bluuebunny/crossref_metadata_2025 huggingface dataset:
Three Conceptions of Quantified Societal Risk
Authors: Stallen Pieter Jan M. , Geerts Rob , Vrijling Han K.
Published: May 2006

In several European countries efforts are undertaken, in particular with regard to fixed industrial installations and transport of dangerous substances, to quantify the “societal risk” (SR) of accidents that may cause more than one victim at a time. This article explores the nature of such efforts. SR‐models are essentially ways to structure the distribution of potential social costs of decisions about hazardous activities (e.g., costs of risk reduction, of land use forgone). First, the various ways to describe SR quantitatively, and to set limits to SR will be presented in short. Next, using a scheme developed by Fischhoff and colleagues, the various approaches will be placed in broad categories of reaching acceptable risk decisions: bootstrapping, formal analysis, and professional judgment. Each of the three categories offers a particular appreciation of the risks as ‘external costs’. This has important political implications. In the discussion it is argued that local SR‐limits, by the very nature of SR, should be set in a way that creates consistency with any potential supra‐local interests involved. Second, particular attention is paid to the validity of claims that SR‐limits should reflect a strong risk aversion.
A Semiparametric Approach to Risk Assessment for Quantitative Outcomes
Authors: Bosch Ronald J. , Wypij David , Ryan Louise M.
Published: May 2006

Characterizing the dose‐effect relationship and estimating acceptable exposure levels are the primary goals of quantitative risk assessment. A semiparametric approach is proposed for risk assessment with continuously measured or quantitative outcomes which has advantages over existing methods by requiring fewer assumptions. The approach is based on pairwise ranking between the response values in the control group and those in the exposed groups. The work generalizes the rank‐based Wilcoxon‐Mann‐Whitney test, which for the two‐group comparison is effectively a test of whether a response from the control group is different from (larger than) a response in an exposed group. We develop a regression framework that naturally extends this metric to model the dose effect in terms of a risk function. Parameters of the regression model can be estimated with standard software. However, inference requires an additional step to estimate the variance structure of the estimated parameters. An effective dose (ED) and associated lower confidence limit (LED) are easily calculated. The method is supported by a simulation study and is illustrated with a study on the effects of aconiazide. The method offers flexible modeling of the dose effect, and since it is rank‐based, it is more resistant to outliers, nonconstant variance, and other departures from normality than previously described approaches.
Comparison of Contact Site Cancer Potency Across Dose Routes: Case Study with Epichlorohydrin*
Authors: Ginsberg Gary L. , Pepelko William E. , Goble Robert L. , Hattis Dale B.
Published: May 2006

Risk assessment for airborne carcinogens is often limited by a lack of inhalation bioassay data. While extrapolation from oral‐based cancer potency factors may be possible for some agents, this is not considered feasible for contact site carcinogens. The change in contact sites (oral: g.i. tract; inhalation: respiratory tract) when switching dose routes leads to possible differences in tissue sensitivity as well as chemical delivery. This research evaluates the feasibility to extrapolate across dose routes for a contact site carcinogen through a case study with epichlorohydrin (EPI). EPI cancer potency at contact sites is compared across three bioassays involving different dose routes (gavage, drinking water, inhalation) through the use of dosimetry models to adjust for EPI delivery to contact sites. Results indicate a large disparity (two orders of magnitude) in potency across the three routes of administration when expressed as the externally applied dose. However, when expressed as peak delivered dose, inhalation and oral potency estimates are similar and overall, the three potency estimates are within a factor of seven. The results suggest that contact site response to EPI is more dependent upon the rate than the route of delivery, with peak concentration the best way to extrapolate across dose routes. These results cannot be projected to other carcinogens without further study.
Assessing Cross‐Media Impacts: A Comparative Risk Approach
Authors: Borys D. S. , Skarzinskas R. D. , Green L. D.
Published: May 2006

The Oregon Department of Environmental Quality has developed a Cross‐Media Comparative Risk Assessment model to address certain regulatory concerns. The model generates a Human and Ecological Risk Index for a facility releasing toxins into the environment. The risk indices are based on chemical fate and transport predictions, toxicity, population density, and ecological sensitive areas. The model can be used to rank facilities for inspection or as a tool to assess the progress of pollution prevention programs. Regulatory permitting departments can use the model to address the cross‐media transfer of pollutants from one environmental compartment to another. The versatility of the model allows adaptation to each specific users needs.
Age and Gender Differences in Perceived Accident Likelihood and Driver Competences
Authors: Glendon A. Ian , Dorn Lisa , Davies D. Roy , Matthews Gerald , Taylor Ray G.
Published: May 2006

