bluuebunny/crossref_metadata_2025 huggingface dataset:
Associations Between 1980 U.S. Mortality Rates and Alternative Measures of Airborne Particle Concentration
Authors: Özkaynak Halûk , Thurston George D.
Published: May 2006

We analyzed the 1980 U.S. vital statistics and available ambient air pollution data bases for sulfates and fine, inhalable, and total suspended particles. Using multiple regression analyses, we conducted a cross‐sectional analysis of the association between various particle measures and total mortality. Results from the various analyses indicated the importance of considering particle size, composition, and source information in modeling of particle pollution health effects. Of the independent mortality predictors considered, particle exposure measures related to the respirable and/or toxic fraction of the aerosols, such as fine particles and sulfates, were most consistently and significantly associated with the reported SMSA‐specific total annual mortality rates. On the other hand, particle mass measures that included coarse particles (e.g., total suspended particles and inhalable particles) were often found to be nonsignificant predictors of total mortality. Furthermore, based on the application of fine particle source apportionment, particles from industrial sources (e.g., from iron/steel emissions) and from coal combustion were suggested to be more significant contributors to human mortality than soil‐derived particles.
Projections of Cancer Risks Attributable to Future Exposure to Asbestos
Authors: Mauskopf Josephine A.
Published: May 2006

To assess the maximum possible impact of further government regulation of asbestos exposure, projections were made of the use of asbestos in nine product categories for the years 1985–2000. A life table risk assessment model was then developed to estimate the excess cases of cancer and lost person‐years of life likely to occur among those occupationally and nonoccupationally exposed to the nine asbestos product categories manufactured in 1985–2000. These estimates were made under the assumption that government regulation remains at its 1985 level. Use of asbestos in the nine product categories was predicted to decline in all cases except for friction products. The risk assessment results show that, although the cancer risks from future exposure to asbestos are significantly less than those from past exposures, in the absence of more stringent regulations, a health risk remains.
A Multiattribute Utility Analysis of Alternative Sites for the Disposal of Nuclear Waste
Authors: Merkhofer Miley W. , Keeney Ralph L.
Published: May 2006

Five potential sites nominated for the Nation's first geologic repository for disposing of nuclear waste are evaluated using multiattribute utility analysis. The analysis was designed to aid the Department of Energy in its selection of 3 sites for characterization, a detailed data‐gathering process that will involve the construction of exploratory shafts for underground testing and that may cost as much as $1 billion per site. The analysis produced insights into the relative advantages and disadvantages of the nominated sites and clarified current uncertainties regarding repository performance.
Public Distrust and Hazard Management Success at the Rocky Flats Nuclear Weapons Plant
Authors: Hohenemser Christoph
Published: May 2006

Based on experience gained while serving a public oversight commission appointed by the governor of Colorado, hazard management at the Department of Energy's Rocky Flats nuclear weapons plant is reviewed. Specific reference is made to the plant's history of controversy, its defense‐in‐depth strategy of hazard control, occupational health issues, public exposure to plutonium, and the assessment of low‐probability, high‐consequence risks. This leads to the conclusion that Rocky Flats is, by any objective standard, a hazard management success. It follows that public distrust of Rocky Flats arises as much from fear and loathing of nuclear weapons themselves as from the manufacturing process by which they are made.
Science Policy Choices and the Estimation of Cancer Risk Associated with Exposure to TCDD
Authors: Gough Michael
Published: May 2006

United States regulatory agencies use no‐threshold models for estimating carcinogenic risks. Other countries use no‐threshold models for carcinogens that are genotoxic and threshold models for carcinogens that are not genotoxic, such as 2, 3, 7, 8‐tetrachlorodibenzo‐P‐dioxin (TCDD or “dioxin”). The U.S. Environmental Protection Agency has proposed a revision of the carcinogenic potency estimate for TCDD that is based on neither a threshold nor a no‐threshold model; instead, it is a compromise between risk numbers generated by the two irreconcilably different models. This paper discusses the revision and its implications.
A Stochastic Two‐Stage Model for Cancer Risk Assessment. I. The Hazard Function and the Probability of Tumor
Authors: Moolgavkar Suresh H. , Dewanji Anup , Venzon David J.
Published: May 2006

We present a mathematical treatment of a two‐mutation model for carcinogenesis with time‐dependent parameters. This model has previously been shown to be consistent with epidemiologic and experimental data. An approximate hazard function used in previous papers is critically evaluated.
The Role of Insurance in Managing Natural Hazard Risks: Private Versus Social Decisions
Authors: Epple Dennis , Lave Lester B.
Published: May 2006

