitivity Analyses for Complex Probabilistic Risk Assessments
Authors: Iman Ronald L. , Helton Jon C.
Published: May 2006

The performance of a probabilistic risk assessment (PRA) for a nuclear power plant is a complex undertaking, involving the assembly of an accident frequency analysis, an accident progression analysis, a source term analysis, and a consequence analysis. Each of these analyses is, in itself, quite complex. Uncertainties enter into a PRA from each of these analyses. An important focus in recent PRAs has been to incorporate these uncertainties at each stage of the analysis, propagate the subsequent uncertainties through the entire analysis, and include uncertainty in the final results. Monte Carlo procedures based on Latin hypercube sampling provide one way to perform propagations of this type. In this paper, the results of two complete and independent Monte Carlo calculations for a recently completed PRA for a nuclear power plant are compared as a means of providing empirical evidence on the repeatability of uncertainty and sensitivity analyses for large‐scale PRA calculations. These calculations use the same variables and analysis structure with two independently generated Latin hypercube samples. The results of the two calculations show a high degree of repeatability for the analysis of a very complex system.
Incentives Policies to Site Hazardous Waste Facilities
Authors: Gregory Robin , Kunreuther Howard , Easterling Doug , Richards Ken
Published: May 2006

This paper addresses the use of mitigation and compensation as incentives policies to stimulate agreement between parties interested in siting a hazardous waste facility and potential host communities. We develop a model of facility siting that distinguishes five key factors which influence the acceptability of a proposed facility when considered in relation to status quo conditions. This model then is used to examine the effectiveness of different incentives policies with regard to (a) mitigating the perceived risks and (b) compensating the adverse impacts of a hazardous waste facility.
A Causal Analysis of Large Vehicle Accidents Through Fault‐Tree Analysis
Authors: Joshua Sarath C. , Garber Nicholas J.
Published: May 2006

Recent trends indicate that vehicle miles traveled for large trucks is increasing at a higher rate than for other vehicles. The resulting competition between large trucks and other vehicles for highway space can be expected to result in more multivehicle collisions involving large trucks. This paper presents the result of an investigation of the causes and the mechanism related to large vehicle accidents. A fault‐tree analysis of large vehicle accidents identifies the individual roles played by driver, vehicle, and environmental factors, as well as their interactions in the accident mechanism. Using accident data for 1984‐1986, the probabilities for different basic events in the fault tree were assessed. The most likely events leading to a large vehicle accident, as well as the most effective counter measures, were then identified. The result indicate that the most prevalent form of accidents due to driver‐related failures is when a normal driver makes an error in judgment and is unsuccessful in his or her evasive action. For vehicle‐related failures, the predominant type of failure is equipment failure, and for environmental‐related failures, excessive demand on driver and vehicle performance created by the environmental or roadway factors.
On Decomposition and Aggregation Error in Estimation: Some Basic Principles and Examples
Authors: Mosleh Ali , Bier Vicki
Published: May 2006

A common strategy in estimation is to decompose the quantity being estimated into several factors, estimate a value for each factor, and then reaggregate these values to obtain an overall estimate. Until now, the extent of decomposition to use has been considered largely a matter of judgment. However, both the extent of decomposition and the manner in which the results are reaggregated can have a significant effect on the resulting estimate. This paper discusses factors affecting the optimum level of decomposition, and presents examples showing that the use of nonoptimal decomposition strategies can lead to significant inaccuracies.
Interspecies Extrapolation: A Reexamination of Acute Toxicity Data
Authors: Watanabe Karen , Bois Frédéric Y. , Zeise Lauren
Published: May 2006