Road traffic accident involvement rates show clear age and gender differences which may in part be accounted for by differences in risk perception and perceptions of driving competence. The present study extends and replicates that of Matthews and Moran (1986). Young (18–30 years) and older (45–60 years) male and female drivers responded to a questionnaire on perceived accident risk and driving competence (judgment and skill) with respect to themselves and four target groups, and also rated a series of videotaped driving sequences with respect to likelihood of accident occurrence and perceived driving competence. Results showed that effects of rater characteristics were generally confined to the questionnaire. Younger males were perceived as most likely to experience an accident and were judged to be lower than other groups in driving competence. Younger groups showed little bias against older groups and vice versa, but gender‐related bias was apparent. The findings of Matthews and Moran were generally confirmed. The results are discussed with reference to four main issues: (1) demographic bias effects—which are generally weak; (2) stereotyping on the basis of gender and/or age of driver; (3) group‐specific bias; (4) self‐appraisal bias.
Risk Characterization and the Weight of Evidence: Adapting Gatekeeping Concepts from the Courts
Authors: Walker Vern R.
Published: May 2006

Risk characterization objectives include evaluating the weight of evidence underlying risk determinations, communicating that evaluation to nonexperts, guiding risk assessors to achieve consistency, and preserving deference for those reasonable expert judgments inherent in any risk determination. Similar objectives are shared by American courts that face the gatekeeping task of screening scientific evidence before it is presented to nonexpert factfinders, such as juries. This article surveys the judicial gatekeeping concepts of relevance, evidentiary reliability, legal sufficiency, presumptions, and standards of proof (particularly, preponderance of the evidence). It examines recent court decisions that have applied these concepts to the kinds of scientific information common in risk assessments, and suggests how to adapt these gatekeeping concepts for use in weight‐of‐evidence characterization. If we can develop and adopt a neutral framework for characterizing the weight of evidence underlying risk assessments, it might help clarify not only the current debate over risk characterization and risk management, but also the drafting of treaty provisions, such as those invoking the Precautionary Principle of international environmental law.
Addressing the Dependency Problem in Access Security System Architecture Design
Authors: Kobza John E. , Jacobson Sheldon H.
Published: May 2006

The objective of this research is to present a method for evaluating the performance of access control security systems, such as airport security operations. This requires the examination of security system architectures, which involve security technology devices and the algorithms that coordinate their operations. Dependence between device responses in multiple‐device systems is a critical practical issue in assessing the performance of such architectures, though no results on this problem have appeared in the literature. This paper presents a method for evaluating when multipledevice security systems with overlapping capabilities are cost‐effective. This is achieved using a dependency structure for security system devices to quantify how various technologies interact and to measure the impact of device dependence on system error probabilities. A measure of device response dependence for a two‐device system is defined and its properties are explored, including bounds on the dependency measure. The effect of dependence on the system Type I and Type II error probabilities is examined for the two‐device system. System performance is compared for independent vs. dependent device responses and desirable dependence relationships are identified. Results are also presented for a cascading sequence of devices. An example is presented to illustrate the results for the two‐device system. Implications of these results are discussed, such as how they can be used to identify the optimal use of security devices and to determine whether new technologies warrant investment.
Evaluation of False Positive and False Negative Outcomes in NTP Long‐Term Rodent Carcinogenicity Studies
Authors: Haseman J. K. , Elwell M. R.
Published: May 2006

The decision‐making process used by the National Toxicology Program (NTP) in its evaluation of long‐term rodent carcinogenicity studies was investigated to determine whether or not this procedure resulted in an excessive number of false positive or false negative outcomes. All site‐specific tumor incidences that were found to be significantly (p < 0.05) increased either by a trend test or by pairwise comparisons of each dosed group against the controls in 218 NTP 2‐year studies with Fischer 344 rats and/or B6C3F1 mice were tabulated and compared to the number of statistically significant tumor increases expected to occur by chance. Our evaluation suggests that false positive rates are fairly low in NTP long‐term studies. Assessing false negative rates is more difficult because of the limited sensitivity of the bioassay for detecting subtle carcinogenic effects. Moreover, reduced body weights frequently occur in dosed animals, and the positive correlation between the incidences of certain site‐specific tumors and body weight may mask the detection of carcinogenic effects. Despite these difficulties, our analysis did identify one tumor showing evidence of false negative outcomes: interstitial cell tumors of the testis in male Fischer 344 (F344) rats. This tumor showed considerably more significant (p > 0.05) increased incidences than expected by chance, yet none were considered to be chemically‐related. However, the biological significance of interstitial cell tumor increases in F344 rats is uncertain because of the high background rate of neoplasia (>90%) for this target site.
Determination of Leukemogenic Benzene Exposure Concentrations: Refined Analyses of the Pliofilm Cohort
Authors: Schnatter A. Robert , Nicolich Mark J. , Bird Michael G.
Published: May 2006