We explore the interaction between individual and collective decisions concerning natural hazards. Collective actions such as building a dam change the risks faced by private individuals. We show that, with proper incentives, individual reactions to such changes in risk can serve to enhance risk management by utilizing individual's decisions to take account of their specialized knowledge about their risk preferences and losses. We demonstrate that the efficient response to construction of a dam may be private actions that lead to a fully anticipated increase in flood damage. In such instances, zoning that focuses on reducing flood damage may lead to less efficient use of the flood plain. More generally, even where incentives for underinvestment in market insurance and self‐insurance are present, constraining use of the flood plain by zoning will not generally lead to efficient outcomes. The model identifying conditions under which informed individuals have the incentives to make efficient decisions is powerful and directs attention toward more fruitful approaches.
Interspecific Scaling of Toxicity Data
Authors: Travis Curtis C. , White Robin K.
Published: May 2006

This paper reexamines the scaling approaches used in cancer risk assessment and proposes a more precise body weight scaling factor. Two approaches are conventionally used in scaling exposure and dose from experimental animals to man: body weight scaling (used by FDA) and surface area scaling (BW0.67—used by EPA). This paper reanalyzes the Freireich et al. (1966) study of the maximum tolerated dose (MTD) of 14 anticancer agents in mice, rats, dogs, monkeys, and humans, the dataset most commonly cited as justification for surface area extrapolation. This examination was augmented with an analysis of a similar dataset by Schein et al. (1970) of the MTD of 13 additional chemotherapy agents. The reanalysis shows that BW0.75 is a more appropriate scaling factor for the 27 direct‐acting compounds in this dataset.
Economic Costs of Misinforming About Risk: The EDB Scare and the Media
Authors: Johnson F. Reed
Published: May 2006

This study reports results of an analysis of consumer responses to news reports of grain‐product contamination by the pesticide ethylene dibromide (EDB). The results demonstrate that it is possible to quantify market disruption related to the dissemination of risk information. Implications include the need for increased awareness among risk managers that public perceptions, regardless of their objective accuracy, can induce real economic costs. Such costs should be considered in designing regulatory and information policies.
Assessment of Human Exposure to Gaseous Pollutants1
Authors: Baskin Leland B. , Falco James W.
Published: May 2006

A mathematical model to aid in assessment of human environmental exposure to volatile organic substances is presented. The model simulates the convective and diffusive transport of gas from the ambient environment into the human body by way of the respiratory and circulatory systems. Data required include easily obtained physical and chemical properties of substances as well as several estimated or measured physiological parameters. Transient and steady‐state tissue concentrations resulting from an input atmospheric partial pressure are predicted. From these concentrations, an effective dose may be calculated, allowing for the determination of an exposure‐response relationship based upon independently obtained dose‐response data. The model's results compare favorably to experimental data on oxygen and halothane. Steady‐state conditions are reached very rapidly. These results suggest that uptake of these substances is limited by both ventilation and perfusion. The sensitivities of steady‐state concentrations to changes in the ventilation and perfusion rates are demonstrated to be essentially linear within the current neighborhoods. Conditions in which the primary processes of ventilation, diffusion, perfusion, and elimination limit uptake of gases are considered. Expressions describing the conditions necessary for a single process to limit gas uptake are derived. Accompanying equations for estimating tissue concentrations under these limiting conditions are presented.
Risk Perceptions of Hong Kongese vs. Americans
Authors: Keown Charles F.
Published: May 2006

Hong Kong students rated the risk of 30 hazards and quantified a subset on six risk characteristics; data are compared to a prior study of American students. Hong Kongese rated 10 hazards substantially higher and five hazards substantially lower than Americans, and factor structures indicated differences on five hazards. Possible explanations for these differences are discussed.
Cost‐Benefit Analysis of All‐Terrain Vehicles at the CPSC1
Authors: Rodgers Gregory B. , Rubin Paul H.
Published: May 2006

The present value of the costs of injuries and deaths associated with each unit of a product is a useful number in conducting cost‐benefit analysis at the CPSC. Before a remedy is known, this value indicates the approximate amount that it is worth spending on a fix; similarly, if a fix is proposed, this number indicates whether it is cost‐justified. The method of analysis is applied to all‐terrain vehicles. Injury costs per vehicle are estimated. Determinants of accidents are estimated using a logit regression model applied to surveys of users and of accident victims; this indicates factors associated with accidents, and is used to estimate marginal probabilities. Costs of various vehicle components are estimated using a hedonic price index. This information (injury costs, accident probabilities, and component cost) is combined in a benefit–cost analysis of proposed remedies.
Traffic Accidents and Convictions: Group Totals Versus Rate per Kilometer Driven
Authors: Mercer G. William
Published: May 2006