We reanalyze the acute toxicity data on cancer chemotherapeutic agents compiled by Freireich et al.(1) and Schein et al.(2) to derive coefficients of the allometric equation for scaling toxic doses across species (toxic dose =a‐[body weight]b). In doing so, we extend the analysis of Travis and White (Risk Analysis, 1988, 8, 119‐125)by addressing uncertainties inherent in the analysis and by including the hamster data, previously not used. Through Monte Carlo sampling, we specifically account for measurement errors when deriving confidence intervals and testing hypotheses. Two hypotheses are considered: first, that the allometric scaling power (b)varies for chemicals of the type studied; second, that the same scaling power, or “scaling law,” holds for all chemicals in the data set. Following the first hypothesis, in 95% of the cases the allometric power of body weight falls in the range from 0.42‐0.97, with a population mean of 0.74. Assuming the second hypothesis to be true–that the same scaling law is followed for all chemicals–the maximum likelihood estimate of the scaling power is 0.74; confidence bounds on the mean depend on the size of measurement error assumed. Under a “best case” analysis, 95% confidence bounds on the mean are 0.71 and 0.77, similar to the results reported by Travis and White. For alternative assumptions regarding measurement error, the confidence intervals are larger and include 0.67, but not 1.00. Although a scaling power of about 0.75 provides the best fit to the data as a whole, a scaling power of 0.67, corresponding to scaling per unit surface area, is not rejected when the nonhomogeneity of variances is taken into account. Hence, both surface area and 0.75 power scaling are consistent with the Freireich et al. and Schein et al. data sets. To illustrate the potential impact of overestimating the scaling power, we compare reported human MTDs to values extrapolated from mouse LD10s.
Biological Markers of Environmental and Ecological Contamination: An Overview
Authors: Shugart Lee R. , McCarthy John F. , Halbrook Richard S.
Published: May 2006

An approach, using biomarkers (biological responses) for assessing the biological and ecological significance of contaminants present in the environment is described. Living organisms integrate exposure to contaminants in their environment and respond in some measurable and predictable way. Responses are observed at several levels of biological organization from the biomolecular level, where pollutants can cause damage to critical cellular macromolecules and elicit defensive strategies such as detoxication and repair mechanisms, to the organismal level, where severe disturbances are manifested as impairment in growth, reproduction, developmental abnormalities, or decreased survival. Biomarkers can provide not only evidence of exposure to a broad spectrum of anthropogenic chemicals, but also a temporally integrated measure of bioavailable contaminant levels. A suite of biomarkers are evaluated over time to determine the magnitude of the problem and possible consequences. Relationships between biomarker response and adverse ecological effects are determined from estimates of animal health and population structure.
Negotiated Compensation for Solid‐Waste Disposal Facility Siting: An Analysis of the Wisconsin Experience
Authors: Nieves Leslie A. , Himmelberger Jeffery J. , Ratick Samuel J. , White Allen L.
Published: May 2006

Since enacting a unique facility siting law in 1981, Wisconsin has had unusual success in siting solid‐waste management facilities. The law mandates a state‐level technical review and licensing process and a local‐level negotiation/arbitration process that deals with host community impacts and concerns. Data from the negotiated compensation agreements, a survey of facility proposers, and secondary data for the host communities are analyzed in relation to compensation levels. Concerns with community image and health risks and with facility management and equity issues are found to significantly and substantially increase negotiated compensation levels. In contrast, a focus on logistics and transportation concerns is associated with lower levels of compensation. Compensation increases with facility capacity but at a less than proportional rate. Higher levels of compensation are obtained by communities that accept compensation “in kind” in the form of free or reduced fees for host community waste disposal.
Probabilistic Connotations of Carcinogen Hazard Classifications: Analysis of Survey Data for Anchoring Effects
Authors: Spedden Sarah E. , Ryan P. Barry
Published: May 2006