Biologic data on benzene metabolite doses, cytotoxicity, and genotoxicity often show that these effects do not vary directly with cumulative benzene exposure (i.e., concentration times time, or c×t). To examine the effect of an alternate exposure metric, we analyzed cell‐type specific leukemia mortality in Pliofilm workers. The work history of each Pliofilm worker was used to define each worker's maximally exposed job/department combination over time and the associated long‐term average concentration associated with the maximally exposed job (LTA‐MEJ). Using this measure, in conjunction with four job exposure estimates, we calculated SMRs for groups of workers with increasing LTA‐MEJs. The analyses suggest that a critical concentration of benzene exposure must be reached in order for the risk of leukemia or, more specifically, AMML to be expressed. The minimum concentration is between 20 and 60 ppm depending on the exposure estimate and endpoint (all leukemias or AMMLs only). We believe these analyses are a useful adjunct to previous analyses of the Pliofilm data. They suggests that (a) AMML risk is shown only above a critical concentration of benzene exposure, measured as a long‐term average and experienced for years, (b) the critical concentration is between 50 and 60 ppm when using a median exposure estimate derived from three previous exposure assessments, and is between 20 and 25 ppm using the lowest exposure estimates, and (c) risks for total leukemia are driven by risks for AMML, suggesting that AMML is the cell type related to benzene exposure.
The Role of Geographic Scale in Monitoring Environmental Justice
Authors: Cutter Susan L. , Holm Danika , Clark Lloyd
Published: May 2006

Utilizing the concept of environmental justice, this paper examines the differential burdens of toxic and hazardous waste facilities locations in low income minority communities. The association between the presence of facilities and socioeconomic characteristics of places are examined for the state of South Carolina at three different spatial scales: counties, census tracts, and census block groups. Three different types of hazardous waste/toxic facilities are also examined: Toxic Release Inventory (TRI) sites, Treatment, Storage, and Disposal sites (TSD), and inactive hazardous waste sites. At the county level, there was some association between the presence of toxic/hazardous waste facilities and race and income. In South Carolina, this translates to a disproportionate burden on White, more affluent communities in metropolitan areas, rather than low income minority communities. At both the census tract and block group levels, there is no association between race and the location of toxic/hazardous waste facilities. There are slight differences in the income levels between tracts and block groups with facilities and those without. This localized ecology of hazard sources must be expanded to include emission/discharge data in order to adequately address environmental justice issues on who bears the burdens of environmental contamination.
Quantifying Water Pathogen Risk in an Epidemiological Framework
Authors: Eisenberg Joseph N. , Seto Edmund Y. W. , Olivieri Adam W. , Spear Robert C.
Published: May 2006

Traditionally, microbial risk assessors have used point estimates to evaluate the probability that an individual will become infected. We developed a quantitative approach that shifts the risk characterization perspective from point estimate to distributional estimate, and from individual to population. To this end, we first designed and implemented a dynamic model that tracks traditional epidemiological variables such as the number of susceptible, infected, diseased, and immune, and environmental variables such as pathogen density. Second, we used a simulation methodology that explicitly acknowledges the uncertainty and variability associated with the data. Specifically, the approach consists of assigning probability distributions to each parameter, sampling from these distributions for Monte Carlo simulations, and using a binary classification to assess the output of each simulation. A case study is presented that explores the uncertainties in assessing the risk of giardiasis when swimming in a recreational impoundment using reclaimed water. Using literature‐based information to assign parameters ranges, our analysis demonstrated that the parameter describing the shedding of pathogens by infected swimmers was the factor that contributed most to the uncertainty in risk. The importance of other parameters was dependent on reducing thea priorirange of this shedding parameter. By constraining the shedding parameter to its lower subrange, treatment efficiency was the parameter most important in predicting whether a simulation resulted in prevalences above or below non outbreak levels. Whereas parameters associated with human exposure were important when the shedding parameter was constrained to a higher subrange. This Monte Carlo simulation technique identified conditions in which outbreaks and/or nonoutbreaks are likely and identified the parameters that most contributed to the uncertainty associated with a risk prediction.
Estimating the Ozone Depletion Potential of Methyl Bromide
Authors: Selwyn Murray R. , Georges James E. , Georgiev Alexander A.
Published: May 2006

Ozone depletion potential (ODP) represents the cumulative ozone depletion induced by a particular halocarbon relative to a reference gas (usually trichlorofluoromethane, CFC‐11). We focus on ODP estimation for methyl bromide. Previous attempts at its estimation have assumed that components of the ODP equation are lognormally distributed. By considering a wide range of modeling scenarios, we show that this restriction (which is based on computational convenience rather than experimental evidence) has obscured the true uncertainty in the ODP value. Moreover, when publishing point estimates for the ODP value, previous authors have given either mean or median values. We submit that a more appropriate choice for a point estimate is the mode since the distribution of ODP is skewed and since the mode is by definition, the most likely value. For each modeling scenario considered, modal values are given. In general, we find these ODP point estimates are considerably lower than those published elsewhere.
Skin Cancer and Inorganic Arsenic: Uncertainty‐Status of Risk
Authors: Brown Kenneth G. , Guo How‐Ran , Kuo Tsung‐Li , Greene Howard L.
Published: May 2006