Using group totals, young drivers, male drivers, and especially young male drivers are substantially over‐represented in terms of both traffic accidents and traffic‐related convictions. On the other hand, when accidents and convictions are considered in terms of their rates while the person is actually driving, older drivers and female drivers gain in importance, with the female drivers' traffic accident rate and rates for some convictions exceeding the male drivers' rates. Similarly, the older drivers' accident rate and rates on some convictions exceeded the younger drivers' rates when considered in terms of driving exposure. In addition, these findings lead one to speculate that recent driving exposure more than driver age is the central factor in traffic accident involvement. The implications for policy makers and educators are clear. Although young male drivers are undeniably a legitimate focus for traffic accident countermeasures, they should not be targeted at the expense of drivers who drive less but have as high or higher accident rates—female and older drivers.
Risk Management for Hazardous Materials Transportation: A Local Study in Lyons
Authors: Hubert Philippe , Pagès Pierre
Published: May 2006

A probabilistic risk assessment study has been undertaken in the French city of Lyons. The issue was to know whether it was justified to forbid hazardous material lorries in the city center and to divert them through the suburbs. Therefore, two routes, the City Center route and the Suburban route were compared. This paper describes the analysis and shows how the results were used in the decision‐making process. It also lists the difficulties that are encountered when trying to incorporate formal risk analysis into actual decision‐making processes. The risk analysis showed that rerouting is an effective option with respect to all criteria. The mathematical expectation of the number of deaths is divided by three, the reduction on the annual frequency of catastrophic accidents is even more important (about one order of magnitude for accidents involving more than 50 deaths). The spatial analysis proved that the risk was more evenly distributed along the Suburban route. However, the annual expected number of death is low: 0.5 in the worst case. So traditional decision‐making approaches do not indicate the necessity of rerouting. Such a situation is believed to be typical for risk management of major hazards. In Lyons, the use of a very small risk aversion factor is sufficient to justify the rerouting option on a formal decision‐aiding basis. This is rather unusual, but it is thought that the recognition of the importance of risk aversion by the decision‐makers themselves is a very positive outcome from this study.
Interpretation of Airborne Asbestos Measurements
Authors: Chesson Jean , Rench Jerry D. , Schultz Bradley D. , Milne Karen L.
Published: May 2006

Transmission electron microscopy (TEM) is the preferred method of measuring airborne asbestos in buildings, but TEM measurements cannot be used directly in the existing equations relating risk to exposure because the equations are based on measurements made with a different technique—phase contrast microscopy (PCM). Comparison between measurements made by different methods is not simple because the methods differ in the size of particles they can detect, and the relationship between exposure and disease is thought to depend on, among other things, asbestos fiber size. Previous suggestions for converting TEM measurements to PCM equivalents lack generality because they fail to take into account the size distribution of the asbestos particles and the expectation that fiber‐size distributions in current nonoccupational environments could differ from the workplaces of the past on which the risk equations are based. A mathematical model is presented for investigating the conversion of airborne asbestos measurements made by one method to an equivalent measurement made by another method. “Equivalent” means having the same potential to cause disease. The model clarifies the issues of concern and suggests approaches for obtaining meaningful conversion factors that will allow TEM measurements to be used in PCM‐based risk equations.
Environmental Tobacco Smoke: Exposure‐Response Relationships in Epidemiologic Studies
Authors: Wu‐Williams Anna H. , Samet Jonathan M.
Published: May 2006

Demonstration of a dose‐response relationship for environmental tobacco smoke (ETS) is an important indication of causality. Central to the analysis and interpretation of dose‐response relations as described in epidemiological studies is the relationship between dose and exposure. It must be recognized that in studies of ETS we have only surrogate measures of dose, and these surrogate measures (based on exposure) are imperfect. The question‐based measures of ETS exposure generally have not been standardized, may have limited validity and reliability, and cannot comprehensively describe total ETS exposure, exposure to individual ETS components, nor doses of biologically relevant agents at target sites. Nevertheless, useful data have been yielded in epidemiologic studies linking ETS exposure to increased respiratory infection and symptoms, reduced lung growth in children, and increased lung cancer in nonsmoking adults. The more consistent exposure‐response data for studies on acute health in children may reflect the greater difficulty in measuring exposure in studies of chronic health in adults.

For children, adverse effects have been causally associated with exposure to ETS. The epidemiological evidence and the supporting toxicological data link ETS to increased lower respiratory illness, increased respiratory symptoms, and reduced lung growth. Exposure‐response relationships have been described for these effect; errors in exposure estimates would tend to lessen rather than to exaggerate these relationships. By contrast, in adults, the evidence for adverse cardiopulmonary effects of ETS exposures, other than lung cancer, it's presently less conclusive. Misclassification of exposure may be more severe for adults than for children, and the resulting bias toward the null may obscure effects of respiratory symptoms and lung function. Research on adults is hindered by the difficulty of estimating exposures received in diverse environments over a lengthy period. Continued controversy related to the effects of ETS exposure in the workplace and in public locations provides a rationale for further research. However, more valid methods for assessing the exposures of adults to ETS are needed for such research.
Review of Radon and Lung Cancer Risk
Authors: Samet Jonathan M. , Hornung Richard W.
Published: May 2006