A study was undertaken to test for anchoring effects when numerical probabilities were elicited for carcinogen hazard designations. Subjects were asked to assign probabilities to both probable and possible. The sequence was randomly varied so that half of the subjects evaluated probable first and half evaluated possible first. While there was no consensus on the numerical probabilistic meanings assigned to these verbal expressions, in general, probable was assigned a higher probability than possible and there were specific values that were assigned frequently, indicating some consistency in interpretation. There appeared to be a fairly constant scaling factor between the probabilities assigned to the designations. Anchoring was manifested in two ways: a smaller difference between the designations when they were evaluated in sequence than when they were evaluated in isolation, and assignment of readily accessible “benchmark” values such as 50% and 75%.
Computer Models Used to Support Cleanup Decision‐Making at Hazardous and Radioactive Waste Sites
Authors: Moskowitz P.D. , Pardi R. , DePhillips M. P. , Meinhold A. F.
Published: May 2006

Massive efforts are underway to clean up hazardous and radioactive waste sites located throughout the United States. To help determine cleanup priorities, computer models are being used to characterize the source, transport, fate, and effects of hazardous chemicals and radioactive materials found at these sites. Although the U.S. Environmental Protection Agency (EPA), the U.S. Department of Energy (DOE), and the U.S. Nuclear Regulatory Commission (NRC)have provided preliminary guidance to promote the use of computer models for remediation purposes, no agency has produced directed guidance on models that must be used in these efforts. As a result, model selection is currently done on an ad hoc basis. This is administratively ineffective and costly, and can also result in technically inconsistent decision‐making. To identify what models are actually being used to support decision‐making at hazardous and radioactive waste sites, a project jointly funded by EPA, DOE, and NRC was initiated. The purpose of this project was to: (1)identify models being used for hazardous and radioactive waste site assessment purposes; and (2)describe and classify these models. This report presents the results of this study. A mail survey was conducted to identify models in use. The survey was sent to 550 persons engaged in the cleanup of hazardous and radioactive waste sites; 87 individuals responded. They represented organizations including federal agencies, national laboratories, and contractor organizations. The respondents identified 127 computer models that were being used to help support cleanup decision‐making. There were a few models that appeared to be used across a large number of sites (e.g., RESRAD). In contrast, the survey results also suggested that most sites were using models which were not reported in use elsewhere. Information is presented on the types of models being used and the characteristics of the models in use. Also shown is a list of models available, but not identified in the survey itself.
Monte Carlo Simulation of Rodent Carcinogenicity Bioassays
Authors: Shlyakhter Alexander , Goodman Gay , Wilson Richard
Published: May 2006

In this paper we describe a simulation, by Monte Carlo methods, of the results of rodent carcinogenicity bioassays. Our aim is to study how the observed correlation between carcinogenic potency (β or ln2/TD50) and maximum tolerated dose (MTD) arises, and whether the existence of this correlation leads to an artificial correlation between carcinogenic potencies in rats and mice. The validity of the bioassay results depends upon, among other things, certain biases in the experimental design of the bioassays. These include selection of chemicals for bioassay and details of the experimental protocol, including dose levels. We use as variables in our simulation the following factors: (1) dose group size, (2) number of dose groups, (3) tumor rate in the control (zero‐dose) group, (4) distribution of the MTD values of the group of chemicals as specified by the mean and standard deviation, (5) the degree of correlation between β and the MTD, as given by the standard deviation of the random error term in the linear regression of log β on log (1/MTD), and (6) an upper limit on the number of animals with tumors. Monte Carlo simulation can show whether the information present in the existing rodent bioassay database is sufficient to reject the validity of the proposed interspecies correlations at a given level of stringency. We hope that such analysis will be useful for future bioassay design, and more importantly, for discussion of the whole NCI/ NTP program.
Carcinogenic Mixtures
Authors: Krewski Daniel , Thomas Richard D.
Published: May 2006