The current U.S. EPA standard for inorganic arsenic in drinking water is 50 ppb (μg/L), dating to the National Interim Primary Drinking Water Regulation of 1976. The current EPA risk analysis predicts an increased lifetime skin cancer risk on the order of 3 or 4 per 1000 from chronic exposure at that concentration. Revision of the standard to only a few ppb, perhaps even less than 1 ppb, may be indicated by the EPA analysis to reduce the lifetime risk to an acceptable level. The cost to water utilities, and ultimately to their consumers, to conform to such a large reduction in the standard could easily reach several billion dollars, so it is particularly important to assess accurately the current risk and the risk reduction that would be achieved by a lower standard. This article addresses the major sources of uncertainty in the EPA analysis with respect to this objective. Specifically, it focuses on uncertainty and variability in the exposure estimates for the landmark study of Tseng and colleagues in Taiwan, analyzed using a reconstruction of the their exposure data. It is concluded that while the available dataset is suitable to establish the hazard of skin cancer, it is too highly summarized for reliable dose‐response assessment. A new epidemiologic study is needed, designed for the requirements of dose‐response assessment.
First‐Order Reliability Analysis of Public Health Risk Assessment
Authors: Hamed Maged M.
Published: May 2006

This paper demonstrates a new methodology for probabilistic public health risk assessment using the first‐order reliability method. The method provides the probability that incremental lifetime cancer risk exceeds a threshold level, and the probabilistic sensitivity quantifying the relative impact of considering the uncertainty of each random variable on the exceedance probability. The approach is applied to a case study given by Thompson et al.(1) on cancer risk caused by ingestion of benzene‐contaminated soil, and the results are compared to that of the Monte Carlo method. Parametric sensitivity analyses are conducted to assess the sensitivity of the probabilistic event with respect to the distribution parameters of the basic random variables, such as the mean and standard deviation. The technique is a novel approach to probabilistic risk assessment, and can be used in situations when Monte Carlo analysis is computationally expensive, such as when the simulated risk is at the tail of the risk probability distribution.
Cybernetic Risk Analysis
Authors: Foster Kevin J.
Published: May 2006

The Pearl Harbor case study reveals that risk analysis failure may be caused by any of a number of factors. However, the most important variables are system load, gain, lead time, and lag time. The dynamics of such cybernetic systems analysis constitute an important aspect in this regard. Four different risk management strategies, or organization designs, have been proposed in this paper. Each has a unique combination of the imputed variables and each has a unique cause of surprise, risk analysis failure, and crisis.
Critical Effects and Exposure Limits
Authors: Hansson Sven Ove
Published: May 2006

The use of critical effects in the determination of occupational exposure limits (OELs) in Sweden is subjected to a statistical study. Many of the present OELs are high in relation to known noeffect levels and effect levels, and the degree of protection has a surprisingly weak correlation with the seriousness of the adverse effect. Several proposals for improved procedures are put forward. One of these is to supplement the concept of critical effects with that of dominant effects. A dominant effect of a substance is a health effect that is at some concentration the most serious health effect.
Categorical Regression Analysis of Acute Exposure to Tetrachloroethylene1
Authors: Guth Daniel J. , Carroll Raymond J. , Simpson Douglas G. , Zhou Haibo
Published: May 2006

Exposure‐response analysis of acute noncancer risks should consider both concentration (C) and duration (T) of exposure, as well as severity of response. Stratified categorical regression is a form of meta‐analysis that addresses these needs by combining studies and analyzing response data expressed as ordinal severity categories. A generalized linear model for ordinal data was used to estimate the probability of response associated with exposure and severity category. Stratification of the regression model addresses systematic differences among studies by allowing one or more model parameters to vary across strata denned, for example, by species and sex. The ability to treat partial information addresses the difficulties in assigning consistent severity scores. Studies containing information on acute effects of tetrachloroethylene in rats, mice, and humans were analyzed. The mouse data were highly uncertain due to lack of data on effects of low concentrations and were excluded from the analysis. A model with species‐specific concentration intercept terms for rat and human central nervous system data improved fit to the data compared with the base model (combined species). More complex models with strata denned by sex and species did not improve the fit. The stratified regression model allows human effect levels to be identified more confidently by basing the intercept on human data and the slope parameters on the combined data (on a C × T plot). This analysis provides an exposure–response function for acute exposures to tetrachloroethylene using categorical regression analysis.
Development of Risk‐Based Ranking Measures of Effectiveness for the United States Coast Guard's Vessel Inspection Program
Authors: Wheeler Timothy A. , Gawande Kishore , Bespalko Stephen
Published: May 2006