Radon, a long‐established cause of lung cancer in uranium and other underground miners, has recently emerged as a potentially important cause of lung cancer in the general population. The evidence for widespread exposure of the population to radon and the well‐documented excess of lung cancer among underground miners exposed to radon decay products have raised concern that exposure to radon progeny might also be a cause of lung cancer in the general population. To date, epidemiological data on the lung cancer risk associated with environmental exposure to radon have been limited. Consequently, the lung cancer hazard posed by radon exposure in indoor air has been addressed primarily through risk estimation procedures. The quantitative risks of lung cancer have been estimated using exposure‐response relations derived from the epidemiological investigations of uranium and other underground miners. We review five of the more informative studies of miners and recent risk projection models for excess lung cancer associated with radon. The principal models differ substantially in their underlying assumptions and consequently in the resulting risk projections. The resulting diversity illustrates the substantial uncertainty that remains concerning the most appropriate model of the temporal pattern of radon‐related lung cancer. Animal experiments, further follow‐up of the miner cohorts, and well‐designed epidemiological studies of indoor exposure should reduce this uncertainty.
Estimation of the Joint Risk from Multiple‐Compound Exposure Based on Single‐Compound Experiments
Authors: Chen James J. , Gaylor David W. , Kodell Ralph L.
Published: May 2006

In the absence of data from multiple‐compound exposure experiments, the health risk from exposure to a mixture of chemical carcinogens is generally based on the results of the individual single‐compound experiments. A procedure to obtain an upper confidence limit on the total risk is proposed under the assumption that total risk for the mixture is additive. It is shown that the current practice of simply summing the individual upper‐confidence‐limit risk estimates as the upper‐confidence‐limit estimate on the total excess risk of the mixture may overestimate the true upper bound. In general, if the individual upper‐confidence‐limit risk estimates are on the same order of magnitude, the proposed method gives a smaller upper‐confidence‐limit risk estimate than the estimate based on summing the individual upper‐confidence‐limit estimates; the difference increases as the number of carcinogenic components increases.
Stochastic Analysis of Intermediate Lesions in Carcinogenesis Experiments
Authors: Luebeck E. Georg , Moolgavkar Suresh H.
Published: May 2006

In many animal model systems for carcinogenesis, well characterized putative premalignant lesions are observed. A much studied example is provided by the enzyme altered foci in rodent hepatocarcinogenesis experiments. In a recent paper, we proposed a method for the quantitative analysis of such premalignant lesions. The model used in that paper assumed that the mean growth of premalignant clones is exponential. However, it has been suggested that such a model is oversimplified. In this paper, we relax the assumption of exponential mean growth. The new model contains one extra parameter that measures departures from exponentiality. Use of the model is illustrated by analysis of ATPase deficient foci in the liver of rats given NNM (N‐nitrosomorpholine) in their drinking water. The analysis suggests that the clonal growth of altered cells is significantly accelerated (superexponential) for nontoxic doses of NNM. Finally, the hazard function of the two‐mutation model for carcinogenesis is briefly discussed under nonexponential (mean) growth of intermediate cells.
The Seveso Directive: An Italian Pilot Study in Enabling Communication
Authors: Marchi Bruna De
Published: May 2006

In 1982 the Council of the European Communities issued a Directive on the Major Accident Hazards of Certain Industrial Activities, commonly known as the Seveso Directive. Besides other requirements, the Directive specifies that members of the public liable to be affected by a major accident from certain industrial activities must be informed of safety measures and how they should behave in the event of an accident. The Directive was subsequently amended in an extensive way. Upon the transposition of the Seveso Directive and its amendments into national legislations, the 12 European Member States are faced with the task of “appropriately and effectively” informing the public about major accident hazards. Delays are observed throughout the community, both in transposing the Directives and implementing public information. A pilot study on “Risk Information Needs” was commissioned and carried out at two Seveso sites in Italy in order to begin to resolve some of the problems involved in the provision of public information and to suggest appropriate guidelines. One hundred subjects answered an experimental protocol designed to assess their “information needs.” This article presents the theoretical background, the pragmatic aims, and the design of the study. It also summarizes its most relevant findings and suggests some recommendations for the provision of information to the public.
More Large Accidents Through Complexity
Authors: Wulff Petter
Published: May 2006

Many would tend to characterize modern society as steeped in complexity. This complexity is seen by a number of professional people to imply risk‐taking — or risk‐making — on a high level. “A single mistake may give consequences of quite different proportions from earlier times,” as one critic puts it. This hypothesis of increasing risks on a high level — of worst things getting worse — has been tested on fires in Sweden. Fire has always been a powerfully upsetting agent to the social fabric. Today industrial fires dominate the picture economically. The cost of industrial fires is about three times the cost of residential fires in Sweden. It is of interest to note that the damage cost of the worst fires (as measured in insurance payments) does not form an increasing part of overall fire damage costs, as one would expect from the above hypothesis. Whether the hypothesis holds with regard to indirect costs due to production stand‐still is more uncertain. We can conclude that the potential of complexity to create large abnormal occurrences may have been somewhat prematurely announced — at least with regard to fires in Sweden.
Parametric Distributions for Soil Ingestion by Children
Authors: Thompson Kimberly M. , Burmaster David E.
Published: May 2006