Human populations are generally exposed simultaneously to a number of toxicants present in the environment, including complex mixtures of unknown and variable origin. While scientific methods for evaluating the potential carcinogenic risks of pure compounds are relatively well established, methods for assessing the risks of complex mixtures are somewhat less developed. This article provides a report of a recent workshop on carcinogenic mixtures sponsored by the Committee on Toxicology of the U.S. National Research Council, in which toxicological, epidemiological, and statistical approaches to carcinogenic risk assessment for mixtures were discussed. Complex mixtures, such as diesel emissions and tobacco smoke, have been shown to have carcinogenic potential. Bioassay‐directed fractionation based on short‐term screening tests for genotoxicity has also been used in identifying carcinogenic components of mixtures. Both toxicological and epidemiological studies have identified clear interactions between chemical carcinogens, including synergistic effects at moderate to high doses. To date, laboratory studies have demonstrated over 900 interactions involving nearly 200 chemical carcinogens. At lower doses, theoretical arguments suggest that risks may be near additive. Thus, additivity at low doses has been invoked as a working hypothesis by regulatory authorities in the absence of evidence to the contrary. Future studies of the joint effects of carcinogenic agents may serve to elucidate the mechanisms by which interactions occur at higher doses.
Upper Confidence Limits on Excess Risk for Quantitative Responses
Authors: Kodell Ralph L. , West Ronnie W.
Published: May 2006

The definition and observation of clear‐cut adverse health effects for continuous (quantitative) responses, such as altered body weights or organ weights, are difficult propositions. Thus, methods of risk assessment commonly used for binary (quantal) toxic responses such as cancer are not directly applicable. In this paper, two methods for calculating upper confidence limits on excess risk for quantitative toxic effects are proposed, based on a particular definition of an adverse quantitative response. The methods are illustrated with data from a dose‐response study, and their performance is evaluated with a Monte Carlo simulation study.
How Tautological Are Interspecies Correlations of Carcinogenic Potencies?
Authors: Freedman David A. , Gold Lois Swirsky , Slone Thomas H.
Published: May 2006

Crouch and Wilson demonstrated a strong correlation between carcinogenic potencies in rats and mice, supporting the extrapolation from mouse to man. Bernstein et al., however, show that the observed correlation is mainly a statistical artifact of bioassay design. Crouch et al. have a comeback. This paper will review the arguments and present some new data. The correlation is largely (but not totally) tautological, confirming results in Bernstein et al.
Re‐evaluation of the Reference Dose for Methylmercury and Assessment of Current Exposure Levels
Authors: Stern Alan H.
Published: May 2006

Methylmercury (Me‐Hg) is widely distributed through freshwater and saltwater food chains and human consumption of fish and shellfish has lead to widespread exposure. Both the U.S. EPA Reference Dose (0.3 μg/kg/day) and the FAO/WHO Permissible Tolerable Weekly Intake (3.3 μg/kg/week) are currently based on the prevention of paraesthesia in adult and older children. However, Me‐Hg exposure in utero is known to result in a range of developmental neurologic effects including clinical CNS symptoms and delayed onset of walking. Based on a critical review of developmental toxicity data from human and animal studies, it is concluded that current guidelines for the prevention of paraesthesia are not adequate to address developmental effects. A dose of 0.07 μ/kg/day is suggested as the best estimate of a potential reference dose for developmental effects. Data on nationwide fish consumption rates and Me‐Hg levels in fish/seafood weighted by proportion of the catch intended for human consumption are analyzed in a Monte Carlo simulation to derive a probability distribution of background Me‐Hg exposure. While various uncertainties in the toxicologic and exposure data limit the precision with which health risk can be estimated, this analysis suggests that at current levels of Me‐Hg exposure, a significant fraction of women of childbearing age have exposures above this suggested reference dose.
Agency Communication, Community Outrage, and Perception of Risk: Three Simulation Experiments
Authors: Sandman Peter M. , Miller Paul M. , Johnson Branden B. , Weinstein Neil D.
Published: May 2006