This paper describes the results of an analysis of the effectiveness of the U.S. Coast Guard's efforts to promote the safety of life and property at sea through its program to inspect large, ocean‐going vessels. The effectiveness of specific U.S. Coast Guard vessel inspection activities was evaluated using risk‐based metrics that linked categories of root causes of accidents to the particular inspection activities designed to reduce the risk of each root cause category. The results demonstrate a risk‐based ranking of USCG inspection activities. These metrics, describes as measures of effectiveness (MOEs), yield insights regarding the most beneficial areas in which to concentrate inspection resources. Insights regarding quality of vessel casualty investigation data and database design as related to risk‐based importance analysis are also discussed. The MOEs constructed in this study are specific to the USCG's Marine Inspection and Boarding Program, but the methodology of the study is based on sound theoretical principles that are probably applicable to a range of maritime safety activities. Hence the methodology applies equally to other important governmental regulatory programs and can be similarly used to measure their effectiveness and as an aid to decision‐making.
Life‐Cycle Assessment in Relation to Risk Assessment: An Evolving Perspective
Authors: Owens J. W.
Published: May 2006

A life‐cycle approach takes a cradle‐to‐grave perspective of a product's numerous activities from the raw material extraction to final disposal. There have been recent efforts to develop life‐cycle assessment (LCA) to assess both environmental and human health issues. The question then arises: what are the capabilities of LCA, especially in relation to risk assessment? To address this question, this paper first describes the LCA mass‐based accounting system and then analyzes the use of this approach for environmental and human health assessment. The key LCA limitations in this respect are loss of spatial, temporal, dose‐response, and threshold information. These limitations affect LCA's capability to assess several environmental issues, and human health in particular. This leads to the conclusion that LCA impact assessment does not predict or measure actual effects, quantitate risks, or address safety. Instead, LCA uses mass loadings with simplifying assumptions and subjective judgments to add independent effects and exposures into an overall score. As a result, LCA identifies possible human health issues on a systemwide basis from a worst case, hypothetical hazard perspective. Ideally, the identified issues would then be addressed by more detailed assessment methods, such as risk assessment.
Risk Associated with Transportation of Spent Nuclear Fuel Under Demanding Security Constraints: The Colombian Experience
Authors: Múnera Héctor A. , Canal María B. , Muñoz Mauricio
Published: May 2006

This note describes some of the safety and security concerns posed by the transportation of highly enriched uranium (HEU) from a nuclear research reactor located in Bogota (Colombia) to a port on the Colombian Caribbean coast. The operation was made at a moment of extremely high guerilla activity in Colombia, so that the decision‐problem belongs in the extension of risk analysis known as threat analysis. By invoking a principle of dispreference for probability based on the concept of stochastic dominance, a qualitative risk comparison was made between the road and air alternatives.
Life Years Lost at Hazardous Waste Sites: Remediation Worker Fatalities vs. Cancer Deaths to Nearby Residents
Authors: Cohen Joshua T. , Beck Barbara D. , Rudel Ruthann
Published: May 2006

We present a hypothetical case study using the Years of Potential Life Lost (YPLL) metric to compare cancer risks incurred by residents living near a Superfund site to occupational fatality risks incurred by workers employed in that site's remediation. Since cancer occurs late in life, and because we assume its mortality rate is 60%, each case results in 8.8 YPLL. Each occupational fatality, which typically occurs earlier in life, results in 38.1 YPLL. In our case study, the residential population of 5000 incurred 1.3 YPLL, compared to 5.7 YPLL incurred by the 500 workers. Several uncertain assumptions may influence our calculations; moreover, occupational risks may be viewed as more “voluntary” than risks incurred by residents. However, because the magnitude of the YPLL incurred by workers and residents may be comparable, risk managers should consider occupational risks when evaluating remedial alternatives.
Bias in Population Estimates of Long‐Term Exposure from Short‐Term Measurements of Individual Exposure
Authors: Buck Robert J. , Hammerstrom Karen A. , Ryan P. Barry
Published: May 2006

A population's long‐term exposure distribution for a specified compound is typically estimated from short‐term measurements of a sample of individuals from the population of interest. In this situation, estimates of a population's long‐term exposure parameters contain two sources of sampling error: the typical sampling error associated with taking a sample from the population and the sampling error from estimating individual long‐term exposure. These components are not separable in the data collected, i.e., the value observed is due partly to the individual sampled and partly to the time at which the individual was sampled. Hence, the distribution of the data collected is not the same as the population exposure distribution. Monte Carlo simulations are used to compare the distribution of the observed data with the population exposure distribution for a simple additive model. A simple adjustment to standard estimates of percentiles and quantils is shown to be effective in reducing bias particularly for the upper percentiles and quantils of the population distribution.
Lognormal Distributions for Body Weight as a Function of Age for Males and Females in the United States, 1976–1980
Authors: Burmaster David E. , Crouch Edmund A. C.
Published: May 2006