This note presents parameterized distributions of estimates of the amount of soil ingested by children based on data collected by Binder et al. (1986). Following discussions with Dr. Binder, we modified the Binder study data by using the actual stool weights instead of the 15 g value used in the original study. After testing the data for lognormality, we generated parameterized distributions for use in risk assessment uncertainty analyses such as Monte Carlo simulations.
Time‐ and Loading‐Dependence in the McKone Model for Dermal Uptake of Organic Chemicals from a Soil Matrix
Authors: Burmaster David E. , Maxwell Nancy Irwin
Published: May 2006

McKone has recently proposed an innovative two‐layer model for dermal uptake of organic chemicals from a soil matrix that explicitly includes variables for properties of the chemical, the soil, the skin, and the exposure. In this note, we investigate the joint time‐ and loading‐dependencies implicit in the model by using MATHEMATICA to find and plot a closed‐form function for the uptake fraction for six aromatic hydrocarbons.
A Prescriptive Risk Framework for Individual Health and Safety Decisions
Authors: Keeney Ralph L. , Winterfeldt Detlof von
Published: May 2006

A conceptual framework is developed for the prescriptive evaluation of health and safety risks to an individual. This framework allows one to compare chronic vs. acute health risks, accidents vs. illness, and physical vs. psychological impacts. To do this, value judgments are necessary to quantify one's health state in terms of both physical and psychological well‐being. Probabilities are necessary to describe implications of activities such as skiing or smoking and conditions such as cancer or third‐degree bums in terms of these health states. Suggestions are made to operationalize and use the framework to evaluate and compare very different individual health and safety risks. Essentially, all existing measures of individual risk can be derived as special cases of the proposed framework.
An Approach to Assessing the Impacts of Incident‐Free Transportation of Radioactive Materials: II. Highway Transportation
Authors: Weiner Ruth F. , LaPlante Patrick A. , Hageman John P.
Published: May 2006

Annual radiation doses and risks to the public living near, and traveling on, public highways, and occupational doses are calculated for highway shipments of radioactive materials under accident‐free and incident‐free conditions (i.e., under normal transportation conditions). The database developed by Sandia National Laboratories is used, and calculations are made using RADTRAN 4.0. This report is one of two reports estimating radiological risk associated with transportation of radioactive materials.
The Role of Cancer Risk in the Regulation of Industrial Pollution
Authors: Pease William S.
Published: May 2006

The extent of carcinogen regulation under existing U.S. environmental statutes is assessed by developing measures of the scope and stringency of regulation. While concern about cancer risk has played an important political role in obtaining support for pollution control programs, it has not provided the predominant rationale for most regulatory actions taken to date. Less than 20% of all standards established to limit concentrations of chemicals in various media address carcinogens. Restrictions on chemical use are more frequently based on concerns about noncancer human health or ecological effects. Of the chemicals in commercial use which have been identified as potential human carcinogens on the basis of rodent bioassays, only a small proportion are regulated. There is an inverse relationship between the scope of regulatory coverage and the stringency of regulatory requirements: the largest percentages of identified carcinogens are affected by the least stringent requirements, such as information disclosure. Standards based on de minimis cancer risk levels have been established for only 10% of identified carcinogens and are restricted to one medium: water. Complete bans on use have affected very few chemicals. The general role that carcinogenicity now plays in the regulatory process is not dramatically different from that of other adverse human health effects: if a substance is identified as a hazard, it may eventually be subject to economically achievable and technically feasible restrictions.
Reassessing Benzene Cancer Risks Using Internal Doses
Authors: Cox Louis Anthony , Ricci Paolo F.
Published: May 2006