Three experimental studies were conducted employing hypothetical news stories to compare the effects on reader risk perceptions of two situations: when agency communication behavior was reported to be responsive to citizens’ risk concerns, vs. when the agency was reported to be unresponsive. In the first two experiments, news stories of public meetings filled with distrust and controversy led to ratings indicating greater perceived risk than news stories reporting no distrust or controversy, even though the risk information was held constant. This effect appeared clearly when the differences in meeting tone were extreme and subjects made their ratings from their recall of the stories, but it was much weaker when the differences were moderate and subjects were allowed to go back over the news stories to help separate risk information from conflict information. In the third experiment, news stories about a spill cleanup systematically varied the seriousness of the spill, the amount of technical information provided in the story, and the agency behavior and resulting community outrage. The outrage manipulation significantly affected affective and cognitive components of perceived risk, but not hypothetical behavioral intentions. Seriousness and technical detail had very little effect on perceived risk.
A Structured Literature Review for Risk Assessment: EMF and Human Health Risk
Authors: Murphy James R. , Armstrong Gail E. , Reynolds Michele , Gordon Stuart G.
Published: May 2006

The volume of publications on any given topic makes it difficult to select an appropriate subset of publications for review by an expert panel. This paper proposes a method for selecting a subset using a protocol that attempts to order publications based upon good research methods. The protocol was followed by graduate students with no expert knowledge of the area they were reviewing. They reduced 11730 articles on the topic of EMF and Health risk to 68 articles that were reviewed by an expert panel. The interrater reliability was 96% and 94% of the relevant articles were captured by this process.
One Agency's Use of Risk Assessment and Risk Communication1
Authors: Fisher Ann , Chitose Atsushi , Gipson Philip S.
Published: May 2006

Few organizations have the courage to evaluate their own use of risk assessment (identifying hazards and estimating their probability and magnitude) and risk communication (interacting with internal and external stakeholder groups about risks). The USDA Animal and Plant Health Inspection Service (APHIS) wants to enhance its overall risk analysis process for managing a wide range of risks to animals, plants, and human health. We gathered survey data for a baseline of APHIS professionals’ understanding and use of risk assessment and risk communication. APHIS professionals spend a surprisingly large share of their time communicating about risks. They perceive that risk estimates influence decisions, but that risk estimates should have more influence. Respondents reported little opposition to APHIS risk management decisions, and little use of channels such as USDA Extension Service for disseminating risk messages. Substantial variance across responses is explained mostly by differences in the roles of the 11 work units (now 10) within the agency. Location also contributes to the variance. Demographic variables seem less important.
Risk Assessment Research: Only the Beginning
Authors: Finkel Adam M.
Published: May 2006

[This editorial is an essentially unedited version of testimony I presented to the House Committee on Science, Space, and Technology (Subcommittee on Technology, Environment, and Aviation) on November 16, 1993. The hearing marked the release of an Office of Technology Assessment (OTA) report entitled “Researching Health Risks,” for which I was part of an advisory panel (along with Curtis Travis and a dozen other experts in risk assessment). The title of my testimony foreshadowed the dual message I hoped to convey: that more research to improve risk assessment is sorely needed, but that we ought not let that need blind us to other deficiencies in risk‐based decision‐making that may deserve equal or greater attention.]
Gender, Race, and Perception of Environmental Health Risks
Authors: Flynn James , Slovic Paul , Mertz C. K.
Published: May 2006

This paper reports the results of a national survey in which perceptions of environmental health risks were measured for 1275 white and 214 nonwhite persons. The results showed that white women perceived risks to be much higher than did white men, a result that is consistent with previous studies. However, this gender difference was not true of nonwhite women and men, whose perceptions of risk were quite similar. Most striking was the finding that white males tended to differ from everyone else in their attitudes and perceptions–on average, they perceived risks as much smaller and much more acceptable than did other people. These results suggest that sociopolitical factors such as power, status, alienation, and trust are strong determiners of people's perception and acceptance of risks.
Morphometric Approaches for Evaluating Pulmonary Toxicity in Mammals: Implications for Risk Assessment
Authors: Hyde Dallas M. , Bolender Robert P. , Harkema Jack R. , Plopper Charles G.
Published: May 2006