Based on results reported from the NHANES II Survey (the National Health and Nutrition Examination Survey II) for people living in the United States during 1976–1980, we use exploratory data analysis, probability plots, and the method of maximum likelihood to fit lognormal distributions to percentiles of body weight for males and females as a function of age from 6 months through 74 years. The results are immediately useful in probabilistic (and deterministic) risk assessments.
Communicating Low Risk Magnitudes: Incidence Rates Expressed as Frequency Versus Rates Expressed as Probability
Authors: Siegrist Michael
Published: May 2006

The study investigated the effects of incidence rates stated as a probability (e.g., 0006) and incidence rate information expressed in terms of frequency (e.g., 600 in 1,000,000) on risk‐avoidant behavior. Subjects were informed about the risks associated with an old and a new, improved medication. They were asked how much they were willing to pay for the safer medicine. Risk information was given either in a frequency or a probability format. The second factor manipulated was the level of risk, either high or low. As expected, analysis of variance yielded a significant interaction. Subjects confronted with high risk in the frequency format were willing to pay the highest prices for the improved medication. The choice between frequency or probability format can be made according to the goal of the communication of risk.
ATSDR Science Panel on the Bioavailability of Mercury in Soils: Lessons Learned
Authors: Canady Richard A. , Hanley Jack E. , Susten Allan S.
Published: May 2006

On the basis of discussion and analysis during and following an ATSDR science panel on the bioavailability of mercury in soils, it is apparent that the default assumption of 100% relative bioavailability for mercury‐contaminated soils is excessively conservative. However, current knowledge does not allow the development of default assumptions or guidelines for determining relative bioavailability of mercury in soils. Until such default assumptions or guidelines can be developed, site‐specific assays of bioavailability, preferably using either animal bioassays or validated in vitro techniques, may provide the best approach for estimating soil‐mercury bioavailability.
Current Views on the Oral Bioavailability of Inorganic Mercury in Soil: Implications for Health Risk Assessments
Authors: Paustenbach Dennis J. , Bruce Gretchen M. , Chrostowski Paul
Published: May 2006

Due to the presence of mercury at a number of major contaminated sites in the United States, the bioavailability of inorganic mercury in soil following ingestion has emerged as an important public health issue. Studies of the leachability/solubility of inorganic mercury in soil have shown that it is largely immobile, thereby suggesting that it will not be readily available for absorption in the gastrointestinal tract. Ignoring the effect of the soil matrix on decreasing bioavailability may result in a substantial overprediction of risks due to ingestion of contaminated soil. This paper discusses current knowledge about the oral bioavailability of inorganic mercury in soil and offers suggestions about how these data may be applied in human health risk assessment. Though precise estimates are not available, in vivo and in vitro estimates of the bioavailability of different inorganic mercury species in different matrices suggest that the bioavailability of mercury in soil is likely to be significantly less, on the order of at least three‐ to tenfold, than the bioavailability of mercuric chloride, the species used to derive the toxicity criteria for inorganic mercury. Because bioavailability can vary significantly with soil type, soil aging, the presence of co‐contaminants and other factors, it is suggested that whenever the fiscal aspects justify a more precise estimate of bioavailability, site‐specific estimates be developed. To develop a database for identifying a less expensive and more efficient method for estimating bioavailability, it is suggested that in vivo studies be conducted concurrently with in vitro studies. However, due to the lack of precision associated with the derivation of the most widely‐used health guidance value for inorganic mercury (the US EPA RfD), additional work to address the uncertainties in the RfD is recommended.
A Simulation Model for Occupational Tuberculosis Transmission
Authors: Nicas Mark , Seto Edmund
Published: May 2006

A simulation model of tuberculosis (TB) transmission among hospital employees is described. A hypothetical cohort of 1000 workers was divided into low‐, medium‐, and high‐risk groups. The number of TB patients admitted daily was treated as a Poisson random variable. A patient imparted a daily infection risk that was identical for all workers within a risk group but that varied between risk groups. In some scenarios, infected employees were assigned a daily risk of developing TB disease. If disease developed, the individual remained on the job for 3 calendar weeks and imparted a substantial infection risk to 25 close contacts. Simulations were run over 5‐year intervals. Cumulative infection incidence increased over time and with more TB patients admitted. Given a scenario in which there were 600, 300, and 100 susceptibles in the low‐, medium‐, and high risk groups, respectively, 50 TB patients admitted annually and accounting for disease among infected employees, at 5 years there were approximately 100 primary infections (due to infection by patients), 40 secondary infections (due to infection by diseased coworkers), five primary disease cases, and two secondary disease cases. The input parameter values and simulation outcomes were reasonably consistent with the sparse information reported in the literature.
Carcinogenicity Studies on MTBE: Critical Review and Interpretation
Authors: Mennear John H.
Published: May 2006