Human cancer risks from benzene exposure have previously been estimated by regulatory agencies based primarily on epidemiological data, with supporting evidence provided by animal bioassay data. This paper reexamines the animal‐based risk assessments for benzene using physiologically‐based pharmacokinetic (PBPK) models of benzene metabolism in animals and humans. It demonstrates that internal doses (interpreted as total benzene metabolites formed) from oral gavage experiments in mice are well predicted by a PBPK model developed by Travis et al. Both the data and the model outputs can also be accurately described by the simple nonlinear regression model total metabolites= 76.4x/(80.75 + x), where x= administered dose in mg/kg/day. Thus, PBPK modeling validates the use of such nonlinear regression models, previously used by Bailer and Hoel. An important finding is that refitting the linearized multistage (LMS) model family to internal doses and observed responses changes the maximum‐likelihood estimate (MLE) dose‐response curve for mice from linear‐quadratic to cubic, leading to low‐dose risk estimates smaller than in previous risk assessments. This is consistent with the conclusion for mice from the Bailer and Hoel analysis. An innovation in this paper is estimation of internal doses for humans based on a PBPK model (and the regression model approximating it) rather than on interspecies dose conversions. Estimates of human risks at low doses are reduced by the use of internal dose estimates when the estimates are obtained from a PBPK model, in contrast to Bailer and Hoel's findings based on interspecies dose conversion. Sensitivity analyses and comparisons with epidemiological data and risk models suggest that our finding of a nonlinear MLE dose‐response curve at low doses is robust to changes in assumptions and more consistent with epidemiological data than earlier risk models.
The Use of Generalized Estimating Equations for Risk Assessment in Developmental Toxicity
Authors: Ryan Louise
Published: May 2006

This paper reviews and compares several approaches to fitting dose‐response models to developmental toxicity data. The main issue of interest is how to appropriately account for litter effects. Among the approaches reviewed are Beta Binomial models, models that attempt to characterize the litter effect through the use of covariates, and models that avoid the complication of correlated offspring by modeling “affected litter” rather than fetus‐specific outcomes. Finally, we discuss our recommended approach, which is to use Generalized Estimating Equations, or quasi‐likelihood. We give a number of reasons for preferring the latter and illustrate its application with an example.
The Effect of Neglecting Correlations When Propagating Uncertainty and Estimating the Population Distribution of Risk
Authors: Smith Andrew E. , Ryan P. Barry , Evans John S.
Published: May 2006

Interest in examining both the uncertainty and variability in environmental health risk assessments has led to increased use of methods for propagating uncertainty. While a variety of approaches have been described, the advent of both powerful personal computers and commercially available simulation software have led to increased use of Monte Carlo simulation. Although most analysts and regulators are encouraged by these developments, some are concerned that Monte Carlo analysis is being applied uncritically. The validity of any analysis is contingent on the validity of the inputs to the analysis. In the propagation of uncertainty or variability, it is essential that the statistical distribution of input variables are properly specified. Furthermore, any dependencies among the input variables must be considered in the analysis. In light of the potential difficulty in specifying dependencies among input variables, it is useful to consider whether there exist rules of thumb as to when correlations can be safely ignored (i.e., when little overall precision is gained by an additional effort to improve upon an estimation of correlation). We make use of well‐known error propagation formulas to develop expressions intended to aid the analyst in situations wherein normally and lognormally distributed variables are linearly correlated.
Modeling the Modification of the Risk of Radon‐Induced Lung Cancer by Environmental Tobacco Smoke
Authors: Crawford‐Brown Douglas J.
Published: May 2006

The presence of environmental tobacco smoke (ETS)in homes has been implicated in the causation of lung cancer. While of interest in its own right, ETS also influences the risk imposed by radon and its decay products. The interaction between radon progeny and ETS alters the exposure, intake, uptake, biokinetics, dosimetry, and radiobiology of those progeny. The present paper details model predictions of the various influences of ETS on these factors in the U.S. population and provides estimates of the resulting change in the risk from average levels of radon progeny. It is predicted that the presence of ETS produces a very small (perhaps unmeasurable)increase in the risk of radiation‐induced tracheobronchial cancer in homes with initially very high particle concentrations for both active and never‐smokers, but significantly lowers the risk in homes with initially lower particle concentrations for both groups when generation 4 of the lung is considered the target site. For generation 16, the presence of ETS generally increases the radon‐induced risk of lung cancer, although the increase should be unmeasurable at high initial particle concentrations. The net effect of ETS on human health is suggested to be a complicated function of the initial housing conditions, the concentration of particles introduced by smoking, the target generation considered, and the smoking status of exposed populations. This situation precludes any simple statements concerning the role of ETS in governing the incidence of lung cancer in a population.
Bayesian Methods for Model Uncertainty Analysis with Application to Future Sea Level Rise
Authors: Patwardhan Anand , Small Mitchell J.
Published: May 2006

This paper addresses the use of data for identifying and characterizing uncertainties in model parameters and predictions. The Bayesian Monte Carlo method is formally presented and elaborated, and applied to the analysis of the uncertainty in a predictive model for global mean sea level change. The method uses observations of output variables, made with an assumed error structure, to determine a posterior distribution of model outputs. This is used to derive a posterior distribution for the model parameters. Results demonstrate the resolution of the uncertainty that is obtained as a result of the Bayesian analysis and also indicate the key contributors to the uncertainty in the sea level rise model. While the technique is illustrated with a simple, preliminary model, the analysis provides an iterative framework for model refinement. The methodology developed in this paper provides a mechanism for the incorporation of ongoing data collection and research in decision‐making for problems involving uncertain environmental change.
Estimating Dermal Uptake of Nonionic Organic Chemicals from Water and Soil: I. Unified Fugacity‐Based Models for Risk Assessments
Authors: McKone Thomas E. , Howd Robert A.
Published: May 2006