Recent advances in quantitative morphology provide all the tools necessary to obtain structural information in the lung that can be quantified and interpreted in the three‐dimensional world of toxicology. Structural hierarchies of conducting airways and parenchyma of the lung provide: (1) numbers of cells per airway, lobe, or lung; (2) surface areas of cells, airways, and alveoli; (3) length of airways and vessels; and (4) volumes of cells, alveoli, airways, vessels, and individual lobes or the entire lung. Unbiased sampling of these subcompartments of the lung requires fractionation of lobes or individual airways. Individual airways of proximal and distal generations are obtained by airway microdissection along one axial pathway and comparisons made between airway generations. Vertical sections of selected airways are used to sample epithelium and interstitium. Using this unbiased approach of quantitative morphology, we have shown that inhalation of low ambient concentrations of ozone ([O3]0.15 ppm) near or at the United States National Ambient Air Quality Standard (NAAQS) (0.12 ppm O3) induces significant alterations in bronchiolar epithelium and interstitium in nonhuman primates but not rats. The alterations do not appear to be concentration‐ or time‐dependent, thereby bringing into question the current NAAQS that may be at or above the threshold for distal airway injury in primates. Unbiased morphometric methods are critical in a quantitative evaluation of toxicological injury of mammalian tracheobronchial airways.
Cell Proliferation and Formaldehyde‐Induced Respiratory Carcinogenesis
Authors: Monticello Thomas M. , Morgan Kevin T.
Published: May 2006

Formaldehyde is a nasal carcinogen in the rat but the cancer risk this chemical poses for humans remains to be determined. Formaldehyde induces nonlinear, concentration‐dependent increases in nasal epithelial cell proliferation and DNA‐protein cross‐link formation following short‐term exposure. Presented in this review are results from a mechanistically based formaldehyde inhalation study in which an important endpoint was the measurement of cell proliferation indices in target sites for nasal tumor induction. Male Fischer 344 rats were exposed to 0, 0.7, 2, 6, 10, or 15 ppm formaldehyde for up to 2 years (6 hr/day, 5 day/week). Statistically significant increases in cell proliferation were confined to the 10 and 15 ppm groups, which remained elevated throughout the study. The concentration‐dependent increases in cell proliferation correlated strongly with the tumor response curve, supporting the proposal that sustained increases in cell proliferation are an important component of formaldehyde carcinogenesis. The nonlinearity observed in formaldehyde‐induced rodent nasal cancer is consistent with a high‐concentration effect of regenerative cell proliferation of the target organ coupled with the genotoxic effects of formaldehyde. Cell kinetic data from these studies provide important information that may be utilized in the assessment of risk for humans exposed to formaldehyde.
Reducing Conservatism in Risk Estimation for Mixtures of Carcinogens
Authors: Kodell Ralph L. , Chen James J.
Published: May 2006

The excess cancer risk that might result from exposure to a mixture of chemical carcinogens usually must be estimated using data from experiments conducted with individual chemicals. In estimating such risk, it is commonly assumed that the total risk due to the mixture is the sum of the risks of the individual components, provided that the risks associated with individual chemicals at levels present in the mixture are low. This assumption, while itself not necessarily conservative, has led to the conservative practice of summing individual upper‐bound risk estimates in order to obtain an upper bound on the total excess cancer risk for a mixture. Less conservative procedures are described here and are illustrated for the case of a mixture of four carcinogens.
Role for Risk Communication in Closing Military Waste Sites
Authors: Klauenberg B. Jon , Vermulen Erik K.
Published: May 2006