Chronic inhalation of toxic concentrations of MTBE caused renal tubular cell neoplasms in male Fischer 344 rats and hepatocellular adenomas in female CD‐1 mice. In Sprague‐Dawley rats the oral administration of MTBE was associated with increased incidences of Leydig cell tumors and of lymphomas and leukemias (combined) in males and females, respectively. Neither lymphomas nor leukemias were individually increased in treated females. Leydig cell tumors are common in rats and do not predict human responses to drugs and chemicals. Neither MTBE nor its metabolite, t‐butyl alcohol, possess mutagenic potential and a second metabolite, formaldehyde, is mutagenic in vitro but in vivo results are equivocal. MTBE‐induced neoplasms are most likely produced through a nongenetic mechanism which requires chronic exposure to toxic doses. Because of the intense odor (and taste) of MTBE, humans will not tolerate either air or water concentrations sufficient to produce the cytotoxic precursors required to promote cellular proliferation.
Public Reliance on Risk Communication Channels in the Wake of a Cryptosporidium Outbreak
Authors: Griffin Robert J. , Dunwoody Sharon , Zabala Fernando
Published: May 2006

In the spring of 1993, about 39% of Milwaukee‐area residents suffered through a nationally publicized illness brought about by cryptosporidium, a parasite that had infested the metropolitan drinking water supply. Our study, based on a telephone survey of 610 local adult residents, indicates that worry about becoming ill in the future with cryptosporidiosis relates more strongly and consistently to public reliance on, and use of, media for cryptosporidium information than do a range of risk perception and experience variables. We propose that more studies should take an audience‐centered approach to understanding risk communication.
A Trivariate Distribution for the Height, Weight, and Fat of Adult Men*
Authors: Burmaster David E. , Murray Donald M.
Published: May 2006

Using exploratory data analysis, probability plots, scatterplots, and computer animations to rotate and visualize the data, we fit a trivariate Normal distribution to data for the height, the natural logarithm of body weight, and the body fat for 646 men between the ages of 50 and 80 years as reported by the medical staff of the U.S. Veterans Administration's “Normative Aging Study” in Boston, MA. Although these data do not include any children, women, or young men, the measurements represent the best data that we could find through a 4‐year search. We believe that these data are well measured and reliable for men in the specified age range and that these data reveal an interesting statistical pattern for use in probabilistic PBPK models.
Judgments of Chemical Risks: Comparisons Among Senior Managers, Toxicologists, and the Public
Authors: Mertz C. K. , Slovic Paul , Purchase I. F. H.
Published: May 2006

Nineteen Senior Managers of a major chemical company in the United Kingdom participated in a survey to determine their attitudes, beliefs, and perceptions regarding risks from chemicals. Similar surveys had previously been conducted with toxicologists and members of the general public in the United States and Canada. In general, the Senior Managers tended to judge risks to be quite small for most chemicals. Moreover, they had lower risk perceptions than did members of the British Toxicological Society and even far lower perceptions of risk than a comparison group of members of the Canadian public. The managers held views that were similar to British toxicologists working in industry and government and dissimilar to the views of toxicologists working in academia. The observed differences between views of managers, toxicologists, and the public must be recognized and understood in order to facilitate communication and constructive efforts to manage chemical risks.
Probabilistic‐Based Structural Specifications
Authors: Moses Fred
Published: May 2006

The construction industry is both the largest civilian industry and the most unique in terms of fragmentation and its approach to controlling risk. Structural specifications establish nominal safety factors and design criteria for engineered structures such as buildings, bridges, dams, and power facilities. The goal is satisfactory strength capacity to safely and economically meet the demands of structural performance. Structures must resist the highly uncertain effects of combined gravity, earthquakes, wind, and snow loads supported by natural and human‐made materials. The public's expectation is that structures should last a long time and have low lifetime risk of structural failure. Historically, specifications have contained safety factors which evolved from past experiences and provided adequate safety or low risk. Due to pressures of economy and the need to optimize structural performance, structural specifications have recently been developed and accepted by industry based on structural reliability and risk‐assessment principles. This paper reviews developments of probabilistic applications in structural specifications including specification format, database, implementation examples, target risk levels, present research activities, and future goals for establishing optimal risk‐design procedures.
A Probabilistic Model for the Failure Frequency of Underground Gas Pipelines
Authors: Cooke Roger , Jager Eric
Published: May 2006

A model is constructed for the failure frequency of underground pipelines per kilometer year, as a function of pipe and environmental characteristics. The parameters in the model were quantified, with uncertainty, using historical data and structured expert judgment. Fifteen experts from institutes in The Netherlands, the United Kingdom, Italy, France, Germany, Belgium, Denmark, and Canada participated in the study.
The Efficacy of Different Methods for Informing the Public About the Range Dependency of Magnetic Fields from High Voltage Power Lines
Authors: Read Daniel , Morgan M. Granger
Published: May 2006