Contamination of water and soil that might eventually contact human skin makes it imperative to include the dermal uptake route in efforts to assess potential environmental health risks. Direct measurements of dermal uptake from either water or soil are only available for a small number of the thousands of chemicals likely to be found in the environment. We propose here a mass‐transfer model for estimating skin permeability and dermal uptake for organic chemicals that contaminate soil and water. Statistical relationships between measured permeabilities and chemical properties reveal that permeability varies primarily with the octanol‐water partition coefficient (Kow)and secondarily with the molecular weight. From these results, we derive a fugacity‐based model for skin permeability that addresses the inherent permeability of the skin, the interaction of the skin with the environmental medium on skin (water or soil), and retains a relatively simple algebraic form. Model predictions are compared to measured human skin permeabilities for some 50 compounds in water and four compounds in soil. The model is adjusted to account for dermal uptake during both short‐term (10‐20 min)and long‐term (several hour)exposures. This model is recommended for compounds with molecular weight less than or equal to 280 g.
Evaluating Risk Communication: Narrative vs. Technical Presentations of Information About Radon
Authors: Golding Dominic , Krimsky Sheldon , Plough Alonzo
Published: May 2006

This paper reports on an experiment to test the hypothesis that people respond better to risk communication that reflects more closely the conditions of their social and cultural lives. The experiment used the case of radon to determine whether technical or narrative forms of risk communication were more effective at drawing people's attention, imparting information, and modifying behavior. Two series of articles on radon were placed in the local newspapers of two Massachusetts communities. Homeowner attitudes, knowledge, and responses were monitored in baseline and follow‐up telephone surveys. A third community was selected for comparison. The newspaper series were developed on the basis of previous research and six focus groups conducted with homeowners. The technical series presented authoritative, factual risk information, in the scientific style of the passive voice with generalized and impersonal language. The narrative series consisted of dramatized accounts of individuals making decisions about radon testing and mitigation, written in a more personal style. The findings from the focus groups confirm the results of previous studies, but the small size of the follow‐up samples was a limiting factor in drawing definitive conclusions about the relative effectiveness of the two formats. The experiment demonstrates the difficulty of any risk communication effort on radon and underscores the need for good research design. The study illustrates the need for further research on the role of sociological and cultural factors in the public perception and response to risk.
Lognormal Distributions for Water Intake by Children and Adults
Authors: Roseberry Ann M. , Burmaster David E.
Published: May 2006

We fit lognormal distributions to data collected in a national survey for both total water intake and tap water intake by children and adults for these age groups in years: 0 < age < 1; 1 ≤ age < 11; 11 ≤ age < 20; 20 ≤ age < 65; 65 ≤ age; and all people in the survey taken as a single group. These distributions are suitable for use in public health risk assessments.
Predicted Infant Exposure to Tetrachloroethene in Human Breastmilk
Authors: Schreiber Judith S.
Published: May 2006

Based on a variety of maternal occupational and residential inhalation exposure scenarios, estimates of infant exposure to the dry‐cleaning solvent tetrachlorothylene (perchloroethylene, PCE) in breastmilk were made. Physiologically based pharmacokinetic (PBPK) modeling indicates that infants may be exposed to elevated levels of PCE in breastmilk due to their mothers’ inhalation of PCE. The PBPK‐predicted breastmilk PCE concentrations agree very well with measured concentrations, where available. Based on this analysis, infants may be exposed to this workplace chemical via breastmilk at doses corresponding to rather high levels of risk. Predicted breastmilk doses provide the infant with little margin of exposure to doses associated with adverse health effects. In addition, the estimated increased cancer risks associated with these infant exposures are large under certain exposure scenarios. The actual concentrations of PCE in breastmilk of exposed mothers can only be known with certainty if monitoring is conducted. Due to the widespread exposure potential, monitoring studies should be undertaken so that the appropriate risk management alternatives can be better evaluated.
Modeling Long‐Term Exposure of the Whole Population to Chemicals in Food
Authors: Slob Wout
Published: May 2006

This paper discusses a statistical exposure model (STEM) that can be used to estimate the percentage of the population exceeding ingestion intake criteria (e.g., ADI or TDI). In addition, STEM may be linked to toxicokinetic models to evaluate the interindividual variability in internal doses that results from variability in consumption habits. The assumptions of STEM are investigated by analyzing dioxin and cadmium intake data for the Dutch population.
A Compartmental Model for the Prediction of Breath Concentration and Absorbed Dose of Chloroform After Exposure While Showering
Authors: Chinery Robert L. , Gleason A. Kevin
Published: May 2006