Lessons learned from environmental and occupational hazard risk management practices over the past 30 years have led the Department of Defense to explore alternative risk management approaches. Policies for cleanup of environmentally hazardous waste sites are undergoing examination and are being reframed. A Demonstration Risk Communication Program is described which incorporates principles that integrate risk‐based scientific information as well as community values, perceptions, and needs in a democratic process that includes the public as an active participant from the earliest stages. A strong scientific foundation for assessment and characterization of risk is viewed as necessary but not sufficient; the public's values must be actively integrated into the negotiated criteria. The Demonstration Program uses a model to prepare the participants and to guide them through the process. A five‐step process is presented: (1) create risk communications process action team including at least one member of the specific site audience; (2) professionally train participants on team dynamics including interpersonal communication skills; (3) train risk communicators to deliver a cogent presentation of the message to secure a decision acceptable to both the government and the public; (4) identify existing biases, perceptions, and values held by all participants; and (5) develop risk message incorporating science and values. The process action team approach assumes the participants enter into the effort with the goal of improved environment and safeguarded public health. The team approach avoids confrontational or adversarial interactions and focuses on a dialogue from which a negotiated team response develops. Central to the program is the recognition that communication is only effective when the dialogue is two‐way.
The NAS Risk Paradigm as a Medium for Communication
Authors: Patton Dorothy E.
Published: May 2006

Many journalists, public interest groups and other recipients of risk assessment information are familiar with the National Academy of Sciences risk assessment paradigm. From time to time, paradigm concepts appear in news features or community group discussions on environmental issues. With knowledge of the paradigm common to scientists, journalists, and other interested parties, the paradigm is a potentially important medium for communication between risk scientists, journalists, and the public. Specifically, the paradigm offers widely‐accepted organizing principles for presenting risk information, a common language for addressing a variety of issues and concepts, and a flexible analytical system that accommodates the diversity of scientific information and policy perspectives that characterize the risk assessment process. In addition, the paradigm outlines important relationships and distinctions between risk assessment and risk management. Informed and creative use of these features of the paradigm can guide and simplify interviews between journalists or community groups and their expert sources, clarify presentation of risk information, and promote collaboration between risk scientists, journalists, and others to assure complete, objective and fair comment on risk issues of interest to the public.
Human Interindividual Variability–A Major Source of Uncertainty in Assessing Risks for Noncancer Health Effects
Authors: Hattis Dale , Silver Ken
Published: May 2006

For noncancer effects, the degree of human interindividual variability plays a central role in determining the risk that can be expected at low exposures. This discussion reviews available data on observations of interindividual variability in (a) breathing rates, based on observations in British coal miners; (b) systemic pharmacokinetic parameters, based on studies of a number of drugs; (c) susceptibility to neurological effects from fetal exposure to methyl mercury, based on observations of the incidence of effects in relation to hair mercury levels; and (d) chronic lung function changes in relation to long‐term exposure to cigarette smoke. The quantitative ranges of predictions that follow from uncertainties in estimates of interindividual variability in susceptibility are illustrated.
Recommended Distributions for Exposure Factors Frequently Used in Health Risk Assessment
Authors: Finley Brent , Proctor Deborah , Scott Paul , Harrington Natalie , Paustenbach Dennis , Price Paul
Published: May 2006

Although there has been nearly complete agreement in the scientific community that Monte Carlo techniques represent a significant improvement in the exposure assessment process, virtually all state and federal risk assessments still rely on the traditional point estimate approach. One of the rate‐determining steps to a timely implementation of Monte Carlo techniques to regulatory decision making is the development of “standard” data distributions that are considered applicable to any setting. For many exposure variables, there is no need to wait any longer to adopt Monte Carlo techniques into regulatory policy since there is a wealth of data from which a robust distribution can be developed and ample evidence to indicate that the variable is not significantly influenced by site‐specific conditions. In this paper, we propose several distributions that can be considered standard and customary for most settings. Age‐specific distributions for soil ingestion rates, inhalation rates, body weights, skin surface area, tapwater and fish consumption, residential occupancy and occupational tenure, and soil‐on‐skin adherence were developed. For each distribution offered in this paper, we discuss the adequacy of the database, derivation of the distribution, and applicability of the distribution to various settings and conditions.