The AC electric and magnetic fields associated with high voltage power lines have become a concern as a possible health risk. In most cases the strength of these fields decreases as the inverse square of the distance from the line. In earlier work, we found that laypeople do not understand how rapidly field strength decreases with distance. Most believe that any high voltage power line they can see is exposing them to strong fields. This paper confirms the earlier finding and explores a number of strategies which might be used in risk communications to correct this misperception. We found it relatively easy to provide subjects with a better understanding of the range‐dependency of magnetic field strength. Moreover, the quality of this acquisition was apparently independent of the manner in which they were instructed. Such successful instruction is markedly different from the well‐established difficulty of teaching people about many qualitative domains, such as physics or ideas in probability. Clearly, while some erroneous beliefs are highly resistant to change, others can be altered quite readily. We suspect that an important distinction between knowledge about the range‐dependency of power‐frequency magnetic fields and less tractable topics involves the presence or absence of prior folk‐theories or “mental models” of the domain.
Characterizing Dose‐Response I: Critical Assessment of the Benchmark Dose Concept
Authors: Murrell James A. , Portier Christopher J. , Morris Richard W.
Published: May 2006

We present a critical assessment of the benchmark dose (BMD) method introduced by Crump(1) as an alternative method for setting a characteristic dose level for toxicant risk assessment. The no‐observed‐adverse‐effect‐level (NOAEL) method has been criticized because it does not use all of the data and because the characteristic dose level obtained depends on the dose levels and the statistical precision (sample sizes) of the study design. Defining the BMD in terms of a confidence bound on a point estimate results in a characteristic dose that also varies with the statistical precision and still depends on the study dose levels.(2) Indiscriminate choice of benchmark response level may result in a BMD that reflects little about the dose‐response behavior available from using all of the data. Another concern is that the definition of the BMD for the quantal response case is different for the continuous response case. Specifically, defining the BMD for continuous data using a ratio of increased effect divided by the background response results in an arbitrary dependence on the natural background for the endpoint being studied, making comparison among endpoints less meaningful and standards more arbitrary. We define a modified benchmark dose as a point estimate using the ratio of increased effect divided by the full adverse response range which enables consistent placement of the benchmark response level and provides a BMD with a more consistent relationship to the dose‐response curve shape.
Air Nicotine and Saliva Cotinine as Indicators of Workplace Passive Smoking Exposure and Risk1
Authors: Repace James L. , Jinot Jennifer , Bayard Steven , Emmons Karen , Hammond S. Katharine
Published: May 2006

We model nicotine from environmental tobacco smoke (ETS) in office air and salivary cotinine in nonsmoking U.S. workers. We estimate that: an average salivary cotinine level of 0.4 ng/ml corresponds to an increased lifetime mortality risk of 1/1000 for lung cancer, and 1/100 for heart disease; >95% of ETS‐exposed office workers exceed OSHA's significant risk level for heart disease mortality, and 60% exceed significant risk for lung cancer mortality; 4000 heart disease deaths and 400 lung cancer deaths occur annually among office workers from passive smoking in the workplace, at the current 28% prevalence of unrestricted smoking in the office workplace.
Worry and Risk Perception
Authors: Sjöberg Lennart
Published: May 2006

Risk perception is sometimes measured by means of judgments about worry, sometimes as perceived risk more directly. However, perceived level of risk calls for a more intellectual judgment and worry tends to refer to emotional reactions. These two are therefore not the same and need not be strongly correlated. Results reported here show that perceived risk and worry are indeed weakly correlated, both for generalized worry and for more specific measures of worry matched with the same hazard as risk ratings. A distinction is suggested between cognitive, abstract hazards and concrete, sensory hazards, with implications for the worry‐perceived risk relationship. It was furthermore found by means of cluster analysis that there were groups of subject displaying different dynamics of risk and worry.
Risk Perceptions of Offshore Workers on UK Oil and Gas Platforms
Authors: Fleming Mark , Flin Rhona , Mearns Kathryn , Gordon Rachael
Published: May 2006

Knowledge of the workforce's risk perceptions and attitudes to safety is necessary for the development of a safety culture, where each person accepts responsibility for working safely. The ACSNI Human Factors report stresses the importance of assessing workforce perceptions of risk to achieve a proper safety culture. Risk perception research has been criticized for insufficient analysis of the causal relationships between risk factors and perceived risk. The present study reports some of the factors which predicted risk perception in a sample of 622 employees from six UKCS offshore oil installations who completed a 15‐section questionnaire. This paper focuses on the accuracy of workers’ risk perceptions and what underlying factors predict the perception of personal risk from both major and minor hazards.