In order to predict the exhaled breath concentration of chloroform in individuals exposed to chloroform while showering, an existing physiologically based pharmacokinetic (PB‐PK) model was modified to include a multicompartment, PB‐PK model for the skin and a completely mixed shower exposure model. The PB‐PK model of the skin included the stratum corneum as the principal resistance to absorption and a viable epidermis which is in dynamic equilibrium with the skin microcirculation. This model was calibrated with measured exhaled breath concentrations of chloroform in individuals exposed while showering with and without dermal absorption. The calibration effort indicated that the expected value of skin‐blood partitioning coefficient would be 1.2 when the degree of transfer of chloroform from shower water into shower air was 61%. The stratum corneum permeability coefficient for chloroform was estimated to be within the range of 0.16‐0.36 cm/hr and the expected value was 0.2 cm/hr. The estimated ratio of the dermally and inhaled absorbed doses ranged between 0.6 and 2.2 and the expected value was 0.75. These results indicate that for the purposes of risk assessment for dermal exposure to chloroform, a simple steady‐state model can be used to predict the degree of dermal absorption and that a reasonable value of skin permeability coefficient for chloroform used in this model would be 0.2 cm/hr. Further research should be conducted to compare the elimination of chloroform via exhaled breath when different exposure routes are being compared. The model results from this study suggest that multiple measurements of exhaled breath concentrations after exposure may be necessary when making comparisons of breath concentrations that involve different exposure routes.
Estimation of Potential Health Effects from Acute Exposure to Hydrogen Fluoride Using a “Benchmark Dose” Approach
Authors: Alexeeff George V. , Lewis David C. , Ragle Nancy L.
Published: May 2006

Communities across the United States are examining the manufacture, use, transport, and storage of hydrogen fluoride (HF) near residential areas as a consequence of a major release of HF in Texas in 1987. Reference exposure levels for routine and accidental HF emissions are calculated using existing animal and human data. The approach employs a logprobit extrapolation of concentration‐response data to the 95% lower confidence limit on the toxic concentration producing a “benchmark dose” of 1% response (TC01), called a practical threshold. Species‐specific and chemical‐specific adjustment factors are applied to develop exposure levels applicable to the general public. Using this method, the 1‐hr reference exposure level to protect the public against any irritation from a routine emission (REL‐1) is 0.7 ppm and the level to protect against severe irritation from a once‐in‐a‐lifetime (REL‐2) release is 2 ppm. This approach is compared to a modified “uncertainty factor” approach.
Evaluating the Risk of Liver Cancer in Humans Exposed to Trichloroethylene Using Physiological Models
Authors: Fisher Jeffrey W. , Allen Bruce C.
Published: May 2006

Trichloroethylene (TCE) is a widespread environmental pollutant. TCE is classified as a rodent carcinogen by the U.S. Environmental Protection Agency (EPA). Using the rodent cancer bioassay findings and estimates of metabolized dose, the EPA has estimated lifetime exposure cancer risks for humans that ingest TCE in drinking water or inhale TCE. In this study, a physiologically based pharmacokinetic (PB‐PK) model for mice was used to simulate selected gavage and inhalation bioassays with TCE. Plausible dose‐metrics thought to be linked with the mechanism of action for TCE carcinogenesis were selected. These dose‐metrics, adjusted to reflect an average amount per day for a lifetime, were metabolism of TCE (AMET, mg/kg/day) and systemic concentration of TCA (AUCTCA, mg/L/day). These dose‐metrics were then used in a linearized multistage model to estimate AMET and AUCTCA values that correspond to liver cancer risks of 1 in 1 million in mice. A human PB‐PK model for TCE was then used to predict TCE concentrations in drinking water and air that would provide AMET and AUCTCA values equal to the predicted mice AMET and AUCTCA values that correspond to liver cancer risks of 1 in 1 million. For the dose‐metrics, AMET and AUCTCA, the TCE concentrations in air were 10.0 and 0.1 ppb TCE (continuous exposure), respectively, and in water, 7 and 4 μg TCE/L, respectively.
Analysis of Uncertainties in Interactive Probabilistic Safety Analysis (PSA) Models
Authors: Paula Henrique M. , Campbell David J. , Guthrie Vernon H.
Published: May 2006

Probabilistic safety analysis (PSA) has been used in nuclear, chemical, petrochemical, and several other industries. The probability and/or frequency results of most PSAs are based on average component unavailabilities during the mission of interest. While these average results are useful, they provide no indication of the significance of the facility's current status when one or more components are known to be out of service. Recently, several interactive computational models have been developed for nuclear power plants to allow the user to specify the plant's status at a particular time (i.e., to specify equipment known to be out of service) and then to receive updated PSA information. As with conventional PSA results, there are uncertainties associated with the numerical updated results. These uncertainties stem from a number of sources, including parameter uncertainty (uncertainty in equipment failure rates and human error probabilities). This paper presents an analysis of the impact of parameter uncertainty on updated PSA